Central Bureau for Astronomical Telegrams
IAUC 6309: GRO J1744-28
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Circular No. 6309
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
T. Augusteijn and G. van de Steene, European Southern
Observatory; D. A. Frail, Very Large Array, National Radio
Astronomy Observatory; J. van Paradijs, University of Alabama at
Huntsville and University of Amsterdam; C. Kouveliotou, Universities
Space Research Association; G. J. Fishman, Marshall Space Flight
Center, NASA; and W. H. G. Lewin, Department of Physics,
Massachusetts Institute of Technology, report: "By comparing the
radio position with the digitized Sky Survey, we find a faint
source that falls within about 2" of the position of the radio
source in the error box of GRO J1744-28 (cf. IAUC 6307). From an
image taken on Jan. 21.360 UT, we find V about 19.8. From an
image taken on Feb. 9.322, we find R = 18.1 +/- 0.1. If GRO
J1744-28 is a normal, low-mass, x-ray binary, one would expect its
absolute visual magnitude to be MV about -3. If the radio source
is the counterpart of the x-ray source, at a distance of 7 kpc,
the visual extinction of the source is at least 8 magnitudes,
corresponding to a column density NH > 2 x 10E22 cmE-2. However,
given the optical magnitudes of the object and the fact that the
source can be seen on the digitized Sky Survey, this indicates that,
if the source is a low-mass x-ray binary, it is not very strongly
reddened. This is also supported by comparison to other stars in
the field seen in the V image and Gunn z images taken shortly
afterwards. If NH < about 10E22 cmE-2 (cf. IAUC 6291), the
weakness of the optical counterpart may require beaming of the
x-ray emission."
T. Strohmayer, Universities Space Research Association; and K.
Jahoda and F. Marshall, Goddard Space Flight Center, NASA,
communicate for the XTE science and instrument teams: "Additional
proportional counter array (PCA) scanning observations of GRO
J1744-28, obtained since the first observations by XTE on Jan. 18-
19 (cf. IAUC 6291), have been analyzed the further to constrain the
object's position. The resulting position obtained by averaging the
results of seven independent determinations is R.A. = 17h44m34s.3
+/- 2s.8, Decl. = -28o45'22" +/- 47" (equinox 2000.0). The quoted
uncertainties are the standard deviations among the positions
determined from seven independent scanning observations. These
uncertainties are consistent with our current understanding of the
possible systematic errors."
(C) Copyright 1996 CBAT
1996 February 9 (6309) Daniel W. E. Green
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