TypeSU Ursae MajorisEclipsing binary systemsSU Ursae Majoris-type variables are characterized by the presence of two types of outbursts called "normal" and "super-outbursts". Normal, short outbursts are similar to those of UGSS stars, while super-outbursts are brighter by 2 mag., are more than five times longer (wider), and occur several times less frequently. During super-outbursts the light curves show superposed periodic oscillations (super-humps), their periods being close to the orbital ones and amplitudes being about 0.2-0.3 mag. in V. Orbital periods are shorter than 0.1 days; companions are of dM spectral type.Eclipsing binary systems. These are binary systems with orbital planes so close to the observer's line of sight (the inclination of the orbital plane to the plane orthogonal to the line of sight is close to 90 deg.) that the components periodically eclipse each other. Consequently, the observer finds changes of the apparent combined brightness of the system with the period coincident with that of the components' orbital motion.AAVSO Alert 351-5/471: September 20, 2012 Drs. Boris Gaensicke (Warwick University), Joseph Patterson (Columbia University, Center for Backyard Astrophysics), and Arne Henden (AAVSO), on behalf of a consortium of 16 astronomers, have requested the help of AAVSO observers in monitoring the ~40 cataclysmic variables in the table below in support of Hubble Space Telescope observations in the coming months. The HST COS (Cosmic Origins Spectrograph) will be carrying out far-ultraviolet spectroscopy of ~40 CVs sequentially, with the aim to measure the temperatures, atmospheric compositions, rotation rates, and eventually masses of their white dwarfs.The primary purpose of the monitoring is to know whether each target is in quiescence immediately prior to the observation window; if it is in outburst it will be too bright for the HST instrumentation. Based on the information supplied by the AAVSO the HST scheduling team will make the decision (usually) the evening before the scheduled observing time as to whether to go forward with the HST observations.
Hills Observatory: 1 January 2013 to 30 March 2020