Central Bureau for Astronomical Telegrams
IAUC 6290: GRO J1744-28; 6P
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Circular No. 6290
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)
GRO J1744-28
M. S. Briggs, University of Alabama, Huntsville (UAH); B. A. Harmon,
NASA Marshall Space Flight Center (MSFC); J. van Paradijs, UAH and
University of Amsterdam; C. Kouveliotou, Universities Space Research
Association; G. J. Fishman, MSFC; and J. Kommers and W. H. G. Lewin,
Massachusetts Institute of Technology, report for the Compton
Observatory BATSE team: "The increased intensity of GRO J1744-28
enables improved spectral analysis. Using burst observations with the
BATSE Large Area Detectors (> 30 keV) and a Spectroscopy Detector
(> 8 keV), unabsorbed power law and OTTB models may be excluded.
Acceptable fits are obtained with a blackbody model with no absorption
and kT = 6 keV and with an OTTB model with kT = 10 keV and absorption
of N(H) = 1.6 times 10**24 cm**-2. Very similar spectral results are
obtained for the persistent spectrum from occultation observations.
This similarity argues for a common emission process for the burst and
persistent emission."
Fishman, Harmon, Kouveliotou, van Paradijs, Briggs, Kommers and
Lewin, with also K. Deal and P. Woods, UAH, report: "The unusual
burster in the galactic center region, identified with the x-ray pulsar
GRO J1744-28 (IAUC 6286), continues to increase in burst intensity and
steady emission. Over the past four weeks, both the peak flux and the
fluence of the individual bursts have increased by about a factor of six.
On Jan. 15 their average values (20-50 keV) were about 2 and about 7
times 10**-7 erg cm**-2 s**-1, respectively. Over the past ten days,
the burstrate has increased to about 25 observed bursts per day (some 40
per day, corrected for earth occultation and livetime) from a previous
average of about 18 observed bursts per day during the preceding month.
The burst durations have remained the same, 4-6 s FWHM, over the entire
period of observation. The associated steady source, as observed by earth
occultation, has increased in intensity to about 2.5 Crab (20-100 keV)
on Jan. 16."
COMET 6P/D'ARREST
Total visual magnitudes: 1995 Aug. 25.56 UT, 8.0 (P. Camilleri,
Cobram, Vic., Australia, 20 x 80 binoculars); Sept. 1.34, 7.8 (A. Hale,
Cloudcroft, NM, 10 x 50 binoculars); 4.40, 7.2 (C. S. Morris, southern
California, 10 x 50 binoculars); 17.25, 8.4 (Hale); 24.35, 8.2 (Morris);
30.04, 7.8 (J. Carvajal, Madrid, Spain, 10 x 70 binoculars); Oct. 3.41,
8.9 (Hale); 15.23, 9.7 (Hale, 0.41-m reflector); 21.28, 9.3 (Morris,
20 x 80 binoculars); 27.21, 10.2 (Hale); Nov. 14.18, 11.0 (Hale); 20.26,
11.3 (Hale); 25.24, 11.4 (Hale).
(C) Copyright 1996 CBAT
1996 January 19 (6290) Brian G. Marsden
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