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— A color image of the IPN error box of SHB 790613 (green polygon) made from P60 BV I imaging. Four galaxies with apparently similar colors are visible (green circles).
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The detection and characterization of the afterglow emission and host galaxies of short-hard gamma-ray bursts (SHBs) is one of the most exciting recent astronomical discoveries. In particular, indications that SHB progenitors belong to old stellar populations, in contrast to the long-soft GRBs, provide a strong clue about the physical nature of the...
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Context 1
... Observatory, revealed a field dense with red galaxies both within and outside of the error box. Four reddish galaxies all with i < 20.5 were within, or on the edge of, this small error box. This is an apparently high density of galaxies even when compared to the surrounding dense area. The imaging data show that these galaxies have similar colors (Fig. 1) and suggest that they are probably physically associated. In order to test whether this galaxy density is unique we extract from the SDSS ( Abazajian et al. 2005) a catalog of galaxies that cover ≈ 24 deg 2 from regions with Galactic extinction comparable to that in the direction of SHB 790613. We find that the probability to find ...
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Citations
... Given the long delay time of NS+He WD binaries (and also the long timescale expected from the subsequent GW shrinking of the orbit to produce the UCXB models studied here), this kind of AIC-driven short gamma-ray burst would therefore be likely to appear in an old stellar population. This is in accordance with the finding that the progenitors of short gamma-ray bursts have a preference for early-type galaxies (Gal-Yam et al. 2008). In addition, Hao & Yuan (2013) found that the typical delay time of short gamma-ray bursts is τ > 3 Gyr. ...
The formation path to ultracompact X-ray binaries (UCXBs) with black hole (BH) accretors is still unclear. In the classical formation scenario, it is difficult to eject the massive envelope of the progenitor star of the BH via the common envelope process. Given that some neutron stars (NSs) in binary systems evidently have birth masses close to ∼2.0 M ⊙ , we explore here the possibility that BH-UCXBs may form via the accretion-induced collapse (AIC) of accreting NSs, assuming that these previously evolved in low-mass X-ray binaries to masses all the way up to the maximum limit of an NS. We demonstrate this formation path by modeling a few cases of NS-UCXBs with initial NS masses close to the maximum mass of an NS that evolve into BH-UCXBs after the NS accretes material from its He white dwarf (WD) companion. We follow the evolution of the post-AIC BH-UCXB and, based on simple arguments, we anticipate that there is about one BH-UCXB with an AIC origin and a He WD donor within the current sample of known UCXBs and that two to five such BH-UCXBs may be detected in gravitational waves by LISA. In addition, we find that the X-ray luminosity of NS-UCXBs near their orbital period minimum exceeds ∼10 ³⁹ erg s ⁻¹ , and thus, such systems may appear as ultraluminous X-ray sources.
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... Early studies on the hosts of few observed SGRBs had concluded that the population of hosts is dominated by passive galaxies and so, the progenitors of SGRBs were thought to be objects with long delay times (see Prochaska et al. 2006;Nakar 2007;Gal-Yam et al. 2008). ...
Recently, the characterisation of binary systems of neutron stars has become central in various fields such as gravitational waves, gamma-ray bursts (GRBs), and the chemical evolution of galaxies. In this work, we explore possible observational proxies that can be used to infer some characteristics of the delay time distribution (DTD) of neutron star mergers (NSMs). We construct a sample of model galaxies that fulfils the observed galaxy stellar mass function, star formation rate versus mass relation, and the cosmic star formation rate density. The star formation history of galaxies is described with a log-normal function characterised by two parameters: the position of the maximum and the width of the distribution. We assume a theoretical DTD that mainly depends on the lower limit and the slope of the distribution of the separations of the binary neutron stars systems at birth. We find that the current rate of NSMs ($\mathcal{R}=320^{+490}_{-240}$ Gpc$^{-3}$yr$^{-1}$) requires that $\sim0.3$ per cent of neutron star progenitors lives in binary systems with the right characteristics to lead to a NSM within a Hubble time. We explore the expected relations between the rate of NSMs and the properties of the host galaxy. We find that the most effective proxy for the shape of the DTD of NSMs is the current star formation activity of the typical host. At present, the fraction of short-GRBs observed in star-forming galaxies favours DTDs with at least $\sim40\%$ of mergers within $100$ Myr. This conclusion will be put on a stronger basis with larger samples of short-GRBs with host association (e.g. $600$ events at $z \leq 1$)
... ,Gal-Yam et al. (2008),Guetta & Piran (2006),Guetta & Stella (2009,Nakar et al. (2006), and Wanderman & Piran ...
