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We developed a grid of stellar rotation models for low-mass and solar-type classical T Tauri stars (CTTS; 0.3 M ⊙ < M * < 1.2 M ⊙). These models incorporate the star–disk interaction and magnetospheric ejections to investigate the evolution of the stellar rotation rate as a function of the mass of the star M *, the magnetic field (B *), and stellar wind ( M ̇ wind ). We compiled and determined stellar parameters for 208 CTTS, such as projected rotational velocity v sin (i) , mass accretion rate M ̇ acc , stellar mass M *, ages, and estimated rotational periods using Transiting Exoplanet Survey Satellite (TESS) data. We also estimated a representative value of the mass-loss rate for our sample using the [O i ] λ 6300 spectral line. Our results confirm that v sin (i) measurements in CTTS agree with the rotation rates provided by our spin models in the accretion-powered stellar winds picture. In addition, we used the approximate Bayesian computation technique to explore the connection between the model parameters and the observational properties of CTTS. We find that the evolution of v sin (i) with age might be regulated by variations in (1) the intensity of B * and (2) the fraction of the accretion flow ejected in magnetic winds, removing angular momentum from these systems. The youngest stars in our sample (∼1 Myr) show a median branching ratio M ̇ wind / M ̇ acc ∼ 0.16 and median B * ∼ 2000 G, in contrast to ∼0.01 and 1000 G, respectively, for stars with ages ≳3 Myr. [ABSTRACT FROM AUTHOR]

We present a study of 15 new brown dwarfs belonging to the ~7 Myr old 25 Orionis group and Orion OB1a subassociation with spectral types between M6 and M9 and estimated masses between ~0.07 and ~0.01 M⊙. By comparing them through a Bayesian method with low-mass stars (0.8 ≲ M/M⊙ ≲ 0.1) from previous works in the 25 Orionis group, we found statistically significant differences in the number fraction of classical T Tauri stars, Weak T Tauri stars, class II, evolved discs and purely photospheric emitters at both sides of the substellar mass limit. Particularly, we found a fraction of 3.9-1.6+2.4 per cent low-mass stars classified as Classic T Tauri star and class II or evolved discs, against a fraction of 33.3-9.8+10.8 per cent in the substellar mass domain. Our results support the suggested scenario in which the dissipation of discs is less efficient for decreasing mass of the central object. [ABSTRACT FROM AUTHOR]