Tomography of X-ray Nova Muscae 1991: Evidence for ongoing mass transfer and stream-disc overflow

TL;DR

This paper uses spectroscopic data from 2009-2010 to analyze Nova Muscae 1991, revealing ongoing mass transfer, a variable hotspot, and evidence of stream-disc overflow in the black hole binary system.

Contribution

It provides the first evidence of ongoing mass transfer and stream-disc overflow in Nova Muscae 1991 through Doppler tomography and spectroscopic analysis.

Findings

Detection of a hotspot indicating ongoing mass transfer

Evidence of stream-disc overflow in the system

Possible Ca II absorption from the donor star

Abstract

We present a spectroscopic analysis of the black hole binary Nova Muscae 1991 in quiescence using data obtained in 2009 with MagE on the Magellan Clay telescope and in 2010 with IMACS on the Magellan Baade telescope at the Las Campanas Observatory. Emission from the disc is observed in H alpha, H beta and Ca II (8662 A). A prominent hotspot is observed in the Doppler maps of all three emission lines. The existence of this spot establishes ongoing mass transfer from the donor star in 2009-2010 and, given its absence in the 1993-1995 observations, demonstrates the presence of a variable hotspot in the system. We find the radial distance to the hotspot from the black hole to be consistent with the circularization radius. Our tomograms are suggestive of stream-disc overflow in the system. We also detect possible Ca II (8662 A) absorption from the donor star.