Disk-jet connection in GRS 1915+105: X-ray soft dips as cause of radio flares

Abstract

We have examined the radio emission characteristics of the micro-quasar GRS 1915+105 during its X-ray emission states as classified by Belloni et al. (2000). We find that the radio emission is high during the &#39;chi_1&#39; and &#39;chi_3&#39; states (the radio ``plateau&#39;&#39; state) and also during the &#39;beta&#39; and &#39;theta&#39; states when X-ray soft dips are present in the X-ray light curve. For all the other X-ray states we find that the radio emission is low (< 20 mJy at 2.25 GHz). This result supports the suggestion made by Naik et al. (2000) that the radio flares are caused by a series of X-ray dip events. To further confirm this result, we have made a systematic study of all the PCA RXTE observations for those days when a radio flare was present. We find 11 such observations and find that all of them are of class &#39;beta&#39;, &#39;theta&#39; or &#39;chi&#39;. Further, we have classified all the RXTE PCA observations obtained from 1996 November to 2000 February (when the radio data is available) and confirm that the radio flux, on an average, is much higher during the states &#39;beta&#39;, &#39;theta&#39; and &#39;chi&#39;. Based on these results, we argue that the radio flares are caused by the X-ray dips in the source.