Central Bureau for Astronomical Telegrams
IAUC 3624: GX 17+2; SNe IN NGC 1316
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Read IAUC 3625
Circular No. 3624
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-864-5758
GX 17+2
M. Oda and the Hakucho Team report: "Hakucho has observed
three x-ray bursts from a position consistent with that of the galactic
bulge x-ray source GX 17+2 = 4U 1813-14 (which has not been
previously known to exhibit burst activity). The times, peak
fluxes (1-30 keV), durations and error-circle diameters for the
three bursts are as follows:
1981 UT Peak flux Duration Error
May 21d05h49m 1.8 Crab ~ 0.5 min 0o.5
25 00 08 0.3 Crab ~ 0.5 min 0o.1
25 12 38 0.6 Crab ~ 1.0 min 0o.5
The persistent flux from GX 17+2 at the time of the burst was 0.6
Crab (1-30 keV). Optical observations of the suggested optical
counterpart (cf. IAUC 3620) would be useful."
S. Kahn, J. Grindlay, J. Halpern and E. Ladd, Center for Astrophysics,
report: "We have independently discovered an x-ray burst
from the vicinity of GX 17+2 with the Monitor Proportional Counter
on the Einstein Observatory. The burst took place on 1980 Mar. 29d
01h45m UT. It was a considerably weaker event than the Hakucho
bursts, with a peak flux of ~ 0.15 Crab in the 2-6-keV band, and it
had a much shorter decay time, ~ 7.5 s. The risetime of the burst
was ~ 2 s. A spectrum obtained at the burst maximum yielded a best
fit blackbody temperature > 1.3 keV (90-percent confidence). The
burst was not observed simultaneously by the Einstein High Resolution
Imager, which is sensitive to lower-energy x-rays. This implies
that the absorbing column density to the burst source must be
> 2.4 x 10**26 m**-2, consistent with the value obtained for the steady
source GX 17+2. The persistent flux from GX 17+2 was 0.56 Crab
(2-6 keV) at the time of the burst."
SUPERNOVAE IN NGC 1316
R. Evans, Maclean, N.S.W., writes that his visual observations
of the Maza supernova indicated a decline by some 1.25 mag in 32
days beginning 1980 Dec. 11, some 7-8 days after first maximum. On
the other hand, the Evans supernova declined a comparable amount
from a comparable time after maximum in only 21 days (beginning
1981 Mar. 18).
1981 August 6 (3624) Brian G. Marsden
Read IAUC 3625
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