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we report ab initio calculations of the s wave pairing gap in neutron matter calculated using realistic nuclear hamiltonians that include two- and three-body interactions. we use a trial state, properly optimized to capture the essential pairing correlations, from which we extract ground state properties by means of au... | the 1s0 pairing gap in neutron matter |
we model the thermal states of both isolated neutron stars and accreting neutron stars in x-ray transients in quiescence and confront them with observations. we use an equation of state calculated using realistic two-body and three-body nucleon interactions, and superfluid nucleon gaps obtained using the same microscop... | thermal states of neutron stars with a consistent model of interior |
accreting neutron stars (nss) are one of the main targets for continuous gravitational wave searches, as asymmetric accretion may lead to quadrupolar deformations, or `mountains', on the crust of the star, which source gravitational wave (gw) emission at twice the rotation frequency. the gw torque may also impact on th... | asymmetric accretion and thermal `mountains' in magnetized neutron star crusts |
neutron star models with maximum mass close to 2 m⊙ reach high central densities, which may activate nucleonic and hyperon direct urca neutrino emission. to alleviate the tension between fast theoretical cooling rates and thermal luminosity observations of moderately magnetized, isolated thermally emitting stars (with ... | fast cooling and internal heating in hyperon stars |
recent observations have found several candidates for old warm neutron stars whose surface temperatures are above the prediction of the standard neutron star cooling scenario, and, thus, require some heating mechanism. motivated by these observations, we study the non-equilibrium beta process in the minimal cooling sce... | cooling theory faced with old warm neutron stars: role of non-equilibrium processes with proton and neutron gaps |
the neutron-proton effective mass splitting in neutron-rich nucleonic matter reflects the spacetime nonlocality of the isovector nuclear interaction. it affects the neutron/proton ratio during the earlier evolution of the universe, cooling of proto-neutron stars, structure of rare isotopes and dynamics of heavy-ion col... | neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions |
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 |
we report on a spectroscopic analysis of the x-ray emission from igr j17062-6143 in the aftermath of its 2020 june intermediate duration type i x-ray burst. using the neutron star interior composition explorer, we started observing the source 3 hr after the burst was detected with the monitor of all-sky x-ray image gas... | on the impact of an intermediate duration x-ray burst on the accretion environment in igr j17062-6143 |
the dissipation of intense crustal electric currents produces high joule heating rates in cooling neutron stars. here, it is shown that joule heating can counterbalance fast cooling, making it difficult to infer the presence of hyperons (which accelerate cooling) from measurements of the observed thermal luminosity lγ.... | thermal luminosity degeneracy of magnetized neutron stars with and without hyperon cores |
we study the timing and spectral properties of the low-magnetic field, transient magnetar swift j1822.3-1606 as it approached quiescence. we coherently phase-connect the observations over a time-span of ∼500 d since the discovery of swift j1822.3-1606 following the swift-burst alert telescope (bat) trigger on 2011 july... | the outburst decay of the low magnetic field magnetar swift j1822.3-1606: phase-resolved analysis and evidence for a variable cyclotron feature |
we study the effects of strangeness on the quark sector of a hybrid-star equation of state. since the model we use to describe quarks is the same as the one we use to describe hadrons, we can also study the effects of strangeness on the chiral symmetry restoration and deconfinement phase transitions (first order or cro... | role of strangeness in hybrid stars and possible observables |
thermonuclear x-ray bursts from accreting neutron stars power brief but strong irradiation of their surroundings, providing a unique way to study accretion physics. we analyze maxi/gas slit camera and swift/xrt spectra of a day-long flash observed from igr j17062-6143 in 2015. it is a rare case of recurring bursts at a... | x-ray reflection and an exceptionally long thermonuclear helium burst from igr j17062-6143 |
crustal cooling of accretion-heated neutron stars provides insight into the stellar interior of neutron stars. the neutron star x-ray transient, ks 1731-260, was in outburst for 12.5 years before returning to quiescence in 2001. we have monitored the cooling of this source since then through chandra and xmm-newton obse... | the thermal state of ks 1731-260 after 14.5 years in quiescence |
