Neutron Star Formation Research Articles

Probing Electromagnetic Gravitational-wave Emission Coincidence in a Type I Binary-driven Hypernova Family of Long Gamma-Ray Bursts at Very High Redshift

The repointing time of the X-Ray Telescope (XRT) instrument on the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying the early X-ray emissions within ≈40 s after a gamma-ray burst (GRB) trigger. To address this issue, we adopt a novel approach that capitalizes on the cosmological time dilation in GRBs with redshifts ranging from 3 to 9. Applying this strategy to Swift/XRT data, we investigate the earliest X-ray emissions of 368 GRBs from the Swift catalog, including short and long GRBs. We compare the observed time delay between the GRB trigger and the initial Swift/XRT observation, measured in the GRB observer frame, and the corresponding cosmological rest-frame time delay (RTD). This technique is here used in the analysis of GRB 090423 at z = 8.233 (RTD ∼8.2 s), GRB 090429B at z ≈ 9.4 (RTD ∼10.1 s), and GRB 220101A at z = 4.61 (RTD ∼14.4 s). The cosmological time dilation enables us to observe the very early X-ray afterglow emission in these three GRBs. We thus validate the observation of the collapse of the carbon–oxygen core and the coeval newborn neutron star (νNS) formation triggering the GRB event in the binary-driven hypernova (BdHN) scenario. We also evidence the νNS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-ray/optical/radio synchrotron afterglow emission. A brief gravitational-wave signal may separate the two stages owing to a fast-spinning νNS triaxial-to-axisymmetric transition. We also analyze the long GRB redshift distribution for the different BdHN types and infer that BdHNe II and III may originate the NS binary progenitors of short GRBs.

ESTIMATING GAMMA-RAY FLUX FROM MILLISECOND PULSARS ORIGINATING IN GLOBULAR CLUSTERS NEAR THE GALACTIC CENTER

In this study, we investigate the contribution of millisecond pulsars (MSPs) to the gamma-ray excess observed in the Galactic Center by analyzing data from high-resolution direct N-body simulations of six globular clusters (GCs) that experience close encounters with the nuclear star cluster. Using the φ-GPU code, we tracked the orbits of individual neutron stars (NSs) formed during the simulations, assuming a fraction of these NSs evolve into MSPs. Our model includes state-of-the-art single stellar evolution code including prescription for neutron star formation. We estimated the gamma-ray flux from these MSPs, considering known values for their gamma-ray emission. Our results show that MSPs originating from the six modeled GCs contribute a small but non-negligible fraction of the observed gamma-ray flux. This finding suggests that the actual gamma-ray flux from MSPs could be much higher when considering the entire population of GCs, potentially significantly contributing to the gamma-ray excess. This study highlights the importance of considering MSPs in the Galactic Center, originating from nearby globular clusters, as a potential source of the observed gamma-ray excess. Future work will involve more sophisticated simulations incorporating binary stellar evolution and comparing the fraction of MSPs in observed GCs to refine our models and improve the accuracy of our estimates.

Swift, NuSTAR, and INTEGRAL observations of the symbiotic X-ray binary IGR J16194-2810

ABSTRACT We report on a simultaneous observational campaign with both Swift/XRT and NuSTAR targeting the symbiotic X-ray binary (SyXB) IGR J16194-2810. The main goal of the campaign was to investigate the possible presence of cyclotron scattering absorption features in the broad-band spectrum of the source, and help advance our understanding of the process of neutron star formation via the accretion-induced collapse of a white dwarf. The 1–30 keV spectrum of the source, as measured during our campaign, did not reveal the presence of any statistically significant absorption feature. The spectrum could be well described using a model comprising a thermal black-body hot component, most likely emerging from the surface of the accreting neutron star, and a power law with no measurable cut-off energy (and affected by a modest absorption column density). Compared to previous analyses in the literature, we could rule out the presence of a colder thermal component emerging from an accretion disc, compatible with the idea that IGR J16194-2810 is a wind-fed binary (as most of the SyXBs). Our results were strengthened by exploiting the archival XRT and INTEGRAL data, extending the validity of the spectral model used up to 0.3–40 keV and demonstrating that IGR J16194-2810 is unlikely to undergo significant spectral variability over time in the X-ray domain.

