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IAUC 3609: Poss. SN IN NGC 5597; GX 339-4 = 4U 1658-48; NOTICE TO SUBSCRIBERS

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                                                  Circular No. 3609
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM     Telephone 617-864-5758

     C. Torres, University of Chile, telexes that M. Wischnjewsky
has discovered a possible supernova in NGC 5597.  An observation by
E. Gonzalez on May 29.124 UT showed the object to be of mpg 17, 17"
west and 13" south of the nucleus of the galaxy.

GX 339-4 = 4U 1658-48
     C. Motch, European Southern 0bservatory; and S. A. Ilovaisky
and C. Chevalier, Observatoire de Meudon, telex: "The optical counterpart
of this x-ray source, previously reported as being in a
faint state (IAUC 3585, 3586, 3594), is now very bright.  Photometry
obtained on May 24 with the ESO 3.6-m telescope gives: J =
12.6, H = 12.1, K = 10.9, L = 9.4.  Photometry on May 28 with the
1.5-m Danish telescope gives: V = 15.4, B-V = +0.8, V-R = +0.6, V-I
= +1.5 (Cousins' VRI system).  Fast photometry with the 1.5-m telescope
on May 28 and 29, using a two-channel (star-sky) photometer
with 10-ms integration times and the full response of a GaAs red-sensitive
photomultiplier, reveals quasi-periodic, 20-s oscillations
of 40 percent full amplitude, throughout the night, as well
as statistically-significant, sharp bursts with timescales down to
20 ms; during these bursts the flux intensity of the object can increase
by a factor of two.  A nearby comparison star of similar
brightness was monitored occasionally and did not show any activity;
counting rates from the second channel (sky) were also normal.  This
rapid optical behavior is unprecedented among x-ray sources, and,
together with a 6-mag change in < 2 months, it suggests that most of
the light is from an accretion disk in a low-mass x-ray binary.
Further optical and x-ray observations are urgently needed."

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1981 June 3                    (3609)              Brian G. Marsden

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