the presence of superfluidity in neutron star interiors can affect the cooling of neutron stars in intricate ways, enhancing certain mechanisms and suppressing others. model calculations employing realistic nuclear potentials in bardeen-cooper-schrieffer theory generally suggest the development of a 3p2-3f2 pairing gap... | triplet pairing in neutron matter |
with our neutron star crust cooling code nscool, we track the thermal evolution of the neutron star in aql x-1 over the full accretion outburst history from 1996 until 2015. for the first time, we model many outbursts (23 outbursts were detected) collectively and in great detail. this allows us to investigate the influ... | a cooling neutron star crust after recurrent outbursts: modelling the accretion outburst history of aql x-1 |
we present the detection of 51 thermonuclear x-ray bursts observed from 4u 1636-536 by the neutron star interior composition explorer (nicer) over the course of a 3 yr monitoring campaign. we perform time-resolved spectroscopy for 40 of these bursts and show the existence of a strong soft excess in all the burst spectr... | burst-disk interaction in 4u 1636-536 as observed by nicer |
context. the possible presence of amorphous and heterogeneous phases in the inner crust of a neutron star is expected to reduce the electrical conductivity of the crust, potentially with significant consequences on the magneto-thermal evolution of the star. in cooling simulations, the disorder is quantified by an impur... | inner crust of a neutron star at the point of crystallization in a multicomponent approach |
the korea-ibs-daegu-skku energy density functional (kids-edf) models, constructed from the perturbative expansion of the energy density in nuclear matter, have been successfully and widely applied in describing the properties of finite nuclei and infinite nuclear matter. in the present work, we extend the applications ... | effect of nucleon effective mass and symmetry energy on the neutrino mean free path in a neutron star |
we derive analytic approximations for the neutrino luminosities and the heat capacities of neutron stars with isothermal nucleon cores as functions of the mass and radius of stars. the neutrino luminosities are approximated for the three basic neutrino emission mechanisms, and the heat capacities for the five basic com... | neutrino luminosities and heat capacities of neutron stars in analytic form |
strong magnetic fields in the magnetospheres of neutron stars (nss) (especially magnetars) and other astrophysical objects may release their energy in violent, intense episodes of magnetic reconnection. while reconnection has been studied extensively, the extreme field strength near nss introduces new effects: radiatio... | bright gamma-ray flares powered by magnetic reconnection in qed-strength magnetic fields |
the thermal evolution of hypernuclear compact stars is studied for stellar models constructed on the basis of covariant density functional theory in hartree and hartree-fock approximation. parametrizations of both types are consistent with the astrophysical mass constraints on compact stars and available hypernuclear d... | cooling of hypernuclear compact stars: hartree-fock models and high-density pairing |
we examine the gravitational wave frequencies from neutron stars during thermal evolution, adopting the relativistic cowling approximation. we particularly focus on the neutron star models, in which the direct urca (rapid cooling process) does not work, without the superfluidity and superconductivity. for such models, ... | gravitational wave asteroseismology on cooling neutron stars |
high luminosity accretion on to a strongly magnetized neutron star results in a radiation pressure dominated, magnetically confined accretion column. we investigate the dynamics of these columns using 2d radiative relativistic magnetohydrodynamic simulations, restricting consideration to modest accretion rates where th... | radiative relativistic magnetohydrodynamic simulations of neutron star column accretion in cartesian geometry |
aims: in this work, we study the structure of neutron stars under the effect of a poloidal magnetic field and determine the limiting largest magnetic field strength that induces a deformation such that the ratio between the polar and equatorial radii does not exceed 2%. we consider that, under these conditions, the des... | limiting magnetic field for minimal deformation of a magnetized neutron star |
the existence of superfluidity of the neutron component in the core of a neutron star, associated specifically with triplet p-wave pairing, is currently an open question that is central to interpretation of the observed cooling curves and other neutron-star observables. ab initio theoretical calculations aimed at resol... | three-nucleon forces and triplet pairing in neutron matter |
