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GCN Circular 461

Subject
GRB991208, optical observations
Date
1999-12-15T19:42:33Z (24 years ago)
From
Vladimir Sokolov at SAO RAS <sokolov@sao.ru>
GRB 991208 SAO RAS follow-up observations

S. Dodonov, V. Afanasiev, V. Sokolov, V. Komarova, T. Fatkhullin, A.
Moiseev report:

"One 2700-sec spectrum and one 4500-sec spectrum of the optical
transient of GRB 991208 detected by A.Castro-Tirado et al., (GCN
#452) were obtained on the nights of the 13th and 14th Dec
1999 UT respectfully with the SAO RAS 6-meter telescope at the Northern
Caucasus. Observational conditions on the night of the 13th of December
were poor. The seeing was 3 arcsec and the transparency was not good.
On the 14th of December the observational conditions were good:
the seeing ~1.5 arcsec (at a zenithal distance of 60 degrees),
a good transparency. So, the first spectrum is with a poor S/N ratio,
the second one is much better. The observations were carried out with
the integral field spectrograph (Multi Pupil Fiber Spectrograph,
MPFS http://www.sao.ru:8100/~gafan/devices/mpfs/mpfs_main.htm)
with 300 lines/mm grating blazed at 6000 A  giving a spectral resolution
of about FWHM=14A/px and effective wavelength coverage of 4100 - 9200 A.
A spectrophotometric standards HZ44 and BD+75d325 (Oke et al. 1995)
were used for the flux calibration. The spectra show a blue continuum and
in the second one with better S/N there are possible two emission lines.
The data are being processed.

On the second night (on Dec 14.14 UT) simultaneously with spectroscopic
observations at the 6-meter telescope we imaged the field of GRB991208
in the R_c band (Cousins) with the SAO RAS 1-m telescope (Zeiss-1000).
Two 10-minute exposures were obtained at an airmass of ~1.6 in good
photometric conditions. The seeing was of ~2 arcseconds. The brightness
estimate was made for optical counterpart of GRB 991208:
R_c = 21.6 +/- 0.3. For photometric calibration Landolt standards
were used.

This message may be cited."

-Vladimir Sokolov, on behalf of the RAS Special Astrophysical Observatory
GRB followup team.
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