Radio holding steady in GRO J1655-40
ATel #425; M. P. Rupen (NRAO/GSFC), A. J. Mioduszewski, V. Dhawan(NRAO)
on 23 Feb 2005; 22:17 UT
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)
Subjects: Radio, Binary, Black Hole, Transient
Referred to by ATel #: 437, 487
Very Large Array (VLA) observations of the black hole X-ray binary GRO
J1655-40 on Feb. 23rd (MJD 53424.6) show that the radio source seen on Feb.
20th (ATEL #419) has remained roughly constant, with flux densities of
1.53 +/- 0.07 mJy at 4.86 GHz, and 1.45 +/- 0.08 mJy at 8.46 GHz. These
data, taken in much better weather conditions, show a
fairly flat spectrum (flux density going as frequency to the -0.10 +/- 0.14),
suggesting a very small (milliarcsecond or less) source. A Gaussian fit to
the 8.46 GHz data yields a more direct upper limit to the size of
about 1.1 arcseconds, compared to the 2.6 x 0.6 arcsec
full-width-at-half-maxmimum of the beam (major axis oriented 6.1 degrees east
of north). Further radio observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
