V4641 Sgr: continued radio flaring

ATel #303; M. P. Rupen, V. Dhawan, A. J. Mioduszewski (NRAO)
on 11 Jul 2004; 22:51 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)

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We report further Very Large Array (VLA) observations of the black hole candidate binary V4641 Sgr, currently active at optical, X-ray, and radio wavelengths (see ATEL #295, ATEL #296, ATEL #297, ATEL #299, ATEL #300, ATEL #302):

•  9 July 2004:
  • 04:34 UT    8.460 GHz:   0.34 +/- 0.10 mJy/beam
  • 07:47 UT    8.460 GHz:   0.29 +/- 0.10 mJy/beam
• 10 July 2004:
  • 04:15 UT    8.460 GHz: 11.12 +/- 0.14 mJy/beam
  • 05:48 UT    8.460 GHz:   1.10 +/- 0.14 mJy/beam
  • 07:03 UT    8.460 GHz:   3.27 +/- 0.16 mJy/beam
  • 08:17 UT    8.460 GHz:   3.29 +/- 0.14 mJy/beam
  • 08:22 UT    4.860 GHz:   3.49 +/- 0.14 mJy/beam
  • 09:35 UT    8.460 GHz:   2.60 +/- 0.13 mJy/beam
•  
• 11 July 2004:
  • 05:47 UT    4.860 GHz:   2.50 +/- 0.14 mJy/beam
  • 09:29 UT    4.860 GHz:   1.67 +/- 0.16 mJy/beam

Each observation lasted about five minutes, centered on the indicated UT.

These data in conjunction with earlier observations from the VLA (ATEL #296), RATAN (ATEL #300), and the ATCA (ATEL #302) indicate that V4641 Sgr continues to be quite active at radio wavelengths, undergoing a series of fairly large flares. Simultaneous X-ray and optical observations would be very valuable (see http://www .aoc.nrao.edu/~mrupen/XRT/V4641Sgr/v4641sgr.shtml).

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