Central Bureau for Astronomical Telegrams
IAUC 2946: X-RAY BURSTS; WRA 977
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Circular No. 2946
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK
Western Union: RAPID SATELLITE CAMBMASS
X-RAY BURSTS
J. Hoffman, Massachusetts Institute of Technology, reports
that the SAS-3 Group has observed a series of three x-ray bursts from
a new source in the galactic center region. The bursts occurred on
Mar. 31.78667, 31.79886 and 31.80178 UT. The 95-percent-probability
contour for the position is an ellipse with major axis 0o.31 in p.a.
69o and minor axis 0o.07 and centered at R.A. = 17h44m.1, Decl. =
-28o28' (equinox 1950.0; l = 0o.59, b = -0o.07). This position does
not overlap with those reported on IAUC 2918. None of the galactic
center bursts reported there or on IAUC 2922 was spaced as
closely as these three were. In two days of observation (Mar. 30
and 31) no bursts were seen from the previously reported positions.
E. P. Aksenov, Sternberg Astronomical Institute, writes that
during 1975 July 22d15h56m-22d16h02m UT E. K. Sheffer and E. I.
Moskalenko detected 19 intense bursts from Cyg X-1 in the 2-10 keV
band. In the 0.2-2 keV band there was no rise in the count rate.
During these bursts the flux from the source increased by 3 to 20
times with a risetime < 1s and decay time < 10s. The spectra of
the bursts may be fitted by bremsstrahlung with temperatures from <
1 up to 4 keV and an amount of matter of more than 10**23 atoms cm**-2.
The charged-particle channel did not show any changes from its main
level. The observations were made by the x-ray telescope Filin on
board the orbital space station Salyut 4.
WRA 977
H. Mauder, Astronomical Institute, University of Tubingen,
writes that U-band observations of WRA 977, the suggested optical
counterpart of 3U 1223-62 (cf. IAUC 2569), were made with the 50-cm
pulse-counting photometric telescope at the European Southern
Observatory during Mar. 16-19 with a time resolution of 2s. The
average counting rate was 230 cts/s, but there seemed to be several
small peaks of duration ~ 1 min. The peaks were not always present,
but when they were, their separation was 11.657 min or a multiple
thereof; within the limits of error, this period is consistent with
the 11.64 +/- 0.02 min reported for the x-ray source (IAUC 2870).
Folding the data with this period into 1-min bins yielded significant
pulse structure, a drop in the counting rate in the bin preceding
the main pulse by 5 min indicating a possible small interpulse.
1976 April 30 (2946) Brian G. Marsden
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