Molecular line search toward the flaring 6.7-GHz methanol masers of G24.33+0.13 and G359.6-0.243: rare maser transitions detected

TL;DR

This study used the Australia Telescope Compact Array to detect rare molecular maser transitions in flaring high-mass star-forming regions, revealing insights into maser activity and stellar accretion processes.

Contribution

First detection of a 23.4-GHz class I methanol maser and an 11th formaldehyde maser in these sources, expanding understanding of maser phenomena in flaring regions.

Findings

Detection of rare maser transitions in G24.33+0.13 and G359.62-0.24

Evidence supporting variable accretion as the driver of flaring activity

Comparison with previous flaring events highlights maser variability

Abstract

We have performed a molecular line search toward the flaring 6.7-GHz masers G24.33+0.13 and G359.62-0.24 using the Australia Telescope Compact Array. We present spectra of the 6.7-GHz class~II methanol and 22.2-GHz water masers toward these sources and provide comparison with other recent flaring events these sources have experienced. We also detect the fourth example of a 23.4-GHz class~I methanol maser, and the eleventh example of a 4.8-GHz formaldehyde maser toward G24.33+0.13. Alongside these results, we observe the previously detected ammonia (3,3) emission and report upper limits on the presence of various other cm-wavelength methanol, ammonia and OH transitions. Our results are consistent with the flaring of G24.33+0.13 being driven by a variable accretion rate in the host high-mass young stellar object.