A possible bright blue supernova in the afterglow of GRB020305
We report on ground-based and HST(+STIS) imaging of the afterglow and host galaxy of the Gamma-Ray Burst (GRB) of March 5, 2002. The GRB occurred in a R=25.17+-0.14 galaxy, which apparently is part of an interacting system. The light curve of the optical afterglow shows are brightening, or at least a plateau, 12-16 days after the gamma-ray event. UBVRIK' multi-band imaging of the afterglow {approx}12 days after the GRB reveals a blue spectral energy distribution (SED). The SED is consistent with a power-law with a spectral index of beta=-0.63+-0.16,but there is tentative evidence for deviations away from a power-law. Unfortunately, a spectroscopic redshift has not been secured for GRB020305. From the SED we impose a redshift upper limit of z<{approx}2.8,hence excluding the pseudo redshift of 4.6 reported for this burst. We discuss the possibilities for explaining the light curve, SED and host galaxy properties for GRB 020305. The most natural interpretation of the light curve and the SED is an associated supernova (SN). Our data can not precisely determine the redshift of the GRB. The most favored explanation is a low redshift (z{approx}0.2) SN, but a higher redshift(z>{approx}0.5) SN can not be excluded. We also discuss less likely scenarios not based on SNe, like a burst occurring in a z=2.5 galaxy with an extinction curve similar to that of the Milky Way.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; National Aeronautics and Space AdministrationContract NAS5-26555 and Proposal GO 9074, Space Telescope ScienceInstitute, Association of Universities for Research in Astronomy; DanishNatural Science Research Council, Spanish Ministries of Science andEducation ESP2002-04124-C03-01 and AYA2004-01515, FEDER Funds
- DOE Contract Number:
- DE-AC02-05CH11231; NASA:43CX01
- OSTI ID:
- 890644
- Report Number(s):
- LBNL-60285; AAEJAF; BnR: 400409900; TRN: US0604734
- Journal Information:
- Astronomy and Astrophysics, Vol. 437, Issue 2; Related Information: Journal Publication Date: July, 2006; ISSN 0004-6361
- Country of Publication:
- United States
- Language:
- English
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