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IAUC 6101: GS 1826-24; X-RAY N IN Sco

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                                                  Circular No. 6101
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)
Phone 617-495-7244/7440/7444     TWX 710-320-6842 ASTROGRAM CAM
MARSDEN@CFA.HARVARD.EDU or GREEN@CFA.HARVARD.EDU (science)


GS 1826-24
     C. Motch, Observatoire de Strasbourg; D. Barret, Centre d'Etude
Spatiale des Rayonnements and Harvard-Smithsonian Center for
Astrophysics; W. Pietsch, Max-Planck-Institut fur Extraterrestrische
Physik; G. Hasinger, Astrophysikalisches Institut, Potsdam; and E.
Giraud, European Southern Observatory (ESO), write:  "We report the
optical identification of the black-hole candidate and x-ray source
GS 1826-24 (Tanaka 1989, ESA SP-296, p. 3) with a faint (V = 19,
B-V = +0.4, U-B = -0.5) ultraviolet-excess object exhibiting the He
II 468.6-nm (equivalent width = -0.4 nm) and H-alpha (EW = -0.18
nm) lines in emission.  Optical observations were obtained with the
ESO New Technology Telescope (+ EMMI) on June 3-4 and Oct. 20.  The
proposed optical counterpart is located at R.A. = 18h29m28s.2, Decl.
= -23o47'49".1 (equinox 2000.0; +/- 2"), well within the ROSAT PSPC
pointing error circle (90-percent confidence radius 18") centered
at position end figures 27s.63, 53".5 (see also Johnston et al.
1994, A.Ap. 289, 763).  The x-ray source was detected during the
ROSAT All-Sky Survey and subsequent 20000-s pointing on 1992 Oct.
9-12, with a mean PSPC countrate of 4 and 2 counts/s, respectively.
Our optical identification indicates that the black-hole candidate
is accreting from a low-mass companion.  Finding charts may be
provided upon request to motch@cdsxb7.u-strasbg.fr."


X-RAY NOVA IN SCORPIUS
     S. N. Zhang, B. A. Harmon, W. S. Paciesas, C. A. Wilson, and
G. J. Fishman report for the Compton Gamma Ray Observatory BATSE
Team:  "The x-ray nova in Scorpius (first reported on IAUC 6046) is
again in outburst.  The source intensity, in mCrab for the band 20-
100 keV, was < 100 mCrab on Oct. 31, then reached 290 +/- 70 on Nov.
1, 360 +/- 25 on Nov. 2, 350 +/- 30 on Nov. 3, 680 +/- 50 on Nov. 5,
740 +/- 30 on Nov. 6, and 710 +/- 35 on Nov. 7.  The flux during
the last two days is near the peak level of the previous outburst
(IAUC 6075).  The photon spectrum is well fit with a power law with
an index of -3.1 +/- 0.2 from 20 to 100 keV.  We urge immediate
follow-up observations of this source at other wavelengths.  It
should be noted that the previous outburst only lasted for about 10
days within the energy range 20-200 keV."


1994 November 9                (6101)            Daniel W. E. Green

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