AGILE Gamma-Ray Detection of the Exceptional GRB 221009A

Gamma-ray emission in the MeV–GeV range from explosive cosmic events is of invaluable relevance to understanding physical processes related to the formation of neutron stars and black holes. Here we report on the detection by the AGILE satellite in the MeV–GeV energy range of the remarkable long-duration gamma-ray burst GRB 221009A. The AGILE onboard detectors have good exposure to GRB 221009A during its initial crucial phases. Hard X-ray/MeV emission in the prompt phase lasted hundreds of seconds, with the brightest radiation being emitted between 200 and 300 s after the initial trigger. Very intense GeV gamma-ray emission is detected by AGILE in the prompt and early afterglow phase up to 10,000 s. Time-resolved spectral analysis shows time-variable MeV-peaked emission simultaneous with intense power-law GeV radiation that persists in the afterglow phase. The coexistence during the prompt phase of very intense MeV emission together with highly nonthermal and hardening GeV radiation is a remarkable feature of GRB 221009A. During the prompt phase, the event shows spectrally different MeV and GeV emissions that are most likely generated by physical mechanisms occurring in different locations. AGILE observations provide crucial flux and spectral gamma-ray information regarding the early phases of GRB 221009A during which emission in the TeV range was reported.

Kilonovae of binary neutron star mergers leading to short-lived remnant neutron star formation

ABSTRACT We study kilonova emission from binary neutron star (BNS) mergers for the case that a remnant massive neutron star (MNS) forms and collapses to a black hole within 20 ms after the onset of the merger (which we refer to as ‘a short-lived case’) by consistently employing numerical relativity and nucleosynthesis results. We find that such kilonovae are fainter and last shorter than those for BNSs resulting in the formation of long-lived (${\gg} 1\, {\rm s}$) MNSs, in particular in the optical band. The resulting light curves are too faint and last for a too short duration to explain the kilonova observation for the BNS associated with GW170817, indicating that the merger remnant formed in GW170817 is unlikely to have collapsed to a black hole within a short period of time (∼20 ms) after the onset of the merger. Our present result implies that early observation is necessary to detect kilonovae associated with BNSs leading to short-lived MNS formation in particular for the optical blue band as well as that kilonovae could be hidden by the gamma-ray burst afterglow for nearly face-on observation. We provide a possible approximate scaling law for near-infrared light curves with the given reference time and magnitude when the decline power of the z-band magnitude, dMz/dlog10t, reaches 2.5. This scaling law suggests that the HK-band follow-up observation should be at least 1 mag deeper than that for the z-band reference magnitude and earlier than 4 times the reference time.

Connecting the young pulsars in Milky Way globular clusters with white dwarf mergers and the M81 fast radio burst

ABSTRACT The detections of four apparently young radio pulsars in the Milky Way globular clusters are difficult to reconcile with standard neutron star formation scenarios associated with massive star evolution. Here, we discuss formation of these young pulsars through white dwarf mergers in dynamically old clusters that have undergone core collapse. Based on observed properties of magnetic white dwarfs, we argue neutron stars formed via white dwarf merger are born with spin periods of roughly $10{\!-\!}100\,$ ms and magnetic fields of roughly $10^{11}{\!-\!}10^{13}\,$ G. As these neutron stars spin down via magnetic dipole radiation, they naturally reproduce the four observed young pulsars in the Milky Way clusters. Rates inferred from N-body cluster simulations as well as the binarity, host cluster properties, and cluster offsets observed for these young pulsars hint further at a white dwarf merger origin. These young pulsars may be descendants of neutron stars capable of powering fast radio bursts analogous to the bursts observed recently in a globular cluster in M81.

