BATSE Observations of Gamma‐Ray Burst Tails

Connaughton, V.

doi:10.1086/338695

Cited by 111 publications

(100 citation statements)

References 28 publications

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“…There was an expectation, based primarily on detections of putative afterglow components in the tails of GRBs (Connaughton 2002;Giblin et al 2002;Lazzati et al 2001) and also from studies extrapolating the X-ray afterglow flux back to the prompt emission (e.g., Costa et al 1997;Piro et al 1998;Frontera et al 2000), that the X-ray afterglows measured by Swift would directly proceed and connect to the prompt emission. That is, the emission at t % 10 2 Y10 4 s was expected to mirror the temporal /spectral properties of the well established later emission plotted in the right panel of Figure 1.…”

Section: Events With No Hardness Variationmentioning

confidence: 99%

X‐Ray Hardness Variations as an Internal/External Shock Diagnostic

Butler

Kocevski

2007

ApJ

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The early, highly time-variable X-ray emission immediately following gamma-ray bursts (GRBs) exhibits strong spectral variations that are unlike the temporally smoother emission that dominates after t $ 10 3 s. The ratio of hardchannel (1.3Y10.0 keV ) to soft-channel (0.3Y1.3 keV ) counts in the Swift X-ray telescope provides a new measure delineating the end time of this emission. We define T H as the time at which this transition takes place and measure for 59 events a range of transition times that spans 10 2 to 10 4 s, on average 5 times longer than the prompt T 90 duration observed in the gamma-ray band. It is very likely that the mysterious light-curve plateau phase and the later powerlaw temporal evolution, both of which typically occur at times greater than T H and hence exhibit very little hardness ratio evolution, are both produced by external shocking of the surrounding medium and not by the internal shocks thought responsible for the earlier emission. We use the apparent lack of spectral evolution to discriminate among proposed models for the plateau phase emission. We favor energy injection scenarios with a roughly linearly increasing input energy versus time for six well-sampled events with nearly flat light curves at t % 10 3 Y10 4 s. Also, using the transition time T H as the delineation between the GRB and afterglow emission, we calculate that the kinetic energy in the afterglow shock is typically a factor of 10 lower than that released in the GRB. Three very bright events suggest that this presents a missing X-ray flux problem rather than an efficiency problem for the conversion of kinetic energy into the GRB. Lack of hardness variations in these three events may be due to a very highly relativistic outflow or due to a very dense circumburst medium. There are a handful of rare cases of very late time t > 10 4 s hardness evolution, which may point to residual central engine activity at very late time.

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Section: Events With No Hardness Variationmentioning

confidence: 99%

X‐Ray Hardness Variations as an Internal/External Shock Diagnostic

Butler

Kocevski

2007

ApJ

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“…Long-lasting hard X-ray/γ-ray (>10 keV) emission from GRBs has been observed on several occasions with detections of up to ∼4000 s (e.g. Connaughton 2002;Giblin et al 2002). Evidence of emission up to ∼1000 s after the trigger has been revealed A&A 567, A84 (2014) which showed highly variable γ-and X-ray emission extending over ∼20 ks (Evans et al 2014).…”

Section: Introductionmentioning

confidence: 99%

GRB 120711A: an intense INTEGRAL burst with long-lasting softγ-ray emission and a powerful optical flash

Martín-Carrillo

Hanlon

Topinka

et al. 2014

A&A

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A long and intense γ-ray burst (GRB) was detected by INTEGRAL on 11 July 2012 with a duration of ∼115 s and fluence of 2.8 × 10 −4 erg cm −2 in the 20 keV−8 MeV energy range. GRB 120711A was at z ∼ 1.405 and produced soft γ-ray emission (>20 keV) for at least ∼10 ks after the trigger. The GRB was observed by several ground-based telescopes that detected a powerful optical flash peaking at an R-band brightness of ∼11.5 mag at ∼126 s after the trigger, or ∼9th magnitude when corrected for the host galaxy extinction (A V ∼ 0.85). The X-ray afterglow was monitored by the Swift, XMM-Newton, and Chandra observatories from 8 ks to 7 Ms and provides evidence for a jet break at ∼0.9 Ms. We present a comprehensive temporal and spectral analysis of the long-lasting soft γ-ray emission detected in the 20−200 keV band with INTEGRAL/IBIS, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow and the optical/near-infrared detections from Watcher, Skynet/PROMPT, GROND, and REM. The prompt emission had a very hard spectrum (E peak ∼ 1 MeV) and yields an E γ,iso ∼ 10 54 erg (1 keV−10 MeV rest frame), making GRB 120711A one of the most energetic GRBs detected so far. We modelled the long-lasting soft γ-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the near-infrared to GeV energies suggest that the emission is produced by a broken power-law spectrum consistent with synchrotron radiation. The afterglow is well modelled using a stratified wind-like environment with a density profile k ∼ 1.2, suggesting a massive star progenitor (i.e. Wolf-Rayet) with a mass-loss rate between ∼10 −5 −10 −6 M yr −1 depending on the value of the radiative efficiency (η γ = 0.2 or 0.5). The analysis of the reverse and forward shock emission reveals an initial Lorentz factor of ∼120−340, a jet half-opening angle of ∼2 • −5 • , and a baryon load of ∼10 −5 −10 −6 M consistent with the expectations of the fireball model when the emission is highly relativistic. Long-lasting soft γ-ray emission from other INTEGRAL GRBs with high peak fluxes, such as GRB 041219A, was not detected, suggesting that a combination of high Lorentz factor, emission above 100 MeV, and possibly a powerful reverse shock are required. Similar long-lasting soft γ-ray emission has recently been observed from the nearby and extremely bright Fermi/LAT burst GRB 130427A.

