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arXiv · 2401.04107

Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162

D. Mata Sánchez·T. Muñoz-Darias·M. Armas Padilla·J. Casares·M. A. P. Torres
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Abstract

We present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope across the bright discovery outburst of the black hole candidate Swift J1727.8-162. The spectra cover the main accretion states and are characterised by the presence of hydrogen and helium emission lines, commonly observed in these objects. They show complex profiles, including double-peaks, but also blue-shifted absorptions (with blue-edge velocities of 1150 km/s), broad emission wings and flat-top profiles, which are usual signatures of accretion disc winds. Moreover, red-shifted absorptions accompanied by blue emission excesses suggest the presence of inflows in at least two epochs, although a disc origin cannot be ruled out. Using pre-outburst imaging from Pan-STARRS, we identify a candidate quiescent optical counterpart with a magnitude of g = 20.8. This implies an outburst optical amplitude of DV = 7.7, supporting an estimated orbital period of 7.6 h, which favours an early K-type companion star. Employing various empirical methods we derive a distance to the source of d = 2.7 +- 0.3 kpc, corresponding to a Galactic Plane elevation of z = 0.48 +- 0.05 kpc. Based on these findings, we propose that Swift J1727.8-162 is a nearby black hole X-ray transient that exhibited complex signatures of optical inflows and outflows throughout its discovery outburst.

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D. Mata Sánchez, T. Muñoz-Darias, M. Armas Padilla, J. Casares, M. A. P. Torres. 2024-01-08. Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162. https://arxiv.org/abs/2401.04107

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