Central Bureau for Astronomical Telegrams
IAUC 6272: GALACTIC CENTER; 4U 0115+634
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Circular No. 6272
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)
GALACTIC CENTER
G. J. Fishman, Marshall Space Flight Center (MSFC), NASA; C.
Kouveliotou, Universities Space Research Association and MSFC; J.
van Paradijs, University of Alabama at Huntsville (UAH) and
University of Amsterdam; B. A. Harmon, MSFC; W. S. Paciesas and M.
S. Briggs, UAH; and J. Kommers and W. H. G. Lewin, Massachusetts
Institute of Technology, report observations from the Compton
Observatory's BATSE experiment: "A transient x-ray source is being
observed that emits bursts at energies between 10 and 50 keV from
the general direction of the Galactic Center. Over 200 bursts with
typical widths between 8 and > 30 s have been seen from the source
since Dec. 2. The rate of the x-ray bursts has declined from a
maximum of about 18 events per hour on Dec. 2.7 UT to a current
average rate of about 1.2 events per hour (corrected for live-time
and earth occultation). The average burst peak flux is about 5 x
10E-8 erg cmE-2 sE-1 and the typical fluence is about 5 x 10E-7
erg/cm2 per burst in the energy band 20-40 keV. No steady emission
is seen from the source. The spectra of the events are similar to
bursts from soft gamma-ray repeaters, but much harder than those of
type-II bursts from the rapid burster 1730-335. The most probable
location of the source is centered at R.A. = 17h52m, Decl. = -23o,
with an error radius of about 6 deg (1 sigma). The behavior
reported here is unlike that previously seen from any x-ray or
gamma-ray transient source."
4U 0115+634
S. Sazonov and R. Sunyaev, Space Research Institute, Moscow,
on behalf of the Granat/WATCH team, report: "The transient x-ray
pulsar 4U 0115+634 is undergoing a strong outburst. The flux from
8 to 20 keV increased at a constant rate of about 100 mCrab/day
from 60 +/- 50 mCrab on Nov. 18 to 670 +/- 60 mCrab on Nov. 25; it
remained at that level in subsequent WATCH observations, on Nov.
26-29 and Dec. 5-8. This outburst already reported by the BATSE
team (IAUC 6266) is the second major outburst observed from the
source with WATCH during the period 1989-1995. It is similar in
temporal behavior and intensity to the previous one observed in
1990 Feb.-Mar. by Granat/WATCH and Ginga. These two outbursts are
separated by 5.8 yr, which is consistent with the 3-yr quasi-
periodicity previously known to exist in 4U 0115+634 (Tamura et al.
1992, Ap.J. 389, 676)."
1995 December 12 (6272) Daniel W. E. Green
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