New PMS K/M Stars in Upper Scorpius

Using the Wide-Field Spectrograph at the Australian National University 2.3 m telescope at Siding Spring, we observed 397 kinematically and photometrically selected candidate members of Upper Scorpius, and identified new members by the presence of lithium absorption.

The HR-diagram of the new members shows a spread of ages, ranging from ~3 to 20Myr, which broadly agrees with the current age estimates of ~5-10Myr. We find a significant range of Li 6708 equivalent widths among the members, and a minor dependence of HR-diagram position on the measured equivalent width of the Li 6708{AA} line, with members that appear younger having more lithium. This could indicate the presence of either populations of different age, or a spread of ages in Upper Scorpius.