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

Burns, Ross; Sugiyama, Koichiro; Hirota, Tomoya; Kim, Kee‐Tae; Соболев, А. М.; Stecklum, B.; MacLeod, G. C.; Yonekura, Yoshinori; Олеч, M.; Orosz, G.; Ellingsen, S. P.; Hyland, Lucas J.; Garatti, A. Caratti o; Brogan, C. L.; Hunter, T. R.; Phillips, Chris; Heever, S. P. van den; Eislöffel, J.; Linz, H.; Surcis, G.; Chibueze, James O.; Baan, Willem A.; Kramer, B. Hutawarakorn

doi:10.1038/s41550-019-0989-3

Cited by 67 publications

(79 citation statements)

References 27 publications

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“…While this knowledge 0.37 0.68 kpc (Brogan et al 2019) which implies a galactocentric one of 1.6 kpc. It is consistent with Gaia distances of visible stars in the G358 region of 5 kpc which impose a lower limit to the distance of the molecular cloud hosting G358 (Burns et al 2020). In mid-January 2019, flaring of the 6.7 GHz CH 3 OH maser line (Menten 1991b) in G358 was announced (Sugiyama et al 2019).…”

Section: Introductionsupporting

confidence: 62%

“…8 seems to indicate that at the first VLBI epoch, the maser sites were likely close to the interface between the outflow lobe and the disk/envelope, that is in a region of relatively low optical depth. The subliminal maser propagation speed reported by Burns et al (2020) implies substantial optical depths. This suggests that the masers likely propagated into the disk rather than on its surface.…”

Section: Methanol Maser Relocationmentioning

confidence: 90%

“…The excitation of new maser spots at larger distance has been observed for the first time during the accretion burst of S255IR-NIRS3 (Moscadelli et al 2017). Notably, for G358 a ring-like propagation of maser spots, likely excited by the heat wave due to the burst, has been witnessed (Burns et al 2020). Further evidence for spatial changes of the G358 maser distribution during and after the burst has been gained (Bayandina et al, in prep.…”

Section: Methanol Maser Relocationmentioning

confidence: 90%

“…At the same time the region below the disk/envelope surface has become warmer and presumably got enriched with gaseous methanol. These conclusions from the RT modeling can be compared to the multi-epoch VLBI observations of the expanding maser ring (Burns et al 2020;Burns et al, in prep.). The vertical dashed black lines mark the circumference of the maser ring from the first and 4th VLBI epoch.…”

Section: Methanol Maser Relocationmentioning

confidence: 97%

“…In all likelihood, the brightest continuum source MM1, which turned out to be a hot molecular core, experienced an accretion burst. For the first time, a spectacular confirmation of the event was achieved by high-resolution, multi-epoch observations of the 6.7-GHz methanol maser emission which revealed outward maser spot propagation, tracing the spread of the thermal radiation emanating from the burst (Burns et al 2020). However, without evidence for a significant rise in (sub)millimeter dust continuum emission from MM1 (Brogan et al 2019), the energetics of the burst remained an open issue.…”

Section: Introductionmentioning

confidence: 92%

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Infrared observations of the flaring maser source G358.93−0.03

Stecklum

Wolf

Linz

et al. 2021

A&A

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Context. Class II methanol masers are signposts of massive young stellar objects (MYSOs). Recent evidence shows that flares of these masers are driven by MYSO accretion bursts. Thus, maser monitoring can be used to identify such bursts which are hard to discover otherwise. Infrared observations reveal burst-induced changes in the spectral energy distribution (first and foremost a luminosity increase), which provide valuable information on a very intense phase of high-mass star formation. Aims. In mid-January 2019, flaring of the 6.7 GHz CH3OH maser (hereafter maser) of the MYSO G358.93-0.03 (hereafter G358) was reported. The international maser community initiated an extensive observational campaign which revealed extraordinary maser activity and yielded the detection of numerous new masering transitions. Interferometric imaging with the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array resolved the maser emitting core of the star forming region and proved the association of the masers with the brightest continuum source (MM1), which hosts a hot molecular core. These observations, however, failed to detect a significant rise in the (sub)millimeter dust continuum emission. Therefore, we performed near-infrared (NIR) and far-infrared (FIR) observations to prove or disprove whether the CH3OH flare was driven by an accretion burst. Methods. NIR imaging with the Gamma-Ray Burst Optical/Near-infrared Detector has been acquired and integral-field spectroscopy with the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS) aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) was carried out on two occasions to detect possible counterparts to the (sub)millimeter sources and compare their photometry to archival measurements. The comparison of pre-burst and burst spectral energy distributions is of crucial importance to judge whether a substantial luminosity increase, caused by an accretion burst, is present and if it triggered the maser flare. Radiative transfer modeling of the spectral energy distribution (SED) of the dust continuum emission at multiple epochs provides valuable information on the bursting MYSO. Results. The FIR fluxes of MM1 measured with FIFI-LS exceed those from Herschel significantly, which clearly confirms the presence of an accretion burst. The second epoch data, taken about 16 months later, still show increased fluxes. Our radiative transfer modeling yielded major burst parameters and suggests that the MYSO features a circumstellar disk which might be transient. From the pre-burst, burst, and post-burst SEDs, conclusions on heating and cooling time-scales could be drawn. Circumstances of the burst-induced maser relocation have been explored. Conclusions. The verification of the accretion burst from G358 is another confirmation that Class II methanol maser flares represent an alert for such events. Thus, monitoring of these masers greatly enhances the chances of identifying MYSOs during periods of intense growth. The few events known to date already indicate that there is a broad range in burst strength and duration as well as environmental characteristics. The G358 event is the shortest and least luminous accretion burst known to date. According to models, bursts of this kind occur most often.

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Section: Introductionsupporting

confidence: 62%

Section: Methanol Maser Relocationmentioning

confidence: 90%

Section: Methanol Maser Relocationmentioning

confidence: 90%

Section: Methanol Maser Relocationmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 92%

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Infrared observations of the flaring maser source G358.93−0.03

Stecklum

Wolf

Linz

et al. 2021

A&A

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Formation and Evolution of Disks Around Young Stellar Objects

et al. 2020

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Expanded Maser Science Opportunities with the ALMA Wideband Sensitivity Upgrade

Brogan

2022

Proc. IAU

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The ALMA Project is embarking on a partner-wide initiative to at least double, and ultimately quadruple the correlated bandwidth of ALMA by @2030. This initiative is called the ALMA Wideband Sensitivity Upgrade (WSU). In this contribution, I briefly describe the main aspects of the upgrade and status. Then I provide several examples of how the WSU will enhance (sub)millimeter maser science by affording the ability to observe more diagnostic maser transitions (and thermal lines) with a single observation.

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

Cited by 67 publications

References 27 publications

Infrared observations of the flaring maser source G358.93−0.03

Infrared observations of the flaring maser source G358.93−0.03

Formation and Evolution of Disks Around Young Stellar Objects

Expanded Maser Science Opportunities with the ALMA Wideband Sensitivity Upgrade

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