We have performed a search for PMS stars in a 160 square-degree region in the Upper Sco association. We identify 39 new PMS stars by their strong 6708 Å Li lines, increasing the number of known PMS stars in this area to 108. The PMS stars cluster in the center of our area and seem to be spatially coincident with the early type members of the Upper Sco association.
We find new PMS stars only among the X-ray selected candidate stars, not among X-ray quiet proper motion candidates. Our result provides no evidence for the existence of a significant population of X-ray quiet T Tauri stars in Upper Sco. We conservatively estimate that our sample of RASS selected PMS stars in the magnitude range is at least 75% complete.
This study is the first step in our project to investigate the low-mass PMS population of the Upper Sco association. Further steps will include photometry for the new PMS stars, analysis of the HRD and finally the investigation of the mass function and star formation history of this interesting association.
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998