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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 accretion1,2. Such accretion events are rare and difficult to observe directly but are known to drive enhanced maser emission3,4,5,6. 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.

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Fig. 1: Spectral profiles of the 6.7-GHz methanol maser emission in G358-MM1.
Fig. 2: Methanol maser distributions in G358-MM1.
Fig. 3: Schematic illustration of the observational data.

Data availability

The data that support the plots within this paper and other findings of this study are available from the PAWSEY data archive ( or from the corresponding author on reasonable request


  1. 1.

    Stamatellos, D., Whitworth, A. P. & Hubber, D. A. The importance of episodic accretion for low-mass star formation. Astrophys. J. 730, 32 (2011).

    ADS  Article  Google Scholar 

  2. 2.

    Meyer, D. M.-A., Vorobyov, E. I., Kuiper, R. & Kley, W. On the existence of accretion-driven bursts in massive star formation. Mon. Not. R. Astron. Soc. 464, L90–L94 (2017).

    ADS  Article  Google Scholar 

  3. 3.

    Hunter, T. R. et al. The extraordinary outburst in the massive protostellar system NGC 6334I-MM1: emergence of strong 6.7 GHz methanol masers. Astrophys. J. 854, 170 (2018).

    ADS  Article  Google Scholar 

  4. 4.

    MacLeod, G. C. et al. A masing event in NGC 6334I: contemporaneous flaring of hydroxyl, methanol, and water masers. Mon. Not. R. Astron. Soc. 478, 1077–1092 (2018).

    ADS  Article  Google Scholar 

  5. 5.

    Szymczak, M., Olech, M., Wolak, P., Gérard, E. & Bartkiewicz, A. Giant burst of methanol maser in S255IR-NIRS3. Astron. Astrophys. 617, A80 (2018).

    ADS  Article  Google Scholar 

  6. 6.

    Moscadelli, L. et al. Extended CH3OH maser flare excited by a bursting massive YSO. Astron. Astrophys. 600, L8 (2017).

    ADS  Article  Google Scholar 

  7. 7.

    Cragg, D. M., Sobolev, A. M. & Godfrey, P. D. Models of class II methanol masers based on improved molecular data. Mon. Not. R. Astron. Soc. 360, 533–545 (2005).

    ADS  Article  Google Scholar 

  8. 8.

    Breen, S. L., Ellingsen, S. P., Caswell, J. L. & Lewis, B. E. 12.2-GHz methanol masers towards 1.2-mm dust clumps: quantifying high-mass star formation evolutionary schemes. Mon. Not. R. Astron. Soc. 401, 2219–2244 (2010).

    ADS  Article  Google Scholar 

  9. 9.

    Bartkiewicz, A., Szymczak, M., van Langevelde, H. J., Richards, A. M. S. & Pihlström, Y. M. The diversity of methanol maser morphologies from VLBI observations. Astron. Astrophys. 502, 155–173 (2009).

    ADS  Article  Google Scholar 

  10. 10.

    Bartkiewicz, A., Szymczak, M. & Langevelde, H. J. European VLBI network imaging of 6.7 GHz methanol masers. Astron. Astrophys. 587, A104 (2016).

    Article  Google Scholar 

  11. 11.

    Ellingsen, S. P. Methanol masers: reliable tracers of the early stages of high-mass star formation. Astrophys. J. 638, 241–261 (2006).

    ADS  Article  Google Scholar 

  12. 12.

    Fujisawa, K. et al. Observations of the bursting activity of the 6.7 GHz methanol maser in G33.641-0.228. Publ. Astron. Soc. Jpn 66, 109 (2014).

    ADS  Article  Google Scholar 

  13. 13.

    Caswell, J. L. et al. The 6-GHz methanol multibeam maser catalogue—I. Galactic Centre region, longitudes 345° to 6°. Mon. Not. R. Astron. Soc. 404, 1029–1060 (2010).

    ADS  Article  Google Scholar 

  14. 14.

    Sugiyama, K., Saito, Y., Yonekura, Y. & Momose, M. Bursting activity of the 6.668-GHz CH3OH maser detected in G 358.93-00.03 using the Hitachi 32-m. Astron. Telegr. 12446 (2019).

  15. 15.

    Yonekura, Y. et al. The Hitachi and Takahagi 32 m radio telescopes: upgrade of the antennas from satellite communication to radio astronomy. Publ. Astron. Soc. Jpn 68, 74 (2016).

    ADS  Article  Google Scholar 

  16. 16.

    Brogan, C. L. et al. Sub-arcsecond (sub)millimeter imaging of the massive protocluster G358.93–0.03: discovery of 14 new methanol maser lines associated with a hot core. Astrophys. J. Lett. 881, L39 (2019).

    ADS  Article  Google Scholar 

  17. 17.

    Breen, S. L. et al. Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G 358.931-0.030. Astrophys. J. 876, L25 (2019).

    ADS  Article  Google Scholar 

  18. 18.

    MacLeod, G. C. et al. Detection of new methanol maser transitions associated with G358.93-0.03. Mon. Not. R. Astron. Soc. 489, 3981–3989 (2019).

    ADS  Article  Google Scholar 

  19. 19.

