The sharpest view on the high-mass star-forming region S255IR. Near-InfraRed Adaptive Optics Imaging on the Outbursting Source NIRS3

Abstract

Massive stars have an impact on their surroundings from early in their formation until the end of their lives. However, very little is known about their formation. Episodic accretion may play a crucial role, but observations of these events have only been reported towards a handful of massive protostars. We aim to investigate the outburst event from the high-mass star-forming region S255IR where recently the protostar NIRS3 underwent an accretion outburst. We follow the evolution of this source both in photometry and morphology of its surroundings. Methods: We perform near-infrared adaptive optics observations on the S255IR central region using the Large Binocular Telescope in the K${}_{\mathrm{s}}$ broad-band and the H${}_2$ and Br$\gamma$ narrow-band filters with an angular resolution of $\sim0\farcs06$, close to the diffraction limit. We discover a new near-infrared knot north-east from NIRS3 that we interpret as a jet knot that was ejected during the last accretion outburst and observed in the radio regime as part of a follow-up after the outburst. We measure a mean tangential velocity for this knot of $450\pm 50\mathrm{km}{\mathrm{s}}^{-1}$. We analyse the continuum-subtracted images from H${}_2$ which traces jet shocked emission, and Br$\gamma$ which traces scattered light from a combination of accretion activity and UV radiation from the central massive protostar. We observe a significant decrease in flux at the location of NIRS3, with K=13.48\,mag being the absolute minimum in the historic series. Our observations strongly suggest a scenario where the episodic accretion is followed by an episodic ejection response in the near-infrared, as it was seen in the earlier radio follow-up. The 30 years of $\sim 2\mu \mathrm{m}$ photometry suggests that NIRS3 might have undergone another outburst in the late 1980s, being the first massive protostar with such evidence observed in the near-infrared.

Accepted for publication in Astronomy and Astrophysics. 10 pages, 8 figures

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Cited by in corpus (8)

• JWST Observations of Young protoStars (JOYS): overview of program and early results
• The Role of Thermal Instability in Accretion Outbursts in High-Mass Stars
• Fine structure and kinematics of the ionized and molecular gas in the jet and disk around S255IR NIRS3 from high resolution ALMA observations
• Near-Infrared Observations of Outflows and YSOs in the Massive Star-Forming Region AFGL 5180
• M17 MIR: A Massive Star is Forming via Episodic Mass Accretion
• Study of the high-mass star-forming region S255IR at various scales
• Evidence for protostellar jets as a population of hadronic gamma-ray sources
• Episodic accretion in high-mass star formation: An analysis of thermal instability for axially symmetric disks