aql x-1 is a prolific transient neutron star low-mass x-ray binary that exhibits an accretion outburst approximately once every year. whether the thermal x-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. in this work,... | constraining the properties of neutron star crusts with the transient low-mass x-ray binary aql x-1 |
type-i x-ray burst oscillations are powered by thermonuclear energy released on the neutron star (ns) surface in low-mass x-ray binaries (lmxbs), where the burst oscillation frequencies are close to the ns spin rates. in this work, we report the detection of oscillation at 584.65 hz during the cooling tail of type-i x-... | discovery of a 584.65 hz burst oscillation in the low-mass x-ray binary 4u 1730-22 |
binary neutron star mergers are believed to eject significant masses with a diverse range of velocities. once these ejected materials begin to be decelerated by a homogeneous medium, relativistic electrons are mainly cooled down by synchrotron radiation, generating a multiwavelength long-lived afterglow. analytic and n... | light curves of a shock-breakout material and a relativistic off-axis jet from a binary neutron star system |
using a theoretical model, we track the thermal evolution of a cooling neutron star crust after an accretion-induced heating period with the goal of constraining the crustal parameters. we present for the first time a crust cooling model - nscool - that takes into account detailed variability during the full outburst b... | neutron star crust cooling in ks 1731-260: the influence of accretion outburst variability on the crustal temperature evolution |
context. it is thought that ultraluminous x-ray sources (ulxs) are mainly powered by super-eddington accreting neutron stars or black holes as shown by the recent discovery of x-ray pulsations and relativistic winds.aims: this work presents a follow-up study of the spectral evolution over two decades of the pulsing ulx... | broadband x-ray spectral variability of the pulsing ulx ngc 1313 x-2 |
the x-ray binary 4u 1954+31 has been classified as a low-mass x-ray binary containing an m giant and a neutron star (ns). it has also been included in the rare class of x-ray symbiotic binaries. the gaia parallax, infrared colors, spectral type, abundances, and orbital properties of the m star demonstrate that the cool... | the m supergiant high-mass x-ray binary 4u 1954+31 |
the radio pulsar gleam-x j162759.5-523504.3 has an extremely long spin period ($p = 1091.17\, \mbox{s}$), and yet seemingly continues to spin-down rapidly ($\dot{p} < 1.2 \times 10^{-9}\, \mbox{ss}^{-1}$). the magnetic field strength that is implied, if the source is a neutron star undergoing magnetic dipole braking... | evolutionary implications of a magnetar interpretation for gleam-x j162759.5-523504.3 |
the study of transiently accreting neutron stars provides a powerful means to elucidate the properties of neutron star crusts. we present extensive numerical simulations of the evolution of the neutron star in the transient low-mass x-ray binary maxi j0556-332. we model nearly 20 observations obtained during the quiesc... | a "hyperburst" in the maxi j0556-332 neutron star: evidence for a new type of thermonuclear explosion |
in this work i briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. in particular, i revise the problem of the strong softening of the eos, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing an... | hyperons in neutron stars |
young pulsars are thought to be highly magnetized neutron stars (nss). the crustal magnetic field of a ns usually decays at different timescales in the forms of hall drift and ohmic dissipation. the magnetization parameter ωbτ is defined as the ratio of the ohmic timescale τohm to the hall drift timescale τhall. during... | estimation of electrical conductivity and magnetization parameter of neutron star crusts and applied to the high-braking-index pulsar psr j1640-4631 |
upgrades to improve the sensitivity of gravitational wave detectors enable more frequent detections and more precise source parameter estimation. unlike other advanced interferometric detectors such as advanced ligo and advanced virgo, kagra requires a different approach for the upgrade since it is the only detector wh... | prospects for improving the sensitivity of the cryogenic gravitational wave detector kagra |
monitoring the cooling of neutron-star crusts heated during accretion outbursts allows us to infer the physics of the dense matter present in the crust. we examine the crust cooling evolution of the low-mass x-ray binary mxb 1659-29 up to ∼505 days after the end of its 2015 outburst (hereafter outburst ii) and compare ... | consistent accretion-induced heating of the neutron-star crust in mxb 1659-29 during two different outbursts |
we report results obtained from the study of 12 thermonuclear x-ray bursts in six astrosat observations of a neutron star x-ray binary and well-known x-ray burster, 4u 1636 - 536. burst oscillations (bos) at ~ 581 hz are observed with 4-5σ confidence in three of these x-ray bursts. the rising phase bos show a decreasin... | thermonuclear x-ray bursts from 4u 1636 - 536 observed with astrosat |
