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Abstract

High-mass stars are thought to accumulate much of their mass via short, infrequent bursts of disk-aided accretion. Such accretion events are rare and difficult to observe directly but are known to drive enhanced maser emission. 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.

Item Type:	Article
Authors/Creators:	Burns, RA and Sugiyama, K and Hirota, T and Kim, KT and Sobolev, AM and Stecklum, B and MacLeod, GC and Yonekura, Y and Olech, M and Orosz, G and Ellingsen, SP and Hyland, H and Caratti o Garatti, A and Brogan, C and Hunter, TR and Phillips, C and van den Heever, SP and Eisloffel, J and Linz, H and Surcis, G and Chibueze, JO and Baan, W and Kramer, B
Keywords:	SM: individual objects (G358.931-0.030) – ISM: molecules – masers – radio lines: ISM – stars: formation
Journal or Publication Title:	Nature Astronomy
Publisher:	Nature Publishing Group
ISSN:	2397-3366
DOI / ID Number:	https://doi.org/10.1038/s41550-019-0989-3
Copyright Information:	© The Author(s), under exclusive licence to Springer Nature Limited 2020
Related URLs:	Google Scholar: Ellingsen, SP UTAS Profile: Ellingsen, SP
Item Statistics:	View statistics for this item

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