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binary star systems composed of two white dwarfs are a natural outcome of stellar evolution. angular momentum losses from gravitational wave radiation cause the binary system's orbit to shrink until the two white dwarfs merge. the final outcome of the merger depends primarily on the masses of the white dwarfs. some pot... | the long-term outcomes of double white dwarf mergers |
the central neutron star in cassiopeia a (cas a ns) has evidence from chandra acis data for a rapid temperature decline (2-3% per decade). if this is correct, it is a crucial constraint on understanding the cooling of young nss, and particularly on superfluidity in their cores. however, systematic uncertainties in acis... | verifying the cooling of the cas a neutron star with hrc-s |
when a neutron star snares material from a stellar companion, we see a flash of x-rays called an x-ray burst. what can an analysis of 51 bursts from a single source tell us about the physics behind these events?bursting binary systemsa view of the neutron star interior composition explorer (nicer), seen at the center o... | a nicer view of a bursting x-ray binary |
the "triaxial star", first proposed by s. chandrasekhar in 1969, has not yet been detected. the recently detected cosmic baby, i.e., swift j1818.0-1607 is the youngest magnetar observed so far. its characteristic age is ∼300 years, with a superfast spin period ∼1.36 s and a strong surface dipole magnetic field ∼3 ×1014... | cosmic baby and the detection of a new compact star - the "triaxial star": a possibility |
i will begin this talk by briefly describing how multi-messengerobservations of neutron stars, when coupled withinformation from nuclear theory and nuclear structure,will provide new information about the equation ofstate, the composition, and the transport propertiesof dense matter. the tidal deformability of a neutro... | multi-messenger neutron star astrophysics and determining the composition of the neutron star core |
the decay of the magnetic field in the interior of a magnetar may trigger electron captures by nuclei in the stellar crust, thus providing an internal source of heating. in turn, the onset of electron captures and the heat released are altered by the magnetic field due to the landau-rabi quantization of electron motion... | heating from electron captures by nuclei in magnetar crusts |
the co-pis of this proposal are wen-fai fong and raffaella margutti. we propose joint chandra-vla-hst observations to continue our monitoring of the binary neutron star merger gw170817 at t 500-850 days since merger. our immediate objectives are: (i) to constrain the broad-band spectral evolution of the non-thermal emi... | late-time monitoring of gw170817 across the electromagnetic spectrum |
maxi j1727-203 is a new transient discovered in june, 5 2018, and due to its spectral properties at the beginning of the outburst it was identified as a black hole candidate. maxi j1727 has been monitored with neutron star interior composition explorer (nicer) on almost daily basis since the beginning of the outburst. ... | nicer observations of the 2018 outburst of the black hole candidate maxi j1727-203 |
the evolutionary paths of neutron stars post-supernova are not fullyunderstood. questions of cooling, magnetic field evolutions, spin downboth steady and via glitches, evolving emission behaviour,environmental influences and more besides are each highly complex, andat the same time intertwined. deciphering the full evo... | neutron star evolution |
we propose xmm-newton observations of 840 kyr old radio-quiet gamma-raypulsar j1957+5033. its short chandra observations revealed the presenceof a very soft x-ray emission in the 0.1--0.3 kev range. this suggeststhat the pulsar x-ray spectrum can have a soft thermal component from thens surface with the temperature of ... | is psr j1957+5033 the coldest neutron star? |
we discuss the effect of compression on urca shells in the ocean and crust of accreting neutron stars, especially in superbursting sources. we find that urca shells may be deviated from chemical equilibrium in neutron stars which accrete at several tenths of the local eddington accretion rate. the deviation depends on ... | net reaction rate and neutrino cooling rate for the urca process in departure from chemical equilibrium in the crust of fast-accreting neutron stars |
ultra luminous x-ray (ulx) sources are among the most intriguing binary systems, that have long been thought to host the elusive intermediate mass black holes. remarkably, within the last years there has been undisputed evidence that at least a few of these systems are powered by accreting neutron stars (ns) that are r... | ulx spectra revisited: observational evidence of accreting envelopes around magnetized neutron stars |
