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IAUC 5499: 1992U; N Mus 1991; Var OBJECT NEAR NGC 4192

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                                                  Circular No. 5499
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

     J. Maza, University of Chile; and M. Hamuy, Cerro Tololo
Interamerican Observatory, report the discovery by R. Antezana of a
supernova located about 18" east and 9" north of the nucleus of the
spiral galaxy ESO 74-G4 (= PGC 65177, R.A. = 20h35m42s, Decl. =
-70d52'21", equinox 1950.0).  The supernova, of mpg about 18.5, was
found on a 20-min unfiltered IIa-O plate taken by Antezana with the
CTIO Curtis Schmidt telescope on Apr. 9.359 UT.  It was not present
(mpg [20) on a IIa-O plate taken with the same telescope by L. Wells
on Apr. 3.  Confirmation was made by Y.-C. Kim from B and V CCD images
obtained in nonphotometric conditions on Apr. 15.4 with the CTIO 0.9-m

     J. McClintock, Harvard-Smithsonian Center for Astrophysics; C.
Bailyn, Yale University; and R. Remillard, Massachusetts Institute of
Technology, communicate: "We obtained spectra (range 440-700 nm,
resolution 0.5 nm) on Apr. 3 with the 4-m telescope at the Cerro
Tololo Interamerican Observatory and photometric data during Apr. 3-8
with the CTIO 0.9-m and 1.5-m telescopes.  The velocity amplitude and
the orbital period were found to be K = 411 +/- 21 km/s and P = 10.42
+/- 0.04 hr (IAUC 5259).  The large value of the mass function, f(M) =
3.1 +/- 0.5 solar masses, provides dynamical evidence that the primary
is a black hole, as suggested by x-ray observers.  Furthermore, the
quiescent optical spectrum is strikingly similar to the spectrum of
the black hole candidate A0620-00.  The most notable spectral features
are a K-dwarf component and broad, double-peaked Balmer emission lines
(FWHM = 1800 km/s).  No other emission lines are apparent in
quiescence (V = 20.35 +/- 0.05).  The lightcurve shows ellipsoidal
variations with an amplitude of +/- 0.2 mag in the I band of and +/- 0.15
mag in a broad band that approximates B + V (IAUC 5451)."

     C. Pollas, Observatoire de la Cote d'Azur, informs us that no
object was detected at the indicated position (IAUC 5498) on exposures
with the 0.9-m Schmidt at Caussols to the following limiting
magnitudes (Tech Pan unless otherwise specified): 1982 Mar. 24.0 UT,
[19.5 mpg; 1983 Mar. 11.0, [19.0 mpg; 1991 Apr. 15.0, [21.0; 18.9,
[21.5; 19.9, [21.5; May 6.9, [21.5; 1992 Mar. 12.1, [20.5.

1992 April 16                  (5499)              Brian G. Marsden

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