Double neutron star formation via consecutive type II supernova explosions

ABSTRACT Since the discovery of the first double neutron star (DNS) system, the number of these exotic binaries has reached 15. Here we investigate a channel of DNS formation in binary systems with components above the mass limit of Type II supernova explosion (SN II), that is, 8M⊙. We apply a spherically symmetric homologous envelope expansion model to account for mass-loss, and follow the dynamical evolution of the system numerically with a high-precision integrator. The first SN occurs in a binary system whose orbital parameters are pre-defined, then, the homologous expansion model is applied again in the newly formed system. Analysing 1 658 880 models we find that DNS formation via subsequent SN II explosions requires a fine-tuning of the initial parameters. Our model can explain DNS systems with a separation greater than 2.95 au. The eccentricity of the DNS systems spans a wide range thanks to the orbital circularization effect due to the second SN II explosion. The eccentricity of the DNS is sensitive to the initial eccentricity of the binary progenitor and the orbital position of the system preceding the second explosion. In agreement with the majority of the observations of DNS systems, we find the system centre-of-mass velocities to be less than 60 km s−1. Neutron stars that become unbound in either explosion gain a peculiar velocity in the range of 0.02 − 240 km s−1. In our model, the formation of tight DNS systems requires a post-explosion orbit-shrinking mechanism, possibly driven by the ejected envelopes.

Magnetar Central Engines in Gamma-Ray Bursts Follow the Universal Relation of Accreting Magnetic Stars

Gamma-ray bursts (GRBs), both long and short, are explosive events whose inner engine is generally expected to be a black hole or a highly magnetic neutron star (magnetar) accreting high-density matter. Recognizing the nature of GRB central engines, and in particular the formation of neutron stars (NSs), is of high astrophysical significance. A possible signature of NSs in GRBs is the presence of a plateau in the early X-ray afterglow. Here we carefully select a subset of long and short GRBs with a clear plateau, and look for an additional NS signature in their prompt emission, namely a transition between the accretion and propeller phases in analogy with accreting, magnetic compact objects in other astrophysical sources. We estimate from the prompt emission the minimum accretion luminosity below which the propeller mechanism sets in, and the NS magnetic field and spin period from the plateau. We demonstrate that these three quantities obey the same universal relation in GRBs as in other accreting compact objects switching from accretion to propeller. This relation provides also an estimate of the radiative efficiency of GRBs, which we find to be several times lower than radiatively efficient accretion in X-ray binaries and in agreement with theoretical expectations. These results provide additional support to the idea that at least some GRBs are powered by magnetars surrounded by an accretion disk.

Inference of protoneutron star properties in core-collapse supernovae from a gravitational-wave detector network

The next Galactic core-collapse supernova (CCSN) will be a unique opportunity to study within a fully multimessenger approach the explosion mechanism responsible for the formation of neutron stars and stellar-mass black holes. State-of-the-art numerical simulations of those events reveal the complexity of the gravitational-wave emission which is highly stochastic. This challenges the possibility to infer the properties of the compact remnant and of its progenitor using the information encoded in the waveforms. In this paper we take further steps in a program we recently initiated to overcome those difficulties. In particular we show how oscillation modes of the protoneutron star (PNS), highly visible in the gravitational-wave signal, can be used to reconstruct the time evolution of their physical properties. Extending our previous work where only the information from a single detector was used, we here describe a new data-analysis pipeline that coherently combines gravitational-wave detectors' data and infers the time evolution of a combination of the mass and radius of the compact remnant. The performance of the method is estimated employing waveforms from 2D and 3D CCSN simulations covering a progenitor mass range between $11{M}_{\ensuremath{\bigodot}}$ and $40{M}_{\ensuremath{\bigodot}}$ and different equations of state for both a network of up to five second-generation detectors and the proposed third-generation detectors Einstein Telescope and Cosmic Explorer. Our study shows that it will be possible to infer PNS properties for CCSN events occurring in the vicinity of the Milky Way, up to the Large Magellanic Cloud, with the current generation of gravitational-wave detectors.