we have investigated the x-ray luminosity and the rotational evolutions of the so-called "high-magnetic-field neutron stars" (hbrps) in the frame of the fallback disk model that was also applied earlier to anomalous x-ray pulsars/soft gamma repeaters (axps/sgrs), and dim isolated neutron stars (xdins). the estimated su... | evolution of high-b radio pulsars in the fallback disk model |
x-ray bursts (type i) are produced by thermonuclear flashes in the accreted surface layers of some neutron stars in low mass x-ray binaries (lmxbs). high frequency oscillations are observed during some of these bursts. these "burst oscillations" result from rotational modulation of an inhomogeneous temperature distribu... | x-ray bursts and oscillations: prospects with nicer |
stars freeze. as they age and cool white dwarfs and neutron stars crystallize, with remarkable materials forming in their interiors. these `astromaterials' have structures similar to terrestrial crystalline solids and liquid crystals, though they are over a trillion times denser. notably, because their material propert... | dissertation award in nuclear physics recipient: astromaterials in neutron stars |
superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. investigations on crust superfluidity carried out so far typically assumed that the cluster component was given by a single representative nucleus and did not consider the fact that at finite temperature a wide distributio... | impact of pairing on thermodynamical properties of stellar matter |
the composition and phase separation of rp-ash on accreting neutron stars determine the thermal properties of the crust which must be understood to interpret observations of crust cooling in x-ray bursts. in this work, we report on recent large scale molecular dynamics simulations of the outer crust. using the crust co... | simualting the phase separated rp-ash |
this talk focuses on the orbital inspiral of a neutron star (ns) through the envelope of its giant-branch companion during a common envelope (ce) episode. these ce episodes are necessary to produce close pairs of nss that can inspiral and merge due to gravitational wave losses in less than a hubble time. yet, as an emb... | limiting the accretion-fed growth of neutron stars during common envelope |
we have followed the structure and thermal evolution of isolated, massive, uniformly rotating and highly magnetized white dwarf stars (wds). we studied the posibility that angular momentum losses driven by magnetic dipole braking developed the physical conditions inside the wd suitable to produce a thermonuclear explos... | time evolution of rotating and magnetized white dwarf stars |
nuclear pasta, with non-spherical shapes, is expected near the base of the crust in neutron stars. large scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. we model a possible low conductivi... | disordered nuclear pasta, magnetic field decay, and crust cooling in neutron stars |
a recent experiment at the national superconducting cyclotron laboratory has resulted in an extension of the nuclear mass surface for neutron-rich isotopes of argon through iron. the time-of-flight technique was employed to experimentally determine the masses of several nuclei for the first time. results include the id... | results from the nscl tof mass measurement of neutron-rich isotopes of argon through iron |
pulsed non-thermal quiescent emission between 10 kev and around 150 kev has been observed in ~10 magnetars. for inner magnetospheric models of such hard x-ray signals, resonant compton upscattering of soft thermal photons from the neutron star surface is the most efficient radiative process. we present angle-dependent ... | hard spectral tails in magnetars |
we use the smoothed particle hydrodynamics (sph) method to simulate the behavior of viscous matter accreting on a neutron star. the fundamental difference between accretion onto black holes and neutron stars is the presence of a hard surface for the latter, which forces matter to stop moving in the radial direction at ... | formation of two-component advective flows around neutron stars |
we propose a 70 ksec observation of the neutron-star transient low-massx-ray binary exo 0748- 676. neutron-star crusts provide the uniqueopportunity to study the extreme conditions introduced by very highdensity matter. the density in a neutron-star crust increases by eightorders of magnitude over only ~1 km, from ~1e6... | crust cooling of the neutron star in exo 0748-676 |
information about the structure and evolution of neutrons stars can be obtained from modeling their thermal evolution. i will present two studies, one of the cooling the crab pulsar, and one of the heating of accreting neutron stars as they accrete matter from a companion star. firstly, there is some circumstantial evi... | the heating and cooling of neutron stars |
cooling of neutron stars has long been recognized as a way to investigate the physics of dense matter in neutron star interiors. because cooling depends on the heat capacity and neutrino emissivity of the matter, it is sensitive to both the particle content, for example the proton fraction, and state of matter, for exa... | a new perspective on neutron star cooling |
