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Observations of Ultracool dwarfs with ULTRACAM on the VLT: a search for weather

S. P. Littlefair·V. S. Dhillon·T. R. Marsh·T. Shahbaz·E. L. Martin
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Abstract

We present multi-colour photometry of four field ultracool dwarfs with the triple-beam photometer ultracam. Data were obtained simultaneously in the Sloan-g' band and a specially designed narrow-band NaI filter. The previously reported 1.8-hr period of Kelu-1 is here recovered in the g'-band, but the lack of any significant variability in the NaI light of this object precludes any conclusion as to the cause of the variability. 2MASS 2057-0252 and DENIS 1441-0945 show no convincing evidence for variability. 2MASS 1300+1912, on the other hand, shows good evidence for gradual trends in both bands at the 5% level. These trends are anti-correlated at a high level of significance, a result which is incompatible with models of starspot-induced variability. It would seem likely that dust cloud "weather" is responsible for the short-term variability in this object.

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S. P. Littlefair, V. S. Dhillon, T. R. Marsh, T. Shahbaz, E. L. Martin. 2006-05-09. Observations of Ultracool dwarfs with ULTRACAM on the VLT: a search for weather. https://doi.org/10.1111/j.1365-2966.2006.10523.x

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