A third cluster of red supergiants in the vicinity of the massive cluster RSGC3

TL;DR

This study confirms a new cluster of red supergiants, Alicante 10, near RSGC3, revealing a significant site of recent star formation with over 35 confirmed red supergiants, despite high reddening and field contamination.

Contribution

The paper identifies and spectroscopically confirms a new red supergiant cluster, Alicante 10, expanding the known stellar population in the RSGC3 complex.

Findings

Alicante 10 contains at least 8 confirmed red supergiants.

The cluster is approximately 6 kpc away with an initial mass over 10,000 solar masses.

Alicante 10 is part of the active RSGC3 complex, indicating recent stellar formation.

Abstract

Recent studies have shown that the area around the massive, obscured cluster RSGC3 may harbour several clusters of red supergiants. In this paper, we analyse a clump of photometrically selected red supergiant candidates 20' south of RSGC3 in order to confirm the existence of another of these clusters. Using medium-resolution infrared spectroscopy around 2.27 microns, we derived spectral types and velocities along the line of sight for the selected candidates, confirming their nature and possible association. We find a compact clump of eight red supergiants and four other candidates at some distance, all of them spectroscopically confirmed red supergiants. The majority of these objects must form an open cluster, which we name Alicante 10. Because of the high reddening and strong field contamination, the cluster sequence is not clearly seen in 2MASS or GPS-UKIDSS. From the observed sources, we derive E(J-Ks)=2.6 and d~6 kpc. Although the cluster is smaller than RSGC3, it has an initial mass in excess of 10000 solar masses, and it seems to be part of the RSGC3 complex. With the new members this association already has 35 spectroscopically confirmed red supergiants, confirming its place as one of the most active sites of recent stellar formation in the Galaxy.