Formation Rate Of Gamma Ray Bursts Research Articles

The Konus–Wind Catalog of Gamma-Ray Bursts with Known Redshifts. II. Waiting-Mode Bursts Simultaneously Detected by Swift/BAT

Abstract In the second part of The Konus–Wind Catalog of Gamma-Ray Bursts with Known Redshifts (the first part: Tsvetkova et al. 2017; T17), we present the results of a systematic study of gamma-ray bursts (GRBs) with reliable redshift estimates detected simultaneously by the Konus–Wind (KW) experiment (in the waiting mode) and by the Swift/BAT (BAT) telescope during the period from 2005 January to the end of 2018. By taking advantage of the high sensitivity of BAT and the wide spectral band of KW, we were able to constrain the peak spectral energies, the broadband energy fluences, and the peak fluxes for the joint KW–BAT sample of 167 weak, relatively soft GRBs (including four short bursts). Based on the GRB redshifts, which span the range 0.04 ≤ z ≤ 9.4, we estimate the rest frame, isotropic-equivalent energy, and peak luminosity. For 14 GRBs with reasonably constrained jet breaks, we provide the collimation-corrected values of the energetics. This work extends the sample of KW GRBs with known redshifts to 338 GRBs, the largest set of cosmological GRBs studied to date over a broad energy band. With the full KW sample, accounting for the instrumental bias, we explore GRB rest-frame properties, including hardness–intensity correlations, GRB luminosity evolution, luminosity and isotropic-energy functions, and the evolution of the GRB formation rate, which we find to be in general agreement with those reported in T17 and other previous studies.

Can the Cosmological Dilation Explain the Skewness in the Gamma-Ray Burst Duration Distribution?

Abstract In order to explain the origin of skewness in the gamma-ray burst (GRB) duration distribution, a statistical model, based on the cosmological time dilation and taking into account the GRB formation rate and instrumental effects, is examined. It is concluded that the considered effects are able to account for only a small fraction of the observed skewness. Therefore, its origin needs to be searched for in the processes governing the progenitors of GRBs​.

Gravitational lensing probability for the Konus-Wind gamma-ray bursts detected in the triggered mode

Although half a century has passed since the discovery of Gamma-ray bursts (GRBs), there is no evidence for any strongly lensed event. Using GRB luminosity function and GRB formation rate estimates for the Konus-Wind burst sample with known redshifts, and a Singular Isothermal Sphere as a gravitational lens model, we predict the detection rate of both GRB images being ≈ 0.02–0.05 events per year. The result is consistent with the non-detection of lensed bursts in the KW triggered GRB sample.

The luminosity function and formation rate of a complete sample of long gamma-ray bursts

ABSTRACT We study the luminosity function and formation rate of long gamma-ray bursts (GRBs) by using a maximum likelihood method. This is the first time this method is applied to a well-defined sample of GRBs that is complete in redshift. The sample is composed of 99 bursts detected by the Swift satellite, 81 of them with measured redshift and luminosity for a completeness level of $82\, {\rm per\, cent}$. We confirm that a strong redshift evolution in luminosity (with an evolution index of $\delta =2.22^{+0.32}_{-0.31}$) or in density ($\delta =1.92^{+0.20}_{-0.21}$) is needed in order to reproduce the observations well. But since the predicted redshift and luminosity distributions in the two scenarios are very similar, it is difficult to distinguish between these two kinds of evolutions only on the basis of the current sample. Furthermore, we also consider an empirical density case in which the GRB rate density is directly described as a broken power-law function and the luminosity function is taken to be non-evolving. In this case, we find that the GRB formation rate rises like $(1+z)^{3.85^{+0.48}_{-0.45}}$ for $z\lesssim 2$ and is proportional to $(1+z)^{-1.07^{+0.98}_{-1.12}}$ for $z\gtrsim 2$. The local GRB rate is $1.49^{+0.63}_{-0.64}$ Gpc−3 yr−1. The GRB rate may be consistent with the cosmic star formation rate (SFR) at $z\lesssim 2$, but shows an enhancement compared to the SFR at $z\gtrsim 2$.

