Recent radio evolution of GRO J1655-40
ATel #489; M. P. Rupen (NRAO/GSFC), V. Dhawan, A. J. Mioduszewski (NRAO)
on 12 May 2005; 14:26 UT
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)
Subjects: Radio, Binary, Black Hole, Transient
Very Large Array (VLA) observations of of the black-hole X-ray binary
GRO J1655-40 show a slight increase in radio flux density corresponding to
the recent change in X-ray and optical/IR state (ATEL #485, ATEL #486, ATEL
#487). The following results were obtained at 4.86 GHz:
- 4may05 UT (MJD 53494.47): 3.1 +/- 0.1 mJy
- 7may05 UT (MJD 53497.40): 0.27 +/- 0.08 mJy/beam (marginal at best)
- 11may05 UT (MJD 53501.42): 0.67 +/- 0.15 mJy
There are two surprises here: first, the relatively strong detection on May
4th, corresponding to the brief X-ray hardening seen between
MJD 53493.6 and MJD 53495.2 in the PCA data (referenced in ATEL #
487);
and second, the comparitive faintness of the detection on May 11th,
despite much more impressive X-ray activity (and hardening). There is no
evidence of extension in any of these observations, with a typical
resolution of 6 x 1 arcsec (full-width at half-maximum of a Gaussian fit),
with the long axis oriented 15-20 degrees east of north.
The full radio light curves are shown at
http://www.aoc.nrao.edu/~mrupen/XRT/GRJ1655-40/grj1655-40.shtml .
Further VLA observations are planned, with the next scheduled for 16may05.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
