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12th of January 2022
ATCA observations of a formaldehyde maser
by McCarthy et al.
McCarthy et al. have performed a molecular line search toward the flaring 6.7-GHz methanol masers G24.33+0.13 and G359.62–0.24, associated with high-mass star-formation regions, using the Australia Telescope Compact Array. One of their detections was just the eleventh known example of a 4.8-GHz formaldehyde maser, toward G24.33+0.13. The figure above shows a comparison of the 4.8-GHz formaldehyde (H2CO) spectra emission toward G24.33+0.13 from the 2019 November (black) and 2021 February observations. For the 2019 epoch, the formaldehyde emission spectrum consists of a primary component with a full-width at half maximum of ∼0.2 km/s at a velocity of 109.3 km/s, along with what appears to be 3 much weaker features. The follow-up epoch from 2021 shows a simplification of this spectral profile to a single narrow component at approximately the same flux density, redshifted with respect to the 2019 peak by 0.3 km/s. The line-width, estimated brightness temperature, similarity with the class II methanol maser emission and variability in the spectral profile between epochs all indicate that this emission is the result of maser processes. The paper will be published in Monthly Notices of the Royal Astronomical Society.

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