2022/12/08 by Jakobus M. Vorster, Vorster, Jakobus M., James O. Chibueze +5
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #FOS: Physical sciences #Gamma-ray bursts and supernovae #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2212.04174
openalex publication_date 2022/12/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The high-mass star-forming region NGC6334I-MM1 underwent an energetic accretion event in January 2015. We report the large-scale (10 - 100 AU) and small-scale (∼ 1 AU) changes in spatial and velocity structures of 22 GHz water masers as observed with VERA before and during the accretion burst. The masers in the northern bow-shock CM2-W2 brightened, and better traced a bow structure during the burst. In the southern regions, there was both activation and disappearance of associations before and during the burst. We measured the amplitudes, central velocities and FWHMs of about 20 features in each epoch. We found that the linear scale of the brightest feature in CM2-W2 grew from 0.6 AU before the burst to 1.4 AU after the burst, possibly indicating that a larger volume of gas was able to sustain masing action as a consequence of the accretion burst. This feature also had a rapid (0.2 yr) brightness increase by a factor of four, which has been previously reported in long-term single-dish monitoring. We propose that the water maser flare could be explained by an increase of the collisional pump rate due to radiative heating of H2 by increased high energy radiation (UV or X-ray) from the inner protostellar core. We also describe the spot and spectral method of maser proper motion calculations. We argue that for high spectral resolution observations the spectral method is more robust for calculating proper motions than the spot method.