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Afterglow Observations of Fermi Large Area Telescope Gamma-ray Bursts and the Emerging Class of Hyper-energetic Events

Cenko, S. B. and Frail, D. A. and Harrison, F. A. and Haislip, J. B. and Reichart, D. E. and Butler, N. R. and Cobb, B. E. and Cucchiara, A. and Berger, E. and Bloom, J. S. and Chandra, P. and Fox, D. B. and Perley, D. A. and Prochaska, J. X. and Filippenko, A. V. and Glazebrook, K. and Ivarsen, K. M. and Kasliwal, M. M. and Kulkarni, S. R. and LaCluyzé, A. P. and Lopez, S. and Morgan, A. N. and Pettini, M. and Rana, V. R. (2011) Afterglow Observations of Fermi Large Area Telescope Gamma-ray Bursts and the Emerging Class of Hyper-energetic Events. Astrophysical Journal, 732 (1). Art. No. 29. ISSN 0004-637X. doi:10.1088/0004-637X/732/1/29.

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We present broadband (radio, optical, and X-ray) light curves and spectra of the afterglows of four long-duration gamma-ray bursts (GRBs; GRBs 090323, 090328, 090902B, and 090926A) detected by the Gamma-Ray Burst Monitor and Large Area Telescope (LAT) instruments on the Fermi satellite. With its wide spectral bandpass, extending to GeV energies, Fermi is sensitive to GRBs with very large isotropic energy releases (10^(54) erg). Although rare, these events are particularly important for testing GRB central-engine models. When combined with spectroscopic redshifts, our afterglow data for these four events are able to constrain jet collimation angles, the density structure of the circumburst medium, and both the true radiated energy release and the kinetic energy of the outflows. In agreement with our earlier work, we find that the relativistic energy budget of at least one of these events (GRB 090926A) exceeds the canonical value of 10^(51) erg by an order of magnitude. Such energies pose a severe challenge for models in which the GRB is powered by a magnetar or a neutrino-driven collapsar, but remain compatible with theoretical expectations for magnetohydrodynamical collapsar models (e.g., the Blandford-Znajek mechanism). Our jet opening angles (θ) are similar to those found for pre-Fermi GRBs, but the large initial Lorentz factors (Γ_0) inferred from the detection of GeV photons imply θΓ_0 ≈ 70-90, values which are above those predicted in magnetohydrodynamic models of jet acceleration. Finally, we find that these Fermi-LAT events preferentially occur in a low-density circumburst environment, and we speculate that this might result from the lower mass-loss rates of their lower-metallicity progenitor stars. Future studies of Fermi-LAT afterglows at radio wavelengths with the order-of-magnitude improvement in sensitivity offered by the Extended Very Large Array should definitively establish the relativistic energy budgets of these events.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cenko, S. B.0000-0003-1673-970X
Harrison, F. A.0000-0003-2992-8024
Reichart, D. E.0000-0002-5060-3673
Berger, E.0000-0002-9392-9681
Bloom, J. S.0000-0002-7777-216X
Fox, D. B.0000-0002-3714-672X
Perley, D. A.0000-0001-8472-1996
Prochaska, J. X.0000-0002-7738-6875
Filippenko, A. V.0000-0003-3460-0103
Kasliwal, M. M.0000-0002-5619-4938
Kulkarni, S. R.0000-0001-5390-8563
Pettini, M.0000-0002-5139-4359
Rana, V. R.0000-0003-1703-8796
Additional Information:© 2011 American Astronomical Society. Received 2010 April 19; accepted 2011 February 16; published 2011 April 12. We wish to thank D. A. Kann, R. Barniol Duran, P. Kumar, and the anonymous referee for valuable comments and discussions regarding this manuscript. We are grateful to the GROND team, in particular to S. McBreen and T. Krühler, for providing their observations of GRB090323, GRB090328, and GRB090902B, and to A. Rau for assistance with the photometric calibration of the field of GRB 090926A. S.B.C. and A.V.F. wish to acknowledge generous support from Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, National Aeronautics and Space Administration (NASA)/Swift grants NNX09AL08G and NNX10AI21G, and National Science Foundation (NSF) grants AST-0607485 and AST-0908886. D.A.F. and F.A.H. were partially supported by NASA/Fermi Guest Investigator grants NNH07ZDA001N and NNH08ZDA001N. B.E.C. gratefully acknowledges support from an NSF Astronomy & Astrophysics Postdoctoral Fellowship (AST-0802333). N.R.B. is supported through the Einstein Fellowship Program (NASA Cooperative Agreement NNG06DO90A). J.S.B. and his group were partially supported by NASA/Swift Guest Investigator grant NNX09AQ66G and a grant from DOE SciDAC. P60 operations are funded in part by NASA through the Swift Guest Investigator Program (grant number NNG06GH61G). This work is based in part on observations obtained at the Gemini Observatory (Programs GS-2009A-Q-23, GS-2009B-Q-5, GN-2009A-Q-26, and GN-2009B-Q-28), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (US), the Particle Physics and Astronomy Research Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina). We wish to thank the entire staff at Gemini for assistance with these observations. SMARTS is supported by NSF grant AST-0707627. Facilities: Fermi (LAT, GBM), VLA, PO:1.5m, Gemini: South (GMOS), Gemini:Gillett (GMOS), CTIO:2MASS (ANDICAM), Swift (XRT, UVOT)
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Richard and Rhoda Goldman FundUNSPECIFIED
NSF Astronomy and Astrophysics FellowshipAST-0802333
NASA Einstein FellowshipNNG06DO90A
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:cosmology: observations; gamma-ray burst: general; radio continuum: general
Issue or Number:1
Classification Code:PACS: 98.70.Rz; 98.80.Cq; 97.10.Ld; 95.85.Pw; 97.60.Jd
Record Number:CaltechAUTHORS:20110504-073756715
Persistent URL:
Official Citation:Afterglow Observations of Fermi Large Area Telescope Gamma-ray Bursts and the Emerging Class of Hyper-energetic Events S. B. Cenko et al. 2011 ApJ 732 29
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23543
Deposited On:05 May 2011 20:03
Last Modified:09 Nov 2021 16:15

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