Detection of new methanol maser transitions associated with G358.93−0.03

MacLeod, G. C.; Sugiyama, Koichiro; Hunter, T. R.; Quick, J.; Baan, Willem A.; Breen, S. L.; Brogan, C. L.; Burns, Ross; Garatti, A. Caratti o; Chen, Xi; Chibueze, James O.; Houde, Martin; Kaczmarek, Jane; Linz, H.; Rajabi, Fereshteh; Yu, Shenghua; Schmidl, S.; Соболев, А. М.; Stecklum, B.; Heever, S. P. van den; Yonekura, Yoshinori

doi:10.1093/mnras/stz2417

Cited by 47 publications

(53 citation statements)

References 37 publications

(67 reference statements)

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“…It has been emphasized that methanol masers play a crucial role in identifying accretion bursts from MYSOs. The maser activity of G358 during its burst was extraordinary and unique in several aspects (Breen et al 2019;Brogan et al 2019;MacLeod et al 2019). 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).…”

Section: Methanol Maser Relocationmentioning

confidence: 87%

“…Thanks to the immediate response, an unprecedented wealth of masering lines, including numerous new transitions, could be observed (Breen et al 2019;Brogan et al 2019;MacLeod et al 2019) and new maser species were discovered (Chen et al 2020a,b). Interferometric imaging in the (sub)millimeter spectral range using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Submillimeter Array (SMA) dissected the star forming region and pinpointed the MYSO which hosts the flaring masers (Brogan et al 2019).…”

Section: Introductionmentioning

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: Methanol Maser Relocationmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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

Stecklum

Wolf

Linz

et al. 2021

A&A

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“…20 The flare commenced around 2019 January 14 (Sugiyama et al 2019). A number of new methanol transitions (about 20 new lines) have been found during its 6.668 GHz methanol flaring event by M2O members (Breen et al 2019;Brogan et al 2019;MacLeod et al 2019). These detections include the first methanol masers from torsionally excited (v t =1 and 2) transitions (Breen et al 2019;Brogan et al 2019).…”

Section: Introductionmentioning

confidence: 93%

¹³CH₃OH Masers Associated With a Transient Phenomenon in a High-mass Young Stellar Object

Chen

Соболев

Breen

et al. 2020

ApJL

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We report the first detection of isotopic methanol ( 13 CH 3 OH) maser emission in interstellar space. The emission was detected toward the high-mass young stellar object G358.93-0.03 during monitoring of a flare in the 6.7 GHz methanol (CH 3 OH) maser emission in this source. We find that the spectral and spatial distribution of the 13 CH 3 OH masers differs from the CH 3 OH masers imaged at the same epoch, contrary to expectations from similarity of their pumping. This conclusively demonstrates that isotopic methanol masers are bright under different physical conditions and suggests that they can provide additional, complementary information to the CH 3 OH masers from the same source. We detect a rapid decay of the 13 CH 3 OH maser lines suggesting that they are transient phenomena (masing for only a few months), likely associated with rapid changes in radiation field due to an accretion burst induced by massive disk fragmentation. Changes in the line flux density are faster than required to achieve equilibrium in the energy level populations, indicating that the pumping of these masers is likely variable.

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“…Other methanol masers transitions presenting high levels of P L were detected at 6.2,7.7,7.8,21,37.7,46 GHz,and at 20.3 GHz by Breen et al (2019) and MacLeod et al (2019), respectively. We could not model non-Zeeman effects because the simulations for these transitions were performed with the N&W92 code, limited to gΩ = 10R.…”

Section: Other Methanol Masersmentioning

confidence: 94%

Polarisation properties of methanol masers

Dall'Olio

Vlemmings

Lankhaar

et al. 2020

A&A

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Context. Astronomical masers have been effective tools in the study of magnetic fields for years. Observations of the linear and circular polarisation of different maser species allow for the determination of magnetic field properties, such as morphology and strength. In particular, methanol can be used to probe different parts of protostars, such as accretion discs and outflows, since it produces one of the strongest and the most commonly observed masers in massive star-forming regions. Aims. We investigate the polarisation properties of selected methanol maser transitions in light of newly calculated methanol Landé g-factors and in consideration of hyperfine components. We compare our results with previous observations and evaluate the effect of preferred hyperfine pumping and non-Zeeman effects. Methods. We ran simulations using the radiative transfer code, CHAMP, for different magnetic field values, hyperfine components, and pumping efficiencies. Results. We find a dependence between the linear polarisation fraction and the magnetic field strength as well as the hyperfine transitions. The circular polarisation fraction also shows a dependence on the hyperfine transitions. Preferred hyperfine pumping can explain some high levels of linear and circular polarisation and some of the peculiar features seen in the S-shape of observed V-profiles. By comparing a number of methanol maser observations taken from the literature with our simulations, we find that the observed methanol masers are not significantly affected by non-Zeeman effects related to the competition between stimulated emission rates and Zeeman rates, such as the rotation of the symmetry axis. We also consider the relevance of other non-Zeeman effects that are likely to be at work for modest saturation levels, such as the effect of magnetic field changes along the maser path and anisotropic resonant scattering. Conclusions. Our models show that for methanol maser emission, both the linear and circular polarisation percentages depend on which hyperfine transition is masing and the degree to which it is being pumped. Since non-Zeeman effects become more relevant at high values of brightness temperatures, it is important to obtain good estimates of these quantities and the maser beaming angles. Better constraints on the brightness temperature will help improve our understanding of the extent to which non-Zeeman effects contribute to the observed polarisation percentages. In order to detect separate hyperfine components, an intrinsic thermal line width that is significantly smaller than the hyperfine separation is required.

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Detection of new methanol maser transitions associated with G358.93−0.03

Cited by 47 publications

References 37 publications

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

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

¹³CH₃OH Masers Associated With a Transient Phenomenon in a High-mass Young Stellar Object

Polarisation properties of methanol masers

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Detection of new methanol maser transitions associated with G358.93−0.03

Cited by 47 publications

References 37 publications

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

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

13CH3OH Masers Associated With a Transient Phenomenon in a High-mass Young Stellar Object

Polarisation properties of methanol masers

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¹³CH₃OH Masers Associated With a Transient Phenomenon in a High-mass Young Stellar Object