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we present independent determinations of cosmological parameters using the distance estimator based on the established correlation between the balmer line luminosity, l(h β), and the velocity dispersion (σ) for h ii galaxies (hiig). these results are based on new vlt-kmos high spectral resolution observations of 41 high-z (1.3 ≤ z ≤2.6) hiig combined with published data for 45 high-z and 107 z ≤0.15 hiig, while the cosmological analysis is based on the multinest markov chain monte carlo (mcmc) procedure not considering systematic uncertainties. using only hiig to constrain the matter density parameter (ωm), we find $\omega _\mathrm{ m} = 0.244^{+0.040}_{-0.049}$ (stat), an improvement over our best previous cosmological parameter constraints, as indicated by a 37 per cent increase of the figure of merit. the marginalized best-fitting parameter values for the plane {ωm; w0} = $\lbrace 0.249^{+0.11}_{-0.065}; -1.18^{+0.45}_{-0.41}\rbrace$ (stat) show an improvement of the cosmological parameters constraints by 40 per cent. combining the hiig hubble diagram, the cosmic microwave background (cmb) and the baryon acoustic oscillation (bao) probes yields ωm = 0.298 ± 0.012 and w0 = -1.005 ± 0.051, which are certainly compatible - although less constraining - than the solution based on the joint analysis of ia supernovae (snia), cmb and bao measurements. an attempt to constrain the evolution of the dark energy with time (cpl model), using a joint analysis of the hiig, cmb, and bao measurements, shows a degenerate 1σ contour of the parameters in the {w0, wa} plane. | independent cosmological constraints from high-z h ii galaxies: new results from vlt-kmos data |
white-dwarf stars are the end product of stellar evolution for most stars in the universe. their interiors bear the imprint of fundamental mechanisms that occur during stellar evolution. moreover, they are important chronometers for dating galactic stellar populations, and their mergers with other white dwarfs now appear to be responsible for producing the type ia supernovae that are used as standard cosmological candles. however, the internal structure of white-dwarf stars—in particular their oxygen content and the stratification of their cores—is still poorly known, because of remaining uncertainties in the physics involved in stellar modelling codes. here we report a measurement of the radial chemical stratification (of oxygen, carbon and helium) in the hydrogen-deficient white-dwarf star kic08626021 (j192904.6+444708), independently of stellar-evolution calculations. we use archival data coupled with asteroseismic sounding techniques to determine the internal constitution of this star. we find that the oxygen content and extent of its core exceed the predictions of existing models of stellar evolution. the central homogeneous core has a mass of 0.45 solar masses, and is composed of about 86 per cent oxygen by mass. these values are respectively 40 per cent and 15 per cent greater than those expected from typical white-dwarf models. these findings challenge present theories of stellar evolution and their constitutive physics, and open up an avenue for calibrating white-dwarf cosmochronology. | a large oxygen-dominated core from the seismic cartography of a pulsating white dwarf |
recent theory predicts that first stars are born with a massive initial mass of ≳100 m ⊙. pair-instability supernova (pisn) is a common fate for such massive stars. our final goal is to prove the existence of pisne and thus the high-mass nature of the initial mass function in the early universe by conducting abundance profiling, in which properties of a hypothetical first star is constrained by metal-poor star abundances. in order to determine reliable and useful abundances, we investigate the pisn nucleosynthesis taking both rotating and nonrotating progenitors for the first time. we show that the initial and co core mass ranges for pisne depend on the envelope structures: nonmagnetic rotating models developing inflated envelopes have a lower shifted co mass range of ∼70-125 m ⊙, while nonrotating and magnetic rotating models with deflated envelopes have a range of ∼80-135 m ⊙. however, we find no significant difference in explosive yields from rotating and nonrotating progenitors, except for large nitrogen production in nonmagnetic rotating models. furthermore, we conduct the first systematic comparison between theoretical yields and a large sample of metal-poor star abundances. we find that the predicted low [na/mg] ∼ -1.5 and high [ca/mg] ∼0.5-1.3 abundance ratios are the most important to discriminate pisn signatures from normal metal-poor star abundances, and confirm that no currently observed metal-poor star matches with the pisn abundance. an extensive discussion on the nondetection is presented. | stellar yields of rotating first stars. ii. pair-instability supernovae and comparison with observations |
context. massive binaries play a crucial role in the universe. knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the milky way.aims: the tarantula massive binary monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (rv) monitoring of 102 massive binaries in the 30 doradus region.methods: in this paper we analyze 32 flames/giraffe observations of 93 o- and 7 b-type binaries. we performed a fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (sb1) and 31 double-lined (sb2) spectroscopic binaries.results: overall, the binary fraction and orbital properties across the 30 doradus region are found to be similar to existing galactic samples. this indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. a small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 doradus than in the galaxy, although this may be compatible within error estimates and differences in the fitting methodology. also, orbital periods in 30 doradus can be as short as 1.1 d, somewhat shorter than seen in galactic samples. equal mass binaries (q> 0.95) in 30 doradus are all found outside ngc 2070, the central association that surrounds r136a, the very young and massive cluster at 30 doradus's core. most of the differences, albeit small, are compatible with expectations from binary evolution. one outstanding exception, however, is the fact that earlier spectral types (o2-o7) tend to have shorter orbital periods than later spectral types (o9.2-o9.7).conclusions: our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (z⊙) to about half solar. this provides the first direct constraints on massive binary properties in massive star-forming galaxies at the universe's peak of star formation at redshifts z 1 to 2 which are estimated to have z 0.5 z⊙. the log of observations and rv measurements for all targets are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/598/a84 | the tarantula massive binary monitoring. i. observational campaign and ob-type spectroscopic binaries |
the galactic center is dominated by the gravity of a super-massive black hole (smbh), sagittarius a*, and is suspected to contain a sizable population of binary stars. such binaries form hierarchical triples with the smbh, undergoing eccentric kozai-lidov (ekl) evolution, which can lead to high-eccentricity excitations for the binary companions’ mutual orbit. this effect can lead to stellar collisions or roche-lobe crossings, as well as orbital shrinking due to tidal dissipation. in this work we investigate the dynamical and stellar evolution of such binary systems, especially with regards to the binaries’ post-main-sequence evolution. we find that the majority of binaries (∼75%) is eventually separated into single stars, while the remaining binaries (∼25%) undergo phases of common-envelope evolution and/or stellar mergers. these objects can produce a number of different exotic outcomes, including rejuvenated stars, g2-like infrared-excess objects, stripped giant stars, type ia supernovae (sne), cataclysmic variables, symbiotic binaries, or compact object binaries. we estimate that, within a sphere of 250 mpc radius, about 7.5-15 sne ia per year should occur in galactic nuclei due to this mechanism, potentially detectable by the zwicky transient facility and asas-sn. likewise, we estimate that, within a sphere of 1 gpc3 volume, about 10-20 compact object binaries form per year that could become gravitational wave sources. based on results of ekl-driven compact object binary mergers in galactic nuclei by hoang et al., this compact object binary formation rate translates to about 15-30 events per year that are detectable by advanced ligo. | the fate of binaries in the galactic center: the mundane and the exotic |
we implement a detailed dust model into the l-galaxies semi-analytical model which includes: injection of dust by type ii and type ia supernovae (sne) and agb stars; grain growth in molecular clouds; and destruction due to supernova-induced shocks, star formation, and reheating. our grain growth model follows the dust content in molecular clouds and the inter-cloud medium separately, and allows growth only on pre-existing dust grains. at early times, this can make a significant difference to the dust growth rate. above z ∼ 8, type ii sne are the primary source of dust, whereas below z ∼ 8, grain growth in molecular clouds dominates, with the total dust content being dominated by the latter below z ∼ 6. however, the detailed history of galaxy formation is important for determining the dust content of any individual galaxy. we introduce a fit to the dust-to-metal (dtm) ratio as a function of metallicity and age, which can be used to deduce the dtm ratio of galaxies at any redshift. at z ≲ 3, we find a fairly flat mean relation between metallicity and the dtm, and a positive correlation between metallicity and the dust-to-gas (dtg) ratio, in good agreement with the shape and normalization of the observed relations. we also match the normalization of the observed stellar mass-dust mass relation over the redshift range of 0-4, and to the dust mass function at z = 0. our results are important in interpreting observations on the dust content of galaxies across cosmic time, particularly so at high redshift. | detailed dust modelling in the l-galaxies semi-analytic model of galaxy formation |
we study the connection of star formation to atomic (h i) and molecular hydrogen (h2) in isolated, low-metallicity dwarf galaxies with high-resolution (mgas = 4 m⊙, nngb = 100) smoothed particle hydrodynamics simulations. the model includes self-gravity, non-equilibrium cooling, shielding from a uniform and constant interstellar radiation field, the chemistry of h2 formation, h2-independent star formation, supernova feedback and metal enrichment. we find that the h2 mass fraction is sensitive to the adopted dust-to-gas ratio and the strength of the interstellar radiation field, while the star formation rate is not. star formation is regulated by stellar feedback, keeping the gas out of thermal equilibrium for densities n < 1 cm-3. because of the long chemical time-scales, the h2 mass remains out of chemical equilibrium throughout the simulation. star formation is well correlated with cold (t ≤ 100 k) gas, but this dense and cold gas - the reservoir for star formation - is dominated by h i, not h2. in addition, a significant fraction of h2 resides in a diffuse, warm phase, which is not star-forming. the interstellar medium is dominated by warm gas (100 k < t ≤ 3 × 104 k) both in mass and in volume. the scaleheight of the gaseous disc increases with radius while the cold gas is always confined to a thin layer in the mid-plane. the cold gas fraction is regulated by feedback at small radii and by the assumed radiation field at large radii. the decreasing cold gas fractions result in a rapid increase in depletion time (up to 100 gyr) for total gas surface densities σ _{h i+h_2} ≲ 10 m⊙ pc-2, in agreement with observations of dwarf galaxies in the kennicutt-schmidt plane. | star formation and molecular hydrogen in dwarf galaxies: a non-equilibrium view |
invisible neutrino decay modes are difficult to target at laboratory experiments, and current bounds on such decays from solar neutrino and neutrino oscillation experiments are somewhat weak. it has been known for some time that cosmology can serve as a powerful probe of invisible neutrino decays. in this work, we show that in order for big bang nucleosynthesis to be successful, the invisible neutrino decay lifetime is bounded to be τν>10-3 s at 95% cl. we revisit cosmic microwave background constraints on invisible neutrino decays, and by using planck2018 observations we find the following bound on the neutrino lifetime: τν>(1.3 - 0.3 )×109 s (mν/0.05 ev ) 3 at 95% cl. we show that this bound is robust to modifications of the cosmological model, in particular that it is independent of the presence of dark radiation. we find that lifetimes relevant for supernova observations (τν∼105 s (mν/0.05 ev ) 3 ) are disfavored at more than 5 σ with respect to λ cdm given the latest planck cmb observations. finally, we show that when including high-ℓ planck polarization data, neutrino lifetimes τν=(2 - 16 )×109 s (mν/0.05 ev ) 3 are mildly preferred—with a 1 -2 σ significance—over neutrinos being stable. | cosmological constraints on invisible neutrino decays revisited |
we consider the possible observation of fast radio bursts (frbs) with planned future radio telescopes, and investigate how well the dispersions and redshifts of these signals might constrain cosmological parameters. we construct mock catalogs of frb dispersion measure (dm) data and employ markov chain monte carlo analysis, with which we forecast and compare with existing constraints in the flat λcdm model, as well as some popular extensions that include dark energy equation of state and curvature parameters. we find that the scatter in dm observations caused by inhomogeneities in the intergalactic medium (igm) poses a big challenge to the utility of frbs as a cosmic probe. only in the most optimistic case, with a high number of events and low igm variance, do frbs aid in improving current constraints. in particular, when frbs are combined with cmb+bao+sne+h 0 data, we find the biggest improvement comes in the {{{ω }}}{{b}}{h}2 constraint. also, we find that the dark energy equation of state is poorly constrained, while the constraint on the curvature parameter, ω k , shows some improvement when combined with current constraints. when frbs are combined with future baryon acoustic oscillation (bao) data from 21 cm intensity mapping, we find little improvement over the constraints from baos alone. however, the inclusion of frbs introduces an additional parameter constraint, {{{ω }}}{{b}}{h}2, which turns out to be comparable to existing constraints. this suggests that frbs provide valuable information about the cosmological baryon density in the intermediate redshift universe, independent of high-redshift cmb data. | future cosmological constraints from fast radio bursts |
the quaternary compound copper manganese tin sulfide cu2mnsns4 is a potential absorber semiconductor material for fabricating thin film solar cells (tfsc) thanks to their promising optoelectronic parameters. this article numerically investigated the performance of cu2mnsns4 (cmts)-based tfsc without and with tin sulphide (sns) back surface field (bsf) thin-film layer. first, the impact of several major influential parameters such as the active material's thickness, doping concentration of photoactive materials, density of bulk and interface defect, working temperature, and metal contact, were studied systematically without a bsf layer. thereafter, the photovoltaic performance of the optimized pristine cell was further investigated with an sns as bsf inserted between the absorber (cmts) with a platinum back metal of an optimized heterostructure of cu/zno:al/i-zno/n-cds/p-cu2mnsns4/pt. thus, the photoconversion efficiency (pce) of 25.43% with a jsc of 34.41 ma/cm2 and voc of 0.883 v was achieved under am1.5g solar spectrum without sns bsf layer. furthermore, an improved pce of 31.4% with a jsc of 36.21 ma/cm2 and voc of 1.07 v was achieved with a quantum efficiency of over 85% in the wavelengths of 450-1000 nm by the addition of sns bsf layer. thus, this obtained systematic and consistent outcomes reveal immense potential of cmts with sns as absorber and bsf, respectively and provide imperious guidance for fabricating highly a massive potential efficient solar cell. | high efficiency cu2mnsns4 thin film solar cells with sns bsf and cds etl layers: a numerical simulation |
we perform smoothed particle hydrodynamics (sph) simulations of an isolated galaxy with a new treatment for dust formation and destruction. to this aim, we treat dust and metal production self-consistently with star formation and supernova (sn) feedback. for dust, we consider a simplified model of grain size distribution by representing the entire range of grain sizes with large and small grains. we include dust production in stellar ejecta, dust destruction by sn shocks, grain growth by accretion and coagulation and grain disruption by shattering. we find that the assumption of fixed dust-to-metal mass ratio becomes no longer valid when the galaxy is older than 0.2 gyr, at which point the grain growth by accretion starts to contribute to the non-linear rise of dust-to-gas ratio. as expected in our previous one-zone model, shattering triggers grain growth by accretion since it increases the total surface area of grains. coagulation becomes significant when the galaxy age is greater than ∼ 1 gyr; at this epoch, the abundance of small grains becomes high enough to raise the coagulation rate of small grains. we further compare the radial profiles of dust-to-gas ratio (d) and dust-to-metal ratio (d/z, i.e. depletion) at various ages with observational data. we find that our simulations broadly reproduce the radial gradients of dust-to-gas ratio and depletion. in the early epoch (≲ 0.3 gyr), the radial gradient of d follows the metallicity gradient with d/z determined by the dust condensation efficiency in stellar ejecta, while the d gradient is steeper than the z gradient at the later epochs because of grain growth by accretion. the framework developed in this paper is applicable to any sph-based galaxy evolution simulations including cosmological ones. | galaxy simulation with dust formation and destruction |
