A heatwave of accretion energy traced by masers in the G358-MM1 high-mass protostar
High-mass stars are thought to accumulate much of their mass via short, infrequent bursts of disk-aided accretion 1 , 2 . Such accretion events are rare and difficult to observe directly but are known to drive enhanced maser emission 3 – 6 . In this Letter we report high-resolution, multi-epoch meth...
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Published in | Nature astronomy Vol. 4; no. 5; pp. 506 - 510 |
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Main Authors | , , , , , , , , , , , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
London
Nature Publishing Group UK
01.05.2020
Nature Publishing Group |
Subjects | |
Online Access | Get full text |
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Summary: | High-mass stars are thought to accumulate much of their mass via short, infrequent bursts of disk-aided accretion
1
,
2
. Such accretion events are rare and difficult to observe directly but are known to drive enhanced maser emission
3
–
6
. In this Letter we report high-resolution, multi-epoch methanol maser observations toward G358.93-0.03, which reveal an interesting phenomenon: the subluminal propagation of a thermal radiation ‘heatwave’ emanating from an accreting high-mass protostar. The extreme transformation of the maser emission implies a sudden intensification of thermal infrared radiation from within the inner (40-mas, 270-au) region. Subsequently, methanol masers trace the radial passage of thermal radiation through the environment at ≥4% of the speed of light. Such a high translocation rate contrasts with the ≤10 km s
−1
physical gas motions of methanol masers typically observed using very-long-baseline interferometry (VLBI). The observed scenario can readily be attributed to an accretion event in the high-mass protostar G358.93-0.03-MM1. While being the third case in its class, G358.93-0.03-MM1 exhibits unique attributes hinting at a possible ‘zoo’ of accretion burst types. These results promote the advantages of maser observations in understanding high-mass-star formation, both through single-dish maser monitoring campaigns and via their international cooperation as VLBI arrays.
A ring of maser emission seemingly expanding at 0.05
c
is actually tracing the propagation of heat through the circumstellar medium around a high-mass protostar rather than subluminal motion. The heatwave is a manifestation of an accretion burst. |
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ISSN: | 2397-3366 2397-3366 |
DOI: | 10.1038/s41550-019-0989-3 |