Complex magnetic topology and strong differential rotation on the low-mass T Tauri star V2247 Oph

TL;DR

This study reveals that the low-mass T Tauri star V2247 Oph has a complex magnetic topology and exhibits strong differential rotation, with variability observed over a week, which may influence its rapid rotation compared to higher-mass counterparts.

Contribution

First detailed magnetic field mapping of a low-mass T Tauri star showing complex topology and rapid variability, highlighting differences from more massive prototypical cTTSs.

Findings

Magnetic field is moderate in strength and highly complex.

Significant variability in spot and magnetic field distribution over one week.

Weak, localized emission suggests an accretion funnel footpoint.

Abstract

From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, we report the detection of Zeeman signatures on the low-mass classical TTauri star (cTTS) V2247Oph. Profile distortions and circular polarisation signatures detected in photospheric lines can be interpreted as caused by cool spots and magnetic regions at the surface of the star. The large-scale field is of moderate strength and highly complex; moreover, both the spot distribution and the magnetic field show significant variability on a timescale of only one week, as a likely result of strong differential rotation. Both properties make V2247Oph very different from the (more massive) prototypical cTTS BPTau; we speculate that this difference reflects the lower mass of V2247Oph. During our observations, V2247Oph was in a low-accretion state, with emission lines showing only weak levels of circular polarisation; we nevertheless find that excess emission apparently concentrates in a mid-latitude region of strong radial field, suggesting that it is the footpoint of an accretion funnel. The weaker and more complex field that we report on V2247Oph may share similarities with those of very-low-mass late-M dwarfs and potentially explain why low-mass cTTSs rotate on average faster than intermediate mass ones. These surprising results need confirmation from new independent data sets on V2247Oph and other similar low-mass cTTSs.