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IAUC 5877: X-RAY N IN Oph; 1993ab; GRO J1008-57

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                                                  Circular No. 5877
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)


X-RAY NOVA IN OPHIUCHUS
     Y. Tanaka, on behalf of the ASCA Team, communicates: "The hard
x-ray transient GRS 1716-249 = GRO J1719-24 was observed from ASCA
on Oct. 5 UT.  The source was detected near the edge of the GRANAT/
SIGMA error circle (IAUC 5874).  The position determined with ASCA
is R.A. = 17h19m35s.2, Decl. = -25o00'42" (equinox 2000.0), with an
error-circle radius of 1', coincident with that of the radio/optical
candidate (cf. IAUC 5876) within 0'.5.  The source intensity is
about 0.24 Crab in the range 0.5-10 keV, with rapid fluctuation of
large amplitudes on time scales to < 1 s (similar to Cygnus X-1).
The spectrum is well approximated by a single power law with a photon
index of about 1.6 and a hydrogen absorption column of about 4
x 10E21 atoms/cm**2."


SUPERNOVA 1993ab IN NGC 1164
     R. Kirshner and S. Gordon, Harvard-Smithsonian Center for
Astrophysics, report that a spectrogram (range 400-800 nm) of SN
1993ab obtained at the Multiple Mirror Telescope on Oct. 8 UT shows
the object to be a typical type-Ia supernova at an age of about 4
months.  This is a different conclusion from that drawn on IAUC 5871.


GRO J1008-57
     R. Petre and N. Gehrels, Goddard Space Flight Center, NASA,
write:  "We have observed the newly discovered transient x-ray
pulsar GRO J1008-57 on Aug. 9 using the ROSAT PSPC.  The source was
detected at a count rate of 0.89 count/s in the band 0.1-2.4 keV.
The best fit source position is R.A. = 10h09m46s, Decl. = -58o17'32"
(equinox 2000.0), with an error radius of 15", dominated by the
systematics in the ROSAT attitude determination.  The error circle
is near the center of the BATSE error box (cf. IAUC 5838), and is
consistent with the larger (1' radius) ASCA error box (IAUC 5851).
The best fit pulse period is 93.4 s.  The source is about 70 percent
pulsed, with a well-defined double-peaked pulse profile.  The
0.5- to 2.0-keV spectrum is most unusual; it is extremely soft:  a
fit to a power-law model requires an energy index in excess of 10,
and a fit to a thermal bremsstrahlung model requires a temperature
of 0.085 +/- 0.02 keV.  The column density is 3 x 10E22 cmE-2, with
a 90-percent confidence range of 2.4-4.7 x 10E22 cmE-2.  The
observed 0.5- to 2.0-keV flux was 6.4 x 10E-12 erg cmE-2 sE-1."


1993 October 9                 (5877)            Daniel W. E. Green

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