Bursting Activity in a High-Mass Star-Forming Region G33.64-0.21 Observed with the 6.7 GHz Methanol Maser

TL;DR

This study reports on the detection of rapid, intense bursts of 6.7 GHz methanol maser emission in a high-mass star-forming region, revealing potential for high-resolution probing of star formation activities.

Contribution

First observation of burst activity in 6.7 GHz methanol masers, linking maser bursts to impulsive energy releases in high-mass star formation.

Findings

Maser flux density increased by a factor of 7 within a day.

Burst region was confined within a 70 AU scale.

Repeated bursts suggest impulsive energy release mechanisms.

Abstract

We report the detection of bursts of 6.7 GHz methanol maser emission in a high-mass star-forming region, G33.64-0.21. One of the spectral components of the maser in this source changed its flux density by 7 times that of the previous day, and it decayed with a timescale of 5 days. The burst occurred repeatedly in the spectral component, and no other components showed such variability. A VLBI observation with the Japanese VLBI Network (JVN) showed that the burst location was at the southwest edge of a spatial distribution, and the bursting phenomenon occurred in a region much smaller than 70 AU. We suggest an impulsive energy release like a stellar flare as a possible mechanism for the burst. These results imply that 6.7 GHz methanol masers could be a useful new probe for studying bursting activity in the process of star formation of high-mass YSOs with a high-resolution of AU scale.