A variability sample catalogue selected from the Sydney Observatory Galactic Survey

摘要

Context. A set of 55 × 10~3stars brighter than about B-magnitude 14 and having at least three observations are identified in the SydneyObservatory Galactic Survey, carried out over the years 1892-1932 along the galactic equator section l∈275°, 335° with galacticlatitude b ∈-7°,7°. Short-term (30 min) and long-term (decades) magnitude variations in the data set are analyzed.Aims. Evidence is sought for a correlation between short-term and long-term variabilities which would identify stars in a non-quiescentphase.Methods. We use a reduced proper motion diagram to classify the stars in our sample into probable dwarfs, giants and other types.The validity of the kinematical classification is checked using objective-prism spectroscopic classification for 10 × 10~3early-typestars. A search is made for statistical correlations between our variability indicators and physical and kinematical stellar properties.Results. We find that suspected photospheric activity for giant and dwarf stellar candidates is correlated with the time to cross thegalactic thin disk. We estimate a significant apparent B-magnitude variation of ±0.25 over the 40 years of photographic observations,and candidates for monitoring for possible photospheric activity at the present time are selected employing a statistical colour-diagramwhich uses the total proper motion component as a distance indicator.Conclusions. Follow up studies of our tentative findings are suggested. Toward this aim the derived data for the set of 55 × 10~3starswith variability information is archived as the variability Sample Catalogue. The data for a set of 2.4 x 105 stars along the sectionof the galactic equator l∈275°, 335°, b≤7°, and a set of 1.7 × 10~5stars along the section galactic meridian 330° ± 5°,b ∈-64°, –7° is also archived as a quick-look facility for seeking long-term magnitude changes since the century-old photographicobservations were obtained.