New pre-main-sequence stars in the Upper Scorpius subgroup of Sco-Cen

作者：Rizzuto A C^*; Ireland M J; Kraus A L

来源：Monthly Notices of the Royal Astronomical Society, 2015, 448(3): 2737-2748.

DOI：10.1093/mnras/stv207

• surveys
• protoplanetary discs
• stars: formation
• stars: pre-main-sequence
• open clusters and associations: individual: Sco-Cen

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 similar to 3 to 20 Myr, which broadly agrees with the current age estimates of similar to 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 angstrom 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-circle dot) Upper Sco stars display an excess that indicates the presence of a gaseous disc.

• 出版日期2015-4-11