Detection of a new methanol maser line with ALMA

TL;DR

This paper reports the serendipitous discovery of a new methanol maser line at 349.1 GHz with ALMA, revealing insights into the structure and kinematics of the gaseous disk around a massive young stellar object.

Contribution

The study identifies a new methanol maser transition and characterizes its spatial and velocity structure, providing novel observational evidence of maser emission in a star-forming region.

Findings

Discovered a new methanol maser line at 349.1 GHz.

The maser emission covers a 1 arcsecond area with a velocity gradient.

No variability was observed over several months.

Abstract

Aims. We aimed at investigating the structure and kinematics of the gaseous disk and outflows around the massive YSO S255 NIRS3 in the S255IR-SMA1 dense clump. Methods. Observations of the S255IR region were carried out with ALMA at two epochs in the compact and extended configurations. Results. We serendipitously detected a new, never predicted, bright maser line at about 349.1 GHz, which most probably represents the CH$_3$OH $14_{1} - 14_{0}$ A$^{- +}$ transition. The emission covers most of the 6.7 GHz methanol maser emission area of almost 1$^{\prime\prime}$ in size and shows a velocity gradient in the same sense as the disk rotation. No variability was found on the time interval of several months. It is classified as Class II maser and probably originates in a ring at a distance of several hundreds AU from the central star.