Classical T-Tauri stars with VPHAS+: II: NGC6383 in Sh 2-012

Abstract

This paper presents optical (ugriH alpha)-infrared (JHKs, 3.6-8.0 mu m) photometry and Gaia astrometry of 55 Classical T-Tauri stars (CTTS) in the star-forming region Sh 2-012 and its central cluster NGC6383. The sample was identified based on photometric Ha emission linewidths, and has a median age of 2.8 +/- 1.6 Myr, with a mass range between 0.3 and 1 M-circle dot. 94 per cent of CTTS with near-infrared cross-matches fall on the near-infrared T-Tauri locus, with all stars having mid-infrared photometry exhibiting evidence for accreting circumstellar discs. CTTS are found concentrated around the central cluster NGC6383, and towards the bright rims located at the edges of Sh 2-012. Stars across the region have similar ages, suggestive of a single burst of star formation. Mass accretion rates ((M) over dot(acc)) estimated via H alpha and u-band line intensities show a scatter (0.3 dex) similar to spectroscopic studies, indicating the suitability of H alpha photometry to estimate (M) over dot(acc). Examining the variation of (M) over dot(acc) with stellar mass (M-*), we find a smaller intercept in the (M) over dot(acc)-M-* relation than oft-quoted in the literature, providing evidence to discriminate between competing theories of protoplanetary disc evolution.