Doppler and modulation tomography of XTE J1118+480 in quiescence

TL;DR

This study uses Doppler and modulation tomography on XTE J1118+480 during quiescence to visualize accretion structures, confirming ongoing mass transfer and disc eccentricity through spectral line analysis.

Contribution

First application of Doppler and modulation tomography to XTE J1118+480 in quiescence revealing detailed accretion features and secondary star imaging.

Findings

Detection of the hot spot in multiple emission lines.

Imaging of the mass-donor star in absorption lines.

Evidence of disc eccentricity from H-Alpha line centroid shifts.

Abstract

We present Doppler and modulation tomography of the X-ray nova XTE J1118+480 with data obtained during quiescence using the 10-m Keck II telescope. The hot spot where the gas stream hits the accretion disc is seen in H-Alpha, H-Beta, He I Lambda-5876, and Ca II Lambda-8662, thus verifying the presence of continued mass transfer within the system. The disc is clearly seen in H-Alpha and Ca II Lambda-8662. We image the mass-donor star in narrow absorption lines of Na I Lambda-Lambda-5890, 5896, 8183, 8195 and Ca II Lambda-8662, implying an origin from the secondary itself rather than the interstellar medium. We also detect deviations in the centroid of the double peak of H-Alpha akin to those found by Zurita et al. 2002 suggesting disc eccentricity.