WISE circumstellar discs in the young Sco-Cen association

Abstract

We present an analysis of the WISE photometric data for 829 stars in the Sco-Cen OB2 association, using thelatest high-mass membership probabilities. We detect infrared excesses associated with 135 BAF-type stars, 99 ofwhich are secure Sco-Cen members. There is a clear increase in excess fraction with membership probability, which can be fitted linearly.We infer that 41 ± 5 per cent of Sco-Cen OB2 BAF stars have excesses, while the field star excess fraction is consistent with zero. This is the first time that the probability of non-membership has been used in the calculation of excess fractions for young stars. We do not observe any significant change in excess fraction between the three subgroups.Within our sample, we have observed that B-type association members have a significantly smaller excess fraction than Aand F-type association members.