Long-term photometry of the ultra-fast rotator LO Peg

摘要

LO Peg is a young main-sequence star of spectral type K3. With its equatorial rotation velocity of 65 km s–1 it is amongst the ultra-fast rotators. Its high equatorial rotation velocity and rapidly changing surface activity features make it an important object in terms of both stellar activity and the evolution of stellar rotation and angular momentum. Since its discovery as a variable star, it has mostly been subject to spectral surface mapping studies such as Doppler Imaging, while there have been very few photometric studies on it. This paper aims to present the first long-term photometric observations and its results covering the years between 2003 and 2009. The UBVR Johnson wide band photometric data showed that the surface activity structures of LO Peg vary in timescales changing between days and months, and parallel to this, the mean, maximum and minimum brightness and amplitudes change dramatically between years and sometimes even within the same observation season. Long-term changes in system brightness and colours, both characteristic features of active stars, were also seen in this ultra-fast young star. The active longitudes, which has a life time of ∼1.3 years and an activity cycle period of ∼4.8 years for LO Peg were estimated (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)