Investigating the Nature of Late-time High-energy GRB Emission through Joint Fermi/Swift Observations

Journal article


Publication Details

Author(s): Ajello M, Baldini L, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Cameron RA, Caputo R, Caraveo PA, Chiaro G, Ciprini S, Cohen-Tanugi J, Costantin D, D'Ammando F, De Palma F, Di Lalla N, Di Mauro M, Di Venere L, Dominguez A, Favuzzi C, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Guiriec S, Holt C, Horan D, Johannesson G, Kocevski D, Kuss M, La Mura G, Larsson S, Li J, Longo F, Loparco F, Lubrano P, Magill JD, Maldera S, Manfreda A, Mazziotta MN, Michelson PF, Mizuno T, Monzani ME, Morselli A, Negro M, Nuss E, Omodei N, Orienti M, Orlando E, Paliya VS, Perkins JS, Persic M, Pesce-Rollins M, Piron F, Principe G, Racusin JL, Raino S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Sgro C, Siskind EJ, Spandre G, Spinelli P, Tak D, Thayer JB, Torres DF, Tosti G, Valverde J, Vogel M, Wood K
Journal: Astrophysical Journal
Publisher: IOP PUBLISHING LTD
Publication year: 2018
Volume: 863
Journal issue: 2
ISSN: 0004-637X


Abstract

We use joint observations by the Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveals that LAT nondetections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the nondetected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1-100 GeV energy range considered for this analysis.


FAU Authors / FAU Editors

Funk, Stefan Prof. Dr.
Lehrstuhl für Physik
Principe, Giacomo
Lehrstuhl für Physik


External institutions with authors

AlbaNova University Centre / Kungliga Tekniska Högskolan AlbaNova Universitetscentrum
California State University, Los Angeles
Clemson University
Deutsches Elektronen-Synchrotron DESY
Hiroshima University
Institució Catalana de Recerca i Estudis Avançats (ICREA) / Catalan Institution for Research and Advanced Studies
Institute of Space Sciences (IEEC-CSIC)
Institut national de physique nucléaire et de physique des particules (IN2P3)
Italian Space Agency / Agenzia Spaziale Italiana (ASI)
National Aeronautics and Space Administration (NASA)
National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF)
National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN)
NYCB Real-Time Computing, Inc.
Politecnico di Bari
Praxis, Inc.
Stanford University
Universidad Complutense de Madrid (UCM)
Università degli Studi di Perugia
University of Iceland (UI)
University of Johannesburg
University of Maryland
University of Maryland, Baltimore County
University of Montpellier / Université Montpellier
University of Padua
University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot
University of Pisa / Università di Pisa (UniPi)


How to cite

APA:
Ajello, M., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E.,... Wood, K. (2018). Investigating the Nature of Late-time High-energy GRB Emission through Joint Fermi/Swift Observations. Astrophysical Journal, 863(2). https://dx.doi.org/10.3847/1538-4357/aad000

MLA:
Ajello, Marco, et al. "Investigating the Nature of Late-time High-energy GRB Emission through Joint Fermi/Swift Observations." Astrophysical Journal 863.2 (2018).

BibTeX: 

Last updated on 2019-18-07 at 08:53