Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639

Олеч, M.; Szymczak, M.; Wolak, P.; Gérard, E.; Bartkiewicz, A.

doi:10.1051/0004-6361/201936943

Cited by 19 publications

(22 citation statements)

References 52 publications

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“…Thus, the rise and fall of the maser emission is coupled to the accretion variability through the dust MIR continuum emission. First direct evidence for this relation has been found by us for the S255IR-NIRS3 burst (Stecklum et al 2018a), see Durjasz et al (2019) and Olech et al (2020) for other cases.…”

Section: Burst Duration and Temporal Evolution Of The Ir Emissionmentioning

confidence: 70%

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: Burst Duration and Temporal Evolution Of The Ir Emissionmentioning

confidence: 70%

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

Stecklum

Wolf

Linz

et al. 2021

A&A

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“…2). The average delay obtained from the results of the three fits is 0.9±0.3 d. The VLBI maps indicate that the 6.7 GHz emission near −7.35 km s −1 comes from clouds located ∼150 au from the putative position of the central star (Olech et al 2020). Thus, if the 6.7 GHz and 12.2 GHz maser coexist, then the observed delay cannot be explained by a simple geometrical effect.…”

Section: Name (L B)mentioning

confidence: 81%

“…In G107, the maser intensity varies with a period of 34.4 days, perhaps due to changes of infrared emission (Olech et al 2020); it is difficult to identify processes that can significantly change the gas density, molecule abundance, and kinetic temperature in the maser regions on such a short timescale. Since the heating and cooling times of dust grains are less than a few minutes and one day, respectively, for the optically thick case (van der Walt et al 2009;Johnstone et al 2013), rapid changes in the maser intensity may be related to variations in the dust temperature (T d ).…”

Section: Flux Density Ratiomentioning

confidence: 99%

Observations of 12.2 GHz methanol masers towards northern high-mass protostellar objects

Durjasz,

Szymczak,

Wolak

et al. 2021

Preprint

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Context. Class II methanol masers at 6.7 and 12.2 GHz occur close to high-mass young stellar objects (HMYSOs). When they are observed simultaneously, such studies may contribute to refining the characterisation of local physical conditions. Aims. We aim to search for the 12.2 GHz methanol emission in 6.7 GHz methanol masers that might have gone undetected in previous surveys of northern sky HMYSOs, mainly due to their variability. Contemporaneous observations of both transitions are used to refine the flux density ratio and examine the physical parameters. Methods. We observed a sample of 153 sites of 6.7 GHz methanol maser emission in the 12.2 GHz methanol line with the Torun 32 m radio telescope, using the newly built X-band receiver.Results. The 12.2 GHz methanol maser emission was detected in 36 HMYSOs, with 4 of them detected for the first time. The 6.7 GHz to 12.2 GHz flux density ratio for spectral features of the contemporaneously observed sources has a median value of 5.1, which is in agreement with earlier reports. The ratio differs significantly among the sources and for the periodic source G107.298+5.639 specifically, the ratio is weakly recurrent from cycle to cycle, but it generally reaches a minimum around the flare peak. This is consistent with the stochastic maser process, where small variations in the physical parameters along the maser path can significantly affect the ratio. A comparison of our data with historical results (from about ten years ago) implies significant (> 50%) variability for about 47% and 14% at 12.2 GHz and 6.7 GHz, respectively. This difference can be explained via the standard model of methanol masers.

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“…Some of them present substantial variability (e.g. Szymczak et al 2018;Durjasz et al 2019;Olech et al 2019Olech et al , 2020, suggesting that protostellar activity fluctuates on timescales ranging from less than a month up to a few years and more. There are also examples proving that massive protostars also show episodic outbursts that can change maser flux density 1 https://maserdb.net by more than two orders of magnitude, namely S255−NIRS3 (Moscadelli et al 2017;Szymczak et al 2018), NGC6334I-MM1B (Hunter et al 2018), and G358.93−0.03 (Burns et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Discovery of recurrent flares of 6.7 GHz methanol maser emission in Cepheus A HW2

Durjasz,

Szymczak,

Olech

et al. 2022

Preprint

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Context. Class II methanol masers at 6.7 GHz originate close to high-mass young stellar objects (HMYSOs). Their high sensitivity to local condition variations makes them a useful marker of the activity of the emerging massive stars. Aims. We aim to closely examine the variability of the 6.7 GHz CH 3 OH masers in Cep A HW2 using the new and archival single-dish and high-resolution Very-Long-Baseline Interferometry (VLBI) datasets. Methods. We monitored 6.7 GHz methanol masers towards the target between 2009 and 2021 using the Torun 32 m radio telescope, and analysed nine datasets of VLBI observations taken over 16 yr. Results. Faint, extremely redshifted maser emission located close to the presumed central star position and coincident with the radio jet shows flaring activity with a period of ∼ 5 yr. Flares have an asymmetric profile with a rise-to-decay time ratio of 0.18 and relative amplitude higher than 10. The velocity of the flaring cloudlets drifts at a rate of 3-4 × 10 −5 km s −1 d −1 for about 11.5 yr of the monitoring. The time-lag between the peaks of the two flaring features implies a propagation speed of the exciting factor of ∼ 1000 km s −1 . Synchronised and anticorrelated variations of the flux density of blue-and redshifted features begin ∼ 2.5 yr after flares of the extremely redshifted emission. Conclusions. Our observations suggest that the recurrent flares are the response of low-gain unsaturated maser regions to a relatively low increase in luminosity, which has little effect on the behaviour of most maser regions of higher gain.

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Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639

Cited by 19 publications

References 52 publications

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

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

Observations of 12.2 GHz methanol masers towards northern high-mass protostellar objects

Discovery of recurrent flares of 6.7 GHz methanol maser emission in Cepheus A HW2

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