Radio and X-ray observations of the 1998 outburst of the recurrent X-ray transient 4U 1630-47

We report radio (NRAO VLA and Australia Telescope Compact Array), soft X-ra y (Rossi X-Ray Timing Explorer ASM), and hard X-ray (Compton Gamma Ray Obse rvatory BATSE) observations of a 1998 outburst in the recurring X-ray trans ient 4U 1630-47, where radio emission was detected for the first time. The radio observations identify the position of 4U 1630-47 to within 1 ". Becau se the radio emission is optically thin with a spectral index of similar to -0.8 during the rise, peak, and decay of the initial radio event, the emiss ion is probably coming from an optically thin radio jet ejected over a peri od of time. The 20-100 keV emission first appeared 1998 January 28 (MJD 508 41), the 2-12 keV emission first appeared 1998 February 3 (MJD 50847), and the first radio emission was detected 1998 February 12.6 (MJD 50856.6). The rise of the radio emission probably began about 1998 February 7 (MJD 50851 ) when the X-rays were in a very hard fluctuating-hardness state, just befo re changing to a softer, more stable hardness state.