The Konus-Wind Catalog of Gamma-Ray Bursts with Known Redshifts. I. Bursts Detected in the Triggered Mode

Abstract In this catalog, we present the results of a systematic study of gamma-ray bursts (GRBs) with reliable redshift estimates detected in the triggered mode of the Konus-Wind (KW) experiment during the period from 1997 February to 2016 June. The sample consists of 150 GRBs (including 12 short/hard bursts) and represents the largest set of cosmological GRBs studied to date over a broad energy band. From the temporal and spectral analyses of the sample, we provide the burst durations, the spectral lags, the results of spectral fits with two model functions, the total energy fluences, and the peak energy fluxes. Based on the GRB redshifts, which span the range , we estimate the rest-frame, isotropic-equivalent energy, and peak luminosity. For 32 GRBs with reasonably constrained jet breaks, we provide the collimation-corrected values of the energetics. We consider the behavior of the rest-frame GRB parameters in the hardness–duration and hardness–intensity planes, and confirm the “Amati” and “Yonetoku” relations for Type II GRBs. The correction for the jet collimation does not improve these correlations for the KW sample. We discuss the influence of instrumental selection effects on the GRB parameter distributions and estimate the KW GRB detection horizon, which extends to , stressing the importance of GRBs as probes of the early universe. Accounting for the instrumental bias, we estimate the KW GRB luminosity evolution, luminosity and isotropic-energy functions, and the evolution of the GRB formation rate, which are in general agreement with those obtained in previous studies.

Modelling the luminosity function of long gamma-ray bursts using Swift and Fermi

I have used a sample of long Gamma Ray Bursts (GRBs) common to both \emph{Swift} and \emph{Fermi} to re-derive the parameters of the Yonetoku correlation. This allowed me to self-consistently estimate pseudo redshifts of all the bursts with unknown redshifts. This is the first time such a large sample of GRBs from these two instruments are used, both individually and in conjunction, to model the long GRB luminosity function. The GRB formation rate is modelled as the product of the cosmic star formation rate and a GRB formation efficiency for a given stellar mass. An exponential cut-off powerlaw luminosity function fits the data reasonably well, with $\nu = 0.6$ and $ L_b = 5.4 \times10^{52} \, \rm{erg.s^{-1}},$ and does not require a cosmological evolution. In the case of a broken powerlaw, it is required to incorporate a sharp evolution of the break given by $L_{b}\sim0.3\times10^{52}\left(1+z\right)^{2.90} \, \rm{erg.s^{-1}},$ and the GRB formation efficiency (degenerate up to a beaming factor of GRBs) decreases with redshift as $\propto\left(1+z\right)^{-0.80}.$ However it is not possible to distinguish between the two models. The derived models are then used as templates to predict the distribution of GRBs detectable by CZTI on board \emph{AstroSat}, as a function of redshift and luminosity. This demonstrates that via a quick localization and redshift measurement of even a few CZTI GRBs, \emph{AstroSat} will help in improving the statistics of GRBs both typical and peculiar.

ASTROBIOLOGICAL EFFECTS OF GAMMA-RAY BURSTS IN THE MILKY WAY GALAXY

A planet having protective ozone within the collimated beam of a Gamma Ray Burst (GRB) may suffer ozone depletion, potentially causing a mass extinction event to existing life on a planet's surface and oceans. We model the dangers of long GRBs to planets in the Milky Way and utilize a static statistical model of the Galaxy that matches major observable properties, such as the inside-out star formation history, metallicity evolution, and 3-dimensional stellar number density distribution. The GRB formation rate is a function of both the star formation history and metallicity; however, the extent to which chemical evolution reduces the GRB rate over time in the Milky Way is still an open question. Therefore, we compare the damaging effects of GRBs to biospheres in the Milky Way using two models. One model generates GRBs as a function of the inside-out star formation history. The other model follows the star formation history, but generates GRB progenitors as a function of metallicity, thereby favoring metal-poor host regions of the Galaxy over time. If the GRB rate only follows the star formation history, the majority of the GRBs occur in the inner Galaxy. However, if GRB progenitors are constrained to low metallicity environments, then GRBs only form in the metal-poor outskirts at recent epochs. Interestingly, over the past 1 Gyr, the surface density of stars (and their corresponding planets) that survive a GRB is still greatest in the inner galaxy in both models. The present day danger of long GRBs to life at the solar radius ($R_\odot=8$ kpc) is low. We find that at least $\sim$65% of stars survive a GRB over the past 1 Gyr. Furthermore, when the GRB rate was expected to have been enhanced at higher redshifts, such as $z\gtrsim0.5$, our results suggest that a large fraction of planets would have survived these lethal GRB events.

