An ultrafast outflow in the black hole candidate MAXI J1810-222?

Abstract

The transient X-ray source MAXI J1810-222 was discovered in 2018 and has been active ever since. A long combined radio and X-ray monitoring campaign was performed with ATCA and Swift respectively. It has been proposed that MAXI J1810-222 is a relatively distant black hole X-ray binary, albeit showing a very peculiar outburst behaviour. Here, we report on the spectral study of this source making use of a large sample of NICER observations performed between 2019 February and 2020 September. We detected a strong spectral absorption feature at $\sim$1 keV, which we have characterised with a physical photoionisation model. Via a deep scan of the parameters space, we obtained evidence for a spectral-state dependent outflow, with mildly relativistic speeds. In particular, the soft and intermediate states point to a hot plasma outflowing at 0.05-0.15 $c$. This speeds rule-out thermal winds and, hence, they suggest that such outflows could be radiation pressure or (most likely) magnetically-driven winds. Our results are crucial to test current theoretical models of wind formation in X-ray binaries.

6 pages, 10 figures, accepted for publication in MNRAS Letter

References in corpus (10)

• Modelling the behaviour of accretion flows in X-ray binaries
• The magnetic nature of disk accretion onto black holes
• XMM-Newton campaign on the ultraluminous X-ray source NGC 247 ULX-1: outflows
• The INTEGRAL view on Black Hole X-ray Binaries
• What powers the wind from the black hole accretion disc in GRO J1655-40?
• Photoionization instability of the Fe K absorbing plasma in the neutron star transient AX J1745.6-2901
• Modeling Magnetic Disk-Wind State Transitions in Black Hole X-ray Binaries
• A unified accretion-ejection paradigm for black hole X-ray binaries. VI. Radiative efficiency and radio-X-ray correlation during four outbursts from GX339-4
• Absorption lines from magnetically driven winds in X-ray binaries II: high resolution observational signatures expected from future X-ray observatories
• Investigating the nature and properties of MAXI J1810-222 with radio and X-ray observations

Cited by in corpus (3)

• Accretion disc winds in X-ray binaries
• The In Situ Growth of Stellar-mass "Light" Seed Black Holes in Nuclear Star Clusters
• A high-resolution X-ray view of the ultra-fast outflow in MAXI J1810-222