scholarly journals A Neutron Star Is Born

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 267
Author(s):  
Débora Peres Menezes
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Nuclear Physics ◽  
Compact Object ◽  
Compact Objects ◽  
Electromagnetic Spectrum ◽  
New Era ◽  
Nuclear Models ◽  
Optical Region ◽  
History Of

A neutron star was first detected as a pulsar in 1967. It is one of the most mysterious compact objects in the universe, with a radius of the order of 10 km and masses that can reach two solar masses. In fact, neutron stars are star remnants, a kind of stellar zombie (they die, but do not disappear). In the last decades, astronomical observations yielded various contraints for neutron star masses, and finally, in 2017, a gravitational wave was detected (GW170817). Its source was identified as the merger of two neutron stars coming from NGC 4993, a galaxy 140 million light years away from us. The very same event was detected in γ-ray, x-ray, UV, IR, radio frequency and even in the optical region of the electromagnetic spectrum, starting the new era of multi-messenger astronomy. To understand and describe neutron stars, an appropriate equation of state that satisfies bulk nuclear matter properties is necessary. GW170817 detection contributed with extra constraints to determine it. On the other hand, magnetars are the same sort of compact object, but bearing much stronger magnetic fields that can reach up to 1015 G on the surface as compared with the usual 1012 G present in ordinary pulsars. While the description of ordinary pulsars is not completely established, describing magnetars poses extra challenges. In this paper, I give an overview on the history of neutron stars and on the development of nuclear models and show how the description of the tiny world of the nuclear physics can help the understanding of the cosmos, especially of the neutron stars.

scholarly journals MULTI-MESSENGER OBSERVATIONS OF NEUTRON-RICH MATTER

2011 ◽  
Vol 20 (10) ◽  
pp. 2077-2100 ◽  
Author(s):  
C. J. HOROWITZ
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Waves ◽  
Nuclear Physics ◽  
Heavy Ion Collisions ◽  
Large Scale ◽  
Heavy Ion ◽  
Compact Objects ◽  
Rare Isotope ◽  
Ion Collisions

At very high densities, electrons react with protons to form neutron-rich matter. This material is central to many fundamental questions in nuclear physics and astrophysics. Moreover, neutron-rich matter is being studied with an extraordinary variety of new tools such as Facility for Rare Isotope Beams (FRIB) and the Laser Interferometer Gravitational Wave Observatory (LIGO). We describe the Lead Radius Experiment (PREX) that uses parity violating electron scattering to measure the neutron radius in 208Pb. This has important implications for neutron stars and their crusts. We discuss X-ray observations of neutron star radii. These also have important implications for neutron-rich matter. Gravitational waves (GW) open a new window on neutron-rich matter. They come from sources such as neutron star mergers, rotating neutron star mountains, and collective r-mode oscillations. Using large scale molecular dynamics simulations, we find neutron star crust to be very strong. It can support mountains on rotating neutron stars large enough to generate detectable gravitational waves. Finally, neutrinos from core collapse supernovae (SN) provide another, qualitatively different probe of neutron-rich matter. Neutrinos escape from the surface of last scattering known as the neutrino-sphere. This is a low density warm gas of neutron-rich matter. Neutrino-sphere conditions can be simulated in the laboratory with heavy ion collisions. Observations of neutrinos can probe nucleosyntheses in SN. Simulations of SN depend on the equation of state (EOS) of neutron-rich matter. We discuss a new EOS based on virial and relativistic mean field calculations. We believe that combing astronomical observations using photons, GW, and neutrinos, with laboratory experiments on nuclei, heavy ion collisions, and radioactive beams will fundamentally advance our knowledge of compact objects in the heavens, the dense phases of QCD, the origin of the elements, and of neutron-rich matter.

Aspects of the Collapse of Compact Objects

1980 ◽  
Vol 4 (1) ◽  
pp. 49-50
Author(s):  
R. A. Gingold ◽  
J. J. Monaghan
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
White Dwarf ◽  
Compact Objects ◽  
Dwarf Star

Misner Thorne and Wheeler (1973), (page 629) suggested that a freshly formed White Dwarf star of several solar masses would, if slowly — rotating, collapse to form a neutron star pancake which would become unstable and eventually produce several, possibly colliding, neutron stars.

