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GRB 120521C at z ~ 6 and the Properties of High-redshift γ-Ray Bursts

Laskar, Tanmoy and Berger, Edo and Tanvir, Nial and Zauderer, B. Ashley and Margutti, Raffaella and Levan, Andrew and Perley, Daniel and Fong, Wen-Fai and Wiersma, Klaas and Menten, Karl M. and Hrudkova, Marie (2014) GRB 120521C at z ~ 6 and the Properties of High-redshift γ-Ray Bursts. Astrophysical Journal, 781 (1). Art. No. 1. ISSN 0004-637X. doi:10.1088/0004-637X/781/1/1.

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We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength data set, we derive a photometric redshift of z ≈ 6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of n ≲ 0.05 cm^−3. The radio observations reveal the presence of a jet break at t_jet ≈ 7 d, corresponding to a jet opening angle of θ_jet ≈ 3°. The beaming-corrected γ-ray and kinetic energies are E_γ ≈ E_K ≈ 3 × 10^50 erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z gsim 6 with radio detections (GRBs 050904 and 090423). We find a jet break at t_jet ≈ 15 d for GRB 090423, in contrast to previous work. Based on these three events, we find that γ-ray bursts (GRBs) at z ≳ 6 appear to explode in constant-density environments, and exhibit a wide range of energies and densities that span the range inferred for lower redshift bursts. On the other hand, we find a hint for narrower jets in the z ≳ 6 bursts, potentially indicating a larger true event rate at these redshifts. Overall, our results indicate that long GRBs share a common progenitor population at least to z ~ 8.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Laskar, Tanmoy0000-0003-1792-2338
Berger, Edo0000-0002-9392-9681
Zauderer, B. Ashley0000-0003-1152-518X
Margutti, Raffaella0000-0003-4768-7586
Perley, Daniel0000-0001-8472-1996
Fong, Wen-Fai0000-0002-7374-935X
Menten, Karl M.0000-0001-6459-0669
Alternate Title:GRB 120521C at z~6 and the Properties of High-redshift GRBs
Additional Information:© 2014 American Astronomical Society. Received 2013 July 24; accepted 2013 October 20; published 2013 December 24. We thank the anonymous referee for detailed comments on the manuscript. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Radio data for GRB 120521C were obtained under VLA project codes 12A-394 and 12A-480. Some of the data presented here were obtained at the Gemini-North Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the NSF on behalf of the Gemini-North partnership. The William Herschel Telescope is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica deCanarias. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. We thank Ofer Yaron and S. R. Kulkarni for the Keck observations. The Berger GRB group at Harvard is supported by the National Science Foundation under grant AST-1107973. T.L. acknowledges support by NRAO. K.W. acknowledges support by STFC.
Funding AgencyGrant Number
National Radio Astronomy ObservatoryUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:gamma-ray burst: general; gamma-ray burst: individual (GRB 120521C, GRB 050904, GRB 090423)
Issue or Number:1
Record Number:CaltechAUTHORS:20140207-112139371
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Official Citation:GRB 120521C at z ~ 6 and the Properties of High-redshift γ-Ray Bursts Tanmoy Laskar et al. 2014 ApJ 781 1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43722
Deposited By: Jason Perez
Deposited On:10 Feb 2014 21:39
Last Modified:10 Nov 2021 16:42

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