Detecting the afterglows of double‐neutron star merger events is a challenging task because of the quick fading of the observed flux. In order to create an efficient observing strategy for their observing method, it is crucial to know their intrinsic rate. Unfortunately, the numerous models existing today predict this rate on a very wide range. Our goal in this paper is to compare the different levels of approximations in order to determine their reliability. We find that there is a significant discrepancy in the expected detection rate between the spherical and axisymmetrical models (∼18 and ≲ 1 yr−1, respectively). In addition, choosing different models for the input parameters (for example, redshift and time delay distribution) has also a strong effect on the results.
... Photometry of SN 2010mb was obtained by the P48, the GRB camera (Cenko et al. 2006) mounted on the Palomar 60" telescope (P60), the Large Format Camera mounted on the Palomar 200" Hale telescope (P200), and the Low Resolution Imaging Spectrograph (LRIS) mounted on the 10m Keck-I telescope (Oke et al. 1995). Data were reduced using the MKDIFFLC photometry routine (Gal-Yam et al. 2004;Gal-Yam et al. 2008), except for P48 data reduced using PSF photometry on image subtractions (e.g., Ofek et al. 2013). We adopt a distance modulus of 38.88 mag, corresponding to a distance of ≈ 599 Mpc, a Galactic extinction correction of 0.04 mag at r-band, and a reddening E(B − V ) = 0.015 mag, taken from NED 2 . ...
We present our observations of SN 2010mb, a Type Ic SN lacking spectroscopic
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agreement with models of pulsational pair-instability SNe described in the
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... The detection of short GRB afterglows starting in mid-2005 provided an opportunity to investigate the various progenitor models through a range of observational tests: the redshift distribution ( Gal-Yam et al. 2008), the host galaxy demographics , the afterglow properties Gehrels et al. 2008;Kann et al. 2008;Nysewander et al. 2009), and perhaps most importantly, their locations relative to the host galaxies ( Fong et al. 2010). As of mid-2010, X-ray and optical afterglows have been detected from 40 and 20 short GRBs, respectively, with the latter sample providing accurate sub-arcsecond positions. ...
[abridged] We investigate the afterglow properties and large-scale
environments of several short-duration gamma-ray bursts (GRBs) with
sub-arcsecond optical afterglow positions but no bright coincident host
galaxies. The purpose of this joint study is to robustly assess the possibility
of significant offsets, a hallmark of the compact object binary merger model.
Five such events exist in the current sample of 20 short bursts with optical
afterglows, and we find that their optical, X-ray, and gamma-ray emission are
systematically fainter. These differences may be due to lower circumburst
densities (by about an order of magnitude), to higher redshifts (by dz~0.5-1),
or to lower energies, although in the standard GRB model the smaller gamma-ray
fluences cannot be explained by lower densities. To study the large-scale
environments we use deep optical observations to place limits on underlying
hosts and to determine probabilities of chance coincidence for galaxies near
each burst. In 4 of the 5 cases the lowest probabilities of chance coincidence
(P(<dR)~0.1) are associated with bright galaxies at separations of dR~10",
while somewhat higher probabilities of chance coincidence are associated with
faint galaxies at separations of ~2". By measuring redshifts for the brighter
galaxies in three cases (z=0.111, 0.473, 0.403) we find physical offsets of
~30-75 kpc, while for the faint hosts the assumption of z>1 leads to offsets of
~15 kpc. Alternatively, the limits at the burst positions (>26 mag) can be
explained by typical short GRB host galaxies (L~0.1-1 L*) at z>2. Thus, two
possibilities exist: (i) ~1/4 of short GRBs explode ~50 kpc or ~15 kpc from the
centers of z~0.3 or z>1 galaxies, respectively, and have fainter afterglows due
to the resulting lower densities; or (ii) ~1/4 of short GRBs occur at z>2 and
have fainter afterglows due to their higher redshifts.