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“…A hint of this result was already available from summed light curves of BATSE SHBs, which led to the possible detection of excess emission peaking ∼ 30 s after the burst with a duration of ∼ 100 s [38,39]. This was originally proposed as evidence for afterglow emission, but there is now evidence from GRBs 050709 and 050724 that this is not the FIGURE 5.…”

Section: Prolonged Engine Activitymentioning

confidence: 89%

The Afterglows and Host Galaxies of Short GRBs: An Overview

Berger

2006

AIP Conference Proceedings

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Abstract. Despite a rich diversity in observational properties, gamma-ray bursts (GRBs) can be divided into two broad categories based on their duration and spectral hardness -the long-soft and the short-hard GRBs. The discovery of afterglows from long GRBs in 1997, and their localization to arcsecond accuracy, was a watershed event. The ensuing decade of intense study led to the realization that long-soft GRBs are located in star forming galaxies, produce about 10 51 erg in collimated relativistic ejecta, are accompanied by supernovae, and result from the death of massive stars. While theoretical arguments suggest that short GRBs have a different physical origin, the lack of detectable afterglows prevented definitive conclusions. The situation changed dramatically starting in May 2005 with the discovery of the first afterglows from short GRBs localized by Swift and HETE-2. Here I summarize the discovery of these afterglows and the underlying host galaxies, and draw initial conclusions about the nature of the progenitors and the properties of the bursts. HISTORY AND MODELSThe detection of short-duration gamma-ray bursts (GRBs) dates back to the Vela satellites [1]. However, only in 1993 the short bursts (with T 90 ∼ < 2 s) were recognized as a separate sub-class from the long GRBs, and were furthermore shown to have on average a harder γ-ray spectrum [2]; hereafter I will refer to short-hard bursts as SHBs. The short durations of SHBs suggest that they are unlikely to result from the death of massive stars, for which the natural timescale (the free-fall time) is significantly longer, t f f ≈ 30 s (M/10 M ⊙ ) −1/2 (R/10 10 cm) 3/2 .Instead the main theoretical thrust has been focused on coalescing compact objects -neutron stars and/or black holes (DNS or NS-BH) -as the progenitors of SHBs [3,4,5,6,7]. In this context the duration, which is set by the viscous timescale of the gas accreting onto the newly-formed black hole, is short due to the small scale of the system. Other progenitors have been proposed in addition to the DNS and NS-BH systems, namely magnetars, thought to be the power source behind soft γ-ray repeaters [8], and accretion-induced collapse (AIC) of neutron stars [9,10]. The magnetar model is unlikely to account for SHBs at cosmological distances, since even the 2004 Dec. 27 giant flare from SGR 1806-20 would only be detected by BATSE or Swift at ∼ < 50 Mpc; magnetars may contribute to a local population of SHBs. The AIC model has not been investigated in detail, but in the case of a white dwarf was shown to be too baryon rich to produce GRBs [11].Naturally, without a distance and energy scale, or an understanding of the microand macro-environments of SHBs, it is nearly impossible to make any quantitative statements about their progenitors or the detailed underlying physics. As in the case of

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BATSE Observations of Gamma‐Ray Burst Tails

Cited by 111 publications

References 28 publications

X‐Ray Hardness Variations as an Internal/External Shock Diagnostic

X‐Ray Hardness Variations as an Internal/External Shock Diagnostic

GRB 120711A: an intense INTEGRAL burst with long-lasting softγ-ray emission and a powerful optical flash

The Afterglows and Host Galaxies of Short GRBs: An Overview

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