after 15 yr, in late 2018, the magnetar xte j1810-197 underwent a second recorded x-ray outburst event and reactivated as a radio pulsar. we initiated an x-ray monitoring campaign to follow the timing and spectral evolution of the magnetar as its flux decays using swift, xmm-newton, nustar, and nicer observations. duri... | the x-ray evolution and geometry of the 2018 outburst of xte j1810-197 |
the role of a strong magnetic field on the neutron-drip transition in the crust of a magnetar is studied. the composition of the crust and the neutron-drip threshold are determined numerically for different magnetic field strengths using the experimental atomic mass measurements from the 2012 atomic mass evaluation com... | role of landau quantization on the neutron-drip transition in magnetar crusts |
experiments aimed at detecting ultralight dark matter typically rely on resonant effects, which are sensitive to the dark matter mass that matches the resonance frequency. in this study, we investigate the nucleon couplings of ultralight axion dark matter using a magnetometer operating in a nuclear magnetic resonance (... | constraining ultralight dark matter through an accelerated resonant search |
nscool is a 1d (i.e., spherically symmetric) neutron star cooling code written in fortran 77. the package also contains a series of eoss (equation of state) to build stars, a series of pre-built stars, and a tov (tolman- oppenheimer-volkoff) integrator to build stars from an eos. it can also handle "strange stars" that... | nscool: neutron star cooling code |
we study the thermal evolution of isolated neutron stars in scalar-tensor theories for the first time. whether rapid cooling due to the direct urca process occurs or not is an interesting question from the viewpoint of the temperature observation of isolated neutron stars. moreover, investigation of the cooling effect ... | neutron star cooling in modified gravity theories |
context. proto-neutron stars are born hot, with temperatures exceeding a few times 1010 k. in these conditions, the crust of the proto-neutron star is expected to be made of a coulomb liquid and composed of an ensemble of different nuclear species.aims: in this work, we perform a study of the beta-equilibrated proto-ne... | the proto-neutron star inner crust in a multi-component plasma approach |
we analyse the origin of the magnetic field decay in normal radio pulsars found by us in a recent study. this decay has a typical time scale ∼ 4 × 105 yr and operates in the range ∼ 105 - few × 105 yr. we demonstrate that this field evolution may be either due to the ohmic decay related to the scattering from phonons, ... | magnetic field decay in normal radio pulsars |
motivated by the various theoretical studies regarding the efficient capturing of dark matter by neutron stars, we explore the possible indirect effects of captured dark matter on the cooling mechanism of a neutron star. the equation of states for different configurations of dark matter admixed star at finite temperatu... | thermal relaxation of dark matter admixed neutron star |
a review of fission product release theory is presented in support of fuel-failure monitoring analysis for the characterization and location of defective fuel. this work is used to describe: (i) the development of the steady-state visual_detect code for coolant activity analysis to characterize failures in the core and... | fission product release modelling for application of fuel-failure monitoring and detection - an overview |
using a model for the equation of state and composition of dense matter and the magnitude of singlet proton superconductivity and triplet neutron superfluidity, we perform the first simultaneous fit of neutron star masses and radii determined from observations of quiescent low-mass x-ray binaries and luminosities and a... | simultaneous fitting of neutron star structure and cooling data |
the inner crust of a mature neutron star is composed of an elastic lattice of neutron-rich nuclei penetrated by free neutrons. these neutrons can flow relative to the crust once the star cools below the superfluid transition temperature. in order to model the dynamics of this system, which is relevant for a range of pr... | the dynamics of neutron star crusts: lagrangian perturbation theory for a relativistic superfluid-elastic system |
supercritical accretion onto compact objects may drive massive winds that are nearly spherical, optically thick, and eddington limited. blackbody emission from the photosphere is the direct observational signature of the wind. here we investigate whether or not it can explain the soft emission component seen in the ene... | linking soft excess in ultraluminous x-ray sources with optically thick wind driven by supercritical accretion |
