IAU Central Bureau for Astronomical Telegrams

Central Bureau for Astronomical Telegrams -- Image credits

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

The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).

Read IAUC 6100  SEARCH Read IAUC 6102

View IAUC 6101 in .dvi or .ps format.
IAUC number

                                                  Circular No. 6101
Central Bureau for Astronomical Telegrams
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

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."

     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

Read IAUC 6100  SEARCH Read IAUC 6102

View IAUC 6101 in .dvi or .ps format.

Our Web policy. Index to the CBAT/MPC/ICQ pages.

Valid HTML 4.01!