A heat-wave of accretion energy traced by masers in the G358-MM1 high-mass protostar

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 sub-luminal propagation of a thermal radiation "heat-wave" emanating from an accreting high-mass proto-star. 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 $\ge$ 4-8\% the speed of light. Such a high translocation rate contrasts with the $\le$ 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 proto-star 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.

Published in Nature Astronomy in 2020

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• The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Strong Increase in Mid-Infrared Continuum Emission
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• Parameter study for the burst mode of accretion in massive star formation
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• Multi-frequency VLBI observations of maser lines during the 6.7~GHz maser flare in the high-mass young stellar object G24.33$+$0.14}
• The accretion burst of the massive young stellar object G323.46 -0.08
• The evolution of the H2O maser emission in the accretion burst source G358.93-0.03
• Detection of periodic flares in 6.7 GHz methanol masers G45.804-0.356 and G49.043-1.079
• The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Spatio-kinematics of Water Masers during a Contemporaneous Flare Event
• Molecular line search toward the flaring 6.7-GHz methanol masers of G24.33+0.13 and G359.6-0.243: rare maser transitions detected
• The burst mode of accretion in massive star formation with stellar inertia
• Resolving the collimation zone of an intermediate-mass protostar
• Ammonia masers toward G358.931-0.030
• Detection of the longest periodic variability in 6.7 GHz methanol masers G5.900-0.430
• Spectral survey of a Hot core with an Eruptive Accretion in S255IR NIRS3 (SHEA): The discovery of class I and class II millimeter methanol maser transitions
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• Discovery of recurrent flares of 6.7 GHz methanol maser emission in Cepheus A HW2
• Identifying the Mechanisms of Water Maser Variability During the Accretion Burst in NGC6334I
• Infrared observations of the flaring maser source G358.93-0.03 -- SOFIA confirms an accretion burst from a massive young stellar object