Finding the most variable stars in the Orion Belt with the All Sky Automated Survey

TL;DR

This study identifies the most variable stars in the Orion Belt using the ASAS-3 survey, discovering new variable young stars, giants, and binary candidates, thus enhancing understanding of stellar variability in this region.

Contribution

It presents a new catalog of highly-variable stars in Orion Belt, including many previously unreported variables, using multi-source data analysis.

Findings

32 highly-variable stars identified, 16 new discoveries.

Most variables are young stars and giants, with some new periodic variables.

Some variables are associated with the sigma Orionis cluster.

Abstract

We look for high-amplitude variable young stars in the open clusters and associations of the Orion Belt. We use public data from the ASAS-3 Photometric V-band Catalogue of the All Sky Automated Survey, infrared photometry from the 2MASS and IRAS catalogues, proper motions, and the Aladin sky atlas to obtain a list of the most variable stars in a survey area of side 5 deg centred on the bright star Alnilam (eps Ori) in the centre of the Orion Belt. We identify 32 highly-variable stars, of which 16 had not been reported to vary before. They are mostly variable young stars and candidates (16) and background giants (8), but there are also field cataclysmic variables, contact binaries, and eclipsing binary candidates. Of the young stars, which typically are active Herbig Ae/Be and T Tauri stars with Halpha emission and infrared flux excess, we discover four new variables and confirm the variability status of another two. Some of them belong to the well known sigma Orionis cluster. Besides, six of the eight giants are new variables, and three are new periodic variables.