1rxs j180408.9-342058 is a low-mass x-ray binary hosting a neutron star, which shows x-ray activity at very different mass-accretion regimes, from very faint to almost the eddington luminosity. in this work, we present a comprehensive x-ray study of this source using data from the neil gehrels swift observatory, nustar... | new insights on the puzzling lmxb 1rxs j180408.9-342058: the intermediate state, the clocked type-i x-ray bursts, and much more |
timing observations of rapidly rotating neutron stars revealed a great number of glitches, observed from both canonical radio pulsars and magnetars. among them, 76 glitches have shown exponential relaxation(s) with characteristic decay times ranging from several days to a few months, followed by a more gradual recovery... | post-glitch exponential relaxation of radio pulsars and magnetars in terms of vortex creep across flux tubes |
the transient neutron star (ns) low-mass x-ray binary maxi j0556-332 provides a rare opportunity to study ns crust heating and subsequent cooling for multiple outbursts of the same source. we examine maxi, swift, chandra, and xmm-newton data of maxi j0556-332 obtained during and after three accretion outbursts of diffe... | different accretion heating of the neutron star crust during multiple outbursts in maxi j0556-332 |
context. measuring the abundances of neutron-capture elements in galactic disk stars is an important part of understanding key stellar and galactic processes. in the optical wavelength regime a number of different neutron-capture elements have been measured; however, only the s-process-dominated element cerium has been... | chemical evolution of ytterbium in the galactic disk |
pulsar-like compact stars provide us a unique laboratory to explore properties of dense matter at supra-nuclear densities. one of the models for pulsar-like stars is that they are totally composed of "strangeons", and in this paper, we studied the pulsar glitches in a strangeon star model. strangeon stars would be soli... | pulsar glitches in a strangeon star model |
the be/x-ray transients v0332+53 and 4u 0115+63 exhibited giant, type-ii outbursts in 2015. here we present swift/xrt follow-up observations at the end of those outbursts. surprisingly, the sources did not decay back to their known quiescent levels but stalled at a (slowly decaying) meta-stable state with luminosities ... | meta-stable low-level accretion rate states or neutron star crust cooling in the be/x-ray transients v0332+53 and 4u 0115+63 |
the first hours following a neutron star merger are considered to provide several ultraviolet (uv)/optical/near-infrared signals: β-decay emission from free neutrons, radioactive decay of shocked heavy elements in the cocoon and cocoon's cooling emission. here, we consider two additional emission sources: β-decay of fr... | electromagnetic signals from the decay of free neutrons in the first hours of neutron star mergers |
background: in order to study structure of protoneutron stars and those in subsequent cooling stages, it is of great interest to calculate inhomogeneous hot and cold nuclear matter in a variety of phases. the finite-temperature hartree-fock-bogoliubov (ft-hfb) theory is a primary choice for this purpose; however, its n... | coordinate-space solver for finite-temperature hartree-fock-bogoliubov calculations using the shifted krylov method |
previous research centered on the hydrodynamics in x-ray pulsar accretion columns has largely focused on the single-fluid model, in which the super-eddington luminosity inside the column decelerates the flow to rest at the stellar surface. this type of model has been relatively successful in describing the overall prop... | a new two-fluid radiation-hydrodynamical model for x-ray pulsar accretion columns |
recently, parthsarathy et al. analysed long-term timing observations of 85 young radio pulsars. they found that 15 objects have absolute values of braking indices ranging ∼10-3000, far from the classical value n = 3. they also noted a mild correlation between measured value of n and characteristic age of a radio pulsar... | braking indices of young radio pulsars: theoretical perspective |
thermal evolution of neutron stars (nss) is studied as a probe of physics beyond the standard model. we first review the standard cooling theory of nss in detail, with an emphasis on the roles of nucleon superfluidity. then we discuss non-standard evolution with axion and dark matter (dm); axion production enhances the... | thermal evolution of neutron stars as a probe of physics beyond the standard model |
we consider the local dynamics of a realistic neutron-star core, including composition gradients, superfluidity and thermal effects. the main focus is on the gravity g-modes, which are supported by composition stratification and thermal gradients. we derive the equations that govern this problem in full detail, paying ... | buoyancy and g-modes in young superfluid neutron stars |
