We employ realistic constraints on astrophysical and instrumental selection effects to model the gamma-ray burst (GRB) redshift distribution using Swift triggered redshift samples acquired from ...optical afterglows and The Optically Unbiased GRB Host survey. Models for the Malmquist bias, redshift desert, and the fraction of afterglows missing because of host galaxy dust extinction are used to show how the 'true' GRB redshift distribution is distorted to its presently observed biased distribution. We also investigate another selection effect arising from a correlation between E
iso and L
opt. The analysis, which accounts for the missing fraction of redshifts in the two data subsets, shows that a combination of selection effects (both instrumental and astrophysical) can describe the observed GRB redshift distribution. Furthermore, the observed distribution is compatible with a GRB rate evolution that tracks the global star formation rate, although the rate at high z cannot be constrained with confidence. Taking optical selection effects into account, it may not be necessary to invoke high-energy GRB luminosity evolution with redshift to explain the observed GRB rate at high z.
ABSTRACT
Short gamma‐ray bursts (SGRBs) observed by Swift potentially reveal the first insight into cataclysmic compact object mergers. To ultimately acquire a fundamental understanding of these ...events requires pan‐spectral observations and knowledge of their spatial distribution to differentiate between proposed progenitor populations. Up to 2012 April, there are only some 30 per cent of SGRBs with reasonably firm redshifts, and this sample is highly biased by the limited sensitivity of Swift to detect SGRBs. We account for the dominant biases to calculate a realistic SGRB rate density out to z ≈ 0.5 using the Swift sample of peak fluxes, redshifts and those SGRBs with a beaming angle constraint from X‐ray/optical observations. We find an SGRB lower rate density of 8−3+5 Gpc −3 yr −1 (assuming isotropic emission) and a beaming corrected upper limit of 1100−470+700 Gpc −3 yr −1. Assuming a significant fraction of binary neutron star mergers produce SGRBs, we calculate lower and upper detection rate limits of (1–180) yr−1 by an Advanced LIGO (aLIGO) and Virgo coincidence search. Our detection rate is similar to the lower and realistic rates inferred from extrapolations using Galactic pulsar observations and population synthesis.
Abstract
Afterglows of gamma-ray bursts (GRBs) from Population III (Pop III) stars could reveal the formation history and properties of these first generation stars. Through detailed simulation, we ...predict the prospects of detecting these afterglows with a range of established, existing and upcoming telescopes across the spectrum from radio waves to X-rays. The simulations show that the afterglow light curves of Pop III GRBs at high redshift (≳8) are very similar to those of Pop I/II GRBs at lower redshift (∼2), with the distinction that Lyα absorption at Pop III redshifts removes any optical and some near-infrared (NIR) component. We calculate that within a single field of view (FOV) of the Australian Square Kilometre Array Pathfinder (ASKAP) telescope there will be on average four detectable Pop III GRB afterglows. This is the product of ASKAP's large FOV and excellent sensitivity at wavelengths where the afterglows are very long-lasting. We show that the exceptional sensitivity of the James Webb Space Telescope (JWST) Near-InfraRed Camera will make this the optimal instrument for afterglow follow-up and redshift measurement, while JWST Near-InfraRed Spectrograph will be able to detect the absorption features of Pop III-enriched environments in 70 per cent of directed Pop III GRB afterglows. We also find that the Atacama Large Millimetre Array is very poorly suited to observe these afterglows, and that the Spectrum-Roentgen-Gamma 4 yr all-sky X-ray survey has a 12 per cent chance of detecting an orphan Pop III GRB afterglow. The optimal strategy for detecting, identifying and studying Pop III GRB afterglows is to have JWST attempt NIR photometry of afterglows with a detected radio component but no detected optical component.
In this article we further constrain the phenomenology and progenitor properties of this peculiar GRB by performing a multiband temporal and spectral analysis of both the prompt and the afterglow ...emission. We use proprietary and publicly available data from Swift, Konus WIND, XMM-Newton, and TAROT, as well as from other ground-based optical and radio telescopes. We find some peculiar properties that are possibly connected to the exceptional nature of this burst, namely: (1) an unprecedented large optical delay of 410 + or - 50 s between the peak time in gamma-rays and the peak time in the optical of a marked multiwavelength flare; (2) multiwavelength prompt emission spectral modeling requires a certain amount of dust in the circumburst environment. (3) we detect the presence of a hard spectral extra power-law component at the end of the X-ray steep steep decay phase and before the start of the X-ray afterglow, which has never been revealed thus far in past GRBs.
GRB160203A: an exploration of lumpy space Crisp, H; Gendre, B; Howell, E J ...
Monthly notices of the Royal Astronomical Society,
06/2021, Letnik:
504, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
GRB160203A is a high redshift long gamma-ray burst presenting a collection of unusual features in the afterglow light curve. We study its optical and X-ray data. We find this event to occur ...within a constant density medium during the first part of the afterglow. However, after 13 ks we spot some flaring activities in the optical and X-ray light curves. We explain these flares by fluctuation of densities of the surrounding medium. Other scenarios, such as energy injection from a magnetar or variation of microphysical parameters are not supported by the data. We tentatively link these fluctuations to an unusual host galaxy, with gas density similar to the Milky Way and a dense cocoon of matter around a stellar progenitor similar to a Wolf–Rayet star. A termination shock scenario is found to be less likely.