The pulse luminosity function ofSwiftgamma-ray bursts

The complete Swift Burst Alert Telescope and X-Ray Telescope light curves of 118 gamma-ray bursts (GRBs) with known redshifts were fitted using the physical model of GRB pulses by Willingale et al. to produce a total of 607 pulses. We compute the pulse luminosity function utilizing three GRB formation rate models: a progenitor that traces the cosmic star formation rate density (CSFRD) with either a single population of GRBs, coupled to various evolutionary parameters, or a bimodal population of high- and low-luminosity GRBs, and a direct fit to the GRB formation rate excluding any a priori assumptions. We find that a single population of GRB pulses with an evolving luminosity function is preferred over all other univariate evolving GRB models, or bimodal luminosity functions in reproducing the observed GRB pulse L-z distribution and that the magnitude of the evolution in brightness is consistent with studies that utilize only the brightest GRB pulses. We determine that the appearance of a GRB formation rate density evolution component is an artifact of poor parametrization of the CSFRD at high redshifts rather than indicating evolution in the formation rate of early epoch GRBs. We conclude that the single brightest region of a GRB light curve holds no special property, by incorporating pulse data from the totality of GRB emission we boost the GRB population statistics by a factor of 5, rule out some models utilized to explain deficiencies in GRB formation rate modelling, and constrain more tightly some of the observed parameters of GRB behaviour.

AN UNEXPECTEDLY LOW-REDSHIFT EXCESS OF SWIFT GAMMA-RAY BURST RATE

Gamma-ray bursts (GRBs) are the most violent explosions in the Universe and can be used to explore the properties of high-redshift universe. It is believed that the long GRBs are associated with the deaths of massive stars. So it is possible to use GRBs to investigate the star formation rate (SFR). In this paper, we use Lynden-Bell's $c^-$ method to study the luminosity function and rate of \emph{Swift} long GRBs without any assumptions. We find that the luminosity of GRBs evolves with redshift as $L(z)\propto g(z)=(1+z)^k$ with $k=2.43_{-0.38}^{+0.41}$. After correcting the redshift evolution through $L_0(z)=L(z)/g(z)$, the luminosity function can be expressed as $\psi(L_0)\propto L_0^{-0.14\pm0.02}$ for dim GRBs and $\psi(L_0)\propto L_0^{-0.70\pm0.03}$ for bright GRBs, with the break point $L_{0}^{b}=1.43\times10^{51}~{\rm erg~s^{-1}}$. We also find that the formation rate of GRBs is almost constant at $z<1.0$ for the first time, which is remarkably different from the SFR. At $z>1.0$, the formation rate of GRB is consistent with the SFR. Our results are dramatically different from previous studies. Some possible reasons for this low-redshift excess are discussed. We also test the robustness of our results with Monte Carlo simulations. The distributions of mock data (i.e., luminosity-redshift distribution, luminosity function, cumulative distribution and $\log N-\log S$ distribution) are in good agreement with the observations. Besides, we also find that there are remarkable difference between the mock data and the observations if long GRB are unbiased tracers of SFR at $z<1.0$.

Gamma-ray bursts: the isotropic-equivalent-energy function and the cosmic formation rate

Gamma-ray bursts (GRBs) are brief but intense emission of soft $\gamma-$rays, mostly lasting from a few seconds to a few thousand seconds. For such kind of high energy transients, their isotropic-equivalent-energy ($E_{\rm iso}$) function may be more scientifically meaningful when compared with GRB isotropic-equivalent-luminosity function ($L_{\rm iso}$), as the traditional luminosity function refers to steady emission much longer than a few thousand seconds. In this work we for the first time construct the isotropic-equivalent-energy function for a sample of 95 bursts with measured redshifts ($z$) and find an excess of high-$z$ GRBs. Assuming that the excess is caused by a GRB luminosity function evolution in a power-law form, we find a cosmic evolution of $E_{\rm iso}\propto(1+z)^{1.80^{+0.36}_{-0.63}}$, which is comparable to that between $L_{\rm iso}$ and $z$, i.e., $L_{\rm iso}\propto(1+z)^{2.30^{+0.56}_{-0.51}}$ (both $1\sigma$). The evolution-removed isotropic-equivalent-energy function can be reasonably fitted by a broken power-law, in which the dim and bright segments are $\psi(E_{\rm iso})\propto E_{\rm iso}^{-0.27\pm0.01}$ and $\psi(E_{\rm iso})\propto E_{\rm iso}^{-0.87\pm0.07}$, respectively ($1\sigma$). For the cosmic GRB formation rate, it increases quickly in the region of $0 \leq z \lesssim 1$, and roughly keeps constant for $1\lesssim z \lesssim 4$, and finally falls with a power index of $-3.80\pm2.16$ for $z\gtrsim 4$, in good agreement with the observed cosmic star formation rate so far.