Recently, the characterisation of binary systems of neutron stars has become central in various fields such as gravitational waves, gamma-ray bursts (GRBs), and the chemical evolution of galaxies. In this work, we explore possible observational proxies that can be used to infer some characteristics of the delay time distribution (DTD) of neutron star mergers (NSMs). We construct a sample of model galaxies that fulfils the observed galaxy stellar mass function, star formation rate versus mass relation, and the cosmic star formation rate density. The star formation history of galaxies is described with a log-normal function characterised by two parameters: the position of the maximum and the width of the distribution. We assume a theoretical DTD that mainly depends on the lower limit and the slope of the distribution of the separations of the binary neutron stars systems at birth. We find that the current rate of NSMs ($\mathcal {R}=320^{+490}_{-240}$ Gpc−3yr−1) requires that ∼0.3 per cent of neutron star progenitors lives in binary systems with the right characteristics to lead to a NSM within a Hubble time. We explore the expected relations between the rate of NSMs and the properties of the host galaxy. We find that the most effective proxy for the shape of the DTD of NSMs is the current star formation activity of the typical host. At present, the fraction of short-GRBs observed in star-forming galaxies favours DTDs with at least $\sim 40\%$ of mergers within 100 Myr. This conclusion will be put on a stronger basis with larger samples of short-GRBs with host association (e.g. 600 events at z ≤ 1).
We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory (PTF) survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average by about 4 and 2 mag, respectively. The SLSNe-I peak absolute magnitudes in rest-frame $g$-band span $-22\lesssim M_g \lesssim-20$ mag, and these peaks are not powered by radioactive $^{56}$Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on a photometric criterion. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly-declining and slowly-declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times the SLSN-I light curves slow down and cluster around the $^{56}$Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 ${\rm M}_\odot$ of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with three exceptions, and can mimic the radioactive decay of $^{56}$Co, up to $\sim400$ days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.
Gamma-ray bursts (GRBs) display a bimodal duration distribution, with a
separation between the short- and long-duration bursts at about 2 sec. The
progenitors of long GRBs have been identified as massive stars based on their
association with Type Ic core-collapse supernovae, their exclusive location in
star-forming galaxies, and their strong correlation with bright ultraviolet
regions within their host galaxies. Short GRBs have long been suspected on
theoretical grounds to arise from compact object binary mergers (NS-NS or
NS-BH). The discovery of short GRB afterglows in 2005, provided the first
insight into their energy scale and environments, established a cosmological
origin, a mix of host galaxy types, and an absence of associated supernovae. In
this review I summarize nearly a decade of short GRB afterglow and host galaxy
observations, and use this information to shed light on the nature and
properties of their progenitors, the energy scale and collimation of the
relativistic outflow, and the properties of the circumburst environments. The
preponderance of the evidence points to compact object binary progenitors,
although some open questions remain. Based on this association, observations of
short GRBs and their afterglows can shed light on the on- and off-axis
electromagnetic counterparts of gravitational wave sources from the Advanced
LIGO/Virgo experiments.
Context. The progenitors of short gamma-ray bursts (SGRBs) have not yet been
well identified. The most popular model is the merger of compact object
binaries (NS-NS/NS-BH). However, other progenitor models cannot be ruled out.
The delay-time distribution of SGRB progenitors, which is an important property
to constrain progenitor models, is still poorly understood. Aims. We aim to
better constrain the luminosity function of SGRBs and the delay-time
distribution of their progenitors with newly discovered SGRBs. Methods. We
present a low-contamination sample of 16 Swift SGRBs that is better defined by
a duration shorter than 0.8 s. By using this robust sample and by combining a
self-consistent star formation model with various models for the distribution
of time delays, the redshift distribution of SGRBs is calculated and then
compared to the observational data. Results. We find that the power-law delay
distribution model is disfavored and that only the lognormal delay distribution
model with the typical delay tau >= 3 Gyr is consistent with the data.
Comparing Swift SGRBs with T90 > 0.8 s to our robust sample (T90 < 0.8 s), we
find a significant difference in the time delays between these two samples.
Conclusions. Our results show that the progenitors of SGRBs are dominated by
relatively long-lived systems (tau >= 3 Gyr), which contrasts the results found
for Type Ia supernovae. We therefore conclude that primordial NS-NS systems are
not favored as the dominant SGRB progenitors. Alternatively, dynamically formed
NS-NS/BH and primordial NS-BH systems with average delays longer than 5 Gyr may
contribute a significant fraction to the overall SGRB progenitors.
