Central Bureau for Astronomical Telegrams
IAUC 6286: GRO J1744-28
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Circular No. 6286
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.
Kommers and W. H. G. Lewin, Massachusetts Institute of Technology;
J. van Paradijs, University of Alabama, Huntsville (UAH) and
University of Amsterdam; G. J. Fishman, Marshall Space Flight
Center (MSFC), NASA; and M. S. Briggs, UAH; report: "Strong
pulsations (about 50 percent modulation) near 2.1 Hz have been
observed in the bursts from the burst source near the galactic
center (IAUC 6275, 6276). Thus this unusual burst source and the
transient pulsar GRO J1744-28 (IAUC 6284, 6285) are the same
source. The hard x-ray bursts are therefore very likely the result
of accretion instabilities on a strongly magnetized neutron star in
a binary system."
K. Hurley, Space Sciences Laboratory, University of California,
Berkeley, on behalf of the Ulysses Gamma-Ray Burst Team;
Kouveliotou, A. Harmon, Fishman, and Briggs, on behalf of the Gamma
Ray Observatory BATSE team; van Paradijs, Kommers, and Lewin, write:
"A refined position for the new repeating x-ray transient source
(IAUC 6272) has been obtained using Ulysses and BATSE (specifically,
one Ulysses/BATSE triggered event on Jan. 8). The position is an
annulus whose halfwidth is 0.047 deg centered at R.A. = 3h02m57s,
Decl. = -61o34'07" (equinox 2000.0), with central radius 83.974 deg.
The intersection of this annulus with the positions reported on
IAUC 6276 and 6284 defines a location that may be approximated by a
box with the following coordinates: R.A. = 17h43m22s, Decl. =
-28o46'.7; 17h45m07s, -28o39'.2; 17h45m35s, -28o43'.1; 17h43m49s,
-28o51'.0. This error box is smaller than, but nested within, the
previous network synthesis localizations."
M. H. Finger, Compton Observatory Science Support Center; R. B.
Wilson, MSFC; and van Paradijs, communicate for the Compton
Observatory BATSE team: "The pulse timing of the 467-ms-period x-
ray pulsar GRO J1744-28 shows a binary orbital motion Doppler
signature. A fit of frequencies observed between 1995 Dec. 21 and
1996 Jan. 10 yields the following parameters: orbital period
11.76(3) days; epoch of superior conjunction JD 2450079.71(2);
a sin i = 2.59(3) light seconds; spin frequency 2.1410016(3) Hz (at
1995 Dec. 31.0 UT); and frequency derivative 8.6(5) x 10E-12 Hz/s.
We find a 90-percent confidence upper limit of 0.026 to the
eccentricity. The x-ray mass function is f(M) = 1.31(4) x 10E-4
solar mass. For a 1.4-solar mass neutron star and an inclination >
30 deg, the companion mass is 0.065-0.14 solar mass, with a Roche
lobe radius of 4.1-5.2 solar radii."
(C) Copyright 1996 CBAT
1996 January 12 (6286) Daniel W. E. Green
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