thermal states of neutron stars in soft x-ray transients (sxrts) are thought to be governed by ``deep crustal heating'' in the accreted matter and cooling via emission of photons at the surface and neutrinos from the interior. previous studies have shown that within nucleons-only model it is difficult to explain the qu... | effect of exotic matter on thermal states of transiently accreting neutron stars |
type-i x-ray bursts are thermonuclear explosions on the surface of weakly magnetized accreting neutron stars (ns) in low-mass x-ray binary (lmxb) systems where the mass donor is typically an evolved star. observationally, x-ray bursts can show a large variety in profiles, but generally they exhibit a fast rise and a lo... | the population of galactic x-ray bursters as seen by integral over 14 years in space |
one of the most interesting kind of neutron stars are the pulsars, which are highly magnetized neutron stars with fields up to 1014 g at the surface. the strength of magnetic field in the center of a neutron star remains unknown. according to the scalar virial theorem, magnetic field in the core could be as large as 10... | effects of neutrino emissivity on the cooling of neutron stars in the presence of a strong magnetic field |
the features of a first-order phase transition at variable pressure in mixed matter, which indicated the non-linear phase structure, have been discussed. the non-linear phase structure leads to the imbalance of the two phases during the phase transition under certain conditions. this novel non-equilibrium process is ve... | novel non-equilibrium phase transition caused by non-linear hadronic-quark phase structure |
we evolve a binary system of two, equal-mass neutron stars in a quasi-circular orbit through and past merger. we consider different nuclear equations of state, which vary from soft to quite stiff, and allow for magnetization of the system and neutrino cooling via a leakage scheme. here, i focus on potential observables... | binary neutron star mergers: prospects for multimessenger observations |
we are developing a concept for a new canadian-led x-ray observatory — colibrì. the main objective of the colibrì mission is to study the structure of accretion flows in the near vicinity of black holes and neutron stars and the study of emission from the surfaces of neutron stars. the colibrì mission will look for ans... | colibrì: taking the pulse of black holes and neutron stars |
quasi-spherical accreion onto magnetized neutron stars from stellar winds in high-mass x-ray binaries is discussed. depending on the x-ray luminosity of the neutron star, the accretion can proceed in two regimes (modes): at l_x ≳ 4× 10^{36} erg/s, compton cooling of accreting matter near magnetosphere leads to a supers... | quasi-spherical accretion in high mass x-ray binaries |
we propose a 70 ks xmm-newton observation of the neutron star in 1rxsj180408.9-342058 (1rxs j1804), a transient lmxb which underwent a ~4.5month accretion outburst in 2015. the neutron star in transient lmxbs mayexperience crust heating during the outburst and subsequent cooling inquiescence. tracking the thermal evolu... | crust cooling of the neutron star in 1rxs j180408.9 342058 |
we study the merger of unequal-mass neutron stars in a quasi-circular orbit with different nuclear equations of state ranging from from soft to stiff with a neutrino cooling scheme. | mergers of unequal mass binary neutron stars |
during a black hole-neutron star merger, baryonic material can be dynamically ejected. because this ejecta is extremely neutron-rich, the r-process rapidly synthesizes heavy nuclides as the material expands and cools. this can contribute to galactic chemical evolution of the r-process elements and lead to a short-lived... | influence of neutrinos on r-process nucleosynthesis in black hole-neutron star mergers |
neutron stars are born with high temperatures and during a few seconds suffer rapid cooling by emission of neutrinos. the direct urca process is the main mechanism to explain this loss of energy. in this work we study the influence of a strong magnetic field on the composition of nuclear matter at high densities and ze... | cooling of neutron stars and emissivity of neutrinos by the direct urca process under influence of a strong magnetic field |
core-collapse supernovae lead to the formation of neutron stars, and both are sensitive to the dense matter equation of state. hans bethe first recognized that the matter in the collapsing core of a massive star has a relatively low entropy which prevents nuclear dissociation until nuclei merge near the nuclear saturat... | hans a. bethe prize: neutron stars and core-collapse supernovae |
