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تسجيل مستخدم جديدGRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe
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Long duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of a massive star. Over the last forty years, our understanding of the GRB phenomenon has progressed dramatically; nevertheless, fortuitous circumstances occasionally arise that provide access to a regime not yet probed. GRB 080319B presented such an opportunity, with extraordinarily bright prompt optical emission that peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. It was captured in exquisite detail by wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous gamma-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation. Here we show that the prompt optical and gamma-ray emissions from this event likely arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow. The chromatic behaviour of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs. These circumstances can explain the extreme properties of this GRB.
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On 19 March 2008, the northern sky was the stage of a spectacular optical transient that for a few seconds remained visible to the naked eye. The transient was associated with GRB 080319B, a gamma-ray burst at a luminosity distance of about 6 Gpc (st
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The first gamma-ray burst (GRB) confirmed to be bright enough to be seen with the naked eye, GRB 080319B at redshift z = 0.937, allowed for exquisite follow-up observations across the electromagnetic spectrum. We present our detailed optical and infr
ared observations of the afterglow, consisting of over 5000 images starting 51 s after the GRB trigger, in concert with our own analysis of the Swift data. The event is extreme not only in observed properties but intrinsically: it was the most luminous event ever recorded at optical and infrared wavelengths and had an exceedingly high isotropic-equivalent energy release in gamma-rays. At early times, the afterglow evolution is broadly consistent with being reverse-shock dominated, but then is subsumed by a forward shock at around 1000 s. The overall spectral energy distribution, spanning from ultraviolet through near-infrared wavelengths, shows no evidence for a significant amount of dust extinction in the host frame. The afterglow evolution, however, is highly chromatic: starting at about 1000 s the index shifts blueward before shifting back to the red at late times. In our deepest late-time observations, we find tentative evidence for an optical jet break and a luminous supernova. Finally, we examine the detectability of such events with current and future facilities and find that such an event could be detected in gamma-rays by BAT out to z = 10.7 (8 sigma), while the nominal EXIST sensitivity would allow detection to z ~ 32. At K band, this source would have been easily detected with meter-class telescopes to z ~ 17.
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