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Thomas Preibisch 1,
Eike Guenther 2,
Hans Zinnecker 3,
Michael Sterzik 4,
Sabine Frink 5 and
Siegfried Röser 5
Received 29 October 1997 / Accepted 30 January 1998
We present the results of an intermediate resolution spectroscopic survey for pre-main sequence (PMS) stars in the Upper Scorpius OB association. In a 160 square-degree area we were able to identify 39 new PMS stars by follow up observations of X-ray selected stars with the multi object spectrograph FLAIR at the UK Schmidt Telescope.
We also investigated the completeness of our X-ray selected sample by observing more than 100 stars that were not detected as X-ray sources, but have proper motions indicating membership to Upper Sco. While the new X-ray selected PMS stars with known proper motions have kinematics consistent with membership, none of the X-ray quiet proper motion candidates is a PMS star. We conclude that our X-ray selected sample of PMS stars seems to be rather complete. For stars in the magnitude interval we derive a conservative lower limit of 75% completeness.
Key words: surveys stars: kinematics stars: pre-main sequence open clusters and associations: individual: Sco-Cen association X-rays: stars
* Based on observations obtained at the UK Schmidt Telescope of the Anglo-Australian Observatory
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© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998