@article{2cfe079a89704313af1da31cd8594c69,
title = "Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission",
abstract = "We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R peak = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g′-R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an {"}untriggered{"} GRB (lack of satellite coverage), an {"}orphan{"} afterglow (viewing-angle effects), and a {"}dirty fireball{"} (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic outbursts lacking associated high-energy emission. If so, such sources will be uncovered in large numbers by future wide-field optical and radio transient surveys.",
keywords = "gamma, ray burst: general, stars: flare, supernovae: general",
author = "Cenko, {S. Bradley} and Kulkarni, {S. R.} and Assaf Horesh and Alessandra Corsi and Fox, {Derek B.} and John Carpenter and Frail, {Dale A.} and Nugent, {Peter E.} and Perley, {Daniel A.} and D. Gruber and Avishay Gal-Yam and Groot, {Paul J.} and G. Hallinan and Ofek, {Eran O.} and Arne Rau and MacLeod, {Chelsea L.} and Miller, {Adam A.} and Bloom, {Joshua S.} and Filippenko, {Alexei V.} and Kasliwal, {Mansi M.} and Law, {Nicholas M.} and Morgan, {Adam N.} and David Polishook and Dovi Poznanski and Quimby, {Robert M.} and Branimir Sesar and Shen, {Ken J.} and Silverman, {Jeffrey M.} and Assaf Sternberg",
year = "2013",
month = jun,
day = "1",
doi = "10.1088/0004-637X/769/2/130",
language = "אנגלית",
volume = "769",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "American Astronomical Society",
number = "2",
}