SiO maser emission from red supergiants across the Galaxy: I. Targets in massive star clusters

TL;DR

This study searches for SiO maser emission in red supergiants within massive star clusters across the Galaxy, detecting new masers and linking their occurrence to stellar properties, aiding in Galactic structure studies.

Contribution

It provides the first detection of SiO masers in many RSGs in the J=2-1 transition and relates maser occurrence to infrared properties, advancing understanding of maser excitation mechanisms.

Findings

Detected SiO masers in 15% of the sample.

Most detections are new in this transition.

Maser detection correlates with infrared colors.

Abstract

Aims. Red supergiants (RSGs) are among the most luminous of all stars, easily detectable in external galaxies, and may ideally serve as kinematic tracers of Galactic structure. Some RSGs are surrounded by circumstellar envelopes detectable by their dust and molecular and, in particular, maser emission. This study consists of a search for maser emission from silicon monoxide (SiO) toward a significant number of RSGs that are members of massive stellar clusters, many of which have only recently been discovered. Further, we aim to relate the occurrence of maser action to properties of the host stars. Methods. Using the IRAM 30 meter telescope, we searched for maser emission in the J = 2 - 1 rotational transition within the first vibrationally excited state of SiO toward a sample of 88 RSGs. Results. With an average rms noise level of 0.25 Jy, we detected maser emission in 15% of the sample, toward most of the sources for the first time in this transition. The peak of the emission provides accurate radial velocities for the RSGs. The dependence of the detection rate on infrared colors supports a radiative pumping mechanism for the SiO masers.