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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 {sub 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),more » 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.« less

Authors:
; ; ; ;  [1]; ; ; ; ; ;  [2];  [3];  [4];  [5]; ;  [6]; ;  [7];  [8];
  1. Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
  2. Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
  3. LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, CA 91125 (United States)
  4. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
  5. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
  6. Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany)
  7. Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel)
  8. Physics Department, United States Naval Academy, 572c Holloway Road, Annapolis, MD 21402 (United States)
Publication Date:
OSTI Identifier:
22342061
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 769; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AFTERGLOW; COSMIC GAMMA BURSTS; DETECTION; EMISSION; FLAMES; FORECASTING; NOVAE; RELATIVISTIC RANGE; SATELLITES; SUPERNOVAE; TRANSIENTS; UNIVERSE; VISIBLE RADIATION; X RADIATION

Citation Formats

Cenko, S. Bradley, Nugent, Peter E., Miller, Adam A., Bloom, Joshua S., Filippenko, Alexei V., Kulkarni, S. R., Horesh, Assaf, Carpenter, John, Perley, Daniel A., Groot, Paul J., Hallinan, G., Corsi, Alessandra, Fox, Derek B., Frail, Dale A., Gruber, D., Rau, Arne, Gal-Yam, Avishay, Ofek, Eran O., MacLeod, Chelsea L., Kasliwal, Mansi M., E-mail: cenko@astro.berkeley.edu, and others, and. Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission. United States: N. p., 2013. Web. doi:10.1088/0004-637X/769/2/130.
Cenko, S. Bradley, Nugent, Peter E., Miller, Adam A., Bloom, Joshua S., Filippenko, Alexei V., Kulkarni, S. R., Horesh, Assaf, Carpenter, John, Perley, Daniel A., Groot, Paul J., Hallinan, G., Corsi, Alessandra, Fox, Derek B., Frail, Dale A., Gruber, D., Rau, Arne, Gal-Yam, Avishay, Ofek, Eran O., MacLeod, Chelsea L., Kasliwal, Mansi M., E-mail: cenko@astro.berkeley.edu, & others, and. Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission. United States. https://doi.org/10.1088/0004-637X/769/2/130
Cenko, S. Bradley, Nugent, Peter E., Miller, Adam A., Bloom, Joshua S., Filippenko, Alexei V., Kulkarni, S. R., Horesh, Assaf, Carpenter, John, Perley, Daniel A., Groot, Paul J., Hallinan, G., Corsi, Alessandra, Fox, Derek B., Frail, Dale A., Gruber, D., Rau, Arne, Gal-Yam, Avishay, Ofek, Eran O., MacLeod, Chelsea L., Kasliwal, Mansi M., E-mail: cenko@astro.berkeley.edu, and others, and. 2013. "Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission". United States. https://doi.org/10.1088/0004-637X/769/2/130.
@article{osti_22342061,
title = {Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission},
author = {Cenko, S. Bradley and Nugent, Peter E. and Miller, Adam A. and Bloom, Joshua S. and Filippenko, Alexei V. and Kulkarni, S. R. and Horesh, Assaf and Carpenter, John and Perley, Daniel A. and Groot, Paul J. and Hallinan, G. and Corsi, Alessandra and Fox, Derek B. and Frail, Dale A. and Gruber, D. and Rau, Arne and Gal-Yam, Avishay and Ofek, Eran O. and MacLeod, Chelsea L. and Kasliwal, Mansi M., E-mail: cenko@astro.berkeley.edu and others, and},
abstractNote = {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 {sub 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.},
doi = {10.1088/0004-637X/769/2/130},
url = {https://www.osti.gov/biblio/22342061}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 769,
place = {United States},
year = {Sat Jun 01 00:00:00 EDT 2013},
month = {Sat Jun 01 00:00:00 EDT 2013}
}