Letter to the Editor

Magnetospheric magnetic reconnection in high-mass young stellar objects and its possible relation to methanol maser flares

¹ Mathematics and Mechanics Faculty, Saint-Petersburg State University, Saint-Petersburg 198504, Russia
² Ural Federal University, Ekaterinburg 620000, Russia
³ Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, China
⁴ Center for Astrophysics, Guangzhou University, Guangzhou 510006, China
⁵ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China

^⋆ Corresponding author: s.khaibrakhmanov@gmail.com

Received: 1 April 2025
Accepted: 14 June 2025

Abstract

Context. Maser emission is an inherent property of regions of high-mass star formation. Often the masers exhibit flares with duration times from several hours to tens of years. The nature of long-time flares can be explained by the model of episodic accretion. The origin of short-time flares is still uncertain.

Aims. Our goal is to elaborate on the physics of short-time maser flares in the region of high-mass star formation G33.641-0.228.

Methods. Based on an analysis of the observational data and predictions of the star formation theory, we hypothesise that the young star in G33.641-0.228 has a magnetosphere and is surrounded by the circumstellar disc threaded by a large-scale magnetic field. We use the equations of the standard accretion disc theory to analyse the interaction of the accretion flow with the magnetosphere. We propose that the boundary of the magnetosphere is a current sheet and analyse possible magnetic reconnection speeds, as well as estimate the corresponding amount and timescales of magnetic energy release.

Results. Our estimates show that the magnetospheric current sheet can exist in two states. In a quiescent state, the magnetic reconnection is slow, and the magnetic energy release is small. In a burst state, interchange and other magneto-hydrodynamic (MHD) instabilities cause turbulence generation in the flow. The magnetic reconnection switches to a fast regime driven by turbulence, and the energy release becomes significant compared to the luminosity of a protostar. The time of fast magnetic reconnection is ≲1 day, which is comparable to observed rise times of maser flares in G33.641-0.228.

Conclusions. Magnetic reconnection of stellar and disc magnetic fields near the magnetosphere can be a mechanism for short-time maser flares in G33.641-0.228 and similar objects. This process can be accompanied by X-ray flares; therefore, coordinated high-angular and high-time observations of maser flares, IR, and X-ray emission represent a promising new way of studying high-mass star formation.