scholarly journals On the delay times of merging double neutron stars

2020 ◽  
Vol 500 (2) ◽  
pp. 1755-1771
Author(s):  
Laura Greggio ◽  
Paolo Simonetti ◽  
Francesca Matteucci
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Milky Way ◽  
Gamma Ray ◽  
Chemical Properties ◽  
Redshift Distribution ◽  
Strong Constraint ◽  
Delay Times ◽  
Best Fitting ◽  
Short Grbs

ABSTRACT The merging rate of double neutron stars (DNS) has a great impact on many astrophysical issues, including the interpretation of gravitational waves signals, of the short gamma-ray bursts (GRBs), and of the chemical properties of stars in galaxies. Such rate depends on the distribution of the delay times (DDT) of the merging events. In this paper, we derive a theoretical DDT of merging DNS following from the characteristics of the clock controlling their evolution. We show that the shape of the DDT is governed by a few key parameters, primarily the lower limit and the slope of the distribution of the separation of the DNS systems at birth. With a parametric approach, we investigate on the observational constraints on the DDT from the cosmic rate of short GRBs and the europium-to-iron ratio in Milky Way stars, taken as tracer of the products of the explosion. We find that the local rate of DNS merging requires that $\sim \! 1 {{\ \rm per\ cent}}$ of neutron stars progenitors live in binary systems which end their evolution as merging DNS within a Hubble time. The redshift distribution of short GRBs does not yet provide a strong constraint on the shape of the DDT, although the best-fitting models have a shallow DDT. The chemical pattern in Milky Way stars requires an additional source of europium besides the products from merging DNS, which weakens the related requirement on the DDT. At present both constraints can be matched with the same DDT for merging DNS.

scholarly journals Microquasars and ULXS: Fossils of GRB Sources

2004 ◽  
Vol 194 ◽  
pp. 14-17 ◽  
Author(s):  
I. F. Mirabell
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Binary Systems ◽  
Gamma Ray ◽  
Massive Stars ◽  
Compact Objects ◽  
Primary Star ◽  
Long Duration ◽  
Supernova Explosions ◽  
Low Mass

AbstractGamma-ray bursts (GRBs) of long duration probably result from the core-collapse of massive stars in binary systems. After the collapse of the primary star the binary system may remain bound leaving a microquasar or ULX source as remnant. In this context, microquasars and ULXs are fossils of GRB sources and should contain physical and astrophysical clues on their GRB-source progenitors. Here I show that the identification of the birth place of microquasars can provide constrains on the progenitor stars of compact objects, and that the runaway velocity can be used to constrain the energy in the explosion of massive stars that leave neutron stars and black holes. The observations show that the neutron star binaries LS 5039, LSI +61°303 and the low-mass black hole GRO J1655-40 formed in energetic supernova explosions, whereas the black holes of larger masses (M ≥ 10 M⊙) in Cygnus X-l and GRS 1915+105 formed promptly, in the dark or in underluminous supornovao. The association with clusters of massive stars of the microquasar LSI +61°303 and the magnetars SGR 1806-20 and SGR 1900+14, suggest that very massive stars (M ≥ 50 M⊙) may -in some cases- leave neutron stars rather than black holes. The models of GRB sources of long duration have the same basic ingredients as microquasars and ULXs: compact objects with accretion disks and relativistic jets in binary systems. Therefore, the analogies between microquasars and AGN may be extended to the sources of GRBs.

scholarly journals Some Constraints on Neutron Star Properties from Gamma Ray Burster Observations

1987 ◽  
Vol 125 ◽  
pp. 489-500
Author(s):  
K. Hurley
Keyword(s):  
Neutron Star ◽  
Low Temperature ◽  
Neutron Stars ◽  
Binary Systems ◽  
Main Sequence ◽  
Gamma Ray ◽  
Cooling Curves ◽  
X Ray ◽  
Upper Limits ◽  
Low Mass

The results of recent soft X-ray and optical searches for quiescent gamma ray burster counterparts are used to constrain the properties of the neutron stars responsible for bursters. Ages are restricted to the range 2×105 y and above based on temperature upper limits and theoretical cooling curves, or 107 y and above if bursters have evolved from pulsars. Velocities are greater than 20 km/s if the neutron stars are unmagnetized. Practically no main sequence star could have escaped detection in the optical/IR searches, so if the neutron stars are in binary systems, the companion is most likely a degenerate, low mass, low temperature object.

scholarly journals Classification of pulsars with Dirichlet process Gaussian mixture model

2020 ◽  
Vol 493 (1) ◽  
pp. 713-722
Author(s):  
Fahrettin Ay ◽  
Gökhan İnce ◽  
Mustafa E Kamaşak ◽  
K Yavuz Ekşi
Keyword(s):  
Neutron Stars ◽  
Gaussian Mixture Model ◽  
Mixture Model ◽  
Dirichlet Process ◽  
Binary Systems ◽  
Gamma Ray ◽  
Transverse Velocity ◽  
Gaussian Mixture ◽  
Compact Objects ◽  
X Ray

ABSTRACT Young isolated neutron stars (INSs) most commonly manifest themselves as rotationally powered pulsars that involve conventional radio pulsars as well as gamma-ray pulsars and rotating radio transients. Some other young INS families manifest themselves as anomalous X-ray pulsars and soft gamma-ray repeaters that are commonly accepted as magnetars, i.e. magnetically powered neutron stars with decaying super-strong fields. Yet some other young INSs are identified as central compact objects and X-ray dim isolated neutron stars that are cooling objects powered by their thermal energy. Older pulsars, as a result of a previous long episode of accretion from a companion, manifest themselves as millisecond pulsars and more commonly appear in binary systems. We use Dirichlet process Gaussian mixture model (DPGMM), an unsupervised machine learning algorithm, for analysing the distribution of these pulsar families in the parameter space of period and period derivative. We compare the average values of the characteristic age, magnetic dipole field strength, surface temperature, and transverse velocity of all discovered clusters. We verify that DPGMM is robust and provide hints for inferring relations between different classes of pulsars. We discuss the implications of our findings for the magnetothermal spin evolution models and fallback discs.

