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On-going radio observations of H1743-322

ATEL # 1384; M.P. Rupen, V. Dhawan, A.J. Mioduszewski (NRAO)
on 11 Feb 2008; 23:45 UT
Password Certification: Michael P. Rupen (mrupen@nrao.edu)

Subjects: Radio, X-ray, Black Holes, Transients
Referred to by ATEL #: 1385

We report on-going observations of the black hole transient H1743-322 (ATel #1348, #1349, #1352, #1378) with the Very Large Array (VLA) in its moderately extended 'B' configuration, under observing program AR642. The 8.46 GHz observations show the following flux density evolution:

       Date       MJD    8.46 GHz flux density      
Jan. 10 54475.72 6.39 +/- 0.06 mJy
Jan. 19 54484.67 1.05 +/- 0.07 mJy
Jan. 21 54486.76 0.81 +/- 0.06 mJy
Feb. 3 54499.74 0.50 +/- 0.07 mJy
Feb. 5 54501.64 0.54 +/- 0.08 mJy
Feb. 6 54502.56 0.39 +/- 0.09 mJy
Feb. 9 54505.66 0.56 +/- 0.05 mJy

Interleaved observations on Feb. 9 gave a flux density of 0.56 +/- 0.06 mJy at 4.86 GHz. This flat spectrum and low radio flux density are consistent with the source entering the low/hard state (cf. ATel #1378).

The error bars above are statistical, and do not include an additional ~10% systematic uncertainty, e.g., due to uncertainties in the flux density scale.

We confirm the tentative detection of linearly polarized radio emission reported in ATel #1352, with an 8 +/- 1% detection on Jan. 10 at 8.46 GHz. This polarized emission was seen at roughly the same flux density (0.5 mJy) and along the same polarization angle (electric field vectors oriented east/west). The magnetic field vectors are thus perpendicular to the (previous) ejection axis, suggesting terminal shock rather than jet emission during the decay of the radio outburst. However, no extended ejecta are seen on any of the above dates. The best limits come from 22.46 GHz imaging on Jan. 10, with a resolution (FWHM) 0.69 x 0.25 arcsec oriented roughly north/south.

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.


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