We show that the redshift and peak flux distributions of gamma-ray bursts (GRBs) have an observation time dependence that can be used to discriminate between different burst populations. We ...demonstrate how observation time relations can be derived from the standard integral distributions and that they can differentiate between GRB populations detected by both the Burst and Transient Source Experiment (BATSE) and Swift satellites. Using Swift data, we show that a redshift-observation time relation (log Z-log T) is consistent with both a peak flux-observation time relation (log P-log T) and a standard log N-log P brightness distribution. As the method depends only on rarer small-z events, it is invariant to high-z selection effects. We use the log Z-log T relation to show that subluminous GRBs are a distinct population occurring at a higher rate of the order of 150+ 180
− 90 Gpc− 3 yr− 1. Our analysis suggests that GRB 060505 - a relatively nearby GRB observed without any associated supernova - is consistent with a subluminous population of bursts. Finally, we show that our relations can be used as a consistency test for some of the proposed GRB spectral energy correlations.
We investigate the prospects of detecting radio afterglows from long Gamma-Ray Bursts (GRBs) from Population III (Pop III) progenitors using the Square Kilometre Array (SKA) precursor instruments MWA ...(Murchison Widefield Array) and ASKAP (Australian SKA Pathfinder). We derive a realistic model of GRB afterglows that encompasses the widest range of plausible physical parameters and observation angles. We define the best case scenario of Pop III GRB energy and redshift distributions. Using probability distribution functions fitted to the observed microphysical parameters of long GRBs, we simulate a large number of Pop III GRB afterglows to find the global probability of detection. We find that ASKAP may be able to detect 35 per cent of Pop III GRB afterglows in the optimistic case, and 27 per cent in the pessimistic case. A negligible number will be detectable by MWA in either case. Detections per image for ASKAP, found by incorporating intrinsic rates with detectable time-scales, are as high as ∼6000 and as low as ∼11, which shows the optimistic case is unrealistic. We track how the afterglow flux density changes over various time intervals and find that, because of their very slow variability, the cadence for blind searches of these afterglows should be as long as possible. We also find Pop III GRBs at high redshift have radio afterglow light curves that are indistinguishable from those of regular long GRBs in the more local Universe.
We compute the intrinsic isotropic peak luminosity function (LF) and formation rate of long gamma-ray bursts (LGRBs) using a novel approach. We complement a standard log N-log P brightness ...distribution and V
max estimations with two observation–time relations: a redshift–observation-time relation (log z-log T) and a new luminosity–observation-time relation (log L-log T). We show that this approach reduces degeneracies that exist between the rate and LF of a brightness distribution. To account for the complex triggering algorithm employed by Swift, we use recent results of Lien et al. (2014) to produce a suite of efficiency functions. Using these functions with the above methods, we show that a log L-log T method can provide good constraints on the form of the LF, particularly the high end. Using a sample of 175 peak luminosities determined from redshifts with well-defined selection criteria, our results suggest that LGRBs occur at a local rate (without beaming corrections) of 0.7 < ρ0 < 0.8 Gpc−3 yr−1. Within this range, assuming a broken power-law LF, we find best estimates for the low- and high-energy indices of −0.95 ± 0.09 and −2.59 ± 0.93, respectively, separated by a break luminosity 0.80 ± 0.43 × 1052 erg s−1.
To assess the risk of cardiovascular morbidity and cardiac risk factors in long-term survivors of testicular cancer according to treatment received.
All resident male patients registered in the ...United Kingdom between 1982 and 1992 attending for follow-up were eligible for recruitment. Patients completed a current health questionnaire and underwent clinical review, along with hematologic, biochemical, and hormonal profiles. For patients not under routine review, follow-up information was sought from their general practitioner and mortality data were sought from the Office of National Statistics. Descriptive analysis was performed on all variables and comparisons were made among patients treated by orchidectomy and follow-up only, chemotherapy alone (C), radiotherapy alone (RT), and radiotherapy and chemotherapy (C/RT).
Data on cardiovascular events were available on 992 patients. After a median follow-up of 10.2 years, 68 events had been reported, including 18 deaths. After adjusting for age, increased risk for cardiac events was seen after C (relative risk RR = 2.59; 95% confidence interval CI, 1.15 to 5.84; P =.022), RT (RR = 2.40; 95% CI, 1.04 to 5.45; P =.036), and C/RT (RR = 2.78; 95% CI, 1.09 to 7.07; P =.032). There were no significant differences in cardiac risk factors. On multivariate analysis, age, treatment group, free thyroxine, protein, and magnesium levels were associated with cardiovascular disease.
In long-term survivors of testicular cancer, we observed a two-fold or greater risk of developing cardiovascular disease. This was not due to increases in cardiac risk factors, which suggests a direct or indirect treatment effect. These data support the continued research into the minimization of treatment in good-prognosis testicular cancer.
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