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The earliest spectroscopy of the GRB 030329 afterglow with 6-m telescope

V. G. Kurt·V. V. Sokolov·T. A. Fatkhullin·V. N. Komarova·V. S. Lebedev·T. N. Sokolova·A. J. Castro-Tirado·A. de Ugarte Postigo·J. Gorosabel·S. Guziy
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Abstract

The earliest BTA (SAO RAS 6-m telescope) spectroscopic observations of the GRB 030329 optical transient (OT) are presented, which almost coincide in time with the "first break" ($t\sim 0.5$ day after the GRB) of the OT light curve. The beginning of spectral changes are seen as early as $\sim 10-12$ hours after the GRB. So, the onset of the spectral changes for $t<1$ day indicates that the contribution from Type Ic supernova (SN) into the OT optical flux can be detected earlier. The properties of early spectra of GRB 030329/SN 2003dh can be consistent with a shock moving into a stellar wind formed from the pre-SN. Such a behavior (similar to that near the UV shock breakout in SNe) can be explained by the existence of a dense matter in the immediate surroundings of massive stellar GRB/SN progenitor). The urgency is emphasized of observation of early GRB/SN spectra for solving a question that is essential for understanding GRB physical mechanism: {\it Do all} long-duration gamma-ray bursts are caused by (or physically connected to) {\it ordinary} core-collapse supernovae? If clear association of normal/ordinary core-collapse SNe (SN Ib/c, and others SN types) and GRBs would be revealed in numbers of cases, we may have strong observational limits for gamma-ray beaming and for real energetics of the GRB sources.

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V. G. Kurt, V. V. Sokolov, T. A. Fatkhullin, V. N. Komarova, V. S. Lebedev, T. N. Sokolova, A. J. Castro-Tirado, A. de Ugarte Postigo, J. Gorosabel, S. Guziy. 2005-05-26. The earliest spectroscopy of the GRB 030329 afterglow with 6-m telescope. https://doi.org/10.1393/ncc%2Fi2005-10097-1

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