Central Bureau for Astronomical Telegrams
IAUC 6484: GALACTIC CENTER; GRO J1744-28
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Circular No. 6484
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
T. Strohmayer, Laboratory for High Energy Astrophysics and
Universities Space Research Association (LHEA/USRA); U. Lee, Tohoku
University, Sendai; and K. Jahoda, LHEA, Goddard Space Flight
Center, report: "We have detected x-ray brightness oscillations
with a frequency of 589 Hz during three type-I x-ray bursts from a
burster in the galactic-center region. The bursts ocurred on May
15.814, June 4.612, and June 19.414 UT during routine monitoring
observations of GRO J1744-28 by the Rossi X-ray Timing Explorer
(RXTE). The oscillations have amplitudes (rms) in the range 2-4
percent (above 8 keV) and are detected only in the few seconds
after burst peak. Each burst shows evidence for modest
photospheric radius expansion. The current data constrain the
source position to a 0.15-degree-wide region whose shape is
approximately that of one quarter of an annulus. The center line
of the annular region extends from (R.A., Decl.) = (17h43m40s.8,
-29o03'00", equinox 2000.0) to (17h45m00s.0, -29o16'48"), with
midpoint at (17h44m07s.2, -29o09'00"), strongly excluding GRO
J1744-28 as the burst source. The known burster nearest to this
region is MXB 1743-29, but at present this association is only
suggestive. This represents the third detection by RXTE of a near-
millisecond oscillation from an x-ray bursting low-mass x-ray
binary (see IAUC 6387, 6437)."
GRO J1744-28
T. Augusteijn and C. Lidman, European Southern Observatory;
and P. Blanco, University of California, San Diego; report: "A re-
analysis of the Feb. 8 K-band image taken of the field of the
transient GRO J1744-28 (IAUC 6321) shows that the source that was
identified as the infrared counterpart of the transient (IAUC 6369)
may not be real. The image is the superposition of ten individual,
mutually-shifted images. The source was in the field-of-view of
seven of these; however, it only appears in two. The detections do
not coincide with any recorded bursts in the Ulysses GRB data (K.
Hurley, private communication), and we suspect that the detections
may be artifacts of the detector. Further analysis of the Feb. 8
and Mar. 28 images do not show any source in the vicinity of the
x-ray position down to K about 16 and varying by > 0.5 mag. We
encourage continuous deep-infrared imaging to secure the
identification of the counterpart of GRO J1744-28."
(C) Copyright 1996 CBAT
1996 October 7 (6484) Daniel W. E. Green
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