scholarly journals Revisiting the luminosity and redshift distributions of long gamma-ray bursts

2021 ◽  
Author(s):  
Guang-Xuan Lan ◽  
Jun-Jie Wei ◽  
Hou-Dun Zeng ◽  
Ye Li ◽  
Xue-Feng Wu
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Information Criterion ◽  
Good Representation ◽  
Redshift Distribution ◽  
Model Free ◽  
Flux Limit ◽  
Best Fitting ◽  
Incomplete Sampling ◽  
Burst Alert Telescope

Abstract In this work, we update and enlarge the long gamma-ray burst (GRB) sample detected by the Swift satellite. Given the incomplete sampling of the faint bursts and the low completeness in redshift measurement, we carefully select a subsample of bright Swift bursts to revisit the GRB luminosity function (LF) and redshift distribution by taking into account the probability of redshift measurement. Here we also explore two general expressions for the GRB LF, i.e. a broken power-law LF and a triple power-law LF. Our results suggest that a strong redshift evolution in luminosity (with an evolution index of $\delta =1.92^{+0.25}_{-0.37}$) or in density ($\delta =1.26^{+0.33}_{-0.34}$) is required in order to well account for the observations, independent of the assumed expression of the GRB LF. However, in a one-on-one comparison using the Akaike information criterion, the best-fitting evolution model involving the triple power-law LF is statistically preferred over the best-fitting one involving the broken power-law LF with a relative probability of ∼94.3 per cent versus ∼5.7 per cent. Extrapolating our fitting results to the flux limit of the whole Swift sample, and considering the trigger probability of Swift/Burst Alert Telescope in detail, we find that the expectations from our evolution models provide a good representation of the observed distributions of the whole sample without the need for any adjustment of the model free parameters. This further confirms the reliability of our analysis results.

scholarly journals Gamma-ray bursts: A brief survey of the diversity

2018 ◽  
Vol 14 (S346) ◽  
pp. 383-387
Author(s):  
Attila Mészáros ◽  
Jakub Řípa
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Statistical Studies ◽  
Short Grbs

AbstractThe separation of the gamma-ray bursts (GRBs) into short/hard and long/soft subclasses, respectively, is well supported both theoretically and observationally. The long ones are coupled to supernovae type Ib/Ic - the short ones are connected to the merging of two neutron stars, where one or even both neutron stars can be substituted by black holes. These short GRBs - as merging binaries - can also serve as the sources of gravitation waves, and are observable as the recently detected macronovae. Since 1998 there are several statistical studies suggesting the existence of more than two subgroups. There can be a subgroup having an intermediate durations; there can be a subgroup with ultra-long durations; the long/soft subgroup itself can be divided into two subclasses with respect to the luminosity of GRBs. The authors with other collaborators provided several statistical studies in this topic. This field of the GRB-diversity is briefly surveyed in this contribution.

scholarly journals High-Mass X-Ray Binaries and OB Runaway Stars

2004 ◽  
Vol 191 ◽  
pp. 128-131 ◽  
Author(s):  
L. Kaper ◽  
A. Van der Meer ◽  
A.H. Tijani
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Gamma Ray ◽  
Compact Star ◽  
Supernova Explosion ◽  
High Mass ◽  
X Ray ◽  
Fundamental Information ◽  
X Ray Binaries ◽  
Runaway Stars

AbstractHigh-mass X-ray binaries (HMXBs) represent an important phase in the evolution of massive binary systems and provide fundamental information on the properties of the OB-star primaries and their compact secondaries (neutron star, black hole). Recent observations indicate that the neutron stars in some of these systems (Vela X-1, 4U 1700-37) are more massive than the canonical mass of 1.35 M⊙. These observations have important consequences for the equation of state at supranuclear densities and the formation mechanism(s) of neutron stars and black holes: supernovae and gamma-ray bursts. As a consequence of the supernova explosion that produced the compact star in these systems, HMXBs have high space velocities and thus are runaways. Alternatively, OB-runaway stars can be ejected from a cluster through dynamical interactions. Observations obtained with the Hipparcos satellite indicate that both scenarios are at work.

scholarly journals Pulsar Observations and Neutron Star Models

1974 ◽  
Vol 53 ◽  
pp. 227-236
Author(s):  
Gerhard Börner ◽  
Jeffrey M. Cohen
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Gamma Ray ◽  
Crab Nebula ◽  
Physical Parameters ◽  
X Ray ◽  
Star Models ◽  
Degree Of Confidence ◽  
The Masses ◽  
The Crab Nebula

Information about the physical parameters of neutron stars is obtained from pulsar observations. The energy balance of the Crab Nebula and the Vela X remnant allows one to derive limits for the masses of the Crab and Vela pulsars. Glitch observations provide further clues on the masses of these two pulsars. The degree of confidence with which one should believe the derived numbers is pointed out. The possibility of observing neutron stars in binary systems as pulsating X-ray sources is discussed. Finally, the importance of observing redshifted gamma ray lines from the surface of neutron stars, and thus directly measuring either individual or statistical properties of these objects, is pointed out.

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