Detectability of micro-variables in the ASAS database
Departement Wiskunde en InformaticaUniversiteit Antwerpen,
Middelheimlaan 1, 2020
2 Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
3 Unidad de Astronomía, Facultad de Ciencias Básicas, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
Accepted: 19 July 2013
Aims. We exploit nine years of photometry in the ASAS V-band catalogue to develop a method to select in an objective way the best quality data and detect low-amplitude variables. We concentrate on bright stars (V < 10) and avoid open cluster stellar densities.
Methods. We use the (probable) members of the Sco-Cen associations as a test sample of bright stars that includes periodic early-type photometric variables as well as young late-type stars with cyclic or irregular variability patterns. We select grade-A observations with consistent photometry in all apertures, amounting to 88 ± 4 per cent of all grade-A data in most cases, and use the aperture with lowest dispersion of magnitudes (excluding one percent of data to avoid sparse surviving outliers) to search for periodicities, cycles and long-term trends. The well-known alias problems, due to the once-per-night observing cadence in the ASAS project, can often be alleviated for the bright stars by use of the Hipparcos satellite photometry.
Results. Micro-variables with a range of variability as low as 0.01–0.02 mag for periodic variables (V magnitudes 7–10) and 0.04 mag for irregular long-term variables are detected. In total 37 light variables are identified: 14 were previously unknown, and another 12 were listed as suspected variables. The light variability in the young associations in Sco-Cen is briefly discussed.
Conclusions. The ASAS database contains much more information on photometric variables than retrieved commonly.
Key words: stars: variables: general / techniques: photometric / stars: individual: HD 46057 / stars: individual: HD 146285 / stars: individual: HD 116794 / stars: individual: HD 119022
© ESO, 2013