we present the results of chandra observations of two non-accreting millisecond pulsars psrs j1640+2224 (j1640) and j1709+2313(j1709), with low inferred magnetic fields in order to constrain their surface temperatures, obtain limits on the amplitude of unstable r-modes in them and make comparisons with similar limits o... | where are the r-modes? chandra observations of millisecond pulsars |
in core-collapse supernovae, the neutron rich matter is believed to have complex structures, such as spherical, slablike, and rodlike shapes. they are collectively called ``nuclear pasta''. supernovae neutrinos may scatter coherently on the ``nuclear pasta'' since the wavelength of the supernovae neutrinos are comparab... | supernovae neutrino pasta interaction |
the use of smoothed particle magneto hydrodynamics (spmhd) is getting nowadays more and more common in astrophysics. from galaxy clusters to neutron starts, there are multiple applications already existing in the literature. i will review some of the common methods used and highlight the successful approach of using ve... | the magnetic universe through vector potential spmhd simulations |
we propose to continue our successful program to use the observed cooling of the crusts in accreting neutron star systems to probe the properties of ultra-dense matter. those crusts are heated due to the accretion of matter onto neutron stars during the x-ray outburst and after the outbursts are over the crusts should ... | crust cooling of accretion-heated neutron stars |
new-generation x-ray polarimeters currently under development promise to open a new window in the study of high-energy astrophysical sources. among them, neutron stars (nss) appear particularly suited for polarization measurements. radiation from the (cooling) surface of an ns is expected to exhibit a large intrinsic p... | polarization of neutron star surface emission: a systematic analysis |
the cooling of the central compact object (cco) in the cassiopeia a snr is of great importance to neutron star and fundamental physics. different setups and modes of the acis instrument (graded mode full frame and faint mode subbarray) resulted in different results for the measured temperature decay. in april 2015, the... | neutron star cooling and the calibration of the acis graded mode |
black hole-neutron star (bh-ns) mergers are exciting events to model, as they are a source of gravitational waves, like those discovered for the first time by advanced ligo earlier this year. these mergers are also the source of gamma-ray bursts and radioactively powered transients. we present here an outline of our en... | black hole - neutron star merger simulations: precessing binaries with neutrino treatment |
in this work we present new observational data for hafnium (72). hf is an important element that is between the lightest rare-earth elements (e.g., la, z = 57) with elements of the third r-process peak (os, ir, pt, z =76-78). hafnium is the heaviest (z = 72) stable element represented by low-excitation (< 1:5 ev) io... | hafnium abundances in fgk dwarf of galaxtic disk |
colibrì is canada's flagship x-ray observatory, proposed to have multiple aperture x-ray optics with cryogenically cooled transition-edge detectors for achieving high-energy and high-time resolution, as well as high throughput and sensitivity in the 0.1-15 kev range. colibrì is designed to probe the physics of matter u... | colibrì's eyes on neutron stars |
in astrophysical conditions prevalent during the late times of stellar evolution, lepton (e- and e+) emission processes compete with the corresponding lepton capture processes. prior to the collapse, lepton emissions significantly affect the cooling of the core and reduce its entropy. therefore the lepton emission rate... | lepton emission rates of 43-64v isotopes under stellar conditions |
neutron stars are a valuable asset to modern nuclear astrophysics in that they provide a unique environment to study matter under extreme conditions. much of the observational data obtained from neutron stars contains information about the structure and dynamics of the crust. using such observations to measure crust pr... | depth and mass of a neutron star crust |
in this talk we would discuss two-temperature accretion solution onto compact objects. it has been known that, in the two temperature regime, the number of flow variables are more than the number of governing equations. the system of equations are not complete and it admits degenrate solutions for the same set of const... | two temperature solution and emergent spectra from compact objects |
pairing in asymmetric nuclear matter has been studied incorporating the effect of finite total momentum. we employ the generalized cooper eigenvalue equation, which can be used to demonstrate the pairing instability and also generates reasonable pairing gaps compared to the traditional bardeen-cooper-schrieffer (bcs) g... | green's function application for pairing correlations and the optical potential |
