Letter to the Editor
Pulsating young brown dwarfs
1
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: palla@arcetri.astro.it
2
CRAL (UMR 5574 CNRS), École Normale Supérieure, 69364 Lyon Cedex 07, France e-mail: ibaraffe@ens-lyon.fr
3
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Brandenburg, Germany
Received:
4
November
2004
Accepted:
30
January
2005
We present the results of a nonadiabatic, linear stability analysis
of models of very low-mass stars (VLMSs) and brown dwarfs (BDs) during the
deuterium burning phase in the center. We find unstable fundamental modes
with periods varying between ~5 h for a 0.1 
star and ~1 h
for a 0.02 BD. The growth time of the instability decreases with
decreasing mass and remains well below the deuterium burning time scale
in the mass range considered (0.1–0.02 ).
These results are robust against variations of the
relevant input physics in the evolutionary models. We identify
possible candidates for pulsational variability among known VLMSs and BDs in
nearby star forming regions whose location in the HR diagram falls within
or close to the boundary of the instability strip. Finally, we discuss the
possibility that the variability observed in a few objects with periods of
~1 h can be interpreted in terms of pulsation.
Key words: stars: low-mass, brown dwarfs / stars: pulsation / stars: HR diagram
© ESO, 2005