SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk
Abstract
We present the results of radio observations of red supergiants in a star cluster, Stephenson (1990, AJ, 99, 1867)'s #2, and of candidates for red supergiants in three star clusters, Mercer et al. (2005, ApJ, 635, 560)'s #4, #8, and #13, in the SiO and H2O maser lines. The Stephenson's #2 cluster and nearby aggregation at the southwest contain more than 15 red supergiants. We detected one red supergiant at the center of Stephenson's #2 and three in a southwest aggregation in the SiO maser line; three out of these four were also detected in the H2O maser line. The average radial velocity of the four detected objects is 97 km s-1, giving a kinematic distance of 5.5 kpc, which locates this cluster near the base of the Scutum-Crux spiral arm. We also detected six SiO emitting objects associated with other star clusters. In addition, mapping observations in the CO J = 1-0 line toward these clusters revealed that an appreciable amount of molecular gas still remains around the Stephenson's #2 cluster in contrast to the prototypical red-supergiant cluster, Bica et al. (2003, A&A, 404, 223)'s #122. This indicates that the time scale of gas expulsion differs considerably in individual clusters.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- April 2010
- DOI:
- 10.1093/pasj/62.2.391
- arXiv:
- arXiv:1002.2492
- Bibcode:
- 2010PASJ...62..391D
- Keywords:
-
- Galaxy: open clusters and associations: individual (Mercer et al.'s #4;
- #8;
- #13; Stephenson's #2);
- masers;
- stars: mass-loss;
- stars: supergiants;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- high res. figures available at http://www.nro.nao.ac.jp/~lib_pub/report/data/no674.pdf. PASJ 62, No.2 (2010, April 25 issue) in press