Spectral survey of a Hot core with an Eruptive Accretion in S255IR NIRS3 (SHEA): The discovery of class I and class II millimeter methanol maser transitions

TL;DR

This study reports the detection of new class I and class II millimeter methanol maser transitions in the high-mass protostar S255IR NIRS3, revealing insights into outflow shocks and maser characteristics during post-burst activity.

Contribution

It presents the first detection of specific class I and class II methanol maser transitions in S255IR NIRS3, combining observational data with LTE modeling to analyze maser and thermal emissions.

Findings

Detection of new class I and II methanol maser transitions.

Distinct intensity and velocity distributions of masers compared to thermal lines.

Evidence of slow outflow shocks from emission components.

Abstract

We report the detection of the millimeter CH$_3$OH masers including a new detection of class I (11$_{0,11}$-10$_{1,10}$A) and class II (6$_{1,5}$-5$_{2,4}$E) maser transitions toward the high-mass protostar S255IR NIRS3 in post-burst phase. The CH$_3$OH emissions were detected as a mixture of maser and thermal characteristics. We examine the detected transitions using an excitation diagram and LTE model spectra and compare the observed properties with those of thermal lines. Class II CH$_3$OH maser transitions showed distinctive intensity and velocity distributions from those of thermal transitions. Bright distinct emission components in addition to the fragmented and arc-shaped emissions are only detected in class I CH$_3$OH maser transitions toward southern and western directions from the protostellar position, implying the presence of the slow outflow shocks.