Koen, Chris2013-12-032013-12-032013Koen, C. (2013). Multicolour time series photometry of three periodic ultracool dwarfs. Monthly Notices of the Royal Astronomical Society, 429(1): 652–6600035-8711http://hdl.handle.net/10566/897Photometry in I, or contemporaneously in I and R, of the known variable ultracool dwarfs Kelu-1 and 2MASS J11553952−3727350 is presented. The nature of the variability of Kelu-1 appears to evolve on time-scales of a day or less. Both the period and amplitude of the variability of 2MASS J11553952−3727350 have changed substantially since publication of earlier observations of the object. DENIS 1454−6604 is a new variable ultracool dwarf, with persistent and prominent brightness modulations at a period of 2.6 h.en© 2013 copyright Oxford University Press. This file may be freely used for educational purposes, as long as it is not altered in any way. Acknowledgement of the authors and the source is required.Stars: low-mass, brown dwarfsStars: variables: generalStars: individual: Kelu-1Stars: individual: 2MASS J11553952-3727350Stars: individual: DENIS-P J145407.8-640447Article