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NICER Spectroscopy of Outflows and Obscuration in GRS 1915+105

Presentation #110.89 in the session “Stellar/Compact (Poster)”.

Published onApr 01, 2022
NICER Spectroscopy of Outflows and Obscuration in GRS 1915+105

GRS 1915+105 is a black hole binary known for its unique variability, strong winds, jets, and persistent brightness; I will report on four years of NICER monitoring of this iconic source. Initial data from 2017-2018 showed strong and variable disk winds, but between mid-2018 and mid-2019 (after 20+ years in outburst), NICER detected a huge change: the X-ray flux dropped by 100x! Spectra suggest a large partial covering obscurer, but this origin of this obscuration—lasting nearly three years already—is not clear. I will discuss spectral constraints on the properties of the obscuring cloud from NICER, including: (1) flares that reveal a highly-ionized stratified medium, (2) strong emission lines in stacked spectra, and (3) time-dependent measurements of the obscuring column density. Continued monitoring with NICER will help us to understand the origin of the new “obscured state” and its connection to the fate of GRS 1915+105.

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