The Gamma-Ray Burst Luminosity Function in the Light of the Swift 2 Year Data

We compute the luminosity function (LF) and the formation rate of long gamma-ray bursts (GRBs) by fitting the observed differential peak flux distribution obtained by BATSE in three different scenarios: (1) GRBs follow the cosmic star formation, and their LF is constant in time; (2) GRBs follow the cosmic star formation, but the LF varies with redshift; and (3) GRBs form preferentially in low-metallicity environments. We find that the differential peak flux number counts obtained by BATSE and by Swift can be reproduced using the same LF and GRB formation rate, indicating that the two satellites are observing the same GRB population. We then check the resulting redshift distributions in light of Swift 2 year data, focusing in particular on the relatively large sample of GRBs detected at z > 2.5. We show that models in which GRBs trace the cosmic star formation and are described by a constant LF are ruled out by the number of high-z Swift detections. This conclusion does not depend on the redshift distribution of bursts that lack optical identification, nor on the existence of a decline in star formation rate at z > 2, nor on the adopted faint end of the GRB LF. Swift observations can be explained by assuming that the LF varies with redshift and/or that GRB formation is limited to low-metallicity environments.

Formation rates of core-collapse supernovae and gamma-ray bursts

Core collapse of massive stars with a relativistic jet expulsion along the rotation axis is a widely discussed scenario for gamma-ray burst (GRB) production. However the nature of the stellar progenitor remains unclear. We study the evolution of stars that may be the progenitors of long-soft GRBs - rotating naked helium stars presumed to have lost their envelopes to winds or companions. Our aim is to investigate the formation and development of single and binary systems and from this population evaluate the rates of interesting individual species. Using a rapid binary-evolution algorithm that enables us to model the most complex binary systems and to explore the effect of metallicity on GRB production, we draw the following conclusions. First, we find that, if we include an approximate treatment of angular momentum transport by mass loss, the resulting spin rates for single stars become too low to form a centrifugally supported disc that can drive a GRB engine, although they do have sufficiently massive cores to form black holes. Secondly, massive stars in binaries result in enough angular momentum -due to spin-orbit tidal interactions - to form a centrifugally supported disc and are thus capable of supplying a sufficient number of progenitors. This holds true even if only a small fraction of bursts are visible to a given observer and the GRB rate is several hundred times larger than the observed rate. Thirdly, low-metallicity stars aid the formation of rapidly rotating, massive helium cores at collapse and so their evolution is likely to be affected by the local properties of the interstellar medium (ISM). This effect could increase the GRB formation rate by a factor of 5-7 at Z = Z ○. /200. Finally we quantify the effects of mass loss, common-envelope evolution and black-hole formation and show that more stringent constraints to many of these evolution parameters are needed in order to draw quantitative conclusions from population synthesis work.

Gamma-ray burst neutrino background and star formation history in the universe

We estimate the flux of the gamma-ray burst (GRB) neutrino background and compute the event rate at SK and TITAND in the collapsar model, assuming that GRB formation rate is proportional to the star formation rate. We find that the predicted background neutrino flux is highly sensitive to unknown model parameters, mainly to the mass–accretion rate, to the fraction of disk energy emitted in thermal neutrinos (as opposed to emission through electromagnetic processes), and to the fraction of collapsar events leading to GRBs. The predicted neutrino flux varies over many orders of magnitude as the values of unknown model parameters are varied. We investigate the detection possibility of thermal neutrinos from collapsars which lead to GRBs by TITAND. We find that the GRB neutrino background might be detected by TITAND within ∼10 yrs only for the optimistic cases in which the average mass–accretion rate is high (≳ a few M ⊙ s −1), and the probability that one collapsar generates a GRB is high ( f=0.5–1.0).