Evolution of eccentric high-mass X-ray binaries

Context. The formation of neutron stars is associated with powerful astrophysical transients such as supernovae. In many cases, asymmetries in the supernova explosions are thought to be responsible for the large observed velocities of neutron stars. Aims. We aim to study the complete evolutionary history of one particular eccentric high-mass X-ray binary containing a neutron star, GX 301–2, and characterize the natal kick at the time of neutron star formation. Methods. We used the publicly available stellar-evolution code MESA to evolve binaries from their initial stages until the core-collapse scenario. We incorporated a natal kick distribution based on observations to continue the evolution during the X-ray binary phase and search for candidates matching current observations of GX 301–2. Results. We find that the range of initial masses is constrained to be less than around 30 M⊙ depending on the initial mass ratio, as higher initial masses will most likely end up producing a black hole. In the completely conservative mass-transfer scenario under study, only is an interaction between the stars when the donor is still burning Hydrogen in its core, the so-called Case A of mass transfer, able to produce progenitors for GX 301–2. The natal kick study favours kicks of variable strength, which in turn increases the tilt angle between the orbital angular momentum and the spin of the neutron star. Conclusions. We conclude that only a narrow initial progenitor parameter space is able to produce a binary such as GX 301–2 when assuming a completely conservative mass transfer. Additionally, the strength of the natal kick can span a wide range of values, but it can be constrained when considering new data concerning the systemic velocity of the binary. Finally, we derive the fraction of the expected number of binaries such as GX 301–2 in the Galaxy to be ∼6 × 10−5, implying a really low chance of finding a binary similar to GX 301–2.

Formation of Fast-spinning Neutron Stars in Close Binaries and Magnetar-driven Stripped-envelope Supernovae

Formation of Fast-spinning Neutron Stars in Close Binaries and Magnetar-driven Stripped-envelope Supernovae

Thermonuclear and electron-capture supernovae from stripped-envelope stars

Context. When stripped from their hydrogen-rich envelopes, stars with initial masses between ∼7 and 11 M⊙ may develop massive degenerate cores and collapse. Depending on the final structure and composition, the outcome can range from a thermonuclear explosion, to the formation of a neutron star in an electron-capture supernova (ECSN). It has recently been demonstrated that stars in this mass range may be more prone to disruption than previously thought: they may initiate explosive oxygen burning when their central densities are still below ρc ≲ 109.6 g cm−3. At the same time, their envelopes expand significantly, leading to the complete depletion of helium. This combination makes them interesting candidates for type Ia supernovae–which we call (C)ONe SNe Ia–and this might have broader implications for the formation of neutron stars via ECSNe. Aims. To constrain the observational counterparts of (C)ONe SNe Ia and the key properties that enable them, it is crucial to constrain the evolution, composition, and precollapse structure of their progenitors, as well as the evolution of these quantities with cosmic time. In turn, this requires a detailed investigation of the final evolutionary stages preceding the collapse, and their sensitivity to input physics. Methods. Here, we modeled the evolution of 252 single, nonrotating helium stars covering the initial mass range 0.8 − 3.5 M⊙, with metallicities between Z = 10−4 and 0.02, and overshoot efficiency factors from fOV = 0.0 to 0.016 across all convective boundaries. We used these models to constrain several properties of these stars, including their central densities, compositions, envelope masses, and radii at the onset explosive oxygen ignition, as well as the final outcome as a function of initial helium star mass. We further investigate the sensitivity of these properties to mass loss rate assumptions using an additional grid of 110 models with varying wind efficiencies. Results. We find that helium star models with masses between ∼1.8 and 2.7 M⊙ are able to evolve onto 1.35−1.37 M⊙ (C)ONe cores that initiate explosive burning at central densities between log10(ρc/g cm−3) ∼ 9.3 and 9.6. We constrained the amount of residual carbon retained after core carbon burning as a function of initial conditions, and conclude that it plays a critical role in determining the final outcome: Chandrasekhar-mass degenerate cores that retain more than approximately 0.005 M⊙ of carbon result in (C)ONe SNe Ia, while those with lower carbon mass become ECSNe. We find that (C)ONe SNe Ia are more likely to occur at high metallicities, whereas at low metallicities ECSNe dominate. However, both SN Ia and ECSN progenitors expand significantly during the final evolutionary stages, so that for the most extended models, a further binary interaction may occur. We constrain the relative ratio between (C)ONe SNe Ia and SNe Ib/c to be 0.17−0.30 at Z = 0.02, and 0.03−0.13 at Z ≤ 10−3. Conclusions. We conclude with a discussion on potential observational properties of (C)ONe SNe Ia and their progenitors. In the few thousand years leading to the explosion, at least some progenitors should be identifiable as luminous metal-rich super-giants, embedded in hydrogen-free circumstellar nebulae.

