Central Bureau for Astronomical Telegrams
IAUC 6414: PSR 1055-52; GRO J1744-28; 22P
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Circular No. 6414
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)
PSR 1055-52
R. Mignani, P. A. Caraveo, and G. F. Bignami, Istituto di
Fisica Cosmica, Milan, report observing the field of this radio/x-
ray/gamma-ray pulsar on May 11 with the Faint Object Camera onboard
the Hubble Space Telescope: "The observation was performed in the
F342 wideband filter centered at 340.2 nm (Delta(lambda) = 70.2 nm)
for a total exposure time of 8900 s. We have identified a point
source of mag 24.88 +/- 0.1 at R.A. = 10h57m58s.83, Decl. =
-52o26'56".3 (equinox 2000.0), coincident within 0".1 with the
radio-pulsar position. The object's flux appears compatible with
the low-energy extrapolation of the ROSAT soft-x-ray spectrum --
i.e., a blackbody curve with a temperature of 750~000 K and a
hydrogen column density of 6 x 10E20."
GRO J1744-28
K. Jahoda, Goddard Space Flight Center (GSFC); T. Strohmayer
and R. Corbet, GSFC and Universities Space Research Association;
and M. Stark, GSFC and University of Maryland, report: "GRO
J1744-28 resumed bursting activity between May 29 and June 1. The
Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA)
observed three bursts during a 151-min observation on June 1, and
seven bursts during a 179-min observation on June 2. The average
power spectrum of the June 2 bursts shows 6-percent rms variability
at the 2.1-Hz pulse period of GRO J1744-28, indicating that these
bursts come from this source, and the peak power at 2.1 Hz reaches
10 percent rms. The brightest burst was 9000 counts/s (0.7 Crab).
All of these bursts have rise times less than a few seconds; while
most of the bursts have durations of 20-30 s, some continue up to
100 s. The burst spectrum can be characterized by a hard power-law
(photon index 1.3) cutoff at about 20 keV with a 10-keV e-folding
energy, similar to the spectrum previously measured for GRO
J1744-28. While a nearby source hampers measurements of the
quiescent flux, the nonbursting pulsed flux is 13 +/- 0.5 counts/s,
an increase of at least a factor of two since May 29.
This suggests that the quiescent flux has also increased. RXTE
will continue to observe GRO J1744-28 regularly."
COMET 22P/KOPFF
Visual m1 estimates: May 18.55 UT, 8.8 (S. O'Meara, Volcano,
HI, 10x35 binoc.); June 2.72, 8.8 (G. Wolf, Wellington, N.Z., 0.12-
m refractor).
(C) Copyright 1996 CBAT
1996 June 4 (6414) Daniel W. E. Green
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