An extensive search for rapid optical variability in ultracool dwarfs
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Date
2013
Authors
Journal Title
Journal ISSN
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Publisher
Oxford University Press
Abstract
In this paper, a summary of optical time-series photometry of 125 ultracool dwarfs is given.
The observing strategy was to monitor each object continuously for 2–3 h in order to ascertain
whether itwas rapidly variable. Many of the targetswere observed atmultiple epochs, to follow
up possible short time-scale variability, or to test for slow brightness changes on longer timescales.
The 353 data sets obtained contain nearly 22 000 individual measurements. Optical
(IC) magnitudes, accurate to roughly 0.1–0.2 mag, were derived for 21 objects for which
there is no optical photometry in the literature. It is shown that photometry is affected by
variable seeing in a large percentage of the time-series observations. Since this could give the
appearance of variability intrinsic to the objects, magnitudes are modelled as functions of both
time and seeing. Several ultracool dwarfs which had not been monitored before are variable,
according to certain model-fitting criteria. A number of objects with multi-epoch observations
appear to be variable on longer time-scales. Since testing for variability is far from being
straightforward, the time-series data are made available so that interested readers can perform
their own analyses.
Description
Keywords
Techniques: photometric, Brown dwarf, Stars: low-mass
Citation
Koen, C. (2013). An extensive search for rapid optical variability in ultracool dwarfs. Monthly Notices of the Royal Astronomical Society. 428: 2824–2839