a neutron star harbors of order $10^{56}$ electrons in its core, and almost the same number of muons, with muon decay prohibited by pauli blocking. however, as macroscopic properties of the star such as its mass, rotational velocity, or magnetic field evolve over time, the equilibrium lepton abundances (dictated by the... | electron and muon dynamics in neutron stars beyond chemical equilibrium |
neutrino-cooled accretion flow around a black hole, produced by a compact binary merger, is a promising scenario for a short duration gamma ray burst central engine. the turbulence caused by magneto-rotational instability is expected to play an important role in driving accretion and thermal equilibrium of the disk. we... | accretion of the magnetized neutrino-cooled torus on a rotating black hole |
we propose and experimentally demonstrate the generation of enhanced optical springs using the optical kerr effect. a nonlinear optical crystal is inserted into a fabry-perot cavity with a movable mirror, and a chain of second-order nonlinear optical effects in the phase-mismatched condition induces the kerr effect. th... | kerr-enhanced optical spring |
the discrepancy between expected and observed cooling rates of x-ray emitting gas has led to the cooling-flow problem at the cores of clusters of galaxies. a variety of models have been proposed to model the observed x-ray spectra and resolve the cooling-flow problem, which involves heating the cold gas through differe... | cooling+heating flows in galaxy clusters: turbulent heating, spectral modeling, and cooling efficiency |
recent evidence for high masses ($\sim 2~ m_\odot$) pulsars psr j1614-2230 and psr j0348-0432 requires neutron star matter to have a stiff equation of state (eos). the thermal evolution of compact stars (cs) with stiff hadronic eos necessitates the application of the "nuclear medium cooling" scenario with a selection o... | cooling of neutron stars with stiff stellar matter |
the cardinal focus of the present review is to explore the role of neutrinos originating from the ultra-dense core of neutron stars composed of quark gluon plasma in the astrophysical scenario. the collective excitations of the quarks involving the neutrinos through the different kinematical processes have been studied... | astrophysical aspects of neutrino dynamics in ultra-degenerate quark gluon plasma |
the interpretation of observations of cooling neutron star crusts in quasi-persistent x-ray transients is affected by predictions of the strength of neutrino cooling via crust urca processes. the strength of crust urca neutrino cooling depends sensitively on the electron-capture and $\beta$-decay ground-state to ground... | $\\beta$-decay of $^{61}$v and its role in cooling accreted neutron star crusts |
proto-neutron stars forming a few seconds after core-collapse supernovae are hot and dense environments where hyperons can be efficiently produced by weak processes. by making use of various state-of-the-art supernova simulations combined with the proper extensions of the equations of state including λ hyperons, we cal... | supernova constraints on dark flavored sectors |
we present, for the first time, a detailed abundance analysis of the carbon star he 1104$-$0957 based on high resolution (r${\sim}$ 50\,000) spectra. our analysis shows that the object is an extremely metal-poor star with [fe/h] $\sim$ $-$2.96. we find that the object shows enhancement of carbon with [c/fe] $\sim$ 1.82... | peculiar abundances of the cool carbon star he 1104-0957 |
observing the cooling of neutron stars reheated by accretion provides unique insights into neutron star structure. using chandra and xmm-newton we have followed in great detail the cooling of the neutron star transient xte j1701-462, which accreted at near/super-eddington rates for 1.6 years before returning to quiesce... | late-time cooling of the neutron star crust in the super-eddington accretor xte j1701-462 |
the sn1987a in the giant magellanic cloud was an amazing and extraordinary event because it was detected in real time for different neutrinos experiments (νs) around the world. approximate ∼ 25 events were observed in three different experiments: kamiokande ii (kii) ∼ 12, irvine-michigan-brookhaven (imb) ∼ 8 e baksan ∼... | evidence for two neutrino bursts from sn1987a |
the relativistic neutrino emissivity of the nucleonic direct urca processes in neutron star matter are investigated within the relativistic hartree-fock approximation. we study particularly the influences of the tensor couplings of vector mesons $\omega$ and $\rho$ on the nucleonic direct urca processes. it is found th... | effects of the tensor couplings on the nucleonic direct urca processes in neutron star matter |
in 1t-tas2‑xsex, the charge density wave (cdw) state features a star of david lattice that expands across layers as the system becomes commensurate upon cooling. the layers can also order along the c-axis, and different stacking orders have been proposed. using neutron scattering on powder samples, we compared the stac... | suppression of stacking order with doping in 1t-tas2‑xsex |
