Long Term Orbital Behavior of Eclipsing SW Sextantis Stars (Abstract)

Volume 46 number 2 (2018)

David Boyd

5 Silver Lane, West Challow, Wantage OX12 9TX, United Kingdom; davidboyd@orion.me.uk

Abstract

(Abstract only) In 2006, encouraged by Boris Gaensicke, I began a long-term project to investigate the orbital behavior of the 18 brightest eclipsing SW Sex stars. These are novalike CVs in which the high rate of mass transfer between the main sequence secondary star and the white dwarf primary via an accretion disc maintains the system in a persistent bright state. The initial aims of the project were to establish accurate ephemerides for these stars and to check if any of them deviated from a linear ephemeris. At the 100th Spring Meeting of the AAVSO in Boston in May 2011 I presented the results of the first five years of the project, which combined new measurements of eclipse times with previously published observations. At that time, the majority of the stars appeared to be behaving consistently with linear ephemerides. However, five stars indicated possible cyclical variation in their orbital periods and three more were clearly not following linear ephemerides. I now have a further seven years of eclipse observations on these stars and it is time to revisit these earlier conclusions. It seems that linear ephemerides are no longer the most common option. Something is happening to upset the regular orbital behavior in several of these systems.