Simultaneous VLBI/GMRT/RXTE observation of SS433

¹ S.N. Bose National Centre for Basic Sciences, JD Block, Salt Lake, Sector III, Kolkata 700098, India e-mail: chakraba@bose.res.in
² Centre for Space Physics, Chalantika 43, Garia Station Rd. Garia, Kolkata 700084, India e-mail: anuj@csp.res.in

Received: 10 December 2005
Accepted: 10 March 2006

Abstract

Aims.Our aim in this paper is to discover the spectral characteristics of the enigmatic compact object SS433 during a very rare occasion when the blue jet was pointing towards us (the precessional phase ) and when the orbital phase ϕ of its companion was nearly zero (inferior conjunction) and compare this with the result obtained when (superior conjunction).

Methods.We employed the Giant Meter Radio Telescope (GMRT) for the photometric observation at 1280 MHz, European VLBI Network (EVN) for photometry and imaging at 4990 MHz, and the Rossi X-ray Timing Explorer (RXTE) for photometry and spectrum at  keV.

Results.At this opportune moment, the companion totally blocked the disk and the base of the jet, the X-ray intensity was reduced by  with respect to the previous day, and the intensity went up by about on the next day. The X-ray intensity is about one-third compared to RXTE results obtained during the superior conjunction on 13 March 2004. By taking the difference in the spectra, we obtained the spectrum of the system core including the contribution from any accretion shock that may have occurred during interaction between the accreting stream and the disk. The EVN observation clearly showed the separation of a radio blob, so using an adiabatic expansion model we estimate when the blob might have been separated.

Conclusions.We see a clear dependence of X-ray intensity emitted from the base of the jet on the photon energy. We find that the core is much brighter in hard X-rays. The conjunction seems to have had no effect on the radio data.