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The Decay of Optical Emission from the gamma-Ray Burst GRB970228The origin of gamma-ray bursts has been one of the great unsolved mysteries in high-energy astrophysics for almost 30 years. The recent discovery of fading sources at X-ray and optical wavelengths coincident with the location of the gamma-ray burst GRB970228 therefore provides an unprecedented opportunity to probe the nature of these high-energy events. The optical counterpart appears to be a transient point source embedded in a region of extended nebulosity, the latter having been tentatively identified as a high-redshift galaxy. This would seem to favour models that place gamma-ray bursts at cosmological distances, although a range of mechanisms for producing the bursts is still allowed. A crucial piece of information for distinguishing between such models is how the brightness of the optical counterpart evolves with time. Here we re-evaluate the existing photometry of the optical counterpart of GRB970228 to construct an optical light curve for the transient event. We find that between 21 hours and six days after the burst, the R-band brightness decreased by a factor of approximately 40, with any subsequent decrease in brightness occurring at a much slower rate. As the point source faded, it also became redder. The initial behaviour of the source appears to be consistent with the 'fireball' model, but the subsequent decrease in the rate of fading may prove harder to explain.
Document ID
19970028955
Acquisition Source
Marshall Space Flight Center
Document Type
Technical Memorandum (TM)
Authors
Galama, T. (Amsterdam Univ. Netherlands)
Groot, P. J. (Amsterdam Univ. Netherlands)
vanParadijs, J. (Amsterdam Univ. Netherlands)
Kouveliotou, C. (NASA Marshall Space Flight Center Huntsville, AL United States)
Robinson, C. R. (NASA Marshall Space Flight Center Huntsville, AL United States)
Fishman, G. J. (NASA Marshall Space Flight Center Huntsville, AL United States)
Meegan, C. A. (NASA Marshall Space Flight Center Huntsville, AL United States)
Sahu, K. C. (Space Telescope Science Inst. Baltimore, MD United States)
Livio, M. (Space Telescope Science Inst. Baltimore, MD United States)
Petro, L. (Space Telescope Science Inst. Baltimore, MD United States)
Macchetto, F. D. (Space Telescope Science Inst. Baltimore, MD United States)
Heise, J. (Space Research Organization Netherlands Utrecht, Netherlands)
Int Zand, J. (Space Research Organization Netherlands Utrecht, Netherlands)
Strom, R. G. (Amsterdam Univ. Netherlands)
Telting, J. (Isaac Newton Group Santa Cruz de La Palma, Spain)
Rutten, R. G. M. (Isaac Newton Group Santa Cruz de La Palma, Spain)
Pettini, M. (Royal Greenwich Observatory Cambridge, United Kingdom)
Tanvir, N. (Institute of Astronomy Cambridge, United Kingdom)
Bloom, J. (Institute of Astronomy Cambridge, United Kingdom)
Date Acquired
September 6, 2013
Publication Date
May 29, 1997
Publication Information
Publication: Letters to Nature
Volume: 387
Subject Category
Space Radiation
Report/Patent Number
NASA-TM-112889
NAS 1.15:112889
Accession Number
97N27665
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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