Astron. Astrophys. 333, 619-628 (1998)

A lithium-survey for pre-main sequence stars in the Upper Scorpius OB association ^{* **}

Thomas Preibisch ¹, Eike Guenther ², Hans Zinnecker ³, Michael Sterzik ⁴, Sabine Frink ⁵ and Siegfried Röser <sup>5

1</sup> Astronomisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
² Thüringer Landessternwarte Tautenburg, Germany
³ Astrophysikalisches Institut Potsdam, Germany
⁴ Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
⁵ Astronomisches Recheninstitut Heidelberg, Germany

Received 29 October 1997 / Accepted 30 January 1998

Abstract

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
** Tables A1 and A2 are also available in electronic form at CDS via anonymous ftp 130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: Thomas Preibisch (preib@astro.uni-wuerzburg.de)

© European Southern Observatory (ESO) 1998

Online publication: April 20, 1998
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