Spectro-interferometric observations of interacting massive stars with VEGA/CHARA

TL;DR

This study uses spectro-interferometry with VEGA/CHARA to observe and analyze the spatial structure of emission lines in interacting massive stars, revealing details about their emission regions and orbital phases.

Contribution

First spectro-interferometric observations of $eta$ Lyrae and $9$ Sgr in the visible, providing spatially resolved emission line data and insights into their binary interactions.

Findings

H$oldsymbol{ ext{alpha}}$ emission region is spatially resolved and offset in $eta$ Lyrae.

Continuum and H$oldsymbol{ ext{alpha}}$ sources are resolved in $9$ Sgr, with emission offset from the primary.

Emission line regions exhibit phase shifts correlated with orbital phase.

Abstract

We obtained spectro-interferometric observations in the visible of $\beta$ Lyrae and $\upsilon$ Sgr using the instrument VEGA of the CHARA interferometric array. For $\beta$ Lyrae, the dispersed fringe visibilities and differential phases were obtained in spectral regions containing the H$\alpha$ and HeI 6678 lines and the H$\beta$ and HeI 4921 lines. Whereas the source is unresolved in the continuum, the source of the emission lines is resolved and the photocenter of the bulk of the H$\alpha$ emission exhibits offsets correlated with the orbital phase. For $\upsilon$ Sgr, both the continuum and H$\alpha$ sources are resolved, but no clear binary signal is detected. The differential phase shift across the line reveals that the bulk of the H$\alpha$ emission is clearly offset from the primary.