using the largest spectroscopic data set of stripped-envelope core-collapse supernovae (stripped sne), we present a systematic investigation of spectral properties of type iib sne (sne iib), type ib sne (sne ib), and type ic sne (sne ic). prior studies have been based on individual objects or small samples. here, we analyze 242 spectra of 14 sne iib, 262 spectra of 21 sne ib, and 207 spectra of 17 sne ic based on the stripped sn data set of modjaz et al. and other published spectra of individual sne. each sn in our sample has a secure spectroscopic id, a date of v-band maximum light, and most have multiple spectra at different phases. we analyze these spectra as a function of subtype and phase in order to improve the sn identification scheme and constrain the progenitors of different kinds of stripped sne. by comparing spectra of sne iib with those of sne ib, we find that the strength of hα can be used to quantitatively differentiate between these two subtypes at all epochs. moreover, we find a continuum in observational properties between sne iib and ib. we address the question of hidden he in sne ic by comparing our observations with predictions from various models that either include hidden he or in which he has been burnt. our results favor the he-free progenitor models for sne ic. finally, we construct continuum-divided average spectra as a function of subtype and phase to quantify the spectral diversity of the different types of stripped sne. | analyzing the largest spectroscopic data set of stripped supernovae to improve their identifications and constrain their progenitors |
we present the observations made by several china-based amateur astronomers that cover the onset of sn 2023ixf. a serendipitous time-lapse observation of m 101 captured the onset of the supernova explosion and constrained the onset time at around 2023 may 18 19:30 to 20:30 ut. | onset of sn 2023ixf observed over east asian longitudes |
we present mid-infrared (mid-ir) imaging of the type iil supernova (sn) 1980k with the james webb space telescope (jwst) more than 40 yr post-explosion. sn 1980k, located in the nearby ($d\approx7$ mpc) "sn factory" galaxy ngc 6946, was serendipitously captured in jwst/miri images taken of the field of sn 2004et in the same galaxy. sn 1980k serves as a promising candidate for studying the transitional phase between young sne and older sn remnants and also provides a great opportunity to investigate its the close environment. sn 1980k can be identified as a clear and bright point source in all eight miri filters from f560w up to f2550w. we fit analytical dust models to the mid-ir spectral energy distribution that reveal a large amount ($m_d \approx 0.002 {m}_{\odot}$) of si-dominated dust at $t_{dust}\approx 150$ k (accompanied by a hotter dust/gas component), and also computed numerical sed dust models. radiative transfer modeling of a late-time optical spectrum obtained recently with keck discloses that an even larger ($\sim 0.24-0.58~{m}_{\odot}$) amount of dust is needed in order for selective extinction to explain the asymmetric line profile shapes observed in sn 1980k. as a conclusion, with jwst, we may see i) pre-existing circumstellar dust heated collisionally (or, partly radiatively), analogous to the equatorial ring of sn 1987a, or ii) the mid-ir component of the presumed newly-formed dust, accompanied by much more colder dust present in the ejecta (as suggested by the late-time the optical spectra). | serendipitous detection of the dusty type iil sn 1980k with jwst/miri |
superradiant clouds may develop around a rotating black hole, if there is a bosonic field with compton wavelength comparable to the size of the black hole. in this paper, we investigate the effects of the cloud on the orbits of nearby compact objects. in particular, we consider the dynamical friction and the backreaction due to level mixing. under these interactions, the probability of a black hole dynamically capturing other compact objects, such as stellar mass black holes and neutron stars, is generally enhanced with the presence of the cloud. for extreme mass ratio inspirals and binary stellar mass binary black holes, the cloud-induced orbital modulation may be detected by observing the gravitational waveform using space borne gravitational wave detectors, such as lisa. interestingly within certain range of boson compton wavelength, the enhanced capture rate of stellar mass black holes could accelerate hierarchical mergers, with a higher-generation merger product being more massive than the mass threshold predicted by supernova pair instability. these observational signatures provide promising ways of searching light bosons with gravitational waves. | dynamic signatures of black hole binaries with superradiant clouds |
we present griz light curves of 251 sne ia from the first 3 years of the dark energy survey supernova program’s (des-sn) spectroscopically classified sample. the photometric pipeline described in this paper produces the calibrated fluxes and associated uncertainties used in the cosmological parameter analysis by employing a scene modeling approach that simultaneously models a variable transient flux and temporally constant host galaxy. we inject artificial point sources onto decam images to test the accuracy of our photometric method. upon comparison of input and measured artificial supernova fluxes, we find that flux biases peak at 3 mmag. we require corrections to our photometric uncertainties as a function of host galaxy surface brightness at the transient location, similar to that seen by the des difference imaging pipeline used to discover transients. the public release of the light curves can be found at https://des.ncsa.illinois.edu/releases/sn. | first cosmology results using type ia supernovae from the dark energy survey: photometric pipeline and light-curve data release |
we present 888 visual-wavelength spectra of 122 nearby type ii supernovae (sne ii) obtained between 1986 and 2009, and ranging between 3 and 363 days post-explosion. in this first paper, we outline our observations and data reduction techniques, together with a characterization based on the spectral diversity of sne ii. a statistical analysis of the spectral matching technique is discussed as an alternative to nondetection constraints for estimating sn explosion epochs. the time evolution of spectral lines is presented and analyzed in terms of how this differs for sne of different photometric, spectral, and environmental properties: velocities, pseudo-equivalent widths, decline rates, magnitudes, time durations, and environment metallicity. our sample displays a large range in ejecta expansion velocities, from ∼9600 to ∼1500 km s-1 at 50 days post-explosion with a median {{{h}}}αvalue of 7300 km s-1. this is most likely explained through differing explosion energies. significant diversity is also observed in the absolute strength of spectral lines, characterized through their pseudo-equivalent widths. this implies significant diversity in both temperature evolution (linked to progenitor radius) and progenitor metallicity between different sne ii. around 60% of our sample shows an extra absorption component on the blue side of the {{{h}}}αp-cygni profile (“cachito” feature) between 7 and 120 days since explosion. studying the nature of cachito, we conclude that these features at early times (before ∼35 days) are associated with si ii λ 6355, while past the middle of the plateau phase they are related to high velocity (hv) features of hydrogen lines. this paper includes data gathered with the 6.5 m magellan telescopes located at las campanas observatory, chile; and the gemini observatory, cerro pachon, chile (gemini program gs-2008b-q-56). based on observations collected at the european organisation for astronomical research in the southern hemisphere, chile (eso programs 076.a-0156, 078.d-0048, 080.a-0516, and 082.a-0526). | type ii supernova spectral diversity. i. observations, sample characterization, and spectral line evolution |
the recent identification of a candidate very massive (70 m⊙) black hole (bh) is at odds with our current understanding of stellar winds and pair-instability supernovae. we investigate alternate explanations for this system by searching the bpass v2.2 stellar and population synthesis models for those that match the observed properties of the system. we find binary evolution models that match the lb-1 system, at the reported gaia distance, with more moderate bh masses of 4-7 m⊙. we also examine the suggestion that the binary motion may have led to an incorrect distance determination by gaia. we find that the gaia distance is accurate and that the binary system is consistent with the observation at this distance. consequently, it is highly improbable that the bh in this system has the extreme mass originally suggested. instead, it is more likely to be representative of the typical bh binary population expected in our galaxy. | weighing in on black hole binaries with bpass: lb-1 does not contain a 70 m⊙ black hole |
we present a full-fledged analysis of brans-dicke cosmology with a cosmological constant and cold dark matter (bd-$\lambda$cdm for short). we extend the scenarios where the current cosmological value of the bd-field is restricted by the local astrophysical domain to scenarios where that value is fixed only by the cosmological observations, which should be more natural in view of the possible existence of local screening mechanims. our analysis includes both the background and perturbations equations in different gauges. we find that the bd-$\lambda$cdm is favored by the overall cosmological data as compared to the concordance gr-$\lambda$cdm model, namely data on distant supernovae, cosmic chronometers, local measurements of the hubble parameter, baryonic acoustic oscillations, large-scale structure formation and the cosmic microwave background under full planck 2018 cmb likelihood. we also test the impact of strong and weak-lensing data on our results, which can be significant. we find that the bd-$\lambda$cdm can mimic effective quintessence with a significance of about $3-3.5\sigma$ c.l. (depending on the lensing datasets). the fact that the bd-$\lambda$cdm behaves effectively as a running vacuum model (rvm) when viewed from the gr perspective helps to alleviate some of the existing tensions with the data, such as the $\sigma_8$ excess predicted by gr-$\lambda$cdm. on the other hand, the bd-$\lambda$cdm model has a crucial bearing on the acute $h_0$-tension with the local measurements, which is rendered virtually harmless owing to the small increase of the effective value of the gravitational constant with the expansion. the simultaneous alleviation of the two tensions is a most remarkable feature of bd-gravity with a cosmological constant in the light of the current observations, and hence goes in support of bd-$\lambda$cdm against gr-$\lambda$cdm | brans-dicke cosmology with a $\\lambda$- term: a possible solution to $\\lambda$cdm tensions |
collective neutrino oscillations are critical to determine the neutrino flavor content, which has striking impacts on core-collapse supernovae or compact binary merger remnants. it is a challenging many-body problem that so far has been mainly studied at the mean-field approximation. we use a setup that captures the relevant physics and allows exact solution for a large number of neutrinos. we find that quantitative deviation from the mean-field evolution can exist even for a large system. the underlying mechanism due to many-body decoherence in flavor space is analyzed, and similar features have been observed in a spin-1 bose-einstein condensate. our results call for more careful examinations on the possible many-body corrections to collective neutrino oscillations in astrophysical environments. | many-body effects of collective neutrino oscillations |
we present at2020mrf (srge j154754.2+443907), an extra-galactic (z = 0.1353) fast blue optical transient (fbot) with a rise time of tg,rise = 3.7 days and a peak luminosity of mg,peak = -20.0. its optical spectrum around peak shows a broad (v ~ 0.1c) emission feature on a blue continuum (t ~ 2 × 104 k), which bears a striking resemblance to at2018cow. its bright radio emission (ν lν= 1.2 × 1039 erg s-1; ν rest = 7.4 ghz; 261 days) is similar to four other at2018cow-like events, and can be explained by synchrotron radiation from the interaction between a sub-relativistic (≳0.07-0.08c) forward shock and a dense environment ( $\dot{m}\lesssim {10}^{-3}\,{m}_{\odot }\,{\mathrm{yr}}^{-1}$ for v w = 103 km s-1). at2020mrf occurs in a galaxy with m * ~ 108 m ⊙ and specific star formation rate ~10-10 yr-1, supporting the idea that at2018cow-like events are preferentially hosted by dwarf galaxies. the x-ray luminosity of at2020mrf is the highest among fbots. at 35-37 days, srg/erosita detected luminous (l x ~ 2 × 1043 erg s-1; 0.3-10 kev) x-ray emission. the x-ray spectral shape (fν∝ ν -0.8) and erratic intraday variability are reminiscent of at2018cow, but the luminosity is a factor of ~20 greater than at2018cow. at 328 days, chandra detected it at l x ~ 1042 erg s-1, which is >200 times more luminous than at2018cow and css161010. at the same time, the x-ray emission remains variable on the timescale of ~1 day. we show that a central engine, probably a millisecond magnetar or an accreting black hole, is required to power the explosion. we predict the rates at which events like at2018cow and at2020mrf will be detected by srg and einstein probe. | the x-ray and radio loud fast blue optical transient at2020mrf: implications for an emerging class of engine-driven massive star explosions |
we provide an end-to-end exploration of a distinct modified gravitational theory in jordan-brans-dicke (jbd) gravity, from an analytical and numerical description of the background expansion and linear perturbations, to the nonlinear regime captured with a hybrid suite of n -body simulations, to the cosmological constraints from existing probes of the expansion history, the large-scale structure, and the cosmic microwave background (cmb). we have focused on jbd gravity as it both approximates a wider class of horndeski scalar-tensor theories on cosmological scales and allows us to adequately model the nonlinear corrections to the matter power spectrum. in a combined analysis of the planck 2018 cmb temperature, polarization, and lensing reconstruction, together with pantheon supernova distances and the baryon oscillation spectroscopic survey (boss) measurements of baryon acoustic oscillation distances, the alcock-paczynski effect, and the growth rate, we constrain the jbd coupling constant to ωbd>970 (95% confidence level; c.l.) in agreement with the general relativistic expectation given by ωbd→∞ . in the unrestricted jbd model, where the effective gravitational constant at present, gmatter/g , is additionally varied, increased dataset concordance (e.g., within 1 σ agreement in s8=σ8√{ωm/0.3 }) enables us to further include the combined ("3 ×2 pt ") dataset of cosmic shear, galaxy-galaxy lensing, and overlapping redshift-space galaxy clustering from the kilo degree survey and the 2-degree field lensing survey (kids ×2 dflens ). in analyzing the weak lensing measurements, the nonlinear corrections due to baryons, massive neutrinos, and modified gravity are simultaneously modeled and propagated in the cosmological analysis for the first time. in the joint analysis of all datasets, we constrain ωbd>1540 (95% c.l.), gmatter/g =0.997 ±0.029 , the sum of neutrino masses, ∑mν<0.12 ev (95% c.l.), and the baryonic feedback amplitude, b <2.8 (95% cl), all in agreement with the standard model expectation. in fixing the sum of neutrino masses, the lower bound on the coupling constant strengthens to ωbd>1460 and ωbd>2230 (both at 95% c.l.) in the restricted and unrestricted jbd models, respectively. we explore the impact of the jbd modeling choices, and show that a more restrictive parametrization of the coupling constant degrades the neutrino mass bound by up to a factor of three. in addition to the improved concordance between kids ×2 dflens and planck, the tension in the hubble constant between planck and the direct measurement of riess et al. (2019) is reduced to ∼3 σ ; however, we find no substantial model selection preference for jbd gravity relative to λ cdm . we further show that a positive shift in the effective gravitational constant suppresses the cmb damping tail, which might complicate future inferences of small-scale physics, given its degeneracy with the primordial helium abundance, the effective number of neutrinos, and the running of the spectral index. | testing gravity on cosmic scales: a case study of jordan-brans-dicke theory |
observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity universe is fundamentally different from our own galaxy. many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (z). the hubble space telescope has devoted 500 orbits to observing ∼250 massive stars at low z in the ultraviolet (uv) with the cos and stis spectrographs under the ullyses programme. the complementary x-shooting ullyses (xshootu) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage x-shooter spectrograph at eso's very large telescope. we present an overview of the xshootu project, showing that combining ullyses uv and xshootu optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of z. as uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the xshootu project is expected to be a game changer for our physical understanding of massive stars at low z. to be able to confidently interpret james webb space telescope spectra of the first stellar generations, the individual spectra of low-z stars need to be understood, which is exactly where xshootu can deliver. table b.1 and full table b.2 are available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/675/a154 based on observations collected at the european southern observatory under eso programme 106.211z.001. | x-shooting ullyses: massive stars at low metallicity. i. project description |
we discuss the dark gauge boson emission from neutron stars via nucleon-nucleon bremsstrahlung. through the rigorous treatment of the effective field theory prescription and the thermal effect, we derive the relevant couplings of dark gauge bosons to hadrons in medium. as a specific example, the u(1)b−l gauge boson scenario is chosen to investigate dark gauge boson emissivities during supernovae and cooling of young neutron stars. from the stellar cooling argument, we obtain the constraints on the b − l gauge coupling for given gauge boson masses in two observations: the duration of the supernova neutrino signal of sn1987a, and the inferred x-ray luminosity of the compact object in the remnant of sn1987a (ns1987a). in particular, the constraint from sn1987a on the u(1)b−l gauge boson scenario is revisited. the excluded gauge coupling due to the emission of transverse polarizations is an order of magnitude enhanced compared to the previous derivation. there is also a newly excluded parameter space due to the emission of longitudinal polarizations. | dark gauge boson production from neutron stars via nucleon-nucleon bremsstrahlung |
