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GCN Circular 2142

Subject
OT GRB 030329: early spectrum
Date
2003-04-16T16:26:08Z (21 years ago)
From
Vladimir Sokolov at SAO RAS <sokolov@sao.ru>
T. Fatkhullin, V. Komarova, V. Sokolov (SAO RAS), V. Kurt (ASC RAS),
A. Cherepashchuk (SAI MSU), K. Postnov (SAI MSU), V. Reshetnikov (AI SPBU),
Alberto J. Castro-Tirado (INTA, Madrid and IAA, Granada)
report:

8 spectra of OT GRB 030329 (Peterson & Prise, GCN 1985; Torii GCN 1986)
were obtained under the program "Optical identification of gamma-ray burst
sources" (observer A. V. Moiseev, LSPEO SAO RAS)
on the night of 29/30 March 2003 (29.934 - 30.004 UT) with the SAO RAS 6-meter telescope
at the Northern Caucasus,  0.45 - 0.52 days after the detection of
GRB 030329 on Mar. 29.484 UT (G. Ricker et al, IAUC No. 8101).
The observations were carried out with
the integral field spectrograph (Multi Pupil Fiber Spectrograph,
MPFS  http://www.sao.ru/~gafan/devices/mpfs/mpfs_main.htm  )

The 4x2 (sums of 2 consequent) spectra and additional info can be seen at
anonymous FTP-site:
	  ftp://ftp.sao.ru/pub2/grb/GRB030329/

With consideration for z=0.168 the first spectra of the OT GRB 030329
remind the very first spectrum of SN 1987A beginning with lambda=3425A,
(Danziger et al, 1987, A&A, 177, L13; Menzies et al. 1987, MNRAS, 227, 39P)
The same spectral behaiour of OT is confirmed by simultaneous UBVRI
observations with the 1-m (Zeiss-1000) of SAO RAS
starting from March 29.717 to 30.015 (UT).
The data are being processed for more accurate calibration.

A possible interpretation (V.Sokolov):
Perhaps, such a behaviour of the very first spectra of OT GRB 030329,
as well as the case of SN 1987A, could be explained by the fact that the burst
of supernova related to the burst of a compact massive star and
recorded in the very beginning of its GRB evolution was observed
in detail for the second time. The physics of the early SN brightness peak
can be related to the exit of a shock wave (or a jet?) onto the surface
of a compact pre-supernova. (e. g. E. Grassberg, V. Imshennik and
D. Nadyozin, 1971, Astroph. Space Sci., 10, 28). Though the difference
between the types of SN 1987A and SN 2003dh (K. Stanek, T. Matheson,
P. Garnavich et al. astro-ph/0304173), and their pre-supernovae should
be certainly taken into consideration.

We are grateful to our colleagues from the Laboratory of Spectroscopy and
Photometry of Extragalactic Objects for their kind assistance in the
spectral observations with the 6-meter telescope of SAO RAS.

This message may be cited."
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