Preparing the COROT space mission: incidence and characterisation of pulsation in the Lower Instability Strip

Abstract

By pursuing the goal to find new variables in the COROT field-of-view we characterised a sample of stars located in the lower part of the instability strip. Our sample is composed of stars belonging to the disk population in the solar neighbourhood. We found that 23% of the stars display multiperiodic light variability up to few mmag of amplitude. uvbyBeta photometry fixed most of the variables in the middle of the instability strip and high-resolution spectroscopy established that they have vsin i>100 km/s. The comparison with delta Sct stars in the whole Galaxy shows slightly different features, i.e., most delta Sct stars have a 0.05-mag redder (b-y)_0 index and lower vsin i values. Additional investigation in the open cluster NGC 6633 confirms the same incidence of variability, i.e., around 20%. The wide variety of pulsational behaviours of delta Sct stars (including unusual objects such as a variable beyond the blue edge or a rapidly rotating high-amplitude pulsator) makes them very powerful asteroseismic tools to be used by COROT. Being quite common among bright stars, delta Sct stars are suitable targets for optical observations from space.

arXiv comment9 pages, 9 figures Accepted for publication in Astronomy & Astrophysics, Main Journal

References in corpus (2)

• On the relationship between the Delta Scuti and Gamma Doradus pulsators
• On the Period-Luminosity-Colour-Metallicity relation and the pulsational characteristics of lambda Bootis type stars

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• The gamma Dor CoRoT target HD49434. I-Results from the ground-based campaign
• Spectroscopic Survey of γ Doradus Stars I. Comprehensive atmospheric parameters and abundance analysis of γ Doradus stars
• GAUDI: a preparatory archive for the COROT mission
• A Volume-Limited Photometric Survey of 114 gamma Doradus Candidates
• Incidence of high-amplitude delta Scuti type variable stars
• Preparing the COROT space mission: new variable stars in the galactic Anticenter direction
• Study of the low-order $\Delta \nu$-$\bar{\rho }$ relation for moderately-rotating $\delta$ Scuti stars and its impact on their characterisation
• The overlooked role of stellar variability in the extended main sequence of LMC intermediate-age clusters
• Differential asteroseismic study of seismic twins observed by CoRoT; Comparison of HD 175272 with HD 181420
• Close-up of primary and secondary asteroseismic CoRoT targets and the ground-based follow-up observations
• Multi-site observations of Delta Scuti stars 7 Aql and 8 Aql (a new Delta Scuti variable): The twelfth STEPHI campaign in 2003