evidence is mounting that recent multiwavelength detections of fast blue optical transients (fbots) in star-forming galaxies comprise a new class of transients, whose origin is yet to be understood. we show that hydrogen-rich collapsing stars that launch relativistic jets near the central engine can naturally explain the entire set of fbot observables. the jet-star interaction forms a mildly relativistic shocked jet (inner cocoon) component, which powers cooling emission that dominates the high velocity optical signal during the first few weeks, with a typical energy of ~1050-1051 erg. during this time, the cocoon radial energy distribution implies that the optical light curve exhibits a fast decay of $l \,\, \buildrel\propto \over \sim \,\,t^{-2.4}$. after a few weeks, when the velocity of the emitting shell is ~0.01 c, the cocoon becomes transparent, and the cooling envelope governs the emission. the interaction between the cocoon and the dense circumstellar winds generates synchrotron self-absorbed emission in the radio bands, featuring a steady rise on a month time-scale. after a few months the relativistic outflow decelerates, enters the observer's line of sight, and powers the peak of the radio light curve, which rapidly decays thereafter. the jet (and the inner cocoon) becomes optically thin to x-rays ~day after the collapse, allowing x-ray photons to diffuse from the central engine that launched the jet to the observer. cocoon cooling emission is expected at higher volumetric rates than gamma-ray bursts (grbs) by a factor of a few, similar to fbots. we rule out uncollimated outflows, however, both grb jets and failed collimated jets are compatible with all observables. | shocked jets in ccsne can power the zoo of fast blue optical transients |
neutrino self-interactions in a dense neutrino gas can induce collective neutrino flavor conversions. fast neutrino flavor conversions (ffcs), one of the collective neutrino conversion modes, potentially change the dynamics and observables in core-collapse supernovae and binary neutron star mergers. in cases without neutrino-matter interactions (or collisions), ffcs are essentially energy independent, and, therefore, the single-energy treatment has been used in previous studies. however, neutrino-matter collisions, in general, depend on neutrino energy, suggesting that energy-dependent features may emerge in ffcs with collisions. in this paper, we perform dynamical simulations of ffcs with isoenergetic scatterings (emulating nucleon scatterings) under multienergy treatment. we find that cancellation between in- and outscatterings happens in the high-energy region, which effectively reduces the number of collisions and then affects the ffc dynamics. in fact, the lifetime of ffcs is extended compared to the single-energy case, leading to large flavor conversions. our result suggests that the multienergy treatment is mandatory to gauge the sensitivity of ffcs to collisions. we also provide a useful quantity to measure the importance of multienergy effects of collisions on ffcs. | effects of energy-dependent scatterings on fast neutrino flavor conversions |
observations of the extragalactic (z = 0.0141) transient at 2018cow established a new class of energetic explosions shocking a dense medium, producing luminous emission at millimeter and submillimeter wavelengths. here we present detailed millimeter- through centimeter-wave observations of a similar transient, ztf 20acigmel (at 2020xnd), at z = 0.2433. using observations from the northern extended millimeter array and the very large array, we model the unusual millimeter and radio emission from at 2020xnd under several different assumptions and ultimately favor synchrotron radiation from a thermal electron population (relativistic maxwellian). the thermal electron model implies a fast but subrelativistic (v ≈ 0.3c) shock and a high ambient density (ne≈ 4 × 103 cm-3) at δt ≈ 40 days. the x-ray luminosity of lx≈ 1043 erg s-1 exceeds simple predictions from the radio and uvoir luminosity and likely has a separate physical origin, such as a central engine. using the fact that month-long luminous (lν≈ 2 × 1030 erg s-1 hz-1 at 100 ghz) millimeter emission appears to be a generic feature of transients with fast (t 1/2 ≈ 3 days) and luminous (m peak ≈ -21 mag) optical light curves, we estimate the rate at which transients like at 2018cow and at 2020xnd will be detected by future wide-field millimeter transient surveys such as cmb-s4 and conclude that energetic explosions in dense environments may represent a significant population of extragalactic transients in the 100 ghz sky. | luminous millimeter, radio, and x-ray emission from ztf 20acigmel (at 2020xnd) |
dust associated with various stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether supernovae (sne) play an important role in dust production. we report evidence of dust formation in the cold, dense shell behind the ejecta-circumstellar medium (csm) interaction in the type ia-csm sn 2018evt three years after the explosion, characterized by a rise in the mid-infrared (mir) emission accompanied by an accelerated decline in the optical radiation of the sn. such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the ha emission line. our model suggests enhanced csm dust concentration at increasing distances from the sn as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. by the time of the last mir observations at day +1041, a total amount of 1.2+-0.2x10^{-2} msun of new dust has been formed by sn 2018evt, making sn 2018evt one of the most prolific dust factories among sne with evidence of dust formation. the unprecedented witness of the intense production procedure of dust may shed light on the perceptions of dust formation in cosmic history. | newly formed dust within the circumstellar environment of snia-csm 2018evt |
in this work, we show that the cold new early dark energy (cold nede) model in its original form can solve both the hubble tension and the s 8 tension without adding any new ingredients at the fundamental level. so far, it was assumed that the trigger field in the cold nede model is completely subdominant. however, relaxing this assumption and letting the trigger field contribute a mere 0.5% of the total energy density leads to a resolution of the s 8 tension while simultaneously improving it as a solution to the h 0 tension. fitting this model to baryonic acoustic oscillations, large-scale-structure, supernovae (including a sh0es prior), and cosmic microwave background data, we report a preferred nede fraction of f nede = 0.134+0.032 -0.025 (68% c.l.), lifting its gaussian evidence for the first time above 5σ (up from 4σ when the trigger contribution to dark matter is negligible). at the same time, we find the new concordance values h 0 = 71.71 ± 0.88 km sec-1 mpc-1 and s 8 = 0.793 ± 0.018. excluding large-scale structure data and the sh0es prior, both gaussian tensions are reduced below the 2σ level. | cold new early dark energy pulls the trigger on the h 0 and s 8 tensions: a simultaneous solution to both tensions without new ingredients |
the process of unstable mass transfer in a stellar binary can result in either a complete merger of the stars or successful removal of the donor envelope leaving a surviving more compact binary. luminous red novae (lrne) are the class of optical transients believed to accompany such merger/common envelope events. past works typically model lrne using analytic formulae for supernova light curves that make assumptions (e.g., radiation-dominated ejecta, neglect of hydrogen recombination energy) not justified in stellar mergers due to the lower velocities and specific thermal energy of the ejecta. we present a one-dimensional model of lrn light curves that accounts for these effects. consistent with observations, we find that lrne typically possess two light-curve peaks, an early phase powered by initial thermal energy of the hot, fastest ejecta layers and a later peak powered by hydrogen recombination from the bulk of the ejecta. we apply our model to a sample of lrne to infer their ejecta properties (mass, velocity, and launching radius) and compare them to the progenitor donor star properties from pretransient imaging. we define the maximum luminosity achievable for a given donor star in the limit that the entire envelope is ejected, finding that several lrne violate this limit. shock interaction between the ejecta and predynamical mass loss may provide an additional luminosity source to alleviate this tension. our model can also be applied to the merger of planets with stars or stars with compact objects. | light-curve model for luminous red novae and inferences about the ejecta of stellar mergers |
we present a velocity-dispersion-based mass calibration of the south pole telescope sunyaev-zel'dovich effect survey (spt-sz) galaxy cluster sample. using a homogeneously selected sample of 100 cluster candidates from 720 deg2 of the survey along with 63 velocity dispersion (σ v ) and 16 x-ray y x measurements of sample clusters, we simultaneously calibrate the mass-observable relation and constrain cosmological parameters. our method accounts for cluster selection, cosmological sensitivity, and uncertainties in the mass calibrators. the calibrations using σ vand y x are consistent at the 0.6σ level, with the σ vcalibration preferring ~16% higher masses. we use the full sptcl data set (sz clusters+σ v +y x) to measure σ8(ωm/0.27)0.3 = 0.809 ± 0.036 within a flat λcdm model. the spt cluster abundance is lower than preferred by either the wmap9 or planck+wmap9 polarization (wp) data, but assuming that the sum of the neutrino masses is ∑m ν = 0.06 ev, we find the data sets to be consistent at the 1.0σ level for wmap9 and 1.5σ for planck+wp. allowing for larger ∑m ν further reconciles the results. when we combine the sptcl and planck+wp data sets with information from baryon acoustic oscillations and type ia supernovae, the preferred cluster masses are 1.9σ higher than the y x calibration and 0.8σ higher than the σ vcalibration. given the scale of these shifts (~44% and ~23% in mass, respectively), we execute a goodness-of-fit test; it reveals no tension, indicating that the best-fit model provides an adequate description of the data. using the multi-probe data set, we measure ωm = 0.299 ± 0.009 and σ8 = 0.829 ± 0.011. within a νcdm model we find ∑m ν = 0.148 ± 0.081 ev. we present a consistency test of the cosmic growth rate using spt clusters. allowing both the growth index γ and the dark energy equation-of-state parameter w to vary, we find γ = 0.73 ± 0.28 and w = -1.007 ± 0.065, demonstrating that the expansion and the growth histories are consistent with a λcdm universe (γ = 0.55; w = -1). | mass calibration and cosmological analysis of the spt-sz galaxy cluster sample using velocity dispersion σ vand x-ray y x measurements |
we examine whether the hubble tension, the mismatch between early and late measurements of h0, can be alleviated by ultralight scalar fields in the early universe, and we assess its plausibility within uv physics. since their energy density needs to rapidly redshift away, we explore decays to massless fields around the era of matter-radiation equality. we highlight a concrete implementation of ultralight pseudo-scalars, axions, that decay to an abelian dark sector. this scenario circumvents major problems of other popular realizations of early universe scalar models in that it uses a regular scalar potential that is quadratic around the minimum, instead of the extreme fine-tuning of many existing models. the idea is that the scalar is initially frozen in its potential until h~ m, then efficient energy transfer from the scalar to the massless field can occur shortly after the beginning of oscillations due to resonance. we introduce an effective fluid model which captures the transition from the frozen scalar phase to the radiation dark sector phase. we perform a fit to a combined planck 2018, bao, sh0es and pantheon supernovae dataset and find that the model gives h0=69.9-0.86+0.84 km/s/mpc with δχ2 ≈ -9 compared to λcdm while inclusions of other data sets may worsen the fit. importantly, we find that large values of the coupling between fields is required for sufficiently rapid decay: for axion-gauge field models phi ftilde f/λ it requires λlesssim f/80, where 2π f is the field range. we find related conclusions for scalar-scalar models ~phi χ2 and for models that utilize perturbative decays. we conclude that these sorts of ultralight scalar models that purport to alleviate the hubble tension, while being reasonable effective field theories, require features that are difficult to embed within uv physics. | ultralight scalar decay and the hubble tension |
the standard model coherent elastic neutrino-nucleus scattering (ceνns) cross section is subject to nuclear form factor uncertainties, mainly driven by the root-mean-square radius of the neutron density distribution. motivated by coherent phases i-iii and future multi-ton direct detection dark matter searches, we evaluate these uncertainties in cesium iodide, germanium, xenon and argon detectors. we find that the uncertainties become relevant for momentum transfers q ≳ 20 mev and are essentially independent of the form factor parameterization. consequently, form factor uncertainties are not important for ceνns induced by reactor or solar neutrinos. taking into account these uncertainties, we then evaluate their impact on measurements of ceνns at coherent, the diffuse supernova background (dsnb) neutrinos and sub-gev atmospheric neutrinos. we also calculate the relative uncertainties in the number of coherent events for different nuclei as a function of recoil energy. for dsnb and atmospheric neutrinos, event rates at a liquid argon detector can be uncertain to more than 5%. finally, we consider the impact of form factor uncertainties on searches for nonstandard neutrino interactions, sterile neutrinos and neutrino generalized interactions. we point out that studies of new physics using ceνns data are affected by neutron form factor uncertainties, which if not properly taken into account may lead to the misidentification of new physics signals. the uncertainties quantified here are also relevant for dark matter direct detection searches. | impact of form factor uncertainties on interpretations of coherent elastic neutrino-nucleus scattering data |
we use microwave temperature maps from two seasons of data from the atacama cosmology telescope at 146 ghz, together with the "constant mass" cmass galaxy sample from the baryon oscillation spectroscopic survey to measure the kinematic sunyaev-zel'dovich (ksz) effect over the redshift range z =0.4 - 0.7 . we use galaxy positions and the continuity equation to obtain a reconstruction of the line-of-sight velocity field. we stack the microwave temperature at the location of each halo, weighted by the corresponding reconstructed velocity. we vary the size of the aperture photometry filter used, thus probing the free electron profile of these halos from within the virial radius out to three virial radii, on the scales relevant for investigating the missing baryons problem. the resulting best fit ksz model is preferred over the no-ksz hypothesis at 3.3 and 2.9 σ for two independent velocity reconstruction methods, using 25,537 galaxies over 660 square degrees. the data suggest that the baryon profile is shallower than the dark matter in the inner regions of the halos probed here, potentially due to energy injection from active galactic nucleus or supernovae. thus, by constraining the gas profile on a wide range of scales, this technique will be useful for understanding the role of feedback in galaxy groups and clusters. the effect of foregrounds that are uncorrelated with the galaxy velocities is expected to be well below our signal, and residual thermal sunyaev-zel'dovich contamination is controlled by masking the most massive clusters. finally, we discuss the systematics involved in converting our measurement of the ksz amplitude into the mean free electron fraction of the halos in our sample. | evidence for the kinematic sunyaev-zel'dovich effect with the atacama cosmology telescope and velocity reconstruction from the baryon oscillation spectroscopic survey |
the hot intra-cluster medium (icm) permeating galaxy clusters and groups is not pristine, as it has been continuously enriched by metals synthesised in type ia (snia) and core-collapse (sncc) supernovae since the major epoch of star formation (z ≃ 2-3). the cluster/group enrichment history and mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of snia and sncc products within the icm. in this paper, we use deep xmm-newton/epic observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (cheers) to constrain the average radial o, mg, si, s, ar, ca, fe, and ni abundance profiles. the radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. specific attention is devoted to a proper modelling of the epic spectral components, and to other systematic uncertainties that may affect our results. we find an overall decrease of the fe abundance with radius out to 0.9 r500 and 0.6 r500 for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. the average radial profiles of all the other elements (x) are also centrally peaked and, when rescaled to their average central x/fe ratios, follow well the fe profile out to at least 0.5 r500. as predicted by recent simulations, we find that the relative contribution of snia (sncc) to the total icm enrichment is consistent with being uniform at all radii, both for clusters and groups using two sets of snia and sncc yield models that reproduce the x/fe abundance pattern in the core well. in addition to implying that the central metal peak is balanced between snia and sncc, our results suggest that the enriching snia and sncc products must share the same origin and that the delay between the bulk of the snia and sncc explosions must be shorter than the timescale necessary to diffuse out the metals. finally, we report an apparent abundance drop in the very core of 14 systems ( 32% of the sample). possible origins of these drops are discussed. | radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals |
mergers of black hole (bh) and neutron star (ns) binaries are expected to be observed by gravitational wave observatories in the coming years. until now, ligo has only set an upper limit on this merger rate. bh-ns binaries are expected to merge in isolation, as their formation is suppressed in star clusters by the mass segregation and the strong heating by bhs in the cluster core. another viable scenario to bh-ns mergers is in triple systems. in this paper, we carry out a systematic statistical study of the dynamical evolution of triples comprised of an inner bh-ns binary by means of high-precision n-body simulations, including post-newtonian (pn) terms up to 2.5pn order. we start from the main-sequence massive stars and model the supernovae (sn) events that lead to the formation of bhs and nss. we adopt different prescriptions for the natal velocity kicks imparted during the sn processes and illustrate that large kicks lead to more compact and massive triples that merge on shorter time-scales. we also show that bh-ns merging in triples have a significant eccentricity in the ligo band, typically much larger than bh-ns merging in isolated binaries. finally, we estimate a rate of γbh-ns ≈ 1.0 × 10-3-3.5 × 10-2 gpc-3 yr-1, for non-zero velocity kicks, and γbh-ns = 19 gpc-3 yr-1, for no natal kicks. our rate estimate overlaps with the expected bh-ns rate in isolated binaries and within the ligo upper limit. | black hole-neutron star mergers from triples |
