Compton Echoes from Gamma‐Ray Bursts
- 1 October 2000
- journal article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 541 (2) , 712-719
- https://doi.org/10.1086/309463
Abstract
Recent observations of gamma-ray bursts (GRBs) have provided growing evidence for collimated outflows and emission, and strengthened the connection between GRBs and supernovae. If massive stars are the progenitors of GRBs, the hard photon pulse will propagate in the pre-burst, dense environment. Circumstellar material will Compton scatter the prompt GRB radiation and give rise to a reflection echo. We calculate luminosities, spectra, and light curves of such Compton echoes in a variety of emission geometries and ambient gas distributions, and show that the delayed hard X-ray flash from a pulse propagating into a red supergiant wind could be detectable by Swift out to z~0.2. Independently of the gamma-ray spectrum of the prompt burst, reflection echoes will typically show a high-energy cutoff between m_ec^2/2 and m_ec^2 because of Compton downscattering. At fixed burst energy per steradian, the luminosity of the reflected echo is proportional to the beaming solid angle, Omega_b, of the prompt pulse, while the number of bright echoes detectable in the sky above a fixed limiting flux increases as Omega_b^{1/2}, i.e. it is smaller in the case of more collimated jets. The lack of an X-ray echo at one month delay from the explosion poses severe constraints on the possible existence of a lateral GRB jet in SN 1987A. The late r-band afterglow observed in GRB990123 is fainter than the optical echo expected in a dense red supergiant environment from a isotropic prompt optical flash. Significant MeV delayed emission may be produced through the bulk Compton (or Compton drag) effect resulting from the interaction of the decelerating fireball with the scattered X-ray radiation.Comment: LaTeX, 18 pages, 4 figures, revised version accepted for publication in the ApKeywords
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This publication has 29 references indexed in Scilit:
- Dust Echoes from Gamma-Ray BurstsThe Astrophysical Journal, 2000
- A Possible Lateral Gamma-Ray Burst Jet from SN 1987AThe Astrophysical Journal, 1999
- The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connectionNature, 1999
- The Faint‐Galaxy Hosts of Gamma‐Ray BurstsThe Astrophysical Journal, 1999
- Gamma-Ray Burst Environments and ProgenitorsThe Astrophysical Journal, 1999
- Observation of contemporaneous optical radiation from a γ-ray burstNature, 1999
- An unusual supernova in the error box of the γ-ray burst of 25 April 1998Nature, 1998
- Discovery of an X-ray afterglow associated with the γ-ray burst of 28 February 1997Nature, 1997
- Circumstellar Interaction in SN 1993JThe Astrophysical Journal, 1996
- Discovery of an unusual hard X-ray source in the region of supernova 1987ANature, 1987