AMI detection of 2 cm radio emission from the XRB BHC J1908+094
ATel #5532; A. P. Rushton, R. Fender, G. Anderson, T. Staley (Uni. of Oxford & Southampton), C. Rumsey, D. Titterington (MRAO, Cambridge)
on 31 Oct 2013; 12:40 UT
Credential Certification: Anthony Rushton (anthony.rushton@soton.ac.uk)
Subjects: Radio, Binary, Black Hole, Transient
In response to the recent Swift/BAT detection of an increase in hard X-ray flux from the XRB black hole candidate, starting from 2013-10-26 (MJD 56491) (Atel #5523), we triggered the Arcminute Microkelvin Imager Large Array (AMI-LA) telescope in Cambridge, UK. Observations were taken between 2013-10-30T14:02-18:00 UT (MJD 56495) at a central frequency of 16.13 GHz, with a bandwidth covering 4.5 GHz. Preliminary pipeline calibration detected the source with a >10 sigma confidence interval, showing a point source flux of 900+/-65 microJy beam^-1.
An unresolved source has also been observed with the JVLA between 2013-10-29T22:51-23:21, reporting a lower flux of 868+/-21 and 807+/-29 microJy beam^-1 at 5.25 and 7.45 GHz respectively (Atel#5530). Our AMI observations are therefore consistent with a flat spectrum compact object. Further pointed X-ray observations taken with Swift/XRT on 2013-10-30 (Atel#5529) suggest the source is in a hard X-ray state. Our radio observations are therefore indicative of a self-absorbed source likely coming from a hard-state steady jet.
The latest Swift/BAT observations (on MJD 56595) suggest the hard flux is still rising, currently peaking at 0.025 +/- 0.0017 ct/s/cm^2 (~100 mCrab). Therefore it is unlikely the source has yet made a state transition, which is associated with discrete ejecta, such as the event observed in 2002 by Rupen et al. (2002, IAUC 7874 ).
Further AMI observations are planned and we encourage simultaneous monitoring at all wavelengths. We also thank the AMI staff for the rapid scheduling of these observations.