we construct a new equation of state (eos) for numerical simulations of core-collapse supernovae and neutron-star mergers based on an extended relativistic mean-field model with a small symmetry energy slope l, which is compatible with both experimental nuclear data and recent observations of neutron stars. the new eos table (eos4) based on the extended tm1 (tm1e) model with l = 40 mev is designed in the same tabular form and compared with the commonly used shen eos (eos2) based on the original tm1 model with l=110.8 mev. this is convenient and useful for performing numerical simulations and examining the influences of symmetry energy and its density dependence on astrophysical phenomena. in comparison with the tm1 model used in eos2, the tm1e model provides a similar maximum neutron-star mass but smaller radius and tidal deformability for a 1.4m⊙ neutron star, which is more consistent with current constraints. by comparing the phase diagram and thermodynamic quantities between eos4 and eos2, it is found that the tm1e model predicts a relatively larger region of nonuniform matter and softer eos for neutron-rich matter. significant differences between eos4 and eos2 are observed in the case with low proton fraction, while the properties of symmetric matter remain unchanged. | effects of symmetry energy on the equation of state for simulations of core-collapse supernovae and neutron-star mergers |
we study the possibility of using csi[na] scintillators as an advantageous target for the detection of coherent elastic neutrino-nucleus scattering (cenns), using the neutrino emissions from the sns spallation source at oak ridge national laboratory. the response of this material to low-energy nuclear recoils like those expected from this process is characterized. backgrounds are studied using a 2 kg low-background prototype crystal in a dedicated radiation shield. the conclusion is that a planned 14 kg detector should measure approximately 550 cenns events per year above a demonstrated 7 kevnr low-energy threshold, with a signal-to-background ratio sufficient for a first measurement of the cenns cross-section. the cross-section for the 208pb(νe ,e-)208bi reaction, of interest for future supernova neutrino detection, can be simultaneously obtained. | coherent neutrino-nucleus scattering detection with a csi[na] scintillator at the sns spallation source |
we present optical observations of supernova sn 2014c, which underwent an unprecedented slow metamorphosis from h-poor type ib to h-rich type iin over the course of one year. the observed spectroscopic evolution is consistent with the supernova having exploded in a cavity before encountering a massive shell of the progenitor star’s stripped hydrogen envelope. possible origins for the circumstellar shell include a brief wolf-rayet fast wind phase that overtook a slower red supergiant wind, eruptive ejection, or confinement of circumstellar material by external influences of neighboring stars. an extended high velocity hα absorption feature seen in near-maximum light spectra implies that the progenitor star was not completely stripped of hydrogen at the time of core collapse. archival pre-explosion subaru telescope suprime-cam and hubble space telescope wide field planetary camera 2 images of the region obtained in 2009 show a coincident source that is most likely a compact massive star cluster in ngc 7331 that hosted the progenitor system. by comparing the emission properties of the source with stellar population models that incorporate interacting binary stars we estimate the age of the host cluster to be 30-300 myr, and favor ages closer to 30 myr in light of relatively strong hα emission. sn 2014c is the best observed member of a class of core-collapse supernovae that fill the gap between events that interact strongly with dense, nearby environments immediately after explosion and those that never show signs of interaction. better understanding of the frequency and nature of this intermediate population can contribute valuable information about the poorly understood final stages of stellar evolution. | metamorphosis of sn 2014c: delayed interaction between a hydrogen poor core-collapse supernova and a nearby circumstellar shell |
kozai-lidov (kl) oscillations in hierarchical triple systems have found application to many astrophysical contexts, including planet formation, type ia supernovae, and supermassive black hole dynamics. the period of these oscillations is known at the order-of-magnitude level, but dependences on the initial mutual inclination or inner eccentricity are not typically included. in this work i calculate the period of kl oscillations (tkl) exactly in the test particle limit at quadrupole order (tpq). i explore the parameter space of all hierarchical triples at tpq and show that except for triples on the boundary between libration and rotation, the period of kl oscillations does not vary by more than a factor of a few. the exact period may be approximated to better than 2 per cent for triples with mutual inclinations between 60° and 120° and initial eccentricities less than ∼0.3. in addition, i derive an analytic expression for the period of octupole-order oscillations due to the `eccentric kl mechanism' (ekm). i show that the time-scale for ekm oscillations is proportional to ɛ _{oct}^{-1/2}, where ɛoct measures the strength of octupole perturbations relative to quadrupole perturbations. | timescales of kozai-lidov oscillations at quadrupole and octupole order in the test particle limit |
context. with growing evidence for the existence of very massive stars at subsolar metallicity, there is an increased need for corresponding stellar evolution models.aims: we present a dense model grid with a tailored input chemical composition appropriate for the large magellanic cloud (lmc).methods: we use a one-dimensional hydrodynamic stellar evolution code, which accounts for rotation, transport of angular momentum by magnetic fields, and stellar wind mass loss to compute our detailed models. we calculate stellar evolution models with initial masses from 70 to 500 m⊙ and with initial surface rotational velocities from 0 to 550 km s-1, covering the core-hydrogen burning phase of evolution.results: we find our rapid rotators to be strongly influenced by rotationally induced mixing of helium, with quasi-chemically homogeneous evolution occurring for the fastest rotating models. above 160 m⊙, homogeneous evolution is also established through mass loss, producing pure helium stars at core hydrogen exhaustion independent of the initial rotation rate. surface nitrogen enrichment is also found for slower rotators, even for stars that lose only a small fraction of their initial mass. for models above ~150 m⊙ at zero age, and for models in the whole considered mass range later on, we find a considerable envelope inflation due to the proximity of these models to their eddington limit. this leads to a maximum zams surface temperature of ~56 000 k, at ~180 m⊙, and to an evolution of stars in the mass range 50 m⊙...100 m⊙ to the regime of luminous blue variables in the hertzsprung-russell diagram with high internal eddington factors. inflation also leads to decreasing surface temperatures during the chemically homogeneous evolution of stars above ~180 m⊙.conclusions: the cool surface temperatures due to the envelope inflation in our models lead to an enhanced mass loss, which prevents stars at lmc metallicity from evolving into pair-instability supernovae. the corresponding spin-down will also prevent very massive lmc stars to produce long-duration gamma-ray bursts, which might, however, originate from lower masses. the dataset of the presented stellar evolution models is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/573/a71appendices are available in electronic form at http://www.aanda.org | the evolution of rotating very massive stars with lmc composition |
aims: we present a comprehensive x-ray study of the population of supernova remnants (snrs) in the large magellanic cloud (lmc). using primarily xmm-newton observations, we conduct a systematic spectral analysis of lmc snrs to gain new insight into their evolution and the interplay with their host galaxy.methods: we combined all the archival xmm-newton observations of the lmc with those of our very large programme lmc survey. we produced x-ray images and spectra of 51 snrs, out of a list of 59 objects compiled from the literature and augmented with newly found objects. using a careful modelling of the background, we consistently analysed all the x-ray spectra and measure temperatures, luminosities, and chemical compositions. the locations of snrs are compared to the distributions of stars, cold gas, and warm gas in the lmc, and we investigated the connection between the snrs and their local environment, characterised by various star formation histories. we tentatively typed all lmc snrs, in order to constrain the ratio of core-collapse to type ia sn rates in the lmc. we also compared the column densities derived from x-ray spectra to h i maps, thus probing the three-dimensional structure of the lmc.results: this work provides the first homogeneous catalogue of the x-ray spectral properties of snrs in the lmc. it offers a complete census of lmc remnants whose x-ray emission exhibits fe k lines (13% of the sample), or reveals the contribution from hot supernova ejecta (39%), which both give clues to the progenitor types. the abundances of o, ne, mg, si, and fe in the hot phase of the lmc interstellar medium are found to be between 0.2 and 0.5 times the solar values with a lower abundance ratio [α/fe] than in the milky way. the current ratio of core-collapse to type ia sn rates in the lmc is constrained to ncc/nia=1.35(-0.24+0.11), which is lower than in local sn surveys and galaxy clusters. our comparison of the x-ray luminosity functions of snrs in local group galaxies (lmc, smc, m31, and m33) reveals an intriguing excess of bright objects in the lmc. finally, we confirm that 30 doradus and the lmc bar are offset from the main disc of the lmc to the far and near sides, respectively. based on observations obtained with xmm-newton, an esa science mission with instruments and contributions directly funded by esa member states and nasa. | the population of x-ray supernova remnants in the large magellanic cloud |
motivated by the recent high-precision measurements of cosmic rays by several new-generation experiments, we have carried out a detailed study to understand the observed energy spectrum and composition of cosmic rays with energies up to about 1018 ev. our study shows that a single galactic component with subsequent energy cut-offs in the individual spectra of different elements, optimised to explain the observed elemental spectra below 1014 ev and the "knee" in the all-particle spectrum, cannot explain the observed all-particle spectrum above 2 × 1016 ev. we discuss two approaches for a second component of galactic cosmic rays - re-acceleration at a galactic wind termination shock, and supernova explosions of wolf-rayet stars, and show that the latter scenario can explain almost all observed features in the all-particle spectrum and the composition up to 1018 ev, when combined with a canonical extra-galactic spectrum expected from strong radio galaxies or a source population with similar cosmological evolution. in this two-component galactic model, the knee at 3 × 1015 ev and the "second knee" at 1017 ev in the all-particle spectrum are due to the cut-offs in the first and second components, respectively. we also discuss several variations of the extra-galactic component, from a minimal contribution to scenarios with a significant component below the "ankle" (at 4 × 1018 ev), and find that extra-galactic contributions in excess of regular source evolution are neither indicated nor in conflict with the existing data. we also provide arguments that an extra-galactic contribution is unlikely to dominate at or below the second knee. our main result is that the second galactic component predicts a composition of galactic cosmic rays at and above the second knee that largely consists of helium or a mixture of helium and cno nuclei, with a weak or essentially vanishing iron fraction, in contrast to most common assumptions. this prediction is in agreement with new measurements from lofar and the pierre auger observatory which indicate a strong light component and a rather low iron fraction between 1017 and 1018 ev. | cosmic-ray energy spectrum and composition up to the ankle: the case for a second galactic component |
host galaxy properties provide strong constraints on the stellar progenitors of superluminous supernovae. by comparing a sample of 19 low-redshift (z < 0.3) superluminous supernova hosts to galaxy populations in the local universe, we show that sub-solar metallicities seem to be a requirement. all superluminous supernovae in hosts with high measured gas-phase metallicities are found to explode at large galactocentric radii, indicating that the metallicity at the explosion site is likely lower than the integrated host value. we found that superluminous supernova hosts do not always have star formation rates higher than typical star-forming galaxies of the same mass. however, we confirm that high absolute specific star formation rates are a feature of superluminous supernova host galaxies, but interpret this as simply a consequence of the anticorrelation between gas-phase metallicity and specific star formation rate and the requirement of on-going star formation to produce young, massive stars greater than ∼10-20 m⊙. based on our sample, we propose an upper limit of ∼ 0.5 z_{⊙} for forming superluminous supernova progenitors (assuming an n2 metallicity diagnostic and a solar oxygen abundance of 8.69). finally, we show that if magnetar powering is the source of the extreme luminosity, then the required initial spins appear to be correlated with metallicity of the host galaxy. this correlation needs further work, but if it applies, it is a powerful link between the supernova parameters and nature of the progenitor population. | superluminous supernova progenitors have a half-solar metallicity threshold |
extremely metal-poor (emp) stars in the milky way (mw) allow us to infer the properties of their progenitors by comparing their chemical composition to the metal yields of the first supernovae. this method is most powerful when applied to mono-enriched stars, i.e. stars that formed from gas that was enriched by only one previous supernova. we present a novel diagnostic to identify this subclass of emp stars. we model the first generations of star formation semi-analytically, based on dark matter halo merger trees that yield mw-like haloes at the present day. radiative and chemical feedbacks are included self-consistently and we trace all elements up to zinc. mono-enriched stars account for only ∼1 per cent of second-generation stars in our fiducial model and we provide an analytical formula for this probability. we also present a novel analytical diagnostic to identify mono-enriched stars, based on the metal yields of the first supernovae. this new diagnostic allows us to derive our main results independently from the specific assumptions made regarding pop iii star formation, and we apply it to a set of observed emp stars to demonstrate its strengths and limitations. our results may provide selection criteria for current and future surveys and therefore contribute to a deeper understanding of emp stars and their progenitors. | descendants of the first stars: the distinct chemical signature of second-generation stars |
using an isolated milky way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. we utilize the infrastructure we have built for the agora high-resolution galaxy simulations comparison project. this includes the common disk initial conditions, common physics models (e.g., radiative cooling and uv background by the standardized package grackle) and common analysis toolkit yt, all of which are publicly available. subgrid physics models such as jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. with numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and kennicutt-schmidt relations. quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ∼3). systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes. | the agora high-resolution galaxy simulations comparison project. ii. isolated disk test |
flavor-specific scalar bosons exist in various standard model extensions and couple to a single generation of fermions via a global flavor symmetry breaking mechanism. given this strategy, we propose a mev flavor-specific scalar model in dimension-5 operator series, which explains the muon g — 2 anomaly and proton radius puzzle by coupling with the muon and down-quark at the same time. the framework is consistent with the null result of high-intensity searches. specifically, the supernova constraints for muon couplings become weakened by including the contribution of down-quark interaction. the parameter space for explaining muon g — 2 discrepancy is available when 10% energy deposition is required in the energy explosion process in the supernova, but this is ruled out by the 1% energy deposition requirement. we also investigate the searches for mediator and dark matter and the resulting constraints on viable parameter space such as nuclear physics constraints, direct detection for light boosted dark matter, and possible cmb constraints. when compared with conventional dark matter production, light dark matter production has two additional modifications: bound state formation and early kinetic equilibrium decoupling. we are now looking into the implications of these effects on the relic density of light dark matter. | probing the flavor-specific scalar mediator for the muon (g — 2) deviation, the proton radius puzzle and the light dark matter production |
ngc 253 hosts the nearest nuclear starburst. previous observations show a region rich in molecular gas, with dense clouds associated with recent star formation. we used the atacama large submillimeter/millimeter array (alma) to image the 350 ghz dust continuum and molecular line emission from this region at 2 pc resolution. our observations reveal ∼14 bright, compact (∼2-3 pc fwhm) knots of dust emission. most of these sources are likely to be forming super star clusters (sscs) based on their inferred dynamical and gas masses, association with 36 ghz radio continuum emission, and coincidence with line emission tracing dense, excited gas. one source coincides with a known ssc, but the rest remain invisible in hubble near-infrared (ir) imaging. our observations imply that gas still constitutes a large fraction of the overall mass in these sources. their high brightness temperature at 350 ghz also implies a large optical depth near the peak of the ir spectral energy distribution. as a result, these sources may have large ir photospheres, and the ir radiation force likely exceeds l/c. still, their moderate observed velocity dispersions suggest that feedback from radiation, winds, and supernovae are not yet disrupting most sources. this mode of star formation appears to produce a large fraction of stars in the burst. we argue for a scenario in which this phase lasts ∼1 myr, after which the clusters shed their natal cocoons but continue to produce ionizing photons. the strong feedback that drives the observed cold gas and x-ray outflows likely occurs after the clusters emerge from this early phase. | forming super star clusters in the central starburst of ngc 253 |
