Letter to the Editor

Do accretion-powered stellar winds help spin down T Tauri stars?

¹ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
² Department of Earth Sciences, University of Hawai’i at Mānoa, Honolulu, Hawai’i 96822, USA
³ SETI Institute, 339 Bernardo Ave., Suite 200, Mountain View, CA 94043, USA
⁴ Visiting Fellow, School of Physics, UNSW Science, Kensington, NSW 2052, Australia
⁵ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA

^⋆ Corresponding author: lukasg90@unet.univie.ac.at

Received: 12 January 2025
Accepted: 3 April 2025

Abstract

How T Tauri stars remain slowly rotating while still accreting material is a long-standing puzzle. Current models suggest that these stars may lose angular momentum through magnetospheric ejections (MEs) of disk material and accretion-powered stellar winds (APSWs). The individual contribution of each mechanism to the stellar spin evolution, however, is also unclear. We explore how these two scenarios could be distinguished by applying stellar spin models to near-term observations. We produced synthetic stellar populations of accreting Class II stars with spreads in the parameters governing the spin-down processes and find that an APSW strongly affects the ratio of the disk truncation radius to the co-rotation radius, ℛ = R_t/R_co. The ME and APSW scenarios are distinguished to a high degree of confidence when at least N_crit ≳ 250 stars have values measured for ℛ. Newly developed light curve analysis methods enable the measuring of ℛ for enough stars to distinguish the spin-down scenarios and will be important in the course of upcoming observing campaigns.