symbiotic stars are a type of interacting stellar binary system consisting of a hot compact object (typically a white dwarf or sometimes a neutron star) and a cool companion (typically a cool giant star) orbiting around their common center of mass. these objects are generally characterized by orbital periods of 100s to... | interferometric modelling and imaging of the symbiotic binary system, eg andromedae |
double white dwarf (dwd) mergers are relevant astrophysical sources expected to produce massive, highly magnetized white dwarfs (wds), supernovae (sne) ia, and neutron stars (nss). although they are expected to be numerous sources in the sky, their detection has evaded the most advanced transient surveys. this article ... | on the optical transients from double white-dwarf mergers |
we present a study of weak, thermonuclear x-ray bursts from the accreting millisecond x-ray pulsar sax j1808.4-3658. we focus on a burst observed with the neutron star interior composition explorer on 2019 august 9, and describe a similar burst observed with the rossi x-ray timing explorer in 2005 june. these bursts oc... | hydrogen-triggered x-ray bursts from sax j1808.4-3658? the onset of nuclear burning |
studying how the heated crust of a neutron star cools after an accretion outburst provides very valuable information about its structure and the nuclear reactions occurring in a neutron-rich high-density environment. we propose 3 chandra too observations (60 ks in total) and 12 ks supporting swift pointings of the freq... | new progress in understanding the crusts of neutron stars |
we use smoothed particle hydrodynamics to study viscous accretion flows around a weakly magnetic neutron star. we show the formation of multiple ``boundary" layers in presence of both cooling and viscosity. we find that with the introduction of a small viscosity in a sub-keplerian flow, much like the wind accretion in ... | timing properties of shocked accretion flows around neutron stars -- ii. viscous disks and boundary layers |
4u 1608-52 is a soft x-ray transient. the analysis presented here of a particular part of its x-ray activity uses observations of rxte/asm and swift/bat. we show a time segment (mjd 54262-mjd 55090) (828 d) in which 4u 1608-52 behaved as a quasi-persistent x-ray source with a series of bumps, with a complicated relatio... | 4u 1608-52 as a quasi-persistent x-ray source |
the observation of x-rays during quiescence from transiently accreting neutron stars provides unique clues about the nature of dense matter. this, however, requires extensive modeling of the crusts and matching the results to observations. the pycnonuclear fusion reaction rates implemented in these models are theoretic... | impact of pycnonuclear fusion uncertainties on the cooling of accreting neutron star crusts |
the rapid neutron capture process (r-process) is responsible for the production of almost half of the natural elements heavier than iron. in order to obtain reliable calculations of r-process abundances for the models of neutron star merger and other potential astrophysical sites, precise and accurate information about... | accessing the last r-process abundance peak at the n=126 factory through high precision mass measurements |
we propose a new chandra epoch of the radio-quiet x-ray thermal isolated neutron star (xtins) rxj0806.4-4123 to measure its proper motion which will enable a kinematic age study. the kinematic ages of xtinss substantially deviate from their characteristic spin-down ages. since the xtinss allow to measure surface temper... | proper motion of the isolated neutron star rx j0806-4123 |
the q-star structures, also called as gray holes with a radius of two times greater than the corresponding schwarzschild radius of same mass and from the compact neutron star family with a very high density, have been obtained by using a generalization of $q$-deformed fermions with two parameters $q$ and $p$ as the con... | compact q-stars with q,p-deformed fermions |
neutron stars are identified as pulsars, x-ray binary components, central objects of supernovae remnants, or isolated thermally emitting sources and at distances beyond 120 pc. a population extrapolation suggests 103 objects within that boundary. potentially, neutron stars could continuously emit gravitational waves at... | search of nearby resolved neutron stars among optical sources |
some models of gamma-ray bursts (grbs) invoke nascent millisecond magnetars as the central engine and address the x-ray afterglows with the interaction of magnetar magnetospheres with fallback discs. we study the evolution of fallback discs interacting with the millisecond magnetars. initially, the accretion rate in th... | evolution of fallback discs around millisecond magnetars: effect of supercritical accretion on grb afterglows |
