Low Quiescent X-Ray and Radio Flux Levels from the Black Hole Transient V4641 Sgr
ATel #105; John A. Tomsick (UCSD), Michael P. Rupen (NRAO), Stephane Corbel (Universite Paris VII and CEA Saclay), Vivek Dhawan (NRAO), Rob Fender (University of Amsterdam), Philip Kaaret (Harvard-Smithsonian CfA), Erik Kuulkers (Utrecht University and SRON), Jon M. Miller (MIT), Amy J. Mioduszewski (NRAO), Jerome A. Orosz (SDSU), Tasso Tzioumis (ATNF) and Rudy Wijnands (MIT)
on 20 Aug 2002; 18:19 UT
Credential Certification: John A. Tomsick (jtomsick@ucsd.edu)
Subjects: Radio, X-ray, Binary, Black Hole, Transient
Referred to by ATel #: 175
Recent X-ray and radio observations of the dynamically confirmed black hole transient and relativistic radio jet source V4641 Sgr indicate that the source may be in a low quiescent state after its high level of activity in 2002 May and June (IAUCs 7906 , 7908 and 7928 ). The source was not detected in the X-ray band during a 4.3 ks Chandra ACIS-S observation made on August 5.2 UT. Assuming a power-law energy spectrum with a photon index of 2 and interstellar absorption with a column density of N_H = 2e21 cm^-2 gives a 3-sigma upper limit on the absorbed 0.5-7 keV flux of 1.3e-14 erg cm^-2 s^-1 and a corresponding luminosity upper limit of 1.0e32 (d/7 kpc)^2 erg s^-1. VLA radio observations at 8.46 GHz on August 1, 3, 6, 8 and 13, each comprising 3-6 minutes on source, gave no detections with rms noise levels between 0.07 and 0.1 mJy/beam. The last VLA detection was on 2002 July 12, when the source varied over the course of 30 minutes between <0.2 and 0.5 mJy/beam.
