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

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Wiley-VCH Verlag Gmbh
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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 (Ƹ 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 Hα 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 σ Orionis cluster. Besides, six of the eight giants are new variables, and three are new periodic variables.
© 2010 WILEY-VCH Verlag GmbH & Co. We thank M. Paegert for his helpful referee report and careful reading of the manuscript, and G. Pojmánski for his kind and prompt answer to our inquiries. JAC formerly was an “Investigador Juan de la Cierva” at the Universidad Complutense de Madrid and currently is an “Investigador Ramón y Cajal” at the Centro de Astrobiología (CSIC-INTA). This research has made use of the SIMBAD, operated at Centre de Données astronomiques de Strasbourg, France, and the NASA’s Astrophysics Data System. Financial support was provided by the Universidad Complutense de Madrid, the Comunidad Autónoma de Madrid, the Spanish Ministerio Educación y Ciencia, and the European Social Fund under grants: AyA2005-04286, AyA2005-24102-E, AyA2008-06423-C03-03, AyA2008-00695, PRICIT S-0505/ESP0237, and CSD2006-0070.
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