15 new brown dwarfs in Orion OB1a/25 Ori group

By comparing them through a Bayesian method with low-mass stars (0.8<~M/M_{sun}_ <~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^+2.4^_-1.6_ percent low-mass stars classified as Classic T Tauri star and class II or evolved discs, against a fraction of 33.3^+10.8^_-9.8_ percent 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.