    Molinari, S. et al. Hi-GAL, the Herschel infrared Galactic Plane Survey: photometric maps and compact source catalogues. First data release for the inner Milky Way: +68° ≥ l ≥ −70°. Astron. Astrophys. 591, A149 (2016).

    Article  Google Scholar 

  20. 20.

    Fischer, C. et al. FIFI-LS: the field-imaging far-infrared line spectrometer on SOFIA. J. Astron. Instrum. 7, 1840003–1840556 (2018).

    Article  Google Scholar 

  21. 21.

    Reid, M. J. et al. Trigonometric parallaxes of high mass star forming regions: the structure and kinematics of the Milky Way. Astrophys. J. 783, 130 (2014).

    ADS  Article  Google Scholar 

  22. 22.

    Bailer-Jones, C. A. L., Rybizki, J., Fouesneau, M., Mantelet, G. & Andrae, R. Estimating distance from parallaxes. IV. Distances to 1.33 billion stars in Gaia data release 2. Astron. J. 156, 58 (2018).

    ADS  Article  Google Scholar 

  23. 23.

    Garay, G., Mardones, D., Rodríguez, L. F., Caselli, P. & Bourke, T. L. Methanol and silicon monoxide observations toward bipolar outflows associated with class 0 objects. Astrophys. J. 567, 980–998 (2002).

    ADS  Article  Google Scholar 

  24. 24.

    Stecklum, B. et al. in Astrophysical Masers: Unlocking the Mysteries of the Universe (eds Tarchi, A., Reid, M. J. & Castangia, P.) 37–40 (IAU Symposium Vol. 336, Cambridge Univ. Press, 2018).

  25. 25.

    Audard, M. et al. in Protostars and Planets VI (eds Beuther, H., Klessen, R. S., Dullemond, C. P. & Henning, T.) 387–410 (Univ. Arizona Press, 2014).

  26. 26.

    Hosokawa, T., Yorke, H. W. & Omukai, K. Evolution of massive protostars via disk accretion. Astrophys. J. 721, 478–492 (2010).

    ADS  Article  Google Scholar 

  27. 27.

    Tan, J. C. in From Interstellar Clouds to Star-Forming Galaxies: Universal Processes? (eds Jablonka, P., André, P. & van der Tak, F.) 154–162 (IAU Symposium Vol. 315, Cambridge Univ. Press, 2016).

  28. 28.

    Caratti o Garatti, A. et al. Disk-mediated accretion burst in a high-mass young stellar object. Nat. Phys. 13, 276–279 (2017).

    Article  Google Scholar 

  29. 29.

    Hunter, T. R. et al. An extraordinary outburst in the massive protostellar system NGC6334I-MM1: quadrupling of the millimeter continuum. Astrophys. J. Lett. 837, L29 (2017).

    ADS  Article  Google Scholar 

  30. 30.

    Burns, R. A., Handa, T., Nagayama, T., Sunada, K. & Omodaka, T. H2O masers in a jet-driven bow shock: episodic ejection from a massive young stellar object. Mon. Not. R. Astron. Soc. 460, 283–290 (2016).

    ADS  Article  Google Scholar 

  31. 31.

    Deller, A. T., Tingay, S. J., Bailes, M. & West, C. DiFX: a software correlator for very long baseline interferometry using multiprocessor computing environments. Publ. Astron. Soc. Pac. 119, 318–336 (2007).

    ADS  Article  Google Scholar 

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R.A.B. acknowledges support through the EACOA Fellowship from the East Asian Core Observatories Association. S.P.E., G.O. and L.H. acknowledge the support of the ARC Discovery Project (project number DP180101061). G.O. was supported by CAS LCWR grant 2018-XBQNXZ-B-021. A.M.S. was supported by the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS”. This work was supported by JSPS KAKENHI grant JP19K03921. T.H. is financially supported by the MEXT/JSPS KAKENHI grants 16K05293 and 17K05398. J.O.C. acknowledges support by the Italian Ministry of Foreign Affairs and International Cooperation (MAECI Grant Number ZA18GR02) and the South African Department of Science and Technology’s National Research Foundation (DST-NRF Grant Number 113121) as part of the ISARP RADIOSKY2020 Joint Research Scheme. This work was supported by the National Science Centre, Poland, through grant 2016/21/B/ST9/01455. The LBA is part of the Australia Telescope National Facility, which is funded by the Australian Government for operation as a National Facility managed by CSIRO. This work was supported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Author information




R.A.B. led the project as principal investigator for the observations, processed the data and authored the manuscript. K.S. and Y.Y. selected the target maser source. B.S., J.E., A.C.G. and A.M.S. provided theoretical interpretations of the data. G.O., S.P.E., L.H. and C.P. conducted the observations. All authors assisted in the interpretation of the results and contributed to the preparation of the manuscript.

Corresponding author

Correspondence to R. A. Burns.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Sandra Etoka and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Source data

Source Data Fig. 1

Spectral line profile data.

Source Data Fig. 3

Velocities and positions of masers.

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Burns, R.A., Sugiyama, K., Hirota, T. et al. A heatwave of accretion energy traced by masers in the G358-MM1 high-mass protostar. Nat Astron 4, 506–510 (2020).

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