Ammonia masers toward G358.931-0.030

Abstract

We report the detection of ammonia masers in the non-metastable (6, 3), (7, 5) and (6, 5) transitions, the latter is the first unambiguous maser detection of that transition ever made. Our observations include the first VLBI detection of ammonia maser emission, which allowed effective constrain of the (6, 5) maser brightness temperature. The masers were detected towards G358.931-0.030, a site of 6.7-GHz class~II methanol maser emission that was recently reported to be undergoing a period of flaring activity. These ammonia masers appear to be flaring contemporaneously with the class~II methanol masers during the accretion burst event of G358.931-0.030. This newly detected site of ammonia maser emission is only the twelfth such site discovered in the Milky Way. We also report the results of an investigation into the maser pumping conditions, for all three detected masing transitions, through radiative transfer calculations constrained by our observational data. These calculations support the hypothesis that the ammonia (6, 5) maser transition is excited through high colour temperature infrared emission, with the (6, 5) and (7, 5) transition line-ratio implying dust temperatures >400K. Additionally, we detect significant linearly polarised emission from the ammonia (6, 3) maser line. Alongside our observational and radiative transfer calculation results, we also report newly derived rest frequencies for the ammonia (6, 3) and (6, 5) transitions.

Accepted into MNRAS 2023 April 24. 13 pages, 5 figures, 3 tables

References in corpus (12)

• Circumventing the radiation pressure barrier in the formation of massive stars via disk accretion
• ExoMol molecular line lists XXXV: a rotation-vibration line list for hot ammonia
• A modular set of synthetic spectral energy distributions for young stellar objects
• Galactocentric variation of the gas-to-dust ratio and its relation with metallicity
• A heat-wave of accretion energy traced by masers in the G358-MM1 high-mass protostar
• Hot ammonia in NGC6334I & I(N)
• Detection of new methanol maser transitions associated with G358.93-0.03
• Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G358.931-0.030
• A New Hardware Correlator in Korea: Performance Evaluation using KVN observations
• New ammonia masers towards NGC6334I
• A multi-transition methanol maser study of the accretion burst source G358.93-0.03-MM1
• A sensitive search for predicted methanol maser transitions with the Australia Telescope Compact Array

Cited by in corpus (1)

• Discovery of widespread non-metastable ammonia masers in the Milky Way