the large neutrino density in the deep interior of core-collapse supernovae and compact binary merger remnants makes neutrino flavor evolution nonlinear because of the coherent forward scattering of neutrinos among themselves. under the assumption of spherical symmetry, we model neutrino decoupling from matter in an idealized setup and present the first nonlinear simulation of flavor evolution in the presence of charged current and neutral current collisions, as well as neutrino advection. within our framework, we find that flavor transformation occurs before neutrinos fully decouple from matter, dynamically affecting the flavor distributions of all neutrino species and shifting the location of the neutrino decoupling surfaces. our results call for further work as they may have implications on the explosion mechanism of supernovae, the nucleosynthesis of the heavy elements, as well as the observable neutrino signal, all of which is yet to be assessed. | neutrino decoupling is altered by flavor conversion |
a redshift tomography of the pantheon type ia supernovae (snia) data focusing on the best fit value of the absolute magnitude m and/or hubble constant h0 in the context of λ cdm indicates a local variation (z ≲0.2 ) at 2 σ level, with respect to the best fit of the full dataset. if this variation is not due to a statistical fluctuation, it can be interpreted as a locally higher value of h0 by about 2%, corresponding to a local matter underdensity δ ρ0/ρ0≃-0.10 ±0.04 . it can also be interpreted as a time variation of newton's constant which implies an evolving chandrasekhar mass and thus an evolving absolute luminosity l and absolute magnitude m of low z snia. the local void scenario would predict a degree of anisotropy in the best fit value of h0 since it is unlikely that we are located at the center of a local spherical underdensity. using a hemisphere comparison method, we find an anisotropy level that is consistent with simulated isotropic pantheon-like datasets. we show however, that the anisotropic sky distribution of the pantheon snia data induces a preferred range of directions even in simulated pantheon data obtained in the context of isotropic λ cdm . we thus construct a more isotropically distributed subset of the pantheon snia and show that the preferred range of directions disappears. using this more isotropically distributed subset we again find no evidence for statistically significant anisotropy using either the hemisphere comparison method or the dipole fit method. in the context of the modified gravity scenario, we allow for an evolving normalized newton's constant consistent with general relativity (gr) at early and late times μ (z )=geff(z ,ga)/gn=1 +gaz2/(1 +z )2-gaz4/(1 +z )4 and fit for the parameter ga assuming l ∼geffb. for b =-3 /2 indicated by some previous studies we find ga=-0.47 ±0.36 which is more than 1.5 σ away from the gr value of ga=0 . this weak hint for weaker gravity at low z coming from snia is consistent with similar evidence from growth and weak lensing cosmological data. | hints of a local matter underdensity or modified gravity in the low z pantheon data |
determining the level of chemical homogeneity in open clusters is of fundamental importance in the study of the evolution of star-forming clouds and that of the galactic disk. yet limiting the initial abundance spread in clusters has been hampered by difficulties in obtaining consistent spectroscopic abundances for different stellar types. without reference to any specific model of stellar photospheres, a model for a homogeneous cluster is that it forms a one-dimensional sequence, with any differences between members due to variations in stellar mass and observational uncertainties. i present a novel method for investigating the abundance spread in open clusters that tests this one-dimensional hypothesis at the level of observed stellar spectra, rather than constraining homogeneity using derived abundances as is traditionally done. using high-resolution apogee spectra for 49 giants in m67, ngc 6819, and ngc 2420 i demonstrate that these spectra form one-dimensional sequences for each cluster. with detailed forward modeling of the spectra and approximate bayesian computation, i derive strong limits on the initial abundance spread of 15 elements: <0.01 (0.02) {dex} for c and fe, ≲0.015 (0.03) {dex} for n, o, mg, si, and ni, ≲0.02 (0.03) {dex} for al, ca, and mn, and ≲0.03 (0.05) {dex} for na, s, k, ti, and v (at 68% and 95% confidence, respectively). the strong limits on c and o imply that no pollution by massive core-collapse supernovae occurred during star formation in open clusters, which, thus, need to form within ≲6 {myr}. further development of this and related techniques will bring the power of differential abundances to stars other than solar twins in large spectroscopic surveys and will help unravel the history of star formation and chemical enrichment in the milky way through chemical tagging. | the chemical homogeneity of open clusters |
rapidly spinning, strongly magnetized protoneutron stars (“millisecond protomagnetars”) are candidate central engines of long-duration gamma-ray bursts (grbs), superluminous supernovae (slsne), and binary neutron star mergers. magnetar birth may be accompanied by the fallback of stellar debris, lasting for seconds or longer following the explosion. accretion alters the magnetar evolution by (1) providing an additional source of rotational energy (or a potential sink, if the propeller mechanism operates), (2) enhancing the spin-down luminosity above the dipole rate by compressing the magnetosphere and expanding the polar cap region of open magnetic field lines, and (3) supplying an additional accretion-powered neutrino luminosity that sustains the wind baryon loading, even after the magnetar’s internal neutrino luminosity has subsided. the more complex evolution of the jet power and magnetization of an accreting magnetar more readily accounts for the high 56ni yields of grb sne and the irregular time evolution of some grb light curves (e.g., bursts with precursors followed by a long quiescent interval before the main emission episode). additional baryon loading from accretion-powered neutrino irradiation of the polar cap lengthens the time frame over which the jet magnetization is in the requisite range σ ≲ 103 for efficient gamma-ray emission, thereby accommodating grbs with ultralong durations. though accretion does not significantly raise the maximum energy budget from the limit of ≲ few × 1052 erg for an isolated magnetar, it greatly expands the range of magnetic field strengths and birth spin periods capable of powering grb jets, reducing the differences between the magnetar properties normally invoked to explain grbs versus slsne. | effects of fallback accretion on protomagnetar outflows in gamma-ray bursts and superluminous supernovae |
this paper presents a short review on the current state of sn ia progenitor origin. type ia supernova explosions (meaning thermonuclear disruption of a white dwarf) are observed to be widely diverse in peak luminosity, lightcurve width and shape, spectral features, and host stellar population environment. in the last decade alone, theoretical simulations and observational data have come together to seriously challenge the long-standing paradigm that all sne ia arise from explosions of chandrasekhar mass white dwarfs. in this review i highlight some of the major developments (and changing views) of our understanding of the nature of sn ia progenitor systems. i give a brief overview of binary star configurations and their plausible explosion mechanisms, and infer links between some of the various (observationally-categorized) sn ia sub-classes and their progenitor origins from a theoretical standpoint. | type ia supernova sub-classes and progenitor origin |
the massive neutron star (ns) or black hole (bh) accretion disk resulting from ns-ns or ns-bh mergers is dense in neutrinos. we present the first study on the role of angular distributions in the neutrino flavor conversion above the remnant disk. in particular, we focus on "fast" pairwise conversions whose rate depends on the local angular intensity of the electron lepton number carried by neutrinos. because of the emission geometry and the flux density of ν¯ e being larger than that of νe, fast conversions prove to be a generic phenomenon in ns-ns and ns-bh mergers for physically motivated disturbances in the mean field of flavor coherence. our findings suggest that, differently from the core-collapse supernova case, fast flavor conversions seem to be unavoidable in compact mergers and could have major consequences for the jet dynamics and the synthesis of elements above the remnant disk. | fast neutrino conversions: ubiquitous in compact binary merger remnants |
we present a simulation of the formation of the earliest population ii stars, starting from cosmological initial conditions and ending when metals created in the first supernovae are incorporated into a collapsing gas cloud. this occurs after a supernova blast-wave collides with a nearby mini-halo, inducing further turbulence that efficiently mixes metals into the dense gas in the centre of the halo. the gas that first collapses has been enriched to a metallicity of z ∼ 2 × 10-5 z⊙. due to the extremely low metallicity, collapse proceeds similarly to metal-free gas until dust cooling becomes efficient at high densities, causing the cloud to fragment into a large number of low-mass objects. this external enrichment mechanism provides a plausible origin for the most metal-poor stars observed, such as smss j031300.36-670839.3, that appear to have formed out of gas enriched by a single supernova. this mechanism operates on shorter time-scales than the time for low-mass mini-haloes (m ≤ 5 × 105 m⊙) to recover their gas after experiencing a supernova. as such, metal-enriched stars will likely form first via this channel if the conditions are right for it to occur. we identify a number of other externally enriched haloes that may form stars in this manner. these haloes have metallicities as high as 0.01 z⊙, suggesting that some members of the first generation of metal-enriched stars may be hiding in plain sight in current stellar surveys. | the first population ii stars formed in externally enriched mini-haloes |
galactic outflows are observed everywhere in star-forming disk galaxies and are critical for galaxy formation. supernovae (sne) play the key role in driving the outflows, but there is no consensus as to how much energy, mass, and metal they can launch out of the disk. we perform 3d, high-resolution hydrodynamic simulations to study sne-driven outflows from stratified media. assuming the sn rate scales with gas surface density σgas as in the kennicutt-schmidt relation, we find that the mass loading factor, η m, defined as the mass outflow flux divided by the star formation surface density, decreases with increasing σgas as {η }{{m}}\propto {{{σ }}}gas}-0.61. approximately σgas ≲ 50 m ⊙ pc-2 marks when η m ≳ 1. about 10%-50% of the energy and 40%-80% of the metals produced by sne end up in the outflows. the tenuous hot phase (t > 3 × 105 k), which fills 60%-80% of the volume at the midplane, carries the majority of the energy and metals in the outflows. we discuss how various physical processes, including the vertical distribution of sne, photoelectric heating, external gravitational field, and sn rate, affect the loading efficiencies. the relative scale height of gas and sne is a very important factor in determining the loading efficiencies. | quantifying supernovae-driven multiphase galactic outflows |
the origin of the baryon asymmetry of the universe (bau) and the nature of dark matter are two of the most challenging problems in cosmology. we propose a scenario in which the gravitational collapse of large inhomogeneities at the quark-hadron epoch generates both the baryon asymmetry and dark matter in the form of primordial black holes (pbhs). this is due to the sudden drop in radiation pressure during the transition from a quark-gluon plasma to non-relativistic hadrons. the collapse to a pbh is induced by fluctuations of a light spectator scalar field in rare regions and is accompanied by the violent expulsion of surrounding material, which might be regarded as a sort of "primordial supernova" . the acceleration of protons to relativistic speeds provides the ingredients for efficient baryogenesis around the collapsing regions and its subsequent propagation to the rest of the universe. this scenario naturally explains why the observed bau is of order the pbh collapse fraction and why the baryons and dark matter have comparable densities. the predicted pbh mass distribution ranges from sub-solar to several hundred solar masses. this is compatible with current observational constraints and could explain the rate, mass and low spin of the black hole mergers detected by ligo-virgo. future observations will soon be able to test this scenario. | a common origin for baryons and dark matter |
collective neutrino oscillations can potentially play an important role in transporting lepton flavor in astrophysical scenarios where the neutrino density is large, typical examples are the early universe and supernova explosions. it has been argued in the past that simple models of the neutrino hamiltonian designed to describe forward scattering can support substantial flavor evolution on very short timescales t ≈log (n )/(gfρν), with n the number of neutrinos, gf the fermi constant and ρν the neutrino density. this finding is in tension with results for similar but exactly solvable models for which t ≈√{n }/(gfρν) instead. in this work we provide a coherent explanation of this tension in terms of dynamical phase transitions (dpt) and study the possible impact that a dpt could have in more realistic models of neutrino oscillations and their mean-field approximation. | dynamical phase transitions in models of collective neutrino oscillations |
we present here the first of a series of papers aimed at better understanding the evolution and properties of giant molecular clouds (gmcs) in a galactic context. we perform high-resolution, three-dimensional arepo simulations of an interacting galaxy inspired by the well-observed m51 galaxy. our fiducial simulations include a non-equilibrium, time-dependent, chemical network that follows the evolution of atomic and molecular hydrogen as well as carbon and oxygen self-consistently. our calculations also treat gas self-gravity and subsequent star formation (described by sink particles), and coupled supernova feedback. in the densest parts of the simulated interstellar medium (ism), we reach sub-parsec resolution, granting us the ability to resolve individual gmcs and their formation and destruction self-consistently throughout the galaxy. in this initial work, we focus on the general properties of the ism with a particular focus on the cold star-forming gas. we discuss the role of the interaction with the companion galaxy in generating cold molecular gas and controlling stellar birth. we find that while the interaction drives large-scale gas flows and induces spiral arms in the galaxy, it is of secondary importance in determining gas fractions in the different ism phases and the overall star formation rate. the behaviour of the gas on small gmc scales instead is mostly controlled by the self-regulating property of the ism driven by coupled feedback. | simulations of the star-forming molecular gas in an interacting m51-like galaxy |
electron capture on nuclei plays an essential role in the dynamics of several astrophysical objects, including core-collapse and thermonuclear supernovae, the crust of accreting neutron stars in binary systems and the final core evolution of intermediate-mass stars. in these astrophysical objects, the capture occurs at finite temperatures and densities, at which the electrons form a degenerate relativistic electron gas. the capture rates can be derived from perturbation theory, where allowed nuclear transitions [gamow–teller (gt) transitions] dominate, except at the higher temperatures achieved in core-collapse supernovae, where forbidden transitions also contribute significantly to the capture rates. there has been decisive progress in recent years in measuring gt strength distributions using novel experimental techniques based on charge-exchange reactions. these measurements not only provide data for the gt distributions of ground states for many relevant nuclei, but also serve as valuable constraints for nuclear models which are needed to derive the capture rates for the many nuclei for which no data yet exist. in particular, models are needed to evaluate stellar capture rates at finite temperatures, where capture can also occur on nuclei in thermally excited states. there has also been significant progress in recent years in the modeling of stellar capture rates. this has been made possible by advances in nuclear many-body models as well as in computer soft- and hardware. specifically, to derive reliable capture rates for core-collapse supernovae, a dedicated strategy has been developed based on a hierarchy of nuclear models specifically adapted to the abundant nuclei and astrophysical conditions present under various collapse conditions. in particular, for the challenging conditions where the electron chemical potential and the nuclear q values are of the same order, large-scale shell-model diagonalization calculations have proved to be an appropriate tool to derive stellar capture rates, often validated by experimental data. such situations are relevant in the early stage of the core collapse of massive stars, for the nucleosynthesis of thermonuclear supernovae, and for the final evolution of the cores of intermediate-mass stars involving nuclei in the mass range a ∼ 20–65. this manuscript reviews the experimental and theoretical progress recently achieved in deriving stellar electron capture rates. it also discusses the impact these improved rates have on our understanding of the various astrophysical objects. | electron capture in stars |
we decompose pantheon + type ia supernovae (sn) in hemispheres on the sky finding angular variations up to 4 km /s /mpc , corresponding to a statistical significance up to 1.9 σ , in the hubble constant h0 both in the sh0es redshift range 0.0233 <z <0.15 and in extended redshift ranges. the variations are driven largely by variations in absolute magnitude from sn in cepheid hosts but are reinforced by sn in the hubble flow. h0 is larger in a hemisphere encompassing the cmb dipole direction. the variations we see exceed the errors on the recent sh0es determination, h0=73.04 ±1.04 km /s /mpc , but are not large enough to explain early versus late universe discrepancies in the hubble constant. nevertheless, the cepheid-sn distance ladder is anisotropic at current precision. the anisotropy may be due to a breakdown in the cosmological principle, or mundanely due to a statistical fluctuation in a small sample of sn in cepheid host galaxies. | anisotropic distance ladder in pantheon+supernovae |