3D code for MAgneto-Thermal evolution in Isolated Neutron Stars, MATINS: the magnetic field formalism

ABSTRACT The long-term evolution of the internal, strong magnetic fields of neutron stars needs a specific numerical modelling. The diversity of the observed phenomenology of neutron stars indicates that their magnetic topology is rather complex and 3D simulations are required, for example, to explain the observed bursting mechanisms and the creation of surface hotspots. We present MATINS, a new 3D numerical code for magnetothermal evolution in neutron stars, based on a finite-volume scheme that employs the cubed-sphere system of coordinates. In this first work, we focus on the crustal magnetic evolution, with the inclusion of realistic calculations for the neutron star structure, composition, and electrical conductivity assuming a simple temperature evolution profile. MATINS follows the evolution of strong fields (1014 − 1015 Gauss) with complex non-axisymmetric topologies and dominant Hall-drift terms, and it is suitable for handling sharp current sheets. After introducing the technical description of our approach and some tests, we present long-term simulations of the non-linear field evolution in realistic neutron star crusts. The results show how the non-axisymmetric Hall cascade redistributes the energy over different spatial scales. Following the exploration of different initial topologies, we conclude that during a few tens of kyr, an equipartition of energy between the poloidal and toroidal components happens at small-scales. However, the magnetic field keeps a strong memory of the initial large scales, which are much harder to be restructured or created. This indicates that large-scale configuration attained during the neutron star formation is crucial to determine the field topology at any evolution stage.

Pulsational pair-instability supernovae: gravitational collapse, black hole formation, and beyond

ABSTRACT We investigate the final collapse of rotating and non-rotating pulsational pair-instability supernova progenitors with zero-age-main-sequence masses of 60, 80, and 115 M⊙ and iron cores between 2.37 and 2.72 M⊙ by 2D hydrodynamics simulations. Using the general relativistic NADA-FLD code with energy-dependent three-flavour neutrino transport by flux-limited diffusion allows us to follow the evolution beyond the moment when the transiently forming neutron star (NS) collapses to a black hole (BH), which happens within 350–580 ms after bounce in all cases. Because of high neutrino luminosities and mean energies, neutrino heating leads to shock revival within ≲ 250 ms post bounce in all cases except the rapidly rotating 60 M⊙ model. In the latter case, centrifugal effects support a 10 per cent higher NS mass but reduce the radiated neutrino luminosities and mean energies by ∼20 per cent and ∼10 per cent, respectively, and the neutrino-heating rate by roughly a factor of two compared to the non-rotating counterpart. After BH formation, the neutrino luminosities drop steeply but continue on a 1–2 orders of magnitude lower level for several 100 ms because of aspherical accretion of neutrino and shock-heated matter, before the ultimately spherical collapse of the outer progenitor shells suppresses the neutrino emission to negligible values. In all shock-reviving models BH accretion swallows the entire neutrino-heated matter and the explosion energies decrease from maxima around 1.5 × 1051 erg to zero within a few seconds latest. Nevertheless, the shock or a sonic pulse moves outward and may trigger mass-loss, which we estimate by long-time simulations with the prometheus code. We also provide gravitational-wave signals.

