Fast infrared winds during the radio-loud and X-ray obscured stages of the black hole transient GRS 1915+105

Sánchez-Sierras, J.; Muñoz-Darias, T.; Motta, S. E.; Fender, R. P.; Bahramian, A.; Martínez-Sebastián, C.; Fernández-Ontiveros, J. A.; Casares, J.; Armas Padilla, M.; Green, D. A.; Mata Sánchez, D.; Strader, J.; Torres, M. A. P.
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Astronomy and Astrophysics

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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 Brγ 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.
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