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The Afterglows of Swift-era Gamma-ray Bursts. I. Comparing pre-Swift and Swift-era Long/Soft (Type II) GRB Optical Afterglows

Kann, D. A. and Nakar, E. (2010) The Afterglows of Swift-era Gamma-ray Bursts. I. Comparing pre-Swift and Swift-era Long/Soft (Type II) GRB Optical Afterglows. Astrophysical Journal, 720 (2). pp. 1513-1558. ISSN 0004-637X.

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We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall

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Additional Information:© 2010 The American Astronomical Society. Received 2007 December 13; accepted 2010 July 15; published 2010 August 23. Based in part on observations obtained with the Very Large Telescope under ESO program 075.D-0787, PI Tagliaferri. Also based partly on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias under program TAC 1238. We thank the anonymous referee for helpful comments that improved this paper. D.A.K. thanks C. Guidorzi for helpful comments as well as the GRB 061007 calibration, D. A. Perley for “better-late-than-never” comments, and A. Zeh for the fitting scripts. D.A.K., S.K., and P.F. acknowledge financial support by DFG grant Kl 766/13-2. B.Z. acknowledges NASA NNG 05GC22G and NNG06GH62G for support. The research activity of J.G. is supported by Spanish research programs ESP2005- 07714-C03-03 and AYA2004-01515. D.M. thanks the Instrument Center for Danish Astrophysics for support. The Dark Cosmology Centre is funded by the Danish National Science Foundation. A.U. acknowledges travel grant Sigma Xi Grant G2007101421517916. We are grateful to K. Antoniuk (CrAO) for observation of the GRB 060927. A.P. acknowledges the CRDF grant RP1-2394-MO-02 which supported observations in CrAO in 2003-2005. S.S. acknowledges support by a Grant of Excellence from the Icelandic Research Fund. I.B., R.B., I.K. and A.G. express thanks to TÜBÍTAK, IKI, and KSU for partial support in using RTT150 (Russian-Turkish 1.5-m telescope in Antalya) with project number 998,999. I.B. and A.G. are grateful for partial support by grants “NSh-4224.2008.2” and “RFBR-09-02-97013-p-povolzh’e-a.” M.I. acknowledges the support from the Creative Research Initiative program, No. 2010-0000712, of the Korea Science and Engineering Foundation (KOSEF) funded by the Korea government (MEST). Furthermore, we thank Scott Barthelmy, NASA, for the upkeep of the GCN Circulars, Jochen Greiner, Garching, for the “GRB Big List,” Robert Quimby et al. for GRBlog and D. A. Perley et al. for GRBOX. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)(Germany)Kl 766/13-2
Spanish research programsESP2005-07714-C03-03
Spanish research programsAYA2004-01515
Instrument Center for Danish Astrophysics UNSPECIFIED
Sigma XiG2007101421517916
Icelandic Research FundUNSPECIFIED
Korea Science and Engineering Foundation (KOSEF) UNSPECIFIED
Subject Keywords:dust, extinction; gamma-ray burst: general
Classification Code:PACS: 98.70.Rz; 98.80.Cq; 95.30.Gv
Record Number:CaltechAUTHORS:20100929-112848569
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Official Citation:D. A. Kann et al 2010 ApJ 720 1513 doi: 10.1088/0004-637X/720/2/1513
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20222
Deposited By: Ruth Sustaita
Deposited On:01 Oct 2010 22:26
Last Modified:26 Dec 2012 12:28

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