Variability survey of brightest stars in selected OB associations

Abstract

The stellar evolution theory of massive stars remains uncalibrated with high-precision photometric observational data mainly due to a small number of luminous stars that are monitored from space. Automated all-sky surveys have revealed numerous variable stars but most of the luminous stars are often overexposed. Targeted campaigns can improve the time base of photometric data for those objects. The aim of this investigation is to study the variability of luminous stars at different timescales in young open clusters and OB associations. We monitored 22 open clusters and associations from 2011 to 2013 using a 0.25-m telescope. Variable stars were detected by comparing the overall light-curve scatter with measurement uncertainties. Variability was analysed by the light curve feature extraction tool FATS. Periods of pulsating stars were determined using the discrete Fourier transform code SigSpec. We then classified the variable stars based on their pulsation periods and available spectral information. We obtained light curves for more than 20000 sources of which 354 were found to be variable. Amongst them we find 80 eclipsing binaries, 31 $\alpha$ Cyg, 13 $\beta$ Cep, 62 Be, 16 slowly pulsating B, 7 Cepheid, 1 $\gamma$ Doradus, 3 Wolf-Rayet and 63 late-type variable stars. Up to 55% of these stars are potential new discoveries as they are not present in the Variable Star Index (VSX) database. We find the cluster membership fraction for variable stars to be 13% with an upper limit of 35%.

36 pages, 11 figures, catalogue in appendix A

References in corpus (10)

• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The first WASP public data release
• The Massive Star Population of Cygnus OB2
• New periodic variable stars coincident with ROSAT sources discovered using SuperWASP
• Populations of rotating stars III. SYCLIST, the new Geneva Population Synthesis code
• CCD BV survey of 42 open clusters
• Variable stars across the observational HR diagram
• Beta Cephei stars in the ASAS-3 data. II. 103 new Beta Cephei stars and a discussion of low-frequency modes
• The Enigma of the Open Cluster M29 (NGC 6913) Solved
• Optical and near-IR photometric study of the open cluster NGC 637 and NGC 957

Cited by in corpus (4)

• MONOS: Multiplicity Of Northern O-type Spectroscopic systems. I. Project description and spectral classifications and visual multiplicity of previously known objects
• Study of changes in the pulsation period of 148 Galactic Cepheid variables
• Planet Hunters TESS IV: A massive, compact hierarchical triple star system TIC 470710327
• New, late-type spectroscopic binaries with X-ray emission