axion-like particles (alps) decaying into photons are known to affect a wide range of astrophysical and cosmological observables. in this study we focus on alps with masses in the kev-mev range and lifetimes between 104 and 1013 seconds, corresponding to decays between the end of big bang nucleosynthesis and the formation of the cosmic microwave background (cmb). using the cosmobit module of the global fitting framework gambit, we combine state-of-the-art calculations of the irreducible alp freeze-in abundance, primordial element abundances (including photodisintegration through alp decays), cmb spectral distortions and anisotropies, and constraints from supernovae and stellar cooling. this approach makes it possible for the first time to perform a global analysis of the alp parameter space while varying the parameters of λcdm as well as several nuisance parameters. we find a lower bound on the alp mass of around ma > 300 kev, which can only be evaded if alps are stable on cosmological timescales. future observations of cmb spectral distortions with a pixie-like mission are expected to improve this bound by two orders of magnitude. | cosmological constraints on decaying axion-like particles: a global analysis |
in the past five years, the number of known double neutron stars (dnss) in the milky way has roughly doubled. we argue that the observed sample can be split into three distinct subpopulations based on their orbital characteristics: (i) short-period, low-eccentricity binaries; (ii) wide binaries; and (iii) short-period, high-eccentricity binaries. these subpopulations also exhibit distinct spin period and spindown rate properties. we focus on subpopulation (iii), which contains the hulse-taylor binary. contrary to previous analysis, we demonstrate that, if they are the product of isolated binary evolution, the p orb and e distribution of these systems requires that the second-born nss must have been formed with small natal kicks (≲25 km s-1) and have pre-sn masses narrowly distributed around 3.2 m ⊙. these constraints challenge binary evolution theory and further predict closely aligned spin and orbital axes, inconsistent with the hulse-taylor binary’s measured spin-orbit misalignment angle of ≈20°. motivated by the similarity of these dnss to b2127+11c, a dns residing in the globular cluster m15, we argue that this subpopulation is consistent with being formed in, and then ejected from, globular clusters. this scenario provides a pathway for the formation and merger of dnss in stellar environments without recent star formation, as observed in the host galaxy population of short gamma-ray bursts and the recent detection by ligo of a merging dns in an old stellar population. | double neutron star populations and formation channels |
we test the possible dipole anisotropy of the finslerian cosmological model and the other three dipole-modulated cosmological models, i.e. the dipole-modulated λcdm, wcdm and chevallier-polarski-linder (cpl) models, by using the recently released pantheon sample of sne ia. the markov chain monte carlo (mcmc) method is used to explore the whole parameter space. we find that the dipole anisotropy is very weak in all cosmological models used. although the dipole amplitudes of four cosmological models are consistent with zero within the 1sigma uncertainty, the dipole directions are close to the axial direction of the plane of the sdss subsample in pantheon. this may imply that the weak dipole anisotropy in the pantheon sample originates from the inhomogeneous distribution of the sdss subsample. a more homogeneous distribution of sne ia is necessary to constrain the cosmic anisotropy. | constraining the anisotropy of the universe with the pantheon supernovae sample |
we present a modified version of the l-galaxies2020 semi-analytic model of galaxy evolution, which includes significantly increased direct metal enrichment of the circumgalactic medium (cgm) by supernovae (sne). these more metal-rich outflows do not require increased mass-loading factors, in contrast to some other galaxy evolution models. this modified l-galaxies2020 model is able to simultaneously reproduce the gas-phase metallicity ( $z_{\rm {g}}$ ) and stellar metallicity (z*) radial profiles observed in nearby disc galaxies by manga and muse, as well as the observed mass - metallicity relations for gas and stars at z = 0 and their evolution back to z ∼ 2-3. a direct cgm enrichment fraction of ∼90 per cent for sne-ii is preferred. we find that massive disc galaxies have slightly flatter $z_{\rm {g}}$ profiles than their lower-mass counterparts in l-galaxies2020, due to more efficient enrichment of their outskirts via inside-out growth and metal-rich accretion. such a weak, positive correlation between stellar mass and $z_{\rm {g}}$ profile slope is also seen in our manga-dr15 sample of 571 star-forming disc galaxies, although below log10(m*/m⊙) ∼ 10.0 this observational result is strongly dependent on the metallicity diagnostic and morphological selection chosen. in addition, a lowered maximum sn-ii progenitor mass of $25\, {\rm m}_{\odot }$ , reflecting recent theoretical and observational estimates, can also provide a good match to observed $z_{\rm {g}}$ and z* profiles at z = 0 in l-galaxies2020. however, this model version fails to reproduce an evolution in $z_{\rm {g}}$ at fixed mass over cosmic time, or the magnesium abundances observed in the intracluster medium (icm). | l-galaxies 2020: the evolution of radial metallicity profiles and global metallicities in disc galaxies |
the observed rapid cooling of the neutron star (ns) located at the center of the supernova remnant cassiopeia a (cas a) can be explained in the minimal ns cooling scenario. this consequence may be changed if there exists an extra cooling source, such as axion emission. in this work, we study the cas a ns cooling in the presence of axion emission, taking account of the temperature evolution in the whole life of the cas a ns. we obtain a lower limit on the axion decay constant, fa≳(5 -7 )×108 gev , if the star has an envelope with a thin carbon layer. this is as strong as existing limits imposed by other astrophysical observations such as sn1987a. | limit on the axion decay constant from the cooling neutron star in cassiopeia a |
in environments with high dense neutrino gases, such as in core-collapse supernovae, the neutrinos can experience collective neutrino oscillation due to their self-interactions. in particular, fast flavor conversion driven by the crossings in the neutrino angular distribution can affect explosion mechanism, nucleosynthesis, and neutrino observation. we perform the numerical computation of nonlinear flavor evolution on the neutrino angular distribution with tiny crossings expected to be generated in the preshock region. we demonstrate that the fast instability is triggered and a cascade develops under a realistic three-flavor model considering muon production and weak magnetism in the supernova dynamics. the tiny crossing excites specific spatial modes, and then the flavor instability propagates into other modes which otherwise remain stable due to the nonlinear effects. our results indicate that fast flavor conversion can rise in the preshock region and have a sufficient impact on the flavor contents. | nonlinear evolution of fast neutrino flavor conversion in the preshock region of core-collapse supernovae |
the origin of the high-energy astrophysical neutrinos discovered by icecube remains largely unknown. multi-messenger studies have indicated that the majority of these neutrinos come from gamma-ray-dark sources. choked-jet supernovae (cjsne), which are supernovae powered by relativistic jets stalled in stellar materials, may lead to neutrino emission via photohadronic interactions while the coproduced gamma rays are absorbed. in this paper, we perform an unbinned-maximum-likelihood analysis to search for correlations between icecube's 10-year muon-track events and our sn ib/c sample, collected from publicly available catalogs. in addition to the conventional power-law models, we also consider the impacts of more realistic neutrino emission models for the first time, and study the effects of the jet beaming factor in the analyses. our results show no significant correlation. even so, the conservative upper limits we set to the contribution of cjsne to the diffuse astrophysical neutrino flux still allow sne ib/c to be the dominant source of astrophysical neutrinos observed by icecube. we discuss implications to the cjsne scenario from our results and the power of future neutrino and supernova observations. | high-energy neutrinos from choked-jet supernovae: searches and implications |
stripped-envelope core-collapse supernovae can be divided into two broad classes: the common type ib/c supernovae (sne ib/c), powered by the radioactive decay of 56ni, and the rare superluminous supernovae (slsne), most likely powered by the spin-down of a magnetar central engine. up to now, the intermediate regime between these two populations has remained mostly unexplored. here, we present a comprehensive study of 40 luminous supernovae (lsne), sne with peak magnitudes of mr= -19 to -20 mag, bound by slsne on the bright end and by sne ib/c on the dim end. spectroscopically, lsne appear to form a continuum between type ic sne and slsne. given their intermediate nature, we model the light curves of all lsne using a combined magnetar plus radioactive decay model and find that they are indeed intermediate, not only in terms of their peak luminosity and spectra, but also in their rise times, power sources, and physical parameters. we subclassify lsne into distinct groups that are either as fast evolving as sne ib/c or as slow evolving as slsne, and appear to be either radioactively or magnetar powered, respectively. our findings indicate that lsne are powered by either an overabundant production of 56ni or by weak magnetar engines, and may serve as the missing link between the two populations. | luminous supernovae: unveiling a population between superluminous and normal core-collapse supernovae |
fast neutrino flavor conversion can occur in core-collapse supernovae or compact binary merger remnants when nonforward collisions are also at play, and neutrinos are not fully decoupled from matter. this work aims to shed light on the conditions under which fast flavor conversion is enhanced or suppressed by collisions. by relying on a neutrino toy model with three angular bins in the absence of spatial inhomogeneities, we consider two angular configurations: the first one with angular distributions of νe and ν¯e that are almost isotropic as expected before complete neutrino decoupling and showing little flavor conversion when collisions are absent. the second one with angular distributions of νe and ν¯e that are forward peaked as expected in the free-streaming regime and showing significant flavor conversion in the absence of collisions. by including angle-independent, direction-changing collisions, we find that collisions are responsible for an overall enhancement (damping) of flavor conversion in the former (latter) angular configuration. these opposite outcomes are due to the nontrivial interplay between collisions, flavor conversion, and the initial angular distributions of the electron type neutrinos. the enhancement in neutrino flavor conversion is found to be anticorrelated with the magnitude of flavor conversions in the absence of collisions. | enhancement or damping of fast neutrino flavor conversions due to collisions |
explosive phenomena such as supernova remnant shocks and solar flares have demonstrated evidence for the production of relativistic particles. interest has therefore been renewed in collisionless shock waves and magnetic reconnection as a means to achieve such energies. although ions can be energized during such phenomena, the relativistic energy of the electrons remains a puzzle for theory. we present supercomputer simulations showing that efficient electron energization can occur during turbulent magnetic reconnection arising from a strong collisionless shock. upstream electrons undergo first-order fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. these results shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves. | stochastic electron acceleration during spontaneous turbulent reconnection in a strong shock wave |
cold dark matter explains a wide range of data on cosmological scales. however, there has been a steady accumulation of evidence for discrepancies between simulations and observations at scales smaller than galaxy clusters. one promising way to affect structure formation on small scales is a relatively strong coupling of dark matter to neutrinos. we construct an experimentally viable, simple, renormalizable model with new interactions between neutrinos and dark matter and provide the first discussion of how these new dark matter-neutrino interactions affect neutrino phenomenology. we show that addressing the small scale structure problems requires asymmetric dark matter with a mass that is tens of mev. generating a sufficiently large dark matter-neutrino coupling requires a new heavy neutrino with a mass around 100 mev. the heavy neutrino is mostly sterile but has a substantial τ neutrino component, while the three nearly massless neutrinos are partly sterile. this model can be tested by future astrophysical, particle physics, and neutrino oscillation data. promising signatures of this model include alterations to the neutrino energy spectrum and flavor content observed from a future nearby supernova, anomalous matter effects in neutrino oscillations, and a component of the τ neutrino with mass around 100 mev. | constraints and consequences of reducing small scale structure via large dark matter-neutrino interactions |
nuclear isomers are populated in the rapid neutron capture process (r process) of nucleosynthesis. the r process may cover a wide range of temperatures, potentially starting from several tens of gk (several mev) and then cooling as material is ejected from the event. as the r-process environment cools, isomers can freeze out of thermal equilibrium or be directly populated as astrophysically metastable isomers (astromers). astromers can undergo reactions and decays at rates very different from the ground state, so they may need to be treated independently in nucleosythesis simulations. two key behaviors of astromers—ground state ↔ isomer transition rates and thermalization temperatures—are determined by direct transition rates between pairs of nuclear states. we perform a sensitivity study to constrain the effects of unknown transitions on astromer behavior. detailed balance ensures that ground → isomer and isomer → ground transitions are symmetric, so unknown transitions are equally impactful in both directions. we also introduce a categorization of astromers that describes their potential effects in hot environments. we provide a table of neutron-rich isomers that includes the astromer type, thermalization temperature, and key unmeasured transition rates. | sensitivity of neutron-rich nuclear isomer behavior to uncertainties in direct transitions |
we use six tilted spatially flat and untilted nonflat dark energy cosmological models in analyses of south pole telescope polarization (sptpol) cosmic microwave background (cmb) data, alone and in combination with planck 2015 cmb data and non-cmb data, namely, the pantheon type ia supernovae apparent magnitudes, a collection of baryon acoustic oscillation data points, hubble parameter measurements, and growth rates. although the cosmological models that best fit the planck cmb and non-cmb data do not provide good fits to the sptpol data, with the χ2's exceeding the expected value, given the uncertainties, in each model the cosmological parameter constraints from the sptpol data and from the planck cmb and non-cmb data are largely mutually consistent. when the smaller angular scale sptpol data are used jointly with either the planck data alone or with the planck cmb and the non-cmb data to constrain untilted nonflat models, spatially closed models remain favored over their corresponding flat limits. when used in conjunction with planck data, non-cmb data (baryon acoustic oscillation measurements in particular, from six experiments) have significantly more constraining power than the sptpol data. | using spt polarization, planck 2015, and non-cmb data to constrain tilted spatially-flat and untilted nonflat λ cdm , xcdm, and ϕ cdm dark energy inflation cosmologies |
by comparing the properties of red supergiant (rsg) supernova (sn) progenitors to those of field rsgs, it has been claimed that there is an absence of progenitors with luminosities l above log (l/l⊙) > 5.2. this is in tension with the empirical upper luminosity limit of rsgs at log (l/l⊙) = 5.5, a result known as the `rsg problem'. this has been interpreted as an evidence for an upper mass threshold for the formation of black holes. in this paper, we compare the observed luminosities of rsg sn progenitors with the observed rsg l-distribution in the magellanic clouds. our results indicate that the absence of bright sn ii-p/l progenitors in this sample can be explained at least in part by the steepness of the l-distribution and a small sample size, and that the statistical significance of the rsg problem is between 1σ and 2σ . secondly, we model the luminosity distribution of ii-p/l progenitors as a simple power law with an upper and lower cut-off, and find an upper luminosity limit of log (l_hi/l_⊙) = 5.20^{+0.17}_{-0.11} (68 per cent confidence), though this increases to ∼5.3 if one fixes the power-law slope to be that expected from theoretical arguments. again, the results point to the significance of the rsg problem being within ∼2σ. under the assumption that all progenitors are the result of single-star evolution, this corresponds to an upper mass limit for the parent distribution of m_hi = 19.2 {m_⊙ }, ± 1.3 {m_⊙ (systematic)}, ^{+4.5}_{-2.3} {m_⊙ } (random; 68 per cent confidence limits). | the `red supergiant problem': the upper luminosity boundary of type ii supernova progenitors |
the past ten years have opened up a new parameter space in time-domain astronomy with the discovery of transients defying our understanding of how stars explode. these extremes of the transient paradigm represent the brightest—called superluminous supernovae—and the fastest—known as fast blue optical transients—of the transient zoo. the number discovered and information gained per event have witnessed an exponential growth that has benefited observational and theoretical studies. the collected data and the understanding of such events have surpassed any initial expectation and opened up a future exploding with potential, spanning from novel tools of high-redshift cosmological investigation to new insights into the final stages of massive stars. here, the observational properties of extreme supernovae are reviewed and put in the context of their physics, possible progenitor scenarios and explosion mechanisms. | observational properties of extreme supernovae |