observational evidence has been accumulating that thermonuclear x-ray bursts ignited on the surface of neutron stars influence the surrounding accretion flow. here, we exploit the excellent sensitivity of nustar up to 79 kev to analyse the impact of an x-ray burst on the accretion emission of the neutron star lmxb 4u 1... | probing the effects of a thermonuclear x-ray burst on the neutron star accretion flow with nustar |
aims: integral has been monitoring the galactic center region for more than a decade. over this time it has detected hundreds of type-i x-ray bursts from the neutron star low-mass x-ray binary 4u 1728-34, also known as the slow burster. our aim is to study the connection between the persistent x-ray spectra and the x-r... | x-ray burst-induced spectral variability in 4u 1728-34 |
the theory of quasi-spherical subsonic accretion onto magnetized rotating neutron star is reviewed. different regimes of quasi-spherical accretion onto a neutron star: supersonic (bondi) accretion, which takes place when the captured matter cools down rapidly and falls supersonically towards the neutron-star magnetosph... | wind accretion - observations vs theory |
we report on the aftermath of a magnetar outburst from the young, high magnetic field radio pulsar psr j1119-6127 that occurred on 2016 july 27. we present the results of a monitoring campaign using the neil gehrels swift x-ray telescope, nustar, and xmm-newton. after reaching a peak absorbed 0.5-10 kev flux of {45}-7+... | the 2016 outburst of psr j1119-6127: cooling and a spin-down-dominated glitch |
we model neutron star cooling, in particular the current rapid cooldown of the neutron star cas a, with a microscopic nuclear equation of state featuring strong direct urca processes and using compatible nuclear pairing gaps as well as effective masses. several scenarios are possible to explain the features of cas a, b... | cassiopeia a and direct urca cooling |
we here present a new version of the publicly available general relativistic magnetohydrodynamic (grmhd) code spritz, which now includes an approximate neutrino leakage scheme able to handle neutrino cooling and heating. the leakage scheme is based on the publicly available zelmanileak code, with a few modifications in... | spritz: general relativistic magnetohydrodynamics with neutrinos |
neutron stars cool down during their lifetime through the combination of neutrino emission from the interior and photon cooling from the surface. strongly magnetized neutron stars, called magnetars, are no exception, but the effect of their strong fields adds further complexities to the cooling theory. besides other fa... | how bright can old magnetars be? assessing the impact of magnetized envelopes and field topology on neutron star cooling |
recent observations of old warm neutron stars suggest the presence of a heating source in these stars, requiring a paradigm beyond the standard neutron-star cooling theory. in this work, we study the scenario where this heating is caused by the friction associated with the creep motion of neutron superfluid vortex line... | vortex creep heating in neutron stars |
social insects host a diversity of viruses. we examined new zealand populations of the globally widely distributed invasive argentine ant (linepithema humile) for rna viruses. we used metatranscriptomic analysis, which identified six potential novel viruses in the dicistroviridae family. of these, three contigs were co... | single-stranded rna viruses infecting the invasive argentine ant, linepithema humile |
aims: we aim to study the possibility of a hadron-quark phase transition in the interior of neutron stars, taking into account different schematic evolutionary stages at finite temperature. we also discuss the strange quark matter stability in the quark matter phase. furthermore, we aim to analyze the astrophysical pro... | constant entropy hybrid stars: a first approximation of cooling evolution |
we model neutron star cooling with several microscopic nuclear equations of state based on different nucleon-nucleon interactions and three-body forces, and compatible with the recent gw170817 neutron star merger event. they all feature strong direct urca processes. we find that all models are able to describe well the... | neutron star cooling with microscopic equations of state |
we present the mass excesses of 52-57sc, obtained from recent time-of-flight nuclear mass measurements at the national superconducting cyclotron laboratory at michigan state university. the masses of 56sc and 57sc were determined for the first time with atomic mass excesses of -24.85 (59 )(-54+0) mev and -21.0 (1.3 ) m... | mass measurement of 56sc reveals a small a =56 odd-even mass staggering, implying a cooler accreted neutron star crust |
we investigate the impacts of the neutrino cooling mechanism inside the neutron star (ns) core on the light curves of type i x-ray bursts and x-ray superbursts. from several observations of ns thermal evolution, physical processes of fast neutrino cooling, such as the direct urca (du) process, are indicated. they signi... | impacts of the direct urca and superfluidity inside a neutron star on type i x-ray bursts and x-ray superbursts |
