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ATEL # 1352; M.P. Rupen, V. Dhawan, A.J. Mioduszewski (NRAO)
on 9 Jan 2008; 21:30 UT
Password Certification: Michael P. Rupen (email@example.com)
Subjects: Radio, X-ray, Black Holes, Transients
Observations with the Very Large Array (VLA) in its moderately extended 'B' configuration confirm the radio outburst of the black hole transient H1743-322 reported in ATel #1349, following the X-ray outburst reported in ATel #1348. The flux densities on Jan. 7 were 15.5 +/- 0.2 mJy at 4.86 GHz and 13.58 +/- 0.13 mJy at 8.46 GHz, somewhat lower than seen by Corbel & Tzioumis on Jan. 3 (ATel #1349); the errors quoted here are statistical, but the absolute flux densities are uncertain at the 5-10% level. The radio spectrum is thus flatter (flux density going as nu^-0.2) than on Jan. 3, suggesting another outburst occurred between these two radio observations.
The VLA observations give a marginal detection of linear polarization at the 4 +/- 1% level at 8.46 GHz, and a nominal value of 1 +/- 1% at 4.86 GHz. As expected, neither frequency shows any circularly polarized emission, with 1-sigma limits of about 0.8% in both cases.
The source is unresolved in these images, which had a resolution at 8.46 GHz of about 1.8 x 0.9 arcsec, oriented roughly north-south. Gaussian fits yield an upper limit to the source size of 0.25 arcsec at 8.46 GHz.
Further VLA observations are on-going.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.