the barium (ba) star phenomenon is unmissable from the study and understanding of nucleosynthetic processes occuring in agb stars. ba stars belong to binary systems, where the former agb polluted the companion, a less evolved star, which became enriched with material produced through the slow neuton capture process (s ... | probing the slow neutron capture process in agb stars using barium star abundances |
the 840-kyr-old pulsar psr j1957+5033, detected so far only in γ- and x-rays, is a nearby and rather cool neutron star with a temperature of 0.2-0.3 mk, a distance of $\lesssim 1$kpc, and a small colour reddening excess e(b - v) ≈ 0.03. these properties make it an ideal candidate to detect in the optical to get additio... | likely optical counterpart of the cool middle-aged pulsar j1957+5033 |
novae are semi-detached binary systems in which a cool star fills its roche lobe. material from the cool star (the secondary) flows through the inner lagrangian point and is deposited onto the surface of a white dwarf (wd) via an accretion disc. in time, the base of the accreted layer becomes degenerate, and a thermonu... | synoptic optical/uv studies of recent recurrent novae – insights from déjá vu |
in the present work, we investigate the neutral-current neutrino-nucleon scattering in the nuclear medium using various energy-density functional models such as kids (korea-ibs-daegu-skku) and sly4, together with the quark-meson coupling model for the nucleon form factors at finite density. the differential cross-secti... | neutrino propagation in the neutron star with uncertainties from nuclear, hadron, and particle physics |
it seems that the wealth of information revealed by the multi-messenger observations of the binary neutron star (ns) merger event, gw170817/grb 170817a/kilonova at2017gfo, places irreconcilable constraints to models of the prompt emission of this gamma-ray burst (grb). the observed time delay between the merger of the ... | revise thermal winds of remnant neutron stars in gamma-ray bursts |
the role of electron captures by nuclei in the shallow heating of magnetars is further investigated using both nuclear measurements and the theoretical atomic mass table hfb-27. starting from the composition of the outer crust in full equilibrium, we have calculated the onset of electron captures and the heat released ... | internal heating in magnetars: role of electron captures |
superbursts of neutron stars are rare but powerful events explained by the explosive burning of carbon in the deep layers of the outer envelope of the star. in this paper we perform a simulation of superbursts and propose a simple method for describing the neutrino stage of their cooling, as well as a method for descri... | neutrino emission of neutron-star superbursts |
statistical methods are frequently built upon assumptions that limit their applicability to certain problems and conditions. failure to recognize these limitations can lead to conclusions that may be inaccurate or biased. an example of such methods is the non-parametric efron-petrosian test statistic used in the studie... | how unbiased statistical methods lead to biased scientific discoveries: a case study of the efron-petrosian statistic applied to the luminosity-redshift evolution of gamma-ray bursts |
there are still some significant and unanswered questions about the incredible very-high-energy γ -ray signatures. to help understand the mechanism, focusing on the linear and quadratic perturbation mode for the subluminal regime, we revisit the expected signature for the lorentz invariance violation (liv) effects on γ... | expected signature for the lorentz invariance violation effects on γ -γ absorption |
this manuscript presents a diagnostic analysis of three dark energy models resulting from the parametrization of the deceleration parameter. these models exhibit intriguing features, including late-time acceleration and a cosmological phase transition from early deceleration to late acceleration. the analysis utilizes ... | diagnostic and comparative analysis of dark energy models with $q(z)$ parametrizations |
we report the radiation damage results of two new types of multi-pixel photon counter (mppc) under the 200 mev proton beam, for cosmic gamma-ray observations with cubesats. the new mppcs, s13360-6050cs and s14160-6050hs, have recently become commercially available by hamamatsu photonics k.k. (hpk). after 100 rad irradi... | annealing of proton radiation damages in si-pm at room temperature |
the correlation between the peak spectra energy (ep) and the equivalent isotropic energy (eiso) of long gamma-ray bursts (grbs), the so-called amati relation, is often used to constrain the high-redshift hubble diagram. assuming lambda cold dark matter cosmology, g.-j. wang et al. [astrophys. j. 836, 103 (2017), 10.384... | reconciling low and high redshift grb luminosity correlations |
