Ldetection of a series of X-ray dips associated with a radio flare in GRS 1915-105

We report the detection of a series of X-ray dips in the Galactic black hol e candidate GRS 1915 + 105 during 1999 June 6-17 from observations carried out with the pointed proportional counters of the Indian X-ray Astronomy Ex periment on board the Indian Remote Sensing Satellite (IRS-P3). The observa tions were made after the source made a transition from a steady low-hard s tate to a chaotic state, which occurred within a few hours. Dips of about 2 0-160 s in duration were observed on most of the days. The X-ray emission o utside the dips shows a quasi-periodic oscillation (QPO) at similar to4 Hz that has characteristics similar to the ubiquitous 0.5-10 Hz QPO seen durin g the low-hard state of the source. During the onset of dips this QPO is ab sent, and, also, the energy spectrum is soft and the variability is low com pared to the nondip periods. These features gradually reappear as the dip r ecovers. The onset of the occurrence of a large number of such dips followe d the start of a huge radio flare of strength 0.48 Jy (at 2.25 GHz). We int erpret these dips as the cause for mass ejection due to the evacuation of m atter from an accretion disk around the black hole. We propose that a super position of a large number of such dip events produces a huge radio jet in GRS 1915 + 105.