86 GHz SiO masers in Galactic Centre OH/IR stars

TL;DR

This study searches for 86 GHz SiO masers in 67 Galactic Centre OH/IR stars, finding a 40-60% detection rate that varies with infrared brightness, indicating SiO masers are linked to less obscured circumstellar environments.

Contribution

First survey of 86 GHz SiO masers in Galactic Centre OH/IR stars, revealing detection rates and their dependence on infrared properties, enhancing understanding of maser occurrence in evolved stars.

Findings

Detected SiO masers in 28 out of 67 stars.

Detection rate varies with infrared brightness, up to 60%.

Serendipitous detection of other molecular lines.

Abstract

We present results on a search for 86.243 GHz SiO (J = 2 -- 1, v = 1) maser emission toward 67 OH/IR stars located near the Galactic Centre. We detected 32 spectral peaks, of which 28 correspond to SiO maser lines arising from the envelopes of these OH/IR stars. In OH/IR stars, we obtained an SiO maser detection rate of about 40%. We serendipitously detected two other lines from OH/IR stars at 86.18 GHz, which could be due to a CCS-molecule transition at 86.181 GHz or probably to an highly excited OH molecular transition at 86.178 GHz. The detection rate of 86 GHz maser emission is found to be about 60% for sources with The Midcourse Space Experiment (MSX) A - E < 2.5 mag; but it drops to 25% for the reddest OH/IR stars with MSX A - E > 2.5 mag. This supports the hypothesis by Messineo et al. (2002) that the SiO masers are primarily found in relatively thinner circumstellar material.