Compact-object Formation, Retention, and Growth through Accretion onto Gas-embedded White Dwarfs/Neutron Stars in Gas-enriched Globular Clusters

Abstract Observations of pulsars in globular clusters (GCs) give evidence that more than >10%–20% of neutron stars (NSs) that ever formed in GCs were retained there. However, the velocity distribution of field pulsars peaks at 5–10 times the escape velocities of GCs. Consequently, only a small fraction of GC NSs should have been retained, which is potentially difficult to explain even accounting for low-velocity NSs formed through electron-capture supernovae (SNe). Thus, too few low-velocity NSs should have been retained, giving rise to the NS retention problem in GCs. Here we suggest a novel solution, in which the progenitors of most GC NSs were ONe white dwarfs (WDs) that accreted ambient intracluster gas and formed low-velocity NSs through accretion-induced collapse (AIC). The existence of an early gas-enriched environment in GCs is supported by observations of multiple stellar populations in GCs. It is thought that 10–100s of megayears after the formation of the first generation of stars, and after ONe WDs were already formed, GCs were replenished with gas, which formed a second generation of stars. Accretion of such replenished gas onto the ONe WDs catalyzed the AIC processes. The number of AIC-formed NSs is then sufficient to explain the large number of NSs retained in GCs. Similar processes might also drive CO WDs to produce Type Ia SNe or to merge and form NSs and similarly drive NSs to AIC and mergers producing BHs. Moreover, the wide variety of gas-catalyzed binary mergers and explosive transients suggested to occur in the gas-rich environments of an active galactic nucleus disk could similarly, and even more efficiently, occur in second-generation gas in GCs.

Core-collapse Supernova Simulations and the Formation of Neutron Stars, Hybrid Stars, and Black Holes

Abstract We investigate observable signatures of a first-order quantum chromodynamics (QCD) phase transition in the context of core-collapse supernovae. To this end, we conduct axially symmetric numerical relativity simulations with multi-energy neutrino transport, using a hadron–quark hybrid equation of state (EOS). We consider four nonrotating progenitor models, whose masses range from 9.6 to 70 M ⊙. We find that the two less-massive progenitor stars (9.6 and 11.2 M ⊙) show a successful explosion, which is driven by the neutrino heating. They do not undergo the QCD phase transition and leave behind a neutron star. As for the more massive progenitor stars (50 and 70 M ⊙), the proto-neutron star (PNS) core enters the phase transition region and experiences the second collapse. Because of a sudden stiffening of the EOS entering to the pure quark matter regime, a strong shock wave is formed and blows off the PNS envelope in the 50 M ⊙ model. Consequently the remnant becomes a quark core surrounded by hadronic matter, leading to the formation of the hybrid star. However, for the 70 M ⊙ model, the shock wave cannot overcome the continuous mass accretion and it readily becomes a black hole. We find that the neutrino and gravitational wave (GW) signals from supernova explosions driven by the hadron–quark phase transition are detectable for the present generation of neutrino and GW detectors. Furthermore, the analysis of the GW detector response reveals unique kHz signatures, which will allow us to distinguish this class of supernova explosions from failed and neutrino-driven explosions.

Dynamical Formation of Scalarized Black Holes and Neutron Stars through Stellar Core Collapse.

