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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/1351
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dc.contributor.authorPandey, S.B.-
dc.contributor.authorSahu, D.K.-
dc.contributor.authorResmi, L.-
dc.contributor.authorSagar, R.-
dc.contributor.authorAnupama, G.C.-
dc.contributor.authorBhattacharya, D.-
dc.contributor.authorMohan, V.-
dc.contributor.authorPrabhu, T.P.-
dc.contributor.authorBhatt, B.C.-
dc.contributor.authorPandey, J.C.-
dc.contributor.authorParihar, Padmakar-
dc.contributor.authorCastro-Tirado, A.J.-
dc.date.accessioned2006-06-12T09:47:04Z-
dc.date.available2006-06-12T09:47:04Z-
dc.date.issued2003-
dc.identifier.citationBulletin of the Astronomical Society of India, 2003, Vol.31, p19-36en
dc.identifier.issn0304-9523-
dc.identifier.urihttp://hdl.handle.net/2289/1351-
dc.description.abstractThe CCD magnitudes in Johnson $B,V$ and Cousins $R$ and $I$ photometric passbands are determined for the bright long duration GRB 021004 afterglow from 2002 October 4 to 16 starting $\sim$ 3 hours after the $\gamma-$ray burst. Light curves of the afterglow emission in $B$,$V$,$R$ and $I$ passbands are obtained by combining these measurements with other published data. The earliest optical emission appears to originate in a revese shock. Flux decay of the afterglow shows a very uncommon variation relative to other well-observed GRBs. Rapid light variations, especially during early times ($\Delta t < 2$ days) is superposed on an underlying broken power law decay typical of a jetted afterglow. The flux decay constants at early and late times derived from least square fits to the light curve are $0.99\pm0.05$ and $2.0\pm0.2$ respectively, with a jet break at around 7 day. Comparison with a standard fireball model indicates a total extinction of $E(B-V)=0.20$ mag in the direction of the burst. Our low-resolution spectra corrected for this extinction provide a spectral slope $\beta = 0.6\pm0.02$. This value and the flux decay constants agree well with the electron energy index $p\sim 2.27$ used in the model. The derived jet opening angle of about $7^{\circ}$ implies a total emitted gamma-ray energy $E_{\gamma} = 3.5\times10^{50}$ erg at a cosmological distance of about 20 Gpc. Multiwavelength observations indicate association of this GRB with a star forming region, supporting the case for collapsar origin of long duration GRBs.en
dc.format.extent1845138 bytes-
dc.format.mimetypeapplication/pdf-
dc.language.isoenen
dc.publisherThe Astronomical Society of Indiaen
dc.relation.urihttp://adsabs.harvard.edu/cgi-bin/bib_query?2003BASI...31...19Pen
dc.rights(2003) by the Astronomical Society of India. Scanned images provided by the NASA ADS Data System.en
dc.subjectPhotometryen
dc.subjectSpectroscopyen
dc.subjectGRB Afterglowen
dc.subjectFlux Decayen
dc.subjectSpectral Indexen
dc.titleOptical observations of the bright long duration peculiar GRB 021004 afterglowen
dc.typeArticleen
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