80 research outputs found
The earliest spectroscopy of the GRB 030329 afterglow with 6-m telescope
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" ( day after the GRB) of the OT light curve.
The beginning of spectral changes are seen as early as hours after
the GRB. So, the onset of the spectral changes for 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.Comment: 4 pages, 5 figures. Proceedings of the 4th Workshop "Gamma-Ray Bursts
in the Afterglow Era", Roma, 2004 October 18-22, eds. L. Piro, L. Amati, S.
Covino, and B. Gendre. Il Nuovo Cimento, in pres
The Multiband Photometry of GRB Host Galaxies: Comparison with the Spectral Energy Distributions of Nearby and Theoretical Modeling Galaxies
We present one of the results of photometry of the hosts of GRB for
the host galaxy of GRB 970508 and the theoretical modeling of its continuum
spectral energy distribution (SED) to show that it is important to take into
account internal extinction in the host galaxies. We compared the BVRI
broad-band flux spectrum of the host to template SEDs of local starburst
galaxies and found that there is a significant internal extintion in this host.
Moreover, this comparison allows us to derive the absolute magnitude
(M_{B_{rest}}) and rouhgly estimate reddening (A_V). Population synthesis
modeling of the continuum SED for different reddening laws demostrates that the
observational data of the host galaxy of GRB 970508 are best fitted by the
spectral properties of a model SED with extinction of A_V\approx 2.Comment: 3 pages, 2 figures, poster presentation on 2nd Rome Workshop on
Gamma-Ray Bursts in the Afterglow Er
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