Classical T-Tauri stars with VPHAS+: II: NGC 6383 in Sh 2-012

Abstract

This paper presents optical (ugriHα)-infrared (JHKs, 3.6-8.0 μm) photometry and Gaia astrometry of 55 Classical T-Tauri stars (CTTS) in the star-forming region Sh 2-012 and its central cluster NGC 6383. The sample was identified based on photometric Hα emission linewidths, and has a median age of 2.8 ± 1.6 Myr, with a mass range between 0.3 and 1 M_⊙. 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 NGC 6383, 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 (\dot{M}_{acc}) estimated via Hα and u-band line intensities show a scatter (0.3 dex) similar to spectroscopic studies, indicating the suitability of Hα photometry to estimate \dot{M}_{acc}. Examining the variation of \dot{M}_{acc} with stellar mass (M_*), we find a smaller intercept in the \dot{M}_{acc}-M_* relation than oft-quoted in the literature, providing evidence to discriminate between competing theories of protoplanetary disc evolution.