DeSSpOt: an instrument for stellar spin orientation determination

TL;DR

DeSSpOt is a specialized instrument that determines stellar spin orientation by analyzing line tilts in high-resolution spectra, validated through observations of spectroscopic binaries.

Contribution

The paper introduces DeSSpOt, a novel instrument and method for measuring stellar spin orientation using spectro-astrometric analysis of line tilts.

Findings

Successfully implemented on a high-resolution spectrograph.

Determined the orbital position angle of Capella.

Validated method with spectroscopic binary observations.

Abstract

We designed and constructed a special instrument to enable the determination of the stellar's spin orientation. The Differential image rotator for Stellar Spin Orientation, DeSSpOt, allows the simultaneous observations of two anti-parallel orientations of the star on the spectrum. On a high resolution \'echelle spectrum, the stellar rotation causes a slight line tilt visible in the spatial direction which is comparable to a rotation curve. We developed a new method, which exploits the variations in these tilts, to estimate the absolute position angle of the rotation axis. The line tilt is retrieved by a spectro-astrometric extraction of the spectrum. In order to validate the method, we observed spectroscopic binaries with known orbital parameters. The determination of the orbital position angle is equivalent to the determination of the stellar position angle, but is easier to to detect. DeSSpOt was successfully implemented on the high resolution Coud\'e spectrograph of the Th\"uringer Landessternwarte Tautenburg. The observations of Capella led to the determination of the orbital position angle.