we report detailed x-ray observations of the unique binary system ϵ lupi, the only known short-period binary consisting of two magnetic early-type stars. the components have comparably strong, but anti-aligned magnetic fields. the orbital and magnetic properties of the system imply that the magnetospheres overlap at al... | discovery of extraordinary x-ray emission from magnetospheric interaction in the unique binary stellar system ϵ lupi |
several candidates for accreting magnetars have been proposed recently by different authors. existence of such systems contradicts the standard magnetic field decay scenario where a large magnetic field of a neutron star reaches ≲a few ×1013 g at ages ≳1 myr. among other sources, the high-mass x-ray binary 4u 0114+65 s... | how to make a mature accreting magnetar |
millisecond pulsars (msps) are old, fast spinning neutron stars (nss) thought to have evolved from classical pulsars in binary systems, where the rapid rotation is caused by the accretion of matter and angular momentum from their companion. during this transition between classical and msps, there is a magnetic field re... | on the weak magnetic field of millisecond pulsars: does it decay before accretion? |
whether fast cooling processes occur or not is crucial for the thermal evolution of neutron stars. in particular, the threshold of the direct urca process, which is one of the fast cooling processes, is determined by the interior proton fraction y_p, or the nuclear symmetry energy. since recent observations indicate th... | possibility of rapid neutron star cooling with a realistic equation of state |
type i x-ray bursts are thermonuclear flashes observed from the surfaces of accreting neutron stars (nss) in low mass x-ray binaries. oscillations have been observed during the rise and/or decay of some of these x-ray bursts. those seen during the rise can be well explained by a spreading hot spot model, but large ampl... | x-ray burst oscillations: from flame spreading to the cooling wake |
<p id="par1">nuclear-powered x-ray millisecond pulsars are the third type of millisecond pulsars, which are powered by thermonuclear fusion processes. the corresponding brightness oscillations, known as burst oscillations, are observed during some thermonuclear x-ray bursts, when the burning and cooling accreted ... | nuclear-powered x-ray millisecond pulsars |
in this paper, we investigate the cooling of neutron stars with relativistic and nonrelativistic models of dense nuclear matter. we focus on the effects of uncertainties originated from the nuclear models, the composition of elements in the envelope region, and the formation of superfluidity in the core and the crust o... | nuclear equation of state and neutron star cooling |
in view of new constraints put forth by recent observations and measurements in the realm of astrophysics and nuclear physics, we update the nonlinear realization of the σ model as to reflect such constraints. by doing this, we obtain new equations of state that may be used to describe neutron stars. such equations of ... | reconciling nuclear and astrophysical constraints |
we present a modification of our previous model for the mechanisms underlying the glitch phenomena in pulsars and young neutron stars. accordingly, pulsars are born with embryonic cores comprising of purely incompressible superconducting gluon-quark superfluid (henceforth susu-cores). as the ambient medium cools and sp... | glitching pulsars: unraveling the interactions of general relativistic and quantum fields in the strong field regimes |
short range correlations (src) have been known to be an important aspect of nuclear theory for some time. recent works have re-ignited interest on this topic, particularly due to the fact that it has recently been demonstrated that src may be responsible for breaking pairing gaps in nuclear matter. in this work we revi... | short-range correlation effects on the neutron star cooling |
an ambitious goal of the astrophysical community is not only to constrain the equation of state (eos) of neutron star (ns) matter by confronting it with astrophysics observations, but ultimately also to infer the ns composition. nevertheless, the composition of the ns core is likely to remain uncertain unless we have a... | inferring the nuclear symmetry energy at suprasaturation density from neutrino cooling |
we discuss the observation that under neutron star conditions of charge neutrality and $\beta-$equilibrium the contribution from the symmetry energy to the equation of state (eos) follows a universal behaviour. we call this behaviour the conjecture of a universal symmetry energy contribution (usec). we find that an use... | universal symmetry energy contribution to the neutron star equation of state |
the interior of mature neutron stars is expected to contain superfluid neutrons and superconducting protons. the influence of temperature and currents on superfluid properties is studied within the self-consistent time-dependent nuclear energy-density functional theory. we find that this theory predicts the existence o... | gapless superfluidity in neutron stars: thermal properties |
