Fast infrared winds during the radio-loud and X-ray obscured stages of the black hole transient GRS 1915+105
J. Sánchez-Sierras, T. Muñoz‐Darias, S. Motta, R. P. Fender, Arash Bahramian, C. Martínez-Sebastián, J. A. Fernández-Ontiveros, J. Casares, M. Armas Padilla, David A. Green, D. Mata Sánchez, Jay Strader, M. A. P. Torres
Abstract
The black hole transient GRS 1915+105 entered a new phase of activity in 2018, generally characterised by low X-ray and radio fluxes. This phase has only been interrupted by episodes of strong and variable radio emission, where high levels of X-ray absorption local to the source were measured. We present 18 epochs of near-infrared spectroscopy (2018–2023) obtained with GTC/EMIR and VLT/X-shooter, spanning both radio-loud and radio-quiet periods. We demonstrate that radio-loud phases are characterised by strong P-Cygni line profiles, indicative of accretion disc winds with velocities of up to ∼3000 km s −1 . This velocity is consistent with those measured in other black hole transients. It is also comparable to the velocity of the X-ray winds detected during the peak outburst phases in GRS 1915+105, reinforcing the idea that massive, multi-phase outflows are characteristic features of the largest and most powerful black hole accretion discs. Conversely, the evolution of the Br γ line profile during the radio-quiet phases follows the expected trend for accretion disc lines in a system that is gradually decreasing its intrinsic luminosity, exhibiting weaker intensities and more pronounced double-peaks.