Variability in Optical Spectra of epsilon Orionis

TL;DR

This study analyzes the spectral variability of epsilon Orionis over multiple seasons, revealing wind and pulsation-related periodicities that suggest complex stellar wind and surface interactions.

Contribution

It provides a detailed time-series analysis of epsilon Ori's spectral variability, identifying multiple periodicities and their potential links to stellar wind and pulsations.

Findings

Detected wind variability in Halpha and He I lines.

Identified multiple periods of 2-7 days related to pulsations and rotation.

Found correlations between wind and photospheric variability.

Abstract

We present the results of a time-series analysis of 130 echelle spectra of epsilon Ori (B0 Ia), acquired over seven observing seasons between 1998 and 2006 at Ritter Observatory. The equivalent widths of Halpha (net) and He I 5876 were measured and radial velocities were obtained from the central absorption of He I 5876. Temporal variance spectra (TVS) revealed significant wind variability in both Halpha and He I 5876. The He I TVS have a double-peaked profile consistent with radial velocity oscillations. A periodicity search was carried out on the equivalent width and radial velocity data, as well as on wavelength-binned spectra. This analysis has revealed several periods in the variability with time scales of 2-7 d. Many of these periods exhibit sinusoidal modulation in the associated phase diagrams. Several of these periods were present in both Halpha and He I, indicating a possible connection between the wind and the photosphere. Due to the harmonic nature of these periods, stellar pulsations may be the origin of some of the observed variability. Periods on the order of the rotational period were also detected in the He I line in the 98-99 season and in both lines during the 04-05 season. These periods may indicate rotational modulation due to structure in the wind.