A large spectroscopic survey for young low-mass members of the
Upper Scorpius OB Association
Thomas Preibisch, Eike Guenther, & Hans Zinnecker
Astronomical Journal, 121, 1040 (2001)
We present the results of a large intermediate-resolution
spectroscopic survey for pre-main sequence (PMS) stars
in the Upper Scorpius OB association, the most nearby region of recent
massive star formation.
Utilizing the multi-object spectrograph 2dF at the Anglo-Australian-Telescope,
we obtained spectra of 576 stars with magnitudes R = [12.5 - 16.5]
in a 6 square-degree area in Upper Scorpius.
Among these objects we were able to identify 98 new PMS stars, nearly
all of them M-type stars, by their strong lithium absorption lines.
We place the new PMS stars into the HR diagram and find that
their ages agree well with the mean age of 5 Myr determined
in our earlier investigation (Preibisch & Zinnecker 1999)
based on a smaller sample of stars.
The number of low-mass (M_star ~ [0.1 - 0.5] M_sun) members
is at least as high as expected from
the know number of high-mass (M_star <= 3 M_sun) association
members and recent
determinations of the field star IMF. Thus, there is no deficit of
low-mass stars in Upper Scorpius.
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You might be also interested in the previous paper
about the young stars in Upper Scorpius, which was the basis of this work.
Some nice images of the Upper Scorpius association can be found
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