Fast spectral variations of OBA stars

TL;DR

This paper investigates rapid spectral line profile variations in OBA stars, revealing short-term periodic changes likely linked to stellar phenomena, using spectropolarimetric and spectroscopic observations.

Contribution

It presents new observations of fast spectral variations in OBA stars, highlighting their periodic nature and discussing potential origins, which advances understanding of stellar variability.

Findings

Detected line profile variations on minutes timescales

Identified periodicities of approximately 4-5 and 32-36 minutes

Discussed possible physical mechanisms behind rapid spectral changes

Abstract

Our search for magnetic fields in selected OBA stars using FOcal Reducer low dispersion Spectrographs FORS 1 and FORS 2 in spectropolarimetric mode revealed the presence of strong line profile variations (LPV) in spectra of magnetic OBA stars. More specifically, we detected moderate line profile variations of selected lines on a time scale of minutes in FORS 2 spectra of the A0 supergiant HD 92207 (Hubrig et al. 2014). Recently, we investigated the variability of line profiles of selected OBA stars with the multi-mode focal reducer SCORPIO at the 6-meter BTA telescope. We discovered regular variations of H and He lines in the spectra of the O-type star HD 93521 (O9.5III) with periods ~4-5 and ~32-36 minutes. The possible origin of short time-scale spectral variations is discussed.