In a certain class of scalar-Gauss-Bonnet gravity, the black holes and the neutron stars can undergo spontaneous scalarization-a strong gravity phase transition triggered by a tachyonic instability due to the nonminimal coupling between the scalar field and the spacetime curvature. Studies of this phenomenon have, so far, been restricted mainly to the study of the tachyonic instability and stationary scalarized black holes and neutron stars. To date, no realistic physical mechanism for the formation of isolated scalarized black holes and neutron stars has been proposed. We study, for the first time, the spherically symmetric fully nonlinear stellar core collapse to a black hole and a neutron star in scalar-Gauss-Bonnet theories allowing for a spontaneous scalarization. We show that the core collapse can produce scalarized black holes and scalarized neutron stars starting with a nonscalarized progenitor star. The possible paths to reach the end (non)scalarized state are quite rich leading to interesting possibilities for observational manifestations.

Formation and evolution of binary neutron stars: mergers and their host galaxies

ABSTRACT In this paper, we investigate the properties of binary neutron stars (BNSs) and their mergers by combining population synthesis models for binary stellar evolution (BSE) with cosmological galaxy formation and evolution models. We obtain constraints on BSE model parameters by using the observed Galactic BNSs and local BNS merger rate density (R0) inferred from gravitational wave (GW) observations, and consequently estimate the host galaxy distributions of BNS mergers. We find that the Galactic BNS observations imply efficient energy depletion in the common envelope (CE) phase, a bimodal kick velocity distribution, and low mass ejection during the secondary supernova explosion. However, the inferred R0 does not necessarily require an extremely high CE ejection efficiency and low kick velocities, different from the previous claims, mainly because the latest inferred R0 is narrowed to a lower value ($320_{-240}^{+490}\, \rm Gpc^{-3}\, yr^{-1}$). The BNS merger rate density resulting from the preferred model can be described by R($z$) ∼ R0(1 + $z$)ζ at low redshift ($z$ ≲ 0.5), with R0 ∼ 316–$784\, \rm Gpc^{-3}\, yr^{-1}$ and ζ ∼ 1.34–2.03, respectively. Our results also show that R0 and ζ depend on settings of BSE model parameters, and thus accurate estimates of these parameters by future GW detections will put strong constraints on BSE models. We further estimate that the fractions of BNS mergers hosted in spiral and elliptical galaxies at $z$ ∼ 0 are ∼81–84 and ∼16–19 per cent, respectively. The BNS merger rate per galaxy can be well determined by the host galaxy stellar mass, star formation rate, and metallicity, which provides a guidance in search for most probable candidates of BNS host galaxies.

Review of low energy nuclear astrophysics

In this review of Low Energy Nuclear Astrophysics, we review the nuclear energy and evolution of the sun. Then we review the estimate of dark matter from galaxy rotation. Next, we discuss neutron star formation from the gravitational collapse of massive stars which produces neutron stars and their velocity. Then the origin of supernovae, the estimate of dark energy from supernovae acceleration, and experiments related to low energy nuclear astrophysics are reviewed.

Thermal properties of hot and dense matter: Influence of rapid rotation on protoneutron stars, hot neutron stars, and neutron star merger remnants

The knowledge of the equation of state is a key ingredient for many dynamical phenomena that depend sensitively on the hot and dense nuclear matter, such as the formation of protoneutron stars and hot neutron stars. In order to accurately describe them, we construct equations of state at FInite temperature and entropy per baryon for matter with varying proton fractions. This procedure is based on the momentum dependent interaction model and state-of-the-art microscopic data. In addition, we investigate the role of thermal and rotation effects on microscopic and macroscopic properties of neutron stars, including the mass and radius, the frequency, the Kerr parameter, the central baryon density, etc. The latter is also connected to the hot and rapidly rotating remnant after neutron star merger. The interplay between these quantities and data from late observations of neutron stars, both isolated and in matter of merging, could provide useful insight and robust constraints on the equation of state of nuclear matter.