Central Bureau for Astronomical Telegrams
IAUC 6310: GRO J1744-28
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Circular No. 6310
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
D. M. Cole, D. E. Vanden Berk, S. A. Severson, R. C. Nichol,
M. C. Miller, J. M. Quashnock, D. Q. Lamb, E. Bergeron, K. Gloria,
and D. Long, University of Chicago, report: "We made near-infrared
observations during Jan. 30.529-30.551 UT, and optical observations
during Feb. 5.534-5.582, of a region of the sky that included the
entire XTE error box (IAUC 6291, 6309) for GRO J1744-28, using the
Astrophysical Research Consortium's 3.5-m telescope at Apache Point
Observatory. We have examined the position of the variable radio
source reported on IAUC 6307 in stacked images in g (665 s), r (665
s), and K' (510 s). In the stacked r image, we find an object at
this position (within 1") that is 3.7 mag fainter in r than a star
with photographic mag bj = 18.26 in COSMOS/NRL scans of the U.K.
Schmidt Southern Sky Survey. Assuming a color of bj-r = +1.1, this
implies an r = 21. Visual examination of an ESO copy of a U.K.
Schmidt Survey red plate also reveals an object at this location at
the limit of the plate. In the stacked g image, the faintest
objects we confidently detect are g = 19.3 (using a color
conversion of bj-g = +0.7), but no object at all is visible at the
position of the radio source. In the stacked K' image, we find an
object of mag 13 at this position. Examination of an earlier (1992)
K-band map of the field kindly provided by M. Merrill and I. Gatley
(NOAO) reveals an object at this location of comparable brightness.
In these observations, the optical/NIR counterpart of the radio
source does not appear significantly brighter than at earlier
epochs. The r band results quoted on IAUC 6309, in conjunction
with our own data, may indicate that the object has brightened in
the past four days."
Further to their item on IAUC 6309, T. Augusteijn et al. add:
"A spectrum (range 400-1000 nm, resolution 2.8 nm) of the star
coinciding with the radio source in the XTE error box of GRO
J1744-28, taken with the New Technology Telescope on Feb. 9.332 UT,
shows that this object is an M0 (+/- 1 subtype) star, likely a
moderately reddened [E(B-V) about 0.5 mag] star at a distance of
500-1000 pc. The spectrum shows no trace of H-alpha emission
(upper limit on its equivalent width 0.05 nm). It is highly
unlikely that this M star is the optical counterpart of GRO
J1744-28. Therefore, if the radio source is connected with the x-
ray source, the optical counterpart must be substantially fainter
than V = 20."
(C) Copyright 1996 CBAT
1996 February 10 (6310) Daniel W. E. Green
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