Modulated accretion in T Tauri star RY Tau -- stable MHD propeller or a planet at 0.2 AU?

Abstract

Planets are thought to form at the early stage of stellar evolution when the mass accretion is still ongoing. RY Tau is a T Tauri type star at the age of a few Myr, with accretion disc seen at high inclination, so that line of sight crosses both the wind and the accretion gas flows. In a long series of spectroscopic monitoring of the star in 2013-2020, we detected variations in H-alpha and NaI D absorptions at radial velocities of infall (accretion) and outflow (wind) with a period of about 22 days. The absorptions in the infalling and the outflowing gas streams vary in anti-phase: an increase of infall is accompanied by a decrease of outflow, and vice versa. These flip-flop oscillations retain phase over several years of observations. We suggest that this may result from the MHD processes at the disk-magnetosphere boundary in the propeller mode. Another possibility is that a massive planet modulates some processes in the disc and provides the observed effects. The period, if Keplerian, corresponds to a distance of 0.2 AU, which is close to the dust sublimation radius in this star. The presence of the putative planet may be confirmed by radial velocity measurements: expected amplitude is > 90 m/s if a planet mass is > 2 Mj.

arXiv comment7 pages, 12 figures, accepted for publication in MNRAS

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Cited by in corpus (7)

• A Census of the Low Accretors. I: The Catalog
• Time-Variable Jet Ejections from RW Aur A, RY Tau and DG Tau
• Monitoring inner regions in the RY Tau jet
• Density streams in the disc winds of Classical T Tauri stars
• Astrometric view of companions in the inner dust cavities of protoplanetary disks
• Potential sublimating exocomets around the young star PDS 70
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