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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.

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