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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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