A spectroscopic census in young stellar regions: the Sigma Orionis cluster

TL;DR

This study provides a comprehensive spectroscopic survey of the Sigma Orionis cluster, identifying members, binary systems, and disk properties, thus enhancing understanding of young stellar populations.

Contribution

It offers the largest homogeneous spectroscopic dataset for Sigma Orionis, including spectral types, radial velocities, and disk characteristics, with detailed analysis of accretion signatures.

Findings

Over half of the stars are confirmed members via lithium absorption or Hα emission.

Identified binary systems and fast rotators that mimic accretion signatures.

Detected stars with disks showing unexpected Hα profiles.

Abstract

We present a spectroscopic survey of the stellar population of the Sigma Orionis cluster. We have obtained spectral types for 340 stars. Spectroscopic data for spectral typing come from several spectrographs with similar spectroscopic coverage and resolution. More than a half of stars of our sample are members confirmed by the presence of lithium in absorption, strong H$\alpha$ in emission or weak gravity-sensitive features. In addition, we have obtained high resolution (R~34000) spectra in the H$\alpha$ region for 169 stars in the region. Radial velocities were calculated from this data set. The radial velocity distribution for members of the cluster is in agreement with previous work. Analysis of the profile of the H$\alpha$ line and infrared observations reveals two binary systems or fast rotators that mimic the H$\alpha$ width expected in stars with accretion disks. On the other hand there are stars with optically thick disks and narrow H$\alpha$ profile not expected in stars with accretion disks. This contribution constitutes the largest homogeneous spectroscopic data set of the Sigma Orionis cluster to date.