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

Abstract

This paper presents optical ($ugri$H$\alpha$)-infrared ($JHK$s,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 it's central cluster NGC 6383. The sample was identified based on photometric H$\alpha$ emission line widths, and has a median age of 2.8$\pm$1.6 Myr, with a mass range between 0.3-1 $M_{\odot}$. 94% 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 ($\dot{M}_{\textrm{acc}}$) 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 $\dot{M}_{\textrm{acc}}$. Examining the variation of $\dot{M}_{\textrm{acc}}$ with stellar mass ($M_{\ast}$), we find a smaller intercept in the $\dot{M}_{\textrm{acc}}$-$M_{\ast}$ relation than oft-quoted in the literature, providing evidence to discriminate between competing theories of protoplanetary disc evolution.