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Astron. Astrophys. 348, 800-804 (1999)


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A search for variability in brown dwarfs and L dwarfs

C.A.L. Bailer-Jones and R. Mundt

Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany

Received 16 April 1999 / Accepted 15 June 1999

Abstract

We have undertaken a differential photometric I band search for variability in three Pleiades brown dwarfs and three very low mass field L dwarfs. Analysis of the resultant time series for the Pleiades brown dwarfs (Teide 1, Calar 3, Roque 11) gives no evidence for variability (above 99% confidence) greater than 0.05 mags in any of these objects on timescales between 25 minutes and 27 hours. Time series of two of the L dwarfs, 2MASSW J0913032+184150 and 2MASSW J1146345+223053, are also consistent with no intrinsic variability (no significant variability above 0.07 mags for 30 mins [FORMULA] 126 hours, and above 0.025 mags for 30 mins [FORMULA] 75 hours, for the two objects respectively). However, the L dwarf 2MASSW J1145572+231730 shows evidence for variability of amplitude 0.04 magnitudes with a tentative period of about 7 hours. It is therefore interesting that Kirkpatrick et al. (1999) report an H[FORMULA] emission line of 4.2 Å equivalent width for this star: If our detection is confirmed as a rotation period, it would support the link between rotation and H[FORMULA] emission in very low mass stars.

Key words: methods: observational – stars: activity – stars: individual: 2MASSW J1145572+231730 – stars: low-mass, brown dwarfs – stars: rotation

Send offprint requests to: Coryn Bailer-Jones (calj@mpia-hd.mpg.de)

© European Southern Observatory (ESO) 1999

Online publication: August 13, 199

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