Burns, R. A.R. A.BurnsSugiyama, K.K.SugiyamaHirota, T.T.HirotaKim, Kee-TaeKee-TaeKimSobolev, A. M.A. M.SobolevStecklum, B.B.StecklumMacLeod, G. C.G. C.MacLeodYonekura, Y.Y.YonekuraOlech, M.M.OlechOrosz, G.G.OroszEllingsen, S. P.S. P.EllingsenHyland, L.L.HylandCARATTI O GARATTI, AlessioAlessioCARATTI O GARATTIBrogan, C.C.BroganHunter, T. R.T. R.HunterPhillips, C.C.Phillipsvan den Heever, S. P.S. P.van den HeeverEislöffel, J.J.EislöffelLinz, H.H.LinzSurcis, GabrieleGabrieleSurcisChibueze, J. O.J. O.ChibuezeBaan, W.W.BaanKramer, B.B.Kramer2021-12-102021-12-1020202397-3366http://hdl.handle.net/20.500.12386/31229High-mass stars are thought to accumulate much of their mass via short, infrequent bursts of disk-aided accretion<SUP>1,2</SUP>. Such accretion events are rare and difficult to observe directly but are known to drive enhanced maser emission<SUP>3-6</SUP>. 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<SUP>-1</SUP> 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.ELETTRONICOenArticle10.1038/s41550-019-0989-3https://www.nature.com/articles/s41550-019-0989-32020NatAs...4..506BFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation