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Preparing the COROT space mission: Incidence and characterisation of pulsation in the lower instability strip
By pursuing the goal to find new variables in the COROT field-of-view wecharacterised a sample of stars located in the lower part of theinstability strip. Our sample is composed of stars belonging to the diskpopulation in the solar neighbourhood. We found that 23% of the starsdisplay multiperiodic light variability up to a few mmag in amplitude,i.e., easily detectable on a single night of photometry. uvbybetaphotometry fixed most of the variables in the middle of the instabilitystrip and high-resolution spectroscopy established that they have vsin i>100 km s-1. An analysis of the Rodríguez &Breger (\cite{Rodr01}) sample (delta Sct stars in the whole Galaxy)shows slightly different features, i.e., most delta Sct stars have a0.05-mag redder (b-y)0 index and lower vsin i values.Additional investigation in the open cluster NGC 6633 confirms the sameincidence of variability, i.e., around 20%. The wide variety ofpulsational behaviours of delta Sct stars (including unusual objectssuch as a variable beyond the blue edge or a rapidly rotatinghigh-amplitude pulsator) makes them very powerful asteroseismic tools tobe used by COROT. Being quite common among bright stars, delta Sctstars are suitable targets for optical observations from space.Based on observations collected at the S. Pedro Martír, SierraNevada, La Silla, Haute-Provence, South African and Roque de LosMuchachos observatories.
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Observation and Astrometry data
| Constellation: | Ophiuchus |
| Right ascension: | 18h28m24.06s |
| Declination: | +03°46'47.4" |
| Apparent magnitude: | 7.891 |
| Distance: | 219.78 parsecs |
| Proper motion RA: | 6.6 |
| Proper motion Dec: | -3.6 |
| B-T magnitude: | 8.263 |
| V-T magnitude: | 7.922 |
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