New Pre-main-Sequence Stars in the Upper Scorpius Subgroup of Sco-Cen

TL;DR

This study reports 237 new pre-main-sequence stars in Upper Scorpius, analyzing their ages, lithium content, and circumstellar disks to better understand star formation and evolution in this nearby region.

Contribution

The paper presents the discovery and spectroscopic confirmation of 237 new young stars in Upper Scorpius, with detailed age and disk presence analysis, expanding current knowledge of this star-forming region.

Findings

Age spread among members from 3 to 20 Myr.

Presence of circumstellar disks in about 11% of M0-M2 stars.

Correlation between lithium absorption and stellar age.

Abstract

We present 237 new spectroscopically confirmed pre-main-sequence K and M-type stars in the young Upper Scorpius subgroup of the Sco-Cen association, the near- est region of recent massive star formation. 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 ~3-20 Myr, which broadly agrees with the current age estimates of ~5-10 Myr. 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 6708A line, with members that appear younger having more Lithium. This could indicate the presence of either popu- lations of different age, or a spread of ages in Upper Scorpius. We also use Wide-Field Infrared Survey Explorer data to infer circumstellar disk presence in 25 of the members on the basis of infrared excesses, including two candidate transition disks. We find that 11.2+-3.4% of the M0-M2 spectral type (0.4-0.8 M_sun) Upper Sco stars display an excess that indicates the presence of a gaseous disk.