context. neutron stars in low-mass binary systems are subject to accretion when material originating from the companion star accumulates on the surface. in most cases, the justified and common assumption in studying the properties of the neutron star crust is the fully accreted crust approximation. however, observation... | partially accreted crusts of neutron stars |
we study the s10 proton pairing gap in β -equilibrated neutron star matter within the framework of chiral effective field theory. we focus on the role of three-body forces, which strongly modify the effective proton-proton spin-singlet interaction in dense matter. we find that three-body forces generically reduce both ... | proton pairing in neutron stars from chiral effective field theory |
a superconductor of paired protons is thought to form in the core of neutron stars soon after their birth. minimum energy conditions suggest magnetic flux is expelled from the superconducting region due to the meissner effect, such that the neutron star core is largely devoid of magnetic fields for some nuclear equatio... | dynamical onset of superconductivity and retention of magnetic fields in cooling neutron stars |
we model the cooling of hybrid neutron stars combining a microscopic nuclear equation of state in the brueckner-hartree-fock approach with different quark models. we then analyse the neutron star cooling curves predicted by the different models and single out the preferred ones. we find that the possibility of neutron ... | cooling of hybrid neutron stars with microscopic equations of state |
we use two-dimensional, general relativistic, viscous, radiation hydrodynamic simulations to study the impact of a type i x-ray burst on a hot and geometrically thick accretion disk surrounding an unmagnetized, non-rotating neutron star. the disk is initially consistent with a system in its low/hard spectral state, and... | simulating the collapse of a thick accretion disk due to a type i x-ray burst from a neutron star |
geometry and dynamical structure of emission regions in accreting pulsars are shaped by the interplay between gravity, radiation, and strong magnetic field, which significantly affects the opacities of a plasma and radiative pressure under such extreme conditions. quantitative consideration of magnetic plasma opacities... | mean opacities of a strongly magnetized high-temperature plasma |
neutron stars in low-mass x-ray binaries exhibit oscillations during thermonuclear bursts, attributed to asymmetric brightness patterns on the burning surfaces. all models that have been proposed to explain the origin of these asymmetries (spreading hotspots, surface waves, and cooling wakes) depend on the accretion ra... | the accretion rate dependence of burst oscillation amplitude |
background: global environmental change is exacerbating human vulnerability to adverse atmospheric conditions including air pollution, aeroallergens such as pollen, and extreme weather events. public information and advisories are a central component of responses to mitigate the human impacts of environmental hazards. ... | using smartphone technology to reduce health impacts from atmospheric environmental hazards |
background: knowing the difference between the neutron and proton densities of nuclei is a significant topic because of its importance for understanding neutron star structures and cooling mechanisms. the coherent-nuclear photoproduction of pions, (γ ,π0 ) , combined with elastic electron scattering, has been suggested... | coherent-nuclear pion photoproduction and neutron radii |
inspired by the well-known anomaly in the lifetime of the neutron, we investigated its consequences inside neutron stars. we first assessed the viability of the neutron decay hypothesis suggested by fornal and grinstein within neutron stars, in terms of the equation of state and compatibility with observed properties. ... | constraining dark boson decay using neutron stars |
phase diagrams of fully ionized binary ionic mixtures are considered within the framework of the linear mixing formalism taking into account recent advances in understanding quantum one-component plasma thermodynamics. we have followed a transformation of azeotropic phase diagrams into peritectic and eutectic types wit... | phase diagrams of binary ionic mixtures and white dwarf cooling |
we report the discovery of an extremely metal-poor (emp) giant, lamost j110901.22+075441.8, which exhibits a large excess of r-process elements with [eu/fe] ∼ +1.16. the star is one of the newly discovered emp stars identified from the lamost low-resolution spectroscopic survey and a high-resolution follow-up observati... | discovery of a strongly r-process enhanced extremely metal-poor star lamost j110901.22+075441.8 |
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