context. the post-main-sequence evolution of massive stars is very sensitive to many parameters of the stellar models. key parameters are the mixing processes, the metallicity, the mass-loss rate, and the effect of a close companion.aims: we study the change in the red supergiant (rsg) lifetimes, the tracks in the hertzsprung-russel diagram (hrd), the positions in this diagram of the pre-supernova progenitor and the structure of the stars at that time for various mass-loss rates during the rsg phase and for two different initial rotation velocities.methods: stellar models were computed with the geneva code for initial masses between 9 and 25 m⊙ at solar metallicity (z = 0.014) with 10 times and 25 times the standard mass-loss rates during the rsg phase, with and without rotation.results: the surface abundances of rsgs are much more sensitive to rotation than to the mass-loss rates during that phase. a change of the rsg mass-loss rate has a strong impact on the rsg lifetimes and in turn on the luminosity function of rsgs. an observed rsg is associated with a model of higher initial mass when models with an enhanced rsg mass-loss rate are used to deduce that mass. at solar metallicity, models with an enhanced mass-loss rate produce significant changes in the populations of blue, yellow, and rsgs. when extended blue loops or blueward excursions are produced by enhanced mass-loss, the models predict that a majority of blue (yellow) supergiants are post-rsg objects. these post-rsg stars are predicted to show much lower surface rotational velocities than similar blue supergiants on their first crossing of the hr gap. enhanced mass-loss rates during the rsg phase have little impact on the wolf-rayet populations. the position in the hrd of the end point of the evolution depends on the mass of the hydrogen envelope. more precisely, whenever at the pre-supernova stage the h-rich envelope contains more than about 5% of the initial mass, the star is a rsg, and whenever the h-rich envelope contains less than 1% of the total mass, the star is a blue supergiant. for intermediate situations, intermediate colors and effective temperatures are obtained. yellow progenitors for core-collapse supernovae can be explained by models with an enhanced mass-loss rate, while the red progenitors are better fitted by models with the standard mass-loss rate. tracks of the enhanced mass loss rates models are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/575/a60 | impact of mass-loss on the evolution and pre-supernova properties of red supergiants |
direct dark matter detection experiments will soon be sensitive to neutrinos from astrophysical sources, including the sun, the atmosphere, and supernovae, which will set an important benchmark and open a new window into neutrino physics and astrophysics. the detection of these neutrinos will be complementary to accelerator- and reactor-based experiments that study neutrinos over the same energy range. we review the physics and astrophysics that can be extracted from the detection of these neutrinos, highlighting the potential of identifying new physics in the form of light mediators that arise from kinetic mixing and hidden sectors, as well as ∼ev-scale sterile neutrinos. we discuss how the physics reach of these experiments will complement searches for new physics at the lhc and dedicated neutrino experiments. | neutrino physics with dark matter detectors |
type ia supernovae are thought to be the result of a thermonuclear runaway in carbon/oxygen white dwarfs, but it is uncertain whether the explosion is triggered by accretion from a non-degenerate companion star or by a merger with another white dwarf. observations of a supernova immediately following the explosion provide unique information on the distribution of ejected material and the progenitor system. models predict that the interaction of supernova ejecta with a companion star or circumstellar debris lead to a sudden brightening lasting from hours to days. here we present data for three supernovae that are likely to be type ia observed during the kepler mission with a time resolution of 30 minutes. we find no signatures of the supernova ejecta interacting with nearby companions. the lack of observable interaction signatures is consistent with the idea that these three supernovae resulted from the merger of binary white dwarfs or other compact stars such as helium stars. | no signature of ejecta interaction with a stellar companion in three type ia supernovae |
despite the many efforts, our theoretical understanding of the ultimate nature of the dark energy component of the universe still lags well behind the astounding experimental evidence achieved from the increasingly sophisticated observational tools at our disposal. while the canonical possibility is a strict cosmological constant, or rigid vacuum energy density ρλ = const., the exceeding simplicity of this possibility lies also at the root of its unconvincing theoretical status, as there is no explanation for the existence of such constant for the entire cosmic history. herein we explore general models of the vacuum energy density slowly evolving with the hubble function h and/or its time derivative, ρλ = ρλ(h,ḣ). some of these models are actually well-motivated from the theoretical point of view and may provide a rich phenomenology that could be explored in future observations, whereas some others have more limitations. in this work, we put them to the test and elucidate which ones are still compatible with the present observations and which ones are already ruled out. we consider their implications on structure formation, in combination with data on type ia supernovae, the cosmic microwave background, the baryonic acoustic oscillations, and the predicted redshift distribution of cluster-size collapsed structures. the relation of these vacuum models on possible evidence of dynamical dark energy recently pointed out in the literature is also briefly addressed. | dynamical vacuum energy in the expanding universe confronted with observations: a dedicated study |
context. we present a large homogeneous set of stellar parameters and abundances across a broad range of metallicities, involving 13 classical dwarf spheroidal (dsph) and ultra-faint dsph (ufd) galaxies. in total, this study includes 380 stars in fornax, sagittarius, sculptor, sextans, carina, ursa minor, draco, reticulum ii, bootes i, ursa major ii, leo i, segue i, and triangulum ii. this sample represents the largest, homogeneous, high-resolution study of dsph galaxies to date.aims: with our homogeneously derived catalog, we are able to search for similar and deviating trends across different galaxies. we investigate the mass dependence of the individual systems on the production of α-elements, but also try to shed light on the long-standing puzzle of the dominant production site of r-process elements.methods: we used data from the keck observatory archive and the eso reduced archive to reanalyze stars from these 13 classical dsph and ufd galaxies. we automatized the step of obtaining stellar parameters, but ran a full spectrum synthesis (1d, local thermal equilibrium) to derive all abundances except for iron to which we applied nonlocal thermodynamic equilibrium corrections where possible.results: the homogenized set of abundances yielded the unique possibility of deriving a relation between the onset of type ia supernovae and the stellar mass of the galaxy. furthermore, we derived a formula to estimate the evolution of α-elements. this reveals a universal relation of these systems across a large range in mass. finally, we show that between stellar masses of 2.1 × 107 m⊙ and 2.9 × 105 m⊙, there is no dependence of the production of heavy r-process elements on the stellar mass of the galaxy.conclusions: placing all abundances consistently on the same scale is crucial to answering questions about the chemical history of galaxies. by homogeneously analyzing ba and eu in the 13 systems, we have traced the onset of the s-process and found it to increase with metallicity as a function of the galaxy's stellar mass. moreover, the r-process material correlates with the α-elements indicating some coproduction of these, which in turn would point toward rare core-collapse supernovae rather than binary neutron star mergers as a host for the r-process at low [fe/h] in the investigated dsph systems. abundances and stellar parameters are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/641/a127 based on data obtained with vlt and the w.m. keck observatory. information of the used program ids is given in the acknowledgments. | neutron-capture elements in dwarf galaxies. iii. a homogenized analysis of 13 dwarf spheroidal and ultra-faint galaxies |
we construct new equations of state for baryons at sub-nuclear densities for the use in core-collapse supernova simulations. the abundance of various nuclei is obtained together with thermodynamic quantities. the formulation is an extension of the previous model, in which we adopted the relativistic mean field theory with the tm1 parameter set for nucleons, the quantum approach for d, t, h and α as well as the liquid drop model for the other nuclei under the nuclear statistical equilibrium. we reformulate the model of the light nuclei other than d, t, h and α based on the quasi-particle description. furthermore, we modify the model so that the temperature dependences of surface and shell energies of heavy nuclei could be taken into account. the pasta phases for heavy nuclei and the pauli- and self-energy shifts for d, t, h and α are taken into account in the same way as in the previous model. we find that nuclear composition is considerably affected by the modifications in this work, whereas thermodynamical quantities are not changed much. in particular, the washout of shell effect has a great impact on the mass distribution above t ∼ 1 mev. this improvement may have an important effect on the rates of electron captures and coherent neutrino scatterings on nuclei in supernova cores. | supernova equations of state including full nuclear ensemble with in-medium effects |
we perform two- (2d) and three-dimensional (3d) hydrodynamics simulations of convective oxygen-shell burning that takes place deep inside a massive progenitor star of a core-collapse supernova. using a one-dimensional (1d) stellar evolution code, we first calculate the evolution of massive stars with an initial mass of 9-40 m ⊙. four different overshoot parameters are applied, and a co-core mass trend similar to previous works is obtained in the 1d models. selecting eleven 1d models that have a coexisting silicon and oxygen layer, we perform 2d hydrodynamics simulations of the evolution for ∼100 s until the onset of core collapse. we find that convection with large-scale eddies and the turbulent mach number of ∼0.1 is obtained in the models having a si/o layer with a scale of 108 cm, whereas most models that have an extended o/si layer up to a few ×109 cm exhibit lower turbulent velocity. our results indicate that the supernova progenitors that possess a thick si/o layer could provide the preferred condition for perturbation-aided explosions. we perform the 3d simulation of a 25 m ⊙ model, which exhibits large-scale convection in the 2d models. the 3d model develops large-scale (ℓ = 2) convection similar to the 2d model; however, the turbulent velocity is lower. by estimating the neutrino emission properties of the 3d model, we point out that a time modulation of the event rates, if observed in kamland and hyper-kamiokande, could provide important information about structural changes in the presupernova convective layer. | one-, two-, and three-dimensional simulations of oxygen-shell burning just before the core collapse of massive stars |
we investigate the generalized cubic covariant galileon model, a kinetically driven dark energy model within the horndeski class of theories. the model extends the cubic covariant galileon by including power laws of the field derivatives in the k-essence and cubic terms which still allow for tracker solutions. we study the shape of the viable parameter space by enforcing stability conditions which include the absence of ghost, gradient and tachyon instabilities and the avoidance of strong coupling at early time. we study here the relevant effects of the modifications induced by the model on some cosmological observables such as the cosmic microwave background (cmb), the lensing potential autocorrelation and the matter power spectrum. for this goal, we perform parameter estimation using data of cmb temperature and polarization, baryonic acoustic oscillations (bao), redshift-space distortions (rsd), supernovae type ia (snia) and cepheids. data analysis with cmb alone finds that the today's hubble parameter h0 is consistent with its determination from cepheids at 1 σ , resolving the famous tension of the cosmological standard models. the joint analysis of cmb, bao, rsd and snia sets a lower bound for the sum of neutrino masses which is σ mν>0.11 ev at 1 σ , in addition to the usual upper limit. the model selection analysis based on the effective χeff2 and deviance information criterion is not able to clearly identify the statistically favored model between λ cdm and the generalized cubic covariant galileon, from which we conclude that the latter model deserves further studies. | phenomenology of the generalized cubic covariant galileon model and cosmological bounds |
in view of the recent measurement of h0 from the hubble space telescope and supernova h0 for the equation of state (sh0es) team, we explore the possibility of existence of a negative cosmological constant [anti-de sitter (ads) vacua in the dark energy sector] in the universe. in this regard, we consider quintessence fields on top of a negative cosmological constant and compare such construction with λ cold dark matter (λcdm) model using a different combination of cosmic microwave background, type ia supernova, baryon acoustic oscillation, and h0 data. various model comparison estimators show that quintessence models with a negative λ are either preferred over λcdm or perform equally as the λcdm model. this suggests that the presence of a negative λ (ads ground state) in our universe, which can naturally arise in string theory, is consistent with cosmological observations. | do cosmological observations allow a negative λ? |
in contrast to regular core-collapse supernovae, explosions of rapidly rotating massive stars can develop jets, fast collimated outflows directed along the rotational axis. depending on the rate of rotation and the magnetic field strength before collapse as well as on possible mechanisms amplifying the magnetic field, such a core can explode magnetorotationally rather than via the standard supernova mechanism based on neutrino heating. this scenario can explain the highest kinetic energies observed in the class of hypernovae. on longer time scales, rotation and magnetic fields can play an important role in the engine of long gamma-ray burst powered by proto-magnetars or hyperaccreting black holes in collapsars. both classes of events are characterized by relativistic jets and winds driven by neutrinos or magnetic spin-down of the central objects. the nucleosynthesis in these events includes the production of fe group elements, including a possibly enhanced synthesis of radioactive 56ni leading to high peak luminosities. additionally, these events are, out of all stellar core-collapse events the ones most likely to allow for the formation of the heaviest nuclei via rapid neutron captures. increasingly sophisticated numerical simulations indicate that at least a limited r-process is possible, though it remains open how robust this result is against variations in the numerical methods and the initial conditions. if so, supernovae with jets could contribute to the observed galactic chemical enrichment, in particular at early times before neutron-star mergers might be able to set in. | nucleosynthesis in jet-driven and jet-associated supernovae |
point defects in the binary group-iv monochalcogenide monolayers of sns, snse, ges, and gese are investigated using density functional theory calculations. several stable configurations are found for oxygen defects, however, we give evidence that these materials are less prone to oxidation than phosphorene, with which monochalcogenides are isoelectronic and share the same orthorhombic structure. concurrent oxygen defects are expected to be vacancies and substitutional oxygen. we show that it is energetically favorable for oxygen to be incorporated into the layers substituting for a chalcogen (os /se defects), and different from most of the other defects investigated, this defect preserves the electronic structure of the material. thus, we suggest that annealing treatments can be useful for the treatment of functional materials where loss mechanisms due to the presence of defects are undesirable. | vacancies and oxidation of two-dimensional group-iv monochalcogenides |
we report the first measurement of low-energy proton-capture cross sections of <mml:mmultiscripts>xe 124 </mml:mmultiscripts> in a heavy-ion storage ring. <mml:mmultiscripts>xe124 </mml:mmultiscripts> 54 + ions of five different beam energies between 5.5 and 8 amev were stored to collide with a windowless hydrogen target. the <mml:mmultiscripts>cs 125 </mml:mmultiscripts> reaction products were directly detected. the interaction energies are located on the high energy tail of the gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. the results serve as an important test of predicted astrophysical reaction rates in this mass range. good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. the newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies. | approaching the gamow window with stored ions: direct measurement of 124xe (p ,γ ) in the esr storage ring |
