Central Bureau for Astronomical Telegrams
IAUC 6209: X-RAY N 1994 IN Sco; GRS 1915+105
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Circular No. 6209
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
X-RAY NOVA 1994 IN SCORPIUS
S. Sazonov and R. Sunyaev, on behalf of the GRANAT/WATCH Team,
report: "GRO J1655-40 is very bright, according to GRANAT/WATCH in
the spectral band 8-20 keV. After the bright outburst of late
July-early Aug. (IAUC 6196, 6201, 6205), the source became
relatively weak (250 +/- 100 mCrab) by Aug. 8. Since that date,
its flux gradually increased to 800 +/- 200 mCrab on Aug. 16 and to
1400 +/- 100 mCrab on Aug. 19."
S. N. Zhang, B. A. Harmon, W. S. Paciesas, and G. J. Fishman,
Marshall Space Flight Center, NASA, report for the Compton
Observatory BATSE Team: "The x-ray/radio transient source GRO
J1655-40 has been undergoing another bright outburst in hard x-rays,
immediately after the last outburst (IAUC 6196) reached a minimum
flux level of about 60 mCrab (20-100 keV) on Aug. 9 (IAUC 6205).
The energy spectrum can be well fitted by a power law with
significant flux detectable up to 200 keV. The peak flux of the
current outburst was 600 +/- 70 mCrab (20-100 keV) on Aug. 17. The
flux has since declined to about 250 +/- 50 mCrab on Aug. 19. The
photon spectral index changed from -2.1 on Aug. 10 to -2.5 on Aug.
17 and to -1.8 on Aug. 19, consistent with the spectral evolution
seen previously from this source. We note that the 8- to 20-keV
flux detected by WATCH/GRANAT continued to rise since Aug. 17 (see
above). The current activity from July 22 appeared in phase with
the previous three major outbursts with peak flux above 1 Crab,
which were separated by 120 days."
GRS 1915+105
Sazanov and Sunyaev also write: "The outburst of GRS 1915+105
detected by GRANAT/WATCH on 19 July (IAUC 6196) is still continuing
as of Aug. 19. During the outburst, the source's flux at 8-20 keV
has been about 700 mCrab with no significant variations in
intensitydetected."
Zhang et al. also report: "Hard x-ray activity from GRS
1915+105 has continued since a previous report (IAUC 6204). The
flux in the band 20-100 keV peaked on Aug. 11 at 220 +/- 25 mCrab,
following the intense radio flare on Aug. 10 (IAUC 6204), then
decreased rapidly until the source was undetectable on Aug. 14. We
note that the 8- to 20-keV flux (see above) continued to increase
after Aug. 11, suggesting a hard-to-soft transition in the spectrum."
1995 August 21 (6209) Daniel W. E. Green
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