Long term photometric studies of nearby young stellar populations

Description

The night sky surrounding the South Celestial Pole hosts several young, pre-main sequence stellar associations with ages ranging from approximately 1-20 million years, that are relatively close to the Sun at distances of 50-150 parsecs. A number of these system have either been discovered or have been characterised by UNSW Canberra astronomers. Some of these groups are believed to be outlier populations of the massive Scorpius-Centaurus-Ophiuchus OB-star association, which is the closest large star forming complex to the Sun.

Study of individual associations gives a snapshot of stellar properties at a given age; study across associations allows us to infer how stellar properties change with increasing age. This is particularly true for photometric properties. As young stars age, properties such as rotation period can either spin up or slow down depending on stellar mass, and whether the star has lost its planet-forming circumstellar disk. Rotation period is measuring by the detection of near-sinusoidal periodic variations induced by dark star spots; also, episodic variations can be measured indicative of the ongoing accretion of material onto the host star, or of flaring activity. However, the long-term nature of periodic and episodic variability in young stars is poorly understood, e.g. the lifetime of star spots in young stars is unknown.

Archival data is available for stars in the southern skies from surveys such as ASAS (the All-Sky Automated Survey) which has been monitoring approximately 20 million stars brighter than magnitude 14 since 1997.

The project is to study the variability of young stars in the solar neighbour, using survey data that has been obtained over the past 20-25 years. Many of the fundamental stellar properties of the individual stars of these associations is known in detail and these data will be used to enhance the analysis of the photometric results.