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GRB 000926 and its optical afterglow: Another evidence for non-isotropic emission

R. Sagar·S. B. Pandey·V. Mohan·D. Bhattacharya·A. J. Castro-Tirado
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Abstract

CCD Johnsons BV and Cousins RI photometric magnitudes are determined for 20 stars in the field of GRB 000926. Using them as calibrators, B and R band light curves are constructed of the afterglow from ours and other published observations. They show a steepening of the flux decay, from a decay constant of 1.4+/-0.1 to 2.6+/-0.06 at about 1.7 days after the burst. Attributing this break to the onset of sideways expansion of a jet-like ejecta, we estimate an initial jet opening angle of ~0.14 radian, and a burst energy of ~10^51 erg. We construct the X-ray-optical-near infrared spectrum of the afterglow and derive a spectral index of ~ -0.9. From the spectrum we also estimate that the source has a rather large intrinsic extinction, amounting to E(B-V)=0.36+/-0.02.

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R. Sagar, S. B. Pandey, V. Mohan, D. Bhattacharya, A. J. Castro-Tirado. 2001-01-25. GRB 000926 and its optical afterglow: Another evidence for non-isotropic emission. https://arxiv.org/abs/astro-ph/0010212

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