New maser species tracing spiral-arm accretion flows in a high-mass young stellar object

Chen, Xi; Соболев, А. М.; Ren, Zhiyuan; Parfenov, S. Yu.; Breen, S. L.; Ellingsen, S. P.; Shen, Zhi-Qiang; Li, Bin; MacLeod, G. C.; Baan, Willem A.; Brogan, C. L.; Hirota, Tomoya; Hunter, T. R.; Linz, H.; Menten, K. M.; Sugiyama, Koichiro; Stecklum, B.; Gong, Y.; Zheng, Xingwu

doi:10.1038/s41550-020-1144-x

Cited by 42 publications

(57 citation statements)

References 43 publications

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“…The system has a low inclination of 22 ± 11 • , which means it is seen close to pole on. This viewing geom-etry agrees with that of the spiral-arm accretion flow of Chen et al (2020b) with i = 25 ± 10 • . The stellar radius amounts to 8.4 + − 15.7 5.5 R .…”

Section: )supporting

confidence: 85%

“…Vorobyov & Basu 2015;Meyer et al 2017) seems to be favorable for a MYSO in an evolutionary stage as early as G358. Interestingly, recent high-resolution radio imaging of MM1 suggests the presence of two spiral-arm accretion flows, winding toward the protostar as traced by methanol masers (Brogan et al 2019;Chen et al 2020b). This is in line with very high-resolution ALMA imaging of high-mass protostars that provided evidence for filamentary streamers pointing onto the central sources (Goddi et al 2018;Johnston et al 2020).…”

Section: Accretion Burst Driversmentioning

confidence: 52%

“…Another important parameter for the maser excitation is the specific column density, N M ∆V −1 , where N M is the methanol column density along the line of sight and ∆V the velocity range of the molecules. The low inclination i obtained from our RT modeling and by Chen et al (2020b) implies that ∆V is only slightly larger than thermal line-width since the radial velocity component of the orbital motion will be small. This increases the prospects for maser to occur.…”

Section: Methanol Maser Relocationmentioning

confidence: 69%

“…However, since MM1 is likely in an earlier evolutionary stage, preceding the ZAMS, the above assumption may not hold. A different and presumably more realistic approach is possible using the stellar radius from the RT modeling of the pre-burst SED together with the stellar mass of 12 ±3 M derived from the kinematic model of the spiral-arm accretion flows (Chen et al 2020b). This leads to M acc = 5.3 + − 3.0 × 10 −3 M yr −1 .…”

Section: Stellar-dependent Burst Parametersmentioning

confidence: 99%

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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: )supporting

confidence: 85%

Section: Accretion Burst Driversmentioning

confidence: 52%

Section: Methanol Maser Relocationmentioning

confidence: 69%

Section: Stellar-dependent Burst Parametersmentioning

confidence: 99%

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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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“…Accretion bursts offer an explanation for the luminosity burst events in regions of massive star formation which have been reported by Hunter et al (2017), Caratti o Garatti et al (2017, and Sugiyama et al (2019) for example. Recently, Chen et al (2020) reported the observation of disk substructures associated with an accretion burst event, thus providing a link between the two phenomena. The simulations in Meyer et al (2017Meyer et al ( , 2018Meyer et al ( , 2019 show accretion bursts; these latter authors performed an extensive analysis of the accretion process and the intensity and frequency of the bursts.…”

Section: Introductionmentioning

confidence: 99%

Modeling disk fragmentation and multiplicity in massive star formation

Oliva

Kuiper

2020

A&A

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Context. There is growing evidence that massive stars grow by disk accretion in a similar way to their low-mass counterparts. Early in evolution, these disks can achieve masses that are comparable to the current stellar mass, and therefore the forming disks are highly susceptible to gravitational fragmentation. Aims. We investigate the formation and early evolution of an accretion disk around a forming massive protostar, focussing on its fragmentation physics. To this end, we follow the collapse of a molecular cloud of gas and dust, the formation of a massive protostar, the formation of its circumstellar disk, and the formation and evolution of the disk fragments. Methods. We used a grid-based, self-gravity radiation hydrodynamics code including a sub-grid module for stellar evolution and dust evolution. We purposely do not use a sub-grid module for fragmentation such as sink particles to allow for all paths of fragment formation and destruction, but instead we keep the spatial grid resolution high enough to properly resolve the physical length scales of the problem, namely the pressure scale height and Jeans length of the disk. Simulations are performed on a grid in spherical coordinates with a logarithmic spacing of the grid cells in the radial direction and a cosine distribution of the grid cells in the polar direction, focusing the spatial resolution on the disk midplane. As a consequence, roughly 25% of the total number of grid cells, corresponding to ~26 million grid cells, are used to model the disk physics. These constitute the highest resolution simulations performed up to now on disk fragmentation around a forming massive star with the physics considered here. For a better understanding of the effects of spatial resolution and to compare our high-resolution results with previous lower resolution studies in the literature, we perform the same simulation at five different resolutions, each run differing in resolution from its predecessor by a factor of two. Results. The cloud collapses and a massive (proto)star is formed in its center surrounded by a fragmenting Keplerian-like accretion disk with spiral arms. The fragments have masses of ~1 M⊙, and their continuous interactions with the disk, spiral arms, and other fragments result in eccentric orbits. Fragments form hydrostatic cores surrounded by secondary disks with spiral arms that also produce new fragments. We identified several mechanisms of fragment formation, interaction, and destruction. Central temperatures of the fragments can reach the hydrogen dissociation limit, form second Larson cores, and evolve into companion stars. Based on this, we study the multiplicity predicted by the simulations and find approximately six companions at different distances from the primary: from possible spectroscopic multiples, to companions at distances between 1000 and 2000 au.

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Identification of interstellar cyanamide towards the hot molecular core G358.93–0.03 MM1

Manna

Pal

2023

Astrophys Space Sci

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New maser species tracing spiral-arm accretion flows in a high-mass young stellar object

Cited by 42 publications

References 43 publications

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

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

Modeling disk fragmentation and multiplicity in massive star formation

Identification of interstellar cyanamide towards the hot molecular core G358.93–0.03 MM1

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