scholarly journals Nuclear equation of state and neutron star cooling

2017 ◽  
Vol 26 (04) ◽  
pp. 1750015 ◽  
Author(s):  
Yeunhwan Lim ◽  
Chang Ho Hyun ◽  
Chang-Hwan Lee
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Thermal Evolution ◽  
Observation Data ◽  
Nuclear Equation Of State ◽  
The Core ◽  
Dense Nuclear Matter ◽  
Nuclear Models

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 of neutron stars. Discovery of [Formula: see text] neutron stars PSR J1614−2230 and PSR J0343[Formula: see text]0432 has triggered the revival of stiff nuclear equation of state at high densities. In the meantime, observation of a neutron star in Cassiopeia A for more than 10 years has provided us with very accurate data for the thermal evolution of neutron stars. Both mass and temperature of neutron stars depend critically on the equation of state of nuclear matter, so we first search for nuclear models that satisfy the constraints from mass and temperature simultaneously within a reasonable range. With selected models, we explore the effects of element composition in the envelope region, and the existence of superfluidity in the core and the crust of neutron stars. Due to uncertainty in the composition of particles in the envelope region, we obtain a range of cooling curves that can cover substantial region of observation data.

scholarly journals Dependence of gravitational wave transient rates on cosmic star formation and metallicity evolution history

2020 ◽  
Vol 493 (1) ◽  
pp. L6-L10 ◽  
Author(s):  
Petra N Tang ◽  
J J Eldridge ◽  
Elizabeth R Stanway ◽  
J C Bray
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Formation Rate ◽  
Compact Objects ◽  
Star Formation History ◽  
Compact Binary ◽  
Formation History ◽  
Order Of Magnitude ◽  
History Of

ABSTRACT We compare the impacts of uncertainties in both binary population synthesis models and the cosmic star formation history on the predicted rates of gravitational wave (GW) compact binary merger events. These uncertainties cause the predicted rates of GW events to vary by up to an order of magnitude. Varying the volume-averaged star formation rate density history of the Universe causes the weakest change to our predictions, while varying the metallicity evolution has the strongest effect. Double neutron star merger rates are more sensitive to assumed neutron star kick velocity than the cosmic star formation history. Varying certain parameters affects merger rates in different ways depending on the mass of the merging compact objects; thus some of the degeneracy may be broken by looking at all the event rates rather than restricting ourselves to one class of mergers.

scholarly journals Spin Evolution of the Progenitors of Binary and Millisecond Pulsars

1996 ◽  
Vol 165 ◽  
pp. 57-64
Author(s):  
Pranab Ghosh
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Binary System ◽  
Neutron Stars ◽  
High Magnetic Field ◽  
Evolutionary History ◽  
Millisecond Pulsars ◽  
History Of ◽  
Low Magnetic Field ◽  
Fast Rotating

In this symposium, I have been given the task of summarizing our current understanding of the evolutionary history of spin periods of the neutron stars that we now see as binary and millisecond pulsars, i.e., recycled pulsars. We believe that a newborn, fast-spinning neutron star (with a rather high magnetic field ∼1011–1013 G) in a binary system first operates as a spin-powered pulsar, subsequently as an accretion-powered pulsar when accretion begins after the pulsar has been spun down adequately, and finally as a spin-powered pulsar for the second time after having been recycled to become a very fast-rotating neutron star (with a rather low magnetic field ∼108–1011 G) (see Ghosh 1994a, b, hereafter G94a, b).

scholarly journals Accretion onto Relativistic Objects

1974 ◽  
Vol 64 ◽  
pp. 194-212
Author(s):  
M. J. Rees
Keyword(s):  
Black Holes ◽  
Interstellar Medium ◽  
Neutron Stars ◽  
Binary Systems ◽  
Compact Object ◽  
Stellar Mass ◽  
Supermassive Black Holes ◽  
Compact Objects ◽  
X Ray ◽  
Intergalactic Space

The physics of spherically symmetrical accretion onto a compact object is briefly reviewed. Neither neutron stars nor stellar-mass black holes are likely to be readily detectable if they are isolated and accreting from the interstellar medium. Supermassive black holes in intergalactic space may however be detectable. The effects of accretion onto compact objects in binary systems are then discussed, with reference to the phenomena observed in variable X-ray sources.

scholarly journals Effect of Compact Objects Near Be Stars

1987 ◽  
Vol 92 ◽  
pp. 516-518
Author(s):  
Krishna M.V. Apparao ◽  
S.P. Tarafdar
Keyword(s):  
Black Holes ◽  
Neutron Star ◽  
Rotation Period ◽  
Compact Object ◽  
Compact Objects ◽  
X Rays ◽  
Be Stars ◽  
Eccentric Orbit ◽  
X Ray ◽  
Be Star

