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IAUC 6392: GRS 1915+105; 1996M; 46P; 65P

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                                                  Circular No. 6392
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)


GRS 1915+105
     E. Morgan and R. Remillard, Massachusetts Institute of
Technology; and J. Greiner, Max-Planck-Institut fur
Extraterrestrische Physik, Garching, communicate:  "Recent RXTE
observations have shown that GRS 1915+105, a galactic x-ray
transient (IAUC 5590) with relativistic radio jets (Mirabel and
Rodriguez 1994, Nature 371, 46), is bright and highly variable in
the range 2-25 keV.  More than 800 measurements from the All Sky
Monitor (ASM) at 2-12 keV during 1996 Feb. 20-Apr. 26 show large
intensity variation from 0.2 to 2.0 Crab.  The ASM captured several
episodes of quasiperiodic oscillations (QPOs) with timescales of
30-40 s and amplitudes as large as 1 Crab.  Five PCA observations
taken in April show many narrow QPO features between 0.5 and 100
mHz with complex spectral and dynamic signatures and large
amplitudes.  There is a trend toward smaller amplitude and higher
frequency variability, although the average intensity has remained
about 1.5 Crab.  In the two most recent PCA observations, we find a
67-Hz QPO.  If this feature is related to the frequency of the
minimum stable Keplerian orbit around a Schwartzschild blackhole,
then the implied blackhole mass is 33 M(sun).  Radio Observations
are urged to look for new episodes of superluminal mass ejection.
RXTE will continue to monitor this source."


SUPERNOVA 1996M IN ANONYMOUS GALAXY
     A. Filippenko, Univerisity of California, reports that SN
1996M is due east of the host galaxy's nucleus, rather than west
(cf. IAUC 6347).


COMET 46P/WIRTANEN
     CCD R magnitude estimates obtained at the European Southern
Observatory:  1995 June 26.23 UT, 24.2 (H. Bohnhardt, with R. M.
West and J. Babion, 2.2-m reflector; stellar appearance); 1996
Apr. 25.33, 21.5 (Bohnhardt and H. Rauer, with S. Mottola and A.
Nathues, 1.5-m Danish reflector; 4" tail in p.a. about 270o).


COMET 65P/GUNN
     Total visual magnitude estimates (cf. IAUC 6368):  Apr. 15.44
UT, 13.3 (A. Hale, Cloudcroft, NM, 0.41-m reflector); 18.06, 13.0
(K. Hornoch, Lelekovice, Czech Republic, 0.35-m reflector); 20.09,
13.1 (R. J. Bouma, Groningen, The Netherlands, 0.25-m reflector);
27.43, 12.9 (Hale).

                      (C) Copyright 1996 CBAT
1996 May 2                     (6392)            Daniel W. E. Green

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