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IAUC 5864: GRS 1009-45; R CrB

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                                                  Circular No. 5864
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

GRS 1009-45
     I. Lapshov, S. Sazonov, and R. Sunyaev, on behalf of the
GRANAT WATCH team (Space Research Institute, Moscow; and Danish
Space Research Institute, Lyngby), report:  "A new hard x-ray
transient source GRS 1009-45 (R.A. = 10h09m, Decl. = -44 55', equinox
1950.0; radius of uncertainty 1 deg) was detected by the GRANAT/
WATCH All Sky Monitor during observations performed on Sept. 12-13.
The source's intensity in the band 8-20 keV (in Crab units) is as
follows:  Sept. 12-13 UT, 0.6 +/- 0.1; 13-14, 0.7 +/- 0.1; 15.1,
0.6 +/- 0.1.  Similarly, in the 20-60 keV band:  Sept. 12.0, 0.4
+/- 0.1; 12-14, 0.8 +/- 0.15; 15.1, 0.7 +/- 0.1.  The source was
too weak on Sept. 11 to be detected by WATCH.  The spectrum of the
source is harder than spectra of Crab Nebula and Vela X-1 observed
simultaneously with the same detector; its hardness is comparable
to that of Cygnus X-1."
     B. A. Harmon, Marshall Space Flight Center (MSFC), NASA; S. N.
Zhang, Universities Space Research Association and MSFC; G. J.
Fishman, MSFC; and W. S. Paciesas, University of Alabama at Huntsville
and MSFC, report for the Compton Gamma Ray Observatory BATSE
team:  "We have detected strong hard x-ray/gamma-ray emission from
GRS 1009-45 in the range 20 to 500 keV.  The source was located using
the newly-developed BATSE occultation transform imaging system,
and was determined to be centered at R.A. = 10h14m, Decl. = -45.5
deg (equinox 2000.0), which is within the WATCH error circle.  The
BATSE location error is +/- 0.2 deg in the northwest-southeast
direction and +/- 0.4 deg in the perpendicular direction.  Daily flux
averages, relative to the Crab nebula, are (errors about 0.1 Crab):
Sept. 12, 0.5; 13, 0.7; 14, 0.9; 15, 0.9; 16, 0.8, with power-law
indices ranging from -2.2 to -2.6.  The Sept. 13-16 average spectrum
is well fit by a single power law with index -2.5 to at least
500 keV."

     Further visual magnitude estimates (cf. IAUC 5851): Aug. 31.83
UT, 7.0 (L. Szentasko, Budapest, Hungary); Sept. 4.82, 7.2 (H.
Bengtsson, Hisings Backa, Sweden); 9.83, 7.4 (A. Pereira, Cabo da
Roca, Portugal); 11.20, 7.4 (C. E. Spratt, Victoria, BC); 13.86,
7.1 (Pereira); 16.19, 7.2 (Spratt); 18.19, 6.9 (Spratt).

1993 September 18              (5864)            Daniel W. E. Green

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