Several Be stars are identified with bright X-ray sources. (Rappaport and Van den Heuvel, 1982). The bright X-ray emission and observed periodicities indicate the existence of compact objects (white dwarfs, neutron stars or black holes) near the Be stars. A prime example is the brightest X-ray source A0538-66 in LMC, which contains a neutron star with a rotation period of 59 ms. Apparao (1985) explained the X-ray emission, which occurs in periodic flares, by considering an inclined eccentric orbit for the neutron star around the assumed Be-star. The neutron star when it enters a gas ring (around the Be-star) accreting matter giving out X-rays.The X-ray emission from the compact objects, when the gas ring from the Be-star envelopes the objects, has interesting consequences. The X-ray emission produces an ionized region (compact object Stromgren sphere or COSS) in the gas surrounding the compact object (CO).

scholarly journals Two-Dimensional Accretion Disk Models of a Neutron Star

1998 ◽  
Vol 188 ◽  
pp. 374-375
Author(s):  
M. Fujita ◽  
T. Okuda
Keyword(s):  
Neutron Star ◽  
Electron Scattering ◽  
Radiation Transport ◽  
Compact Object ◽  
Compact Objects ◽  
High Mass ◽  
Two Dimensional ◽  
Accretion Rates ◽  
The Difference ◽  
Characteristic Features

We investigate the accretion disks around compact objects with high mass accretion rates near the Eddington's critical value ME, where radiation pressure and electron scattering are dominant. This raises next problems: (a) whether stable disks could exist in relation to the theory of thermal instabilities of the disk and (b) what characteristic features the disks have if the stable disks exist. A non-rotating neutron star with the mass M = 1.4M⊙, radius R* = 107cm and the accretion rate Mac = 2.0 and 0.5Mac (models 1 and 2) is considered as the compact object. We assume the α-model for the viscosity and solve the set of two-dimensional time-dependent hydrodynamic equations coupled with radiation transport. The numerical method used is basically the same as one described by Kley and Hensler (1987) and Kley (1989) but we include some improvements in solving the difference equations (Okuda et al. 1997). The initial configuration consists of a cold, dense, and optically thick disk which is given by the standard α-model (Shakura and Sunyaev 1973) and a rarefied optically thin atmosphere around the disk.

scholarly journals Anisotropic neutron stars by gravitational decoupling

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
V. A. Torres-Sánchez ◽  
E. Contreras
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Perfect Fluid ◽  
Compact Object ◽  
Adiabatic Index ◽  
X Ray ◽  
Binary Pulsar ◽  
Stable Solutions ◽  
X Ray Binaries ◽  
Fluid Configuration

Abstract In this work we obtain an anisotropic neutron star solution by gravitational decoupling starting from a perfect fluid configuration which has been used to model the compact object PSR J0348+0432. Additionally, we consider the same solution to model the Binary Pulsar SAX J1808.4-3658 and X-ray Binaries Her X-1 and Cen X-3 ones. We study the acceptability conditions and obtain that the MGD-deformed solution obey the same physical requirements as its isotropic counterpart. Finally, we conclude that the most stable solutions, according to the adiabatic index and gravitational cracking criterion, are those with the smallest compactness parameters, namely SAX J1808.4-3658 and Her X-1.

scholarly journals Constraint on Hybrid Stars with Gravitational Wave Events

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 231
Author(s):  
Kilar Zhang ◽  
Feng-Li Lin
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Compact Object ◽  
Compact Objects ◽  
Compact Stars ◽  
Hybrid Star ◽  
Hybrid Stars

Motivated by the recent discoveries of compact objects from LIGO/Virgo observations, we study the possibility of identifying some of these objects as compact stars made of dark matter called dark stars, or the mix of dark and nuclear matters called hybrid stars. In particular, in GW190814, a new compact object with 2.6 M⊙ is reported. This could be the lightest black hole, the heaviest neutron star, and a dark or hybrid star. In this work, we extend the discussion on the interpretations of the recent LIGO/Virgo events as hybrid stars made of various self-interacting dark matter (SIDM) in the isotropic limit. We pay particular attention to the saddle instability of the hybrid stars which will constrain the possible SIDM models.

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