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Multiwavelength observations of GRB 050820A : an exceptionally energetic event followed from start to finish

Cenko, S. B. and Kasliwal, M. M. and Harrison, F. A. and Pal'shin, V. and Frail, D. A. and Cameron, P. B. and Berger, E. and Fox, D. B. and Gal-Yam, A. and Kulkarni, S. R. and Moon, D.-S. and Nakar, E. and Ofek, E. O. and Penprase, B. E. and Price, P. A. and Sari, R. and Schmidt, B. P. and Soderberg, A. M. and Aptekar, R. and Frederiks, D. and Golenetskii, S. and Burrows, D. N. and Chevalier, R. A. and Gehrels, N. and McCarthy, P. J. and Nousek, J. A. and Piran, T. (2006) Multiwavelength observations of GRB 050820A : an exceptionally energetic event followed from start to finish. Astrophysical Journal, 652 (1). pp. 490-506. ISSN 0004-637X. doi:10.1086/508149.

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We present observations of the unusually bright and long γ-ray burst GRB 050820A, one of the best sampled broadband data sets in the Swift era. The γ-ray light curve is marked by a soft precursor pulse some 200 s before the main event; the lack of any intervening emission suggests that it is due to a physical mechanism distinct from the GRB itself. The large time lag between the precursor and the main emission enabled simultaneous observations in the γ-ray, X-ray, and optical bandpasses, something only achieved for a handful of events to date. While the contemporaneous X-rays are the low-energy tail of the prompt emission, the optical does not directly track the γ-ray flux. Instead, the early-time optical data appear consistent with the forward shock synchrotron peak passing through the optical and are therefore likely the beginning of the afterglow. On hour timescales after the burst, the X-ray and optical light curves are inconsistent with an adiabatic expansion of the shock into the surrounding region, but rather indicate that there is a period of energy injection. Observations at late times allow us to constrain the collimation angle of the relativistic outflow to 6°.8 ≾ θ ≾ 9°.3. Our estimates of both the kinetic energy of the afterglow (EKE = 5.2^(+7.9)_(4.1) × 10^(51) ergs) and the prompt γ-ray energy release (Eγ = 7.5^(+6.7)-(2.4) × 10^(51) ergs) make GRB 050820A one of the most energetic events for which such values could be determined.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cenko, S. B.0000-0003-1673-970X
Kasliwal, M. M.0000-0002-5619-4938
Harrison, F. A.0000-0003-2992-8024
Berger, E.0000-0002-9392-9681
Fox, D. B.0000-0002-3714-672X
Gal-Yam, A.0000-0002-3653-5598
Kulkarni, S. R.0000-0001-5390-8563
Moon, D.-S.0000-0003-4200-5064
Nakar, E.0000-0002-4534-7089
Ofek, E. O.0000-0002-6786-8774
Sari, R.0000-0002-1084-3656
Schmidt, B. P.0000-0001-6589-1287
Piran, T.0000-0002-7964-5420
Additional Information:© 2006 The American Astronomical Society. Received 2006 May 18; accepted 2006 August 2. We would like to thank the anonymous referee for helpful comments on this manuscript. S. B. C. and A. M. S. are supported by the NASA Graduate Student Research Program. E. B. is supported by NASA through Hubble Fellowship grant HSTHF- 01171.01 awarded by STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. A. G. acknowledges support by NASA through Hubble Fellowship grant HST-HF-01158.01 awarded by STScI. The Konus-Wind experiment is supported by Russian Space Agency contract and RFBR grant 06-02-16070. GRB research at Caltech is supported through NASA. This publication has made use of data obtained from the Swift interface of the High-Energy Astrophysics Archive (HEASARC), provided by NASA’s Goddard Space Flight Center. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. The Digitized Sky Survey was produced at the Space Telescope Science Institute under US Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
NASA Graduate Student Research FellowshipUNSPECIFIED
NASA Hubble FellowshipHSTHF-01171.01
NASA Hubble FellowshipHST-HF-01158.01
Russian Space Agency06-02-16070
Russian Foundation for Basic ResearchUNSPECIFIED
Space Telescope Science InstituteUNSPECIFIED
Subject Keywords:gamma rays: bursts; X-rays: individual (GRB 050820A)
Issue or Number:1
Record Number:CaltechAUTHORS:CENapj06
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13700
Deposited By: Tony Diaz
Deposited On:09 Jul 2009 18:11
Last Modified:08 Nov 2021 22:39

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