while it is clear that type ia supernovae (sne) are the result of thermonuclear explosions in c/o white dwarfs (wds), a great deal remains uncertain about the binary companion that facilitates the explosive disruption of the wd. here, we present a comprehensive analysis of a large, unique data set of 127 sne ia with exquisite coverage by the zwicky transient facility (ztf). high-cadence (six observations per night) ztf observations allow us to measure the sn rise time and examine its initial evolution. we develop a bayesian framework to model the early rise as a power law in time, which enables the inclusion of priors in our model. for a volume-limited subset of normal sne ia, we find that the mean power-law index is consistent with 2 in the rztf-band ( ${\alpha }_{r}=2.01\pm 0.02$ ), as expected in the expanding fireball model. there are, however, individual sne that are clearly inconsistent with ${\alpha }_{r}=2$ . we estimate a mean rise time of 18.9 days (with a range extending from ∼15 to 22 days), though this is subject to the adopted prior. we identify an important, previously unknown, bias whereby the rise times for higher-redshift sne within a flux-limited survey are systematically underestimated. this effect can be partially alleviated if the power-law index is fixed to α = 2, in which case we estimate a mean rise time of 21.7 days (with a range from ∼18 to 23 days). the sample includes a handful of rare and peculiar sne ia. finally, we conclude with a discussion of lessons learned from the ztf sample that can eventually be applied to observations from the vera c. rubin observatory. | ztf early observations of type ia supernovae. ii. first light, the initial rise, and time to reach maximum brightness |
context. gaia data release 2 (dr2) provides a unique all-sky catalogue of 550 737 variable stars, of which 151 761 are long-period variable (lpv) candidates with g variability amplitudes larger than 0.2 mag (5-95% quantile range). about one-fifth of the lpv candidates are mira candidates, the majority of the rest are semi-regular variable candidates. for each source, g, gbp, and grp photometric time-series are published, together with some lpv-specific attributes for the subset of 89 617 candidates with periods in g longer than 60 days.aims: we describe this first gaia catalogue of lpv candidates, give an overview of its content, and present various validation checks.methods: various samples of lpvs were used to validate the catalogue: a sample of well-studied very bright lpvs with light curves from the american association of variable star observers that are partly contemporaneous with gaia light curves, a sample of gaia lpv candidates with good parallaxes, the all-sky automated survey for supernovae catalogue of lpvs, and the optical gravitational lensing experiment (ogle) catalogues of lpvs towards the magellanic clouds and the galactic bulge.results: the analyses of these samples show a good agreement between gaia dr2 and literature periods. the same is globally true for bolometric corrections of m-type stars. the main contaminant of our dr2 catalogue comes from young stellar objects (ysos) in the solar vicinity (within 1 kpc), although their number in the whole catalogue is only at the percent level. a cautionary note is provided about parallax-dependent lpv attributes published in the catalogue.conclusions: this first gaia catalogue of lpvs approximately doubles the number of known lpvs with amplitudes larger than 0.2 mag, despite the conservative candidate selection criteria that prioritise low contamination over high completeness, and despite the limited dr2 time coverage compared to the long periods characteristic of lpvs. it also contains a small set of yso candidates, which offers the serendipitous opportunity to study these objects at an early stage of the gaia data releases. | gaia data release 2. the first gaia catalogue of long-period variable candidates |
we extract cosmological information from the anisotropic power-spectrum measurements from the recently completed baryon oscillation spectroscopic survey (boss), extending the concept of clustering wedges to fourier space. making use of new fast-fourier-transform-based estimators, we measure the power-spectrum clustering wedges of the boss sample by filtering out the information of legendre multipoles ℓ > 4. our modelling of these measurements is based on novel approaches to describe non-linear evolution, bias and redshift-space distortions, which we test using synthetic catalogues based on large-volume n-body simulations. we are able to include smaller scales than in previous analyses, resulting in tighter cosmological constraints. using three overlapping redshift bins, we measure the angular-diameter distance, the hubble parameter and the cosmic growth rate, and explore the cosmological implications of our full-shape clustering measurements in combination with cosmic microwave background and type ia supernova data. assuming a λ cold dark matter (λcdm) cosmology, we constrain the matter density to ω m= 0.311_{-0.010}^{+0.009} and the hubble parameter to h_0 = 67.6_{-0.6}^{+0.7} km s^{-1 mpc^{-1}}, at a confidence level of 68 per cent. we also allow for non-standard dark energy models and modifications of the growth rate, finding good agreement with the λcdm paradigm. for example, we constrain the equation-of-state parameter to w = -1.019_{-0.039}^{+0.048}. this paper is part of a set that analyses the final galaxy-clustering data set from boss. the measurements and likelihoods presented here are combined with others in alam et al. to produce the final cosmological constraints from boss. | the clustering of galaxies in the completed sdss-iii baryon oscillation spectroscopic survey: cosmological implications of the fourier space wedges of the final sample |
spectroscopic surveys of the galaxy reveal that its disc stars exhibit a spread in [α/fe] at fixed [fe/h], manifest at some locations as a bimodality. the origin of these diverse, and possibly distinct, stellar populations in the galactic disc is not well understood. we examine the fe and α-element evolution of 133 milky way-like galaxies from the eagle simulation, to investigate the origin and diversity of their [α/fe]-[fe/h] distributions. we find that bimodal [α/fe] distributions arise in galaxies whose gas accretion histories exhibit episodes of significant infall at both early and late times, with the former fostering more intense star formation than the latter. the shorter characteristic consumption time-scale of gas accreted in the earlier episode suppresses its enrichment with iron synthesized by type ia sne, resulting in the formation of a high-[α/fe] sequence. we find that bimodality in [α/fe] similar to that seen in the galaxy is rare, appearing in approximately 5 per cent of galaxies in our sample. we posit that this is a consequence of an early gas accretion episode requiring the mass accretion history of a galaxy's dark matter halo to exhibit a phase of atypically rapid growth at early epochs. the scarcity of eagle galaxies exhibiting distinct sequences in the [α/fe]-[fe/h] plane may therefore indicate that the milky way's elemental abundance patterns, and its accretion history, are not representative of the broader population of ∼l⋆ disc galaxies. | the origin of diverse α-element abundances in galaxy discs |
neutrinos are densely populated deep inside the core of massive stars after their gravitational collapse to produce supernova explosions and form compact stars such as neutron stars and black holes. it has been considered that they may change their flavor identities through so-called fast-pairwise conversions induced by mutual forward scatterings. if that is really the case, the dynamics of supernova explosion will be influenced, since the conversion may occur near the neutrino sphere, from which neutrinos are effectively emitted. in this paper, we conduct a pilot study of such possibilities based on the results of fully self-consistent, realistic simulations of a core-collapse supernova explosion in two spatial dimensions under axisymmetry. as we solved the boltzmann equations for neutrino transfer in the simulation not as a postprocess but in real time, the angular distributions of neutrinos in momentum space for all points in the core at all times are available, a distinct feature of our simulations. we employ some of these distributions extracted at a few selected points and times from the numerical data and apply linear analysis to assess the possibility of the conversion. we focus on the vicinity of the neutrino sphere, where different species of neutrinos move in different directions and have different angular distributions as a result. this is a pilot study for a more thorough survey that will follow soon. we find no positive sign of conversion unfortunately at least for the spatial points and times we studied in this particular model. we hence investigate rather in detail the condition for the conversion by modifying the neutrino distributions rather arbitrarily by hand. | linear analysis of fast-pairwise collective neutrino oscillations in core-collapse supernovae based on the results of boltzmann simulations |
in this work we explore an alternative phenomenological model to chaplygin gas proposed by hova et al. (int j mod phys d 26:1750178, 2017), consisting on a modification of a perfect fluid, to explain the dynamics of dark matter and dark energy at cosmological scales immerse in a flat or curved universe. adopting properties similar to a chaplygin gas, the proposed model is a mixture of dark matter and dark energy components parameterized by only one free parameter denoted as μ . we focus on contrasting this model with the most recent cosmological observations of type ia supernovae and hubble parameter measurements. our joint analysis yields a value μ = 0.843^{+0.014}_{-0.015} (0.822^{+0.022}_{-0.024}) for a flat (curved) universe. furthermore, with these constraints we also estimate the deceleration parameter today q_0=-0.67 ± 0.02 (-0.51± 0.07), the acceleration-deceleration transition redshift z_t=0.57± 0.04 (0.50 ± 0.06), and the universe age t_a = 13.108^{+0.270}_{-0.260} × (12.314^{+0.590}_{-0.430}) gyrs. we also report a best value of ω_k = 0.183^{+0.073}_{-0.079} consistent at 3σ with the one reported by planck collaboration. our analysis confirm the results by hova et al. this chaplygin gas-like is a plausible alternative to explain the nature of the dark sector of the universe. | cosmological constraints on alternative model to chaplygin fluid revisited |
neutrino-neutrino refraction in dense media can cause self-induced flavor conversion triggered by collective run-away modes of the interacting flavor oscillators. the growth rates were usually found to be of order a typical vacuum oscillation frequency δ m2/2e. however, even in the simple case of a νe beam interacting with an opposite-moving bar nue beam, and allowing for spatial inhomogeneities, the growth rate of the fastest-growing fourier mode is of order μ=√2 gf nν, a typical ν-ν interaction energy. this growth rate is much larger than the vacuum oscillation frequency and gives rise to flavor conversion on a much shorter time scale. this phenomenon of "fast flavor conversion" occurs even for vanishing δ m2/2e and thus does not depend on energy, but only on the angle distributions. moreover, it does not require neutrinos to mix or to have masses, except perhaps for providing seed disturbances. we also construct a simple homogeneous example consisting of intersecting beams and study a schematic supernova model proposed by ray sawyer, where νe and bar nue emerge with different zenith-angle distributions, the key ingredient for fast flavor conversion. what happens in realistic astrophysical scenarios remains to be understood. | self-induced neutrino flavor conversion without flavor mixing |
half of the heavy elements including all actinides are produced in r-process nucleosynthesis, whose sites and history remain a mystery. if continuously produced, the interstellar medium is expected to build-up a quasi-steady state of abundances of short-lived nuclides (with half-lives ≤100 my), including actinides produced in r-process nucleosynthesis. their existence in today’s interstellar medium would serve as a radioactive clock and would establish that their production was recent. in particular 244pu, a radioactive actinide nuclide (half-life=81 my), can place strong constraints on recent r-process frequency and production yield. here we report the detection of live interstellar 244pu, archived in earth’s deep-sea floor during the last 25 my, at abundances lower than expected from continuous production in the galaxy by about 2 orders of magnitude. this large discrepancy may signal a rarity of actinide r-process nucleosynthesis sites, compatible with neutron-star mergers or with a small subset of actinide-producing supernovae. | abundance of live 244pu in deep-sea reservoirs on earth points to rarity of actinide nucleosynthesis |
we present results from general-relativistic (gr) three-dimensional (3d) core-collapse simulations with approximate neutrino transport for three nonrotating progenitors (11.2, 15, and 40 m ⊙) using different nuclear equations of state (eoss). we find that the combination of progenitor’s higher compactness at bounce and the use of softer eos leads to stronger activity of the standing accretion shock instability (sasi). we confirm previous predications that the sasi produces characteristic time modulations both in neutrino and gravitational-wave (gw) signals. by performing a correlation analysis of the sasi-modulated neutrino and gw signals, we find that the correlation becomes highest when we take into account the time-delay effect due to the advection of material from the neutrino sphere to the proto-neutron star core surface. our results suggest that the correlation of the neutrino and gw signals, if detected, would provide a new signature of the vigorous sasi activity in the supernova core, which can be hardly seen if neutrino-convection dominates over the sasi. | correlated signatures of gravitational-wave and neutrino emission in three-dimensional general-relativistic core-collapse supernova simulations |
the regulation of the baryonic content in dwarf galaxies is a long-standing problem. supernovae (sne) are supposed to play a key role in forming large-scale galactic winds by removing important amounts of gas from galaxies. sne are efficient accelerators of non-thermal particles, so-called cosmic rays (crs), which can substantially modify the dynamics of the gas and conditions to form large-scale galactic winds. we investigate how cr injection by sne impacts the star formation and the formation of large-scale winds in dwarf galaxies, and whether it can produce galaxy star-formation rates (sfr) and wind properties closer to observations. we ran cr magneto-hydrodynamical simulations of dwarf galaxies at high resolution (9 pc) with the adaptive mesh refinement code ramses. those disc galaxies are embedded in isolated halos of mass of 1010 and 1011 m⊙, and crs are injected by sne. we included cr isotropic and anisotropic diffusion with various diffusion coefficients, cr radiative losses, and cr streaming. the injection of cr energy into the interstellar medium smooths out the highest gas densities, which reduces the sfr by a factor of 2-3. mass outflow rates are significantly greater with cr diffusion, by 2 orders of magnitudes for the higher diffusion coefficients. without diffusion and streaming, crs are inefficient at generating winds. cr streaming alone allows for the formation of winds but which are too weak to match observations. the formation of galactic winds strongly depends on the diffusion coefficient: for low coefficients, cr energy stays confined in high density regions where cr energy losses are highest, and higher coefficients, which allow for a more efficient leaking of crs out of dense gas, produce stronger winds. cr diffusion leads to colder and denser winds than without crs, and brings outflow rates and mass loading factors much closer to observations. | cosmic ray feedback from supernovae in dwarf galaxies |
context. the remnants of core-collapse supernovae (sne) are probes of the physical processes associated with their parent sne.aims: here we aim to explore to which extent the remnant keeps memory of the asymmetries that develop stochastically in the neutrino-heating layer due to hydrodynamic instabilities (e.g., convective overturn and the standing accretion shock instability; sasi) during the first second after core bounce.methods: we coupled a three-dimensional (3d) hydrodynamic model of a neutrino-driven sn explosion, which has the potential to reproduce the observed morphology of the cassiopeia a (cas a) remnant, with 3d (magneto)-hydrodynamic simulations of the remnant formation. the simulations cover ≈2000 yr of expansion and include all physical processes relevant to describe the complexities in the sn evolution and the subsequent interaction of the stellar debris with the wind of the progenitor star.results: the interaction of large-scale asymmetries left from the earliest phases of the explosion with the reverse shock produces, at the age of ≈350 yr, an ejecta structure and a remnant morphology which are remarkably similar to those observed in cas a. small-scale structures in the large-scale fe-rich plumes that were created during the initial stages of the sn, combined with hydrodynamic instabilities that develop after the passage of the reverse shock, naturally produce a pattern of ring- and crown-like structures of shocked ejecta. the consequence is a spatial inversion of the ejecta layers with si-rich ejecta being physically interior to fe-rich ejecta. the full-fledged remnant shows voids and cavities in the innermost unshocked ejecta, which are physically connected with ring-like features of shocked ejecta in the main shell in most cases, resulting from the expansion of fe-rich plumes and their inflation due to the decay of radioactive species. the asymmetric distributions of 44ti and 56fe, which are mostly concentrated in the northern hemisphere, and pointing opposite to the kick velocity of the neutron star, as well as their abundance ratio are both compatible with those inferred from high-energy observations of chandra and nustar. finally, the simulations show that the fingerprints of the sn can still be visible ≈2000 yr after the explosion.conclusions: the main asymmetries and features observed in the ejecta distribution of cas a can be explained by the interaction of the reverse shock with the initial large-scale asymmetries that developed from stochastic processes (e.g., convective overturn and sasi activity) that originate during the first seconds of the sn blast. movies associated to figs. 7, 8, 12, 15 are available at https://www.aanda.org | the fully developed remnant of a neutrino-driven supernova. evolution of ejecta structure and asymmetries in snr cassiopeia a |
observations restrict the parameter space of holographic dark energy (hde) so that a turning point in the hubble parameter h(z) is inevitable. concretely, cosmic microwave background, baryon acoustic oscillations and type ia supernovae (sne) data put the turning point in the future, but removing sne results in an observational turning point at positive redshift. from the perspective of theory, not only does the turning point violate the null energy condition, but as we argue, it may be interpreted as an evolution of the hubble constant h0 with redshift, which is at odds with the very flrw framework within which data has been analysed. tellingly, neither of these are problems for the flat λcdm model, and a direct comparison of fits further disfavours hde relative to flat λcdm. | a critique of holographic dark energy |
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