Central Bureau for Astronomical Telegrams
IAUC 6369: GRO J1744-28
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Circular No. 6369
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
C. Kouveliotou, Universities Space Research Association; J.
Greiner, Max-Planck-Institut fur Extraterrestrische Physik; J. van
Paradijs, University of Alabama in Huntsville (UAH) and University
of Amsterdam; G.~J. Fishman, NASA/Marshall Space Flight Center;
W. H. G. Lewin, R. Rutledge, and J. M. Kommers, Massachusetts
Institute of Technology; and M. S. Briggs, UAH, report: "In a ROSAT
HRI observation on Mar. 14 (exposure time 824 s), this source was
detected at a mean countrate of 0.3 count/s, corresponding to
roughly 1 mCrab in the band 0.1-2.4 keV. The best-fit x-ray
position is R.A. = 17h44m33s.1, Decl. = -28o44'29" (equinox 2000.0;
estimated error +/- 8"). The variable radio source reported on
IAUC 6307 and 6323 is 1'.5 from this x-ray position and thus not
related to GRO J1744-28. Therefore, none of the candidate optical
counterparts reported earlier are related to GRO J1744-28. Using a
power-law model with photon index -1.22 and a column density
N(sub)H = 5.1 x 10E22 cmE-2, the observed mean countrate
corresponds to an unabsorbed luminosity of 3 x 10E37 erg/s (D/10
kpc)**2. The error box of GRO J1744-28 was in the field-of-view of
several ROSAT PSPC pointings in early 1992 March, during which the
source was not detected. The deepest exposure gives a 3-sigma upper
limit of 2 x 10E-4 count/s (PSPC). Using the same spectral
assumptions as above, this countrate limit corresponds to an
unabsorbed luminosity limit of 4 x 10E33 erg/s (D/10 kpc)**2."
T. Augusteijn, European Southern Observatory (ESO); and van
Paradijs, Kouveliotou, Greiner, Fishman, Rutledge, and Lewin
further report: "We have taken a K-band image of the ROSAT error
box of GRO J1744-28 with the ESO New Technology Telescope on Mar.
28. A comparison of this image with the one taken on Feb. 8 by
Blanco et al. (IAUC 6321) reveals the infrared counterpart of GRO
J1744-28. The star is located at R.A. = 17h44m33s.1 +/- 0s.1,
Decl. = -28o44'19".5 +/- 1".5 (equinox 2000.0), which is about 9".5
due north of the center of the ROSAT error box reported by
Kouveliotou et al. The star is detected at K = 15.7 +/- 0.3 on
Feb. 8, but it is undetected and at least 1 mag fainter on Mar. 28.
The infrared brightness decrease indicates that GRO J1744-28 is a
low-mass x-ray binary. Its K magnitude on Feb. 8 is consistent
with that expected from an x-ray heated accretion disk in such a
system with a 12-day orbital period and an x-ray luminosity of
several times 10E38 erg/s (Paradijs and McClintock 1994, A.Ap. 290,
133)."
(C) Copyright 1996 CBAT
1996 April 1 (6369) Daniel W. E. Green
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