Infrared observations of the flaring maser source G358.93-0.03 -- SOFIA confirms an accretion burst from a massive young stellar object

Abstract

Class II methanol masers are signs of massive young stellar objects (MYSOs). Recent findings show that MYSO accretion bursts cause flares of these masers. Thus, maser monitoring can be used to identify such bursts. Burst-induced SED changes provide valuable information on a very intense phase of high-mass star formation. In mid-January 2019, a maser flare of the MYSO G358.93-0.03 was reported. ALMA and SMA imaging resolved the core of the star forming region and proved the association of the masers with the brightest continuum source MM1. However, no significant flux rise of the (sub)mm dust continuum was found. Thus, we performed NIR imaging with GROND and IFU spectroscopy with FIFI-LS aboard SOFIA to detect possible counterparts to the (sub)mm sources, and compare their photometry to archival measurements. The comparison of pre-burst and burst SEDs is of crucial importance to judge whether a luminosity increase due to the burst is present and if it triggered the maser flare. 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 RT modeling yielded major burst parameters and suggests that the MYSO features a circumstellar disk which might be transient. From the multi-epoch SEDs, conclusions on heating and cooling time-scales could be drawn. Circumstances of the burst-induced maser relocation have been explored. The verification of the accretion burst from G358 is another confirmation that Class II methanol maser flares represent an alert for such events. 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 MYSO accretion burst so far.

22 pages, 11 figures, accepted by A&A. Abstract abridged for arxiv submission

References in corpus (36)

• Initial Performance of the NEOWISE Reactivation Mission
• GROND - a 7-channel imager
• Early Science with SOFIA, the Stratospheric Observatory for Infrared Astronomy
• Variable protostellar accretion with episodic bursts
• An extraordinary outburst in the massive protostellar system NGC6334I-MM1: quadrupling of the millimeter continuum
• A hot compact dust disk around a massive young stellar object
• On the existence of accretion-driven bursts in massive star formation
• A 24 Micron Point Source Catalog of the Galactic Plane from Spitzer/MIPSGAL
• A modular set of synthetic spectral energy distributions for young stellar objects
• The $AKARI$ Far-Infrared All-Sky Survey Maps
• Point Sources from a Spitzer IRAC Survey of the Galactic Center
• Galactocentric variation of the gas-to-dust ratio and its relation with metallicity
• Protostellar Outflows and Radiative Feedback from Massive Stars. II. Feedback, Star Formation Efficiency, and Outflow Broadening
• On the Relationship of UC H II Regions and Class II Methanol Masers: I. Source Catalogs
• A heat-wave of accretion energy traced by masers in the G358-MM1 high-mass protostar
• The outburst of the eruptive young star OO Serpentis between 1995 and 2006
• The Herschel exploitation of local galaxy Andromeda (HELGA) V: Strengthening the case for substantial interstellar grain growth
• Monitoring observations of 6.7 GHz methanol masers
• The chemistry of episodic accretion in embedded objects. 2D radiation thermo-chemical models of the post-burst phase
• Spiral arms and instability within the AFGL 4176 mm1 disc
• Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers
• Spitzer-IRAC GLIMPSE of high mass protostellar objects II - SED modelling of a bonafide sample
• Detection of new methanol maser transitions associated with G358.93-0.03
• Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G358.931-0.030
• The Pointing System of the Herschel Space Observatory. Description, Calibration, Performance and Improvements
• The Relationship between Mid-Infrared and Sub-Millimetre Variability of Deeply Embedded Protostars
• Non-thermal desorption of complex organic molecules: Cosmic-ray sputtering of CH3OH embedded in CO2 ice
• A pilot survey of the binarity of Massive Young Stellar Objects with $K$ band adaptive optics
• Medium resolution near-infrared spectroscopy of Massive Young Stellar Objects
• On the episodic excursions of massive protostars in the Hertzsprung-Russell diagram
• A Catalog of 24um Sources Toward the Galactic Center
• Observational signatures of outbursting protostars -- II: Exploring a wide range of eruptive protostars
• InfraRed Astronomy Satellite Swarm Interferometry (IRASSI): Overview and Study Results
• Spectral Energy Distributions of High Mass Proto Stellar Objects - Evidence for High Accretion Rates
• Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639
• A highly variable methanol maser in G111.256-0.770