New pre-main-sequence stars in the Upper Scorpius subgroup of Sco-Cen
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 nearest 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 to 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 6708 Å 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. We also use Wide-Field Infrared Survey Explorer data to infer circumstellar disc presence in 25 of the members on the basis of infrared excesses, including two candidate transition discs. We find that 11.2 ± 3.4 per cent of the M0-M2 spectral type (0.4-0.8 M⊙) Upper Sco stars display an excess that indicates the presence of a gaseous disc.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2015
- DOI:
- 10.1093/mnras/stv207
- arXiv:
- arXiv:1501.07270
- Bibcode:
- 2015MNRAS.448.2737R
- Keywords:
-
- surveys;
- protoplanetary discs;
- stars: formation;
- stars: pre-main-sequence;
- open clusters and associations: individual: Sco-Cen;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 11 figures, 3 tables, accepted for publication in MNRAS