Title: Hard X-ray States with Faint Radio Emission in the Microquasar GRS1915+105

Title: Hard X-ray States with Faint Radio Emission in the Microquasar GRS1915+105

Proposal ID: 0120218
Subject category: Compact Object
Principal investigator: Remillard
Institute: Massachusetts Institute of Technology

Abstract

The microquasar GRS1915+105 exhibits steady and hard X-ray emission in both radio-loud and radio-faint states. In the former case, a "radio plateau state", which is linked to a steady radio jet, has been associated with a flat X-ray spectrum and a cutoff near 100 keV, similar to the low-hard states of Cyg X-1 and GX339-4. However, we are particularly interested in alternative conditions where the X-ray spectrum is also steady and dominated by nonthermal emission, but the radio flux is weaker (< 20 mJy). Our objective is to combine INTEGRAL, RXTE, VLA, and MRAO to investigate nonthermal high-energy emission when the jet is weak or absent. Such occasions are poorly studied in this source, and such observations are required to gain insights regarding emission mechanisms at high luminoisity and the conditions that regulate the strength of the jets.