Speaker
Description
Young high mass stellar objects (HMYSOs, $M_* > 8 M_\odot$) contribute significantly to the energetics of the interstellar medium through radiation fields and supernovae. However, they are rare, and form in deeply embedded cores. Simulations suggest that they gain $\sim 50\%$ of their initial mass in short bursts of accretion in $\sim 3 \%$ of their formation time. A few accretion bursts in HMYSOs have been studied in detail through early warning with 6.7 GHz methanol maser monitoring. In order to increase the sample of detected and studied accretion bursts, novel observational methods are required to effectively monitor accretion burst tracers. In this talk, we will introduce the maser monitoring program with the Metsähovi Compact Array (MCA) at the Metsähovi Radio Observatory. Our program will be one of the first long term interferometric maser monitoring programs. We aim to demonstrate that interferometric monitoring with smaller dishes can function with the same capabilities as monitoring with large (> 25 m) single dishes at reduced cost. The MCA will consist of four 5.5 m parabolic antennas with receivers at 4$-$8 GHz. The MCA baselines will span 50 $-$ 150 m, giving an angular resolution of 1 arcmin in interferometric mode with a 34 arcmin field of view. The first three MCA antennas are operational in single dish and interferometric mode. The fourth MCA antenna will be commissioned in mid 2028. In single dish automated modes, with MCA1, MCA2 and MCA3, we have monitored more than sixty high mass star forming regions with short daily integrations since mid 2024. We will show how an automatic monitoring system, source-based averaging and automatic flare alerts can allow small facilities as the MCA as to operate as competitive accretion burst detectors. Lastly, we will outline the upcoming interferometric monitoring program and imaging with the MCA. The MCA maser monitoring project, if successful, can serve as a template for small-dish maser monitoring projects to improve the accretion burst detection rate so that we can investigate the role of episodic accretion on the formation of stars and planets.