neutron star mergers are cosmic catastrophes that produce some of the most energetic observed phenomena: short gamma-ray bursts, gravitational wave signals, and kilonovae. the latter are optical transients, powered by radioactive nuclides which are synthesized when the neutron-rich ejecta of a disrupted neutron star un... | realistic kilonova up close |
we present a catalog of the redshift estimates and probability distributions for 1366 individual long-duration gamma-ray bursts (lgrbs) detected by the burst and transient source experiment (batse). this result is based on a careful classification and modeling of the population distribution of batse lgrbs in the 5-dime... | a catalog of redshift estimates for 1366 batse long-duration gamma-ray bursts: evidence for strong selection effects on the phenomenological prompt gamma-ray correlations |
baryon acoustic oscillations (bao) datasets use very precise measurements of the spatial distribution of large-scale structures as a distance ladder to help constrain cosmological parameters. in a recent article,1 we combined 17 uncorrelated bao measurements in the effective redshift range 0.106 ≤ z ≤ 2.36 with the cos... | hints for the h0 — rd tension in uncorrelated baryon acoustic oscillations dataset |
the dispersion of fast radio bursts (frbs) is a measure of the large-scale electron distribution. it enables measurements of cosmological parameters, especially of the expansion rate and the cosmic baryon fraction. the number of events is expected to increase dramatically over the coming years, and of particular intere... | cosmological covariance of fast radio burst dispersions |
aims: long gamma-ray bursts (lgrbs) have been shown to be powerful probes of the universe, in particular for studying the star formation rate up to very high redshift (z ∼ 9). since lgrbs are produced by only a small fraction of massive stars, it is paramount to have a good understanding of their underlying intrinsic p... | constraining the intrinsic population of long gamma-ray bursts: implications for spectral correlations, cosmic evolution, and their use as tracers of star formation |
in this work, we use the angular diameter distances of 38 galaxy clusters with joint x-ray/sze observation to circumvent the circularity problem in the amati relation for gamma-ray bursts (grbs). assuming the validity of cosmic-distance duality relation, we obtain the luminosity distance from the cluster angular diamet... | low redshift calibration of the amati relation using galaxy clusters |
in this work, we restudy the dependence of luminosity function and event rates for different gamma-ray burst samples on the criteria of sample selection and threshold effect. to compare with many previous studies, we have chosen two samples including 88 and 118 long bursts with known redshift and peak flux over 2.6 ph ... | a comparative study of luminosity functions and event rate densities of long grbs with non-parametric method |
in this paper, we investigate the energy function, formation rate, and environment of fast radio bursts (frbs) using parkes sample and australian square kilometer array pathfinder (askap) sample. for the first time, the metallicity effect on the formation rate is considered. if frbs are produced by the mergers of compa... | energy function, formation rate, and low-metallicity environment of fast radio bursts |
we perform zoom-in cosmological simulations of a suite of dwarf galaxies, examining the impact of cosmic rays (crs) generated by supernovae, including the effect of diffusion. we first look at the effect of varying the uncertain cr parameters by repeatedly simulating a single galaxy. then we fix the comic ray model and... | cosmological simulations of dwarf galaxies with cosmic ray feedback |
the delay in arrival times between high and low energy photons from cosmic sources can be used to test the violation of the lorentz invariance (liv), predicted by some quantum gravity theories, and to constrain its characteristic energy scale eqg that is of the order of the planck energy. gamma-ray bursts (grbs) and bl... | limits on quantum gravity effects from swift short gamma-ray bursts |
we investigate the possibilities of reconstructing the cosmic equation of state (eos) for high redshift. in order to obtain general results, we use two model-independent approaches. the first reconstructs the eos using comoving distance and the second makes use of the hubble parameter data. to implement the first metho... | reconstruction of the cosmic equation of state for high redshift |
the cosmic evolution of gamma-ray burst (grb) luminosity is essential for revealing the grb physics and for using grbs as cosmological probes. we investigate the luminosity evolution of long grbs with a large sample of 258 swift/bat grbs. by describing the peak luminosity evolution of individual grbs as {l}{{p}}\propto... | cosmic evolution of long gamma-ray burst luminosity |
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