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IAUC 5377: V1251 Cyg; GRS 1758-258; VZ Sgr

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IAUC number

                                                  Circular No. 5377
Central Bureau for Astronomical Telegrams
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

     This eruptive variable (R.A. = 21h39m.0, Decl. = +48 26', equinox
1950.0) is in outburst, apparently for the first time since 1963
(IBVS 123), as reported by M. Moriyama, Nagasaki, Japan (via T. Kato
and G. M. Hurst), and by P. Schmeer, Bischmisheim, Germany.  Visual
magnitude estimates:  Oct. 15.90 UT, [14.2 (Schmeer); 25.54, 12.4
(Moriyama); 26.89, 12.4 (Moriyama); 26.833, 12.7 (Schmeer); 27.880,
12.5 (Schmeer).

GRS 1758-258
     B. Cordier, J. P. Roques, E. Churazov, and M. Gilfanov, on
behalf of the GRANAT/SIGMA team (Service d'Astrophysique du CEA,
Saclay; Centre d'Etude Spatiale des Rayonnements, Toulouse; Space
Research Institute, Moscow), report:  "Since the end of 1991 August,
the GRANAT space observatory is performing a new set of observations
of the Galactic Center (GC).  During the observations of Sept. 21-25,
the SIGMA telescope aboard GRANAT did not detect hard x-ray emission
from GRS 1758-258, the hard x-ray source discovered by GRANAT in
1990 March (IAUC 5032), which was the brightest hard x-ray source in
the vicinity of the GC since the fading of 1E 1740.7-2942 (observed
by GRANAT in 1991 February; cf. IAUC 5204).  An upper limit (at the
3-sigma confidence level) on the source luminosity in the 40- to
110-keV spectral band is 1.2 x 10E-10 erg sE-1 cmE-2.  This is about
5 times lower than the average luminosity of GRS 1758-258, as
measured by SIGMA during all the observations performed in 1990 and
from 1991 February to April."

     This object is recovering from its recent minimum, as indicated
by the following visual magnitude estimates (cf. IAUC 5355):  Oct.
1.5 UT, 12.6 (T. Cragg, Coonabarabran, N.S.W., Australia); 4.1, 12.1
(D. York, Abiquiu, NM); 7.44, 12.2 (P. F. Williams, Heathcote,
N.S.W.); 8.5, 11.7 (Cragg); 9.00, 12.0 (J. E. Bortle, Stormville,
NY); 10.12, 11.3 (R. Royer, Wrightwood, CA); 14.10, 11.3 (York);
16.75, 10.9 (D. Overbeek, Edenvale, South Africa); 18.73, 10.8

1991 October 28                (5377)             Daniel W. E. Green

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