Central Bureau for Astronomical Telegrams
IAUC 5245: 1991S; GALACTIC CENTER
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Circular No. 5245
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 1991S IN UGC 5691
E. Cappellaro, Padua Observatory; and L. Pasquini, European
Southern Observatory, communicate: "We obtained two spectra of SN
1991S, on Apr. 14.1 UT at the ESO 3.6-m telescope and on Apr. 17.0
at the ESO/Max-Planck-Institut 2.2-m telescope, both equipped with
EFOSC. The first spectrum (range 380-670 nm; low S/N) shows a very
blue continuum and only two strong lines with P-Cyg profile.
Absorptions are measured at 402 and 463 nm. A redshift of about
0.055 is found for the parent galaxy. In the second spectrum
(range 420-750 nm), of better quality, the continuum appears redder.
Several strong lines show up with absorptions measured at 465, 506,
534, 600, and 648 nm. The blue continuum and the main features
indicate a type-I supernova near maximum. The line at 648 nm,
identified with Si II (635.5 nm), gives an expansion velocity of 10 500
km/s and defines SN 1991S as type Ia. However, the Si II is not so
strong as in other type-Ia supernovae near maximum, being comparable
to the 600 nm (Na I + He I) line."
GALACTIC CENTER
R. Sunyaev, P. Mandrou, and J. Paul, on behalf of the Granat/
Sigma Team (Space Research Institute, Moscow; Centre d'Etude Spatiale
des Rayonnements, Toulouse; Service d'Astrophysique du CEA, Saclay),
report: "In March the Granat Observatory continued observations
of the Galactic Center (GC) region. The source 1E 1740.7-2942,
observed by the Sigma telescope as the brightest source in 100 deg2
around the GC at the energies above 35 keV in 1990 Mar./Apr. and
Sept./Oct. (IAUC 5032, 5140), continues to be in a low state (IAUC
5204), with luminosity varying from one-third (4.5-sigma detection)
of the 1990 level to less than one-fourth of that level. GRS 1758-
258 has been detected in each observation in the 35- to 110-keV band,
approximately at the same level as in 1990. The well-known x-ray
pulsar GX 1+4 was found to be in a high state at the energies above
35 keV, starting Mar. 22. This source has become the brightest in
this field at the energies 40-100 keV, with the 40- to 150-keV
luminosity being about 1.2 x 10E37 erg/s (source distance assumed to
be 8.5 kpc). The pulsations were significantly detected in this
band, with a period of 115.095 +/- 0.013 s (Mar. 31) at the solar
system barycenter. The apparent spin-down was detected between Mar.
22 and Apr. 1, in spite of high source luminosity."
1991 April 19 (5245) Daniel W. E. Green
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