Central Bureau for Astronomical Telegrams
IAUC 5204: 1991L; GALACTIC CENTER
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Circular No. 5204
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
SUPERNOVA 1991L IN MCG +07-34-134
A. V. Filippenko and J. C. Shields, University of California at
Berkeley; and K. Nomoto, University of Tokyo, communicate: "
Uncalibrated CCD spectra (range 390-700 nm, resolution 1-2 nm), obtained
on Mar. 9 and 10 UT with the Shane 3-m reflector at Lick Observatory,
show that SN 1991L is probably a type-Ib or -Ic supernova within a
month of maximum brightness. A redshift of 0.03 was measured for
the parent galaxy."
GALACTIC CENTER
R. Sunyaev, on behalf of the GRANAT Team (Space Research
Institute, Moscow; Centre d'Etude Spatiale des Rayonnements, Toulouse;
Service d'Astrophysique, Centre d'Etudes Nucleaires de Saclay),
reports: "The GRANAT observatory began a new set of observations of
the Galactic Center (GC). During the first observation on Feb. 22-
23, the ART-P and SIGMA telescopes did not detect x-rays from
1E 1740.7-2942, which is the brightest hard x-ray source in the
vicinity of the GC (cf. IAUC 5032, 5140). An upper limit (at three
standard deviations level) on the source luminosity was 2.5 x 10E36
erg/s in the 4- to 30-keV band and 3.5 x 10E36 erg/s in the 40- to
120-keV band (the source distance was assumed to be 8.5 kpc). This
is about four times lower than the average luminosity of the source
detected during GRANAT observations of 1990 in the ART-P band and
about three times lower in the SIGMA band. In the same field-of-
view, SIGMA found GRS 1758-258 (cf. IAUC 5032) at approximately the
same luminosity level as that averaged over the 1990 observations (6
x 10E36 erg/s in the 40- to 120-keV band). Two other bright x-ray
sources in this field, A1742-294 and SLX 1744-299, both only 30'
from 1E 1740.7-2942, were observed with confidence on the same ART-P
image. During the next session on Feb. 23-24, the flux from
1E 1740.7-2942 was detected by the ART-P telescope again. Its x-ray
luminosity in the 4- to 30-keV band was 3 times lower than the usual
level. In two subsequent sessions during Feb. 26-28, ART-P observed
1E 1740.7-2942 at approximately the same level of luminosity but
with lower confidence. In the SIGMA images, only GRS 1758-258 was
present during each of the Feb. 22-28 observations."
1991 March 11 (5204) Daniel W. E. Green
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