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arXiv · 1504.05196

The number fraction of discs around brown dwarfs in Orion OB1a and the 25 Orionis group

Juan José Downes·Carlos Román-Zúñiga·Javier Ballesteros-Paredes·Cecilia Mateu·César Briceño·Jesús Hernández·Monika G. Petr-Gotzens·Nuria Calvet·Lee Hartmann·Karina Mauco
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Abstract

We present a study of 15 new brown dwarfs belonging to the $\sim7$ Myr old 25 Orionis group and Orion OB1a sub-association with spectral types between M6 and M9 and estimated masses between $\sim0.07$M$_\odot$ and $\sim0.01$ M$_\odot$. By comparing them through a Bayesian method with low mass stars ($0.8\lesssim$ M/M$_\odot\lesssim0.1$) 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 sub-stellar mass limit. Particularly we found a fraction of $3.9^{+2.4}_{-1.6}~\%$ low mass stars classified as CTTS and class II or evolved discs, against a fraction of $33.3^{+10.8}_{-9.8}~\%$ in the sub-stellar mass domain. Our results support the suggested scenario in which the dissipation of discs is less efficient for decreasing mass of the central object.

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Juan José Downes, Carlos Román-Zúñiga, Javier Ballesteros-Paredes, Cecilia Mateu, César Briceño, Jesús Hernández, Monika G. Petr-Gotzens, Nuria Calvet, Lee Hartmann, Karina Mauco. 2015-04-20. The number fraction of discs around brown dwarfs in Orion OB1a and the 25 Orionis group. https://arxiv.org/abs/1504.05196

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