Pre-Main Sequence stars in the star forming complex Sh 2-284

TL;DR

This study characterizes 23 pre-main sequence stars in the low-metallicity HII region Sh 2-284, revealing their properties, ages, and potential pulsation behavior, and suggests ongoing triggered star formation in the region.

Contribution

It provides the first detailed spectroscopic and photometric analysis of PMS stars in Sh 2-284, including their physical parameters and potential pulsation candidates, in a low-metallicity environment.

Findings

Identified 23 PMS stars with derived ages and masses.

Estimated the distance to Sh 2-284 as 4 Kpc.

Found a significant fraction of PMS stars retain their disks/envelopes.

Abstract

Located at the galactic anticenter, Sh 2-284 is a HII region which harbors several young open clusters; Dolidze 25, a rare metal poor (Z~0.004) young cluster, is one of these. Given its association with Sh 2-284, it is reasonable to assume the low metallicity for the whole HII region. Sh~2-284 is expected to host a significant population of Pre-Main Sequence (PMS) stars of both low and intermediate mass stars (Herbig Ae stars). We aim at characterizing these stars by means of a spectroscopic and photometric survey conducted with VIMOS@VLT and complemented with additional optical and infrared observations. In this survey we selected and characterized 23 PMS objects. We derived the effective temperature, the spectral energy distribution and luminosity of these objects; using theoretical PMS evolutionary tracks, with the appropriate metallicity, we estimated the mass and the age of the studied objects. We also estimated a distance of 4 Kpc for Sh 2-284 by using spectroscopic parallax of 3 OB stars. From the age determination we concluded that triggered star formation is in act in this region. Our results show that a significant fraction of the young stellar objects (YSOs) may have preserved their disk/envelopes, in contrast with what is found in other recent studies of low-metallicity star forming regions in the Galaxy. Finally, among the 23 bona fide PMS stars, we identified 8 stars which are good candidates to pulsators of the delta Scuti type.