High-speed photometry of the eclipsing polar UZ Fornacis

¹ South African Astronomical Observatory (SAAO), PO Box 9, Observatory 7935, Cape Town, South Africa
e-mail: khangalezn@saao.ac.za
² Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa

Received: 7 August 2018
Accepted: 21 November 2018

Abstract

We present 33 new mid-eclipse times spanning approximately eight years of the eclipsing polar UZ Fornacis. We have used our new observations to test the two-planet model previously proposed to explain the variations in its eclipse times measured over the past ~35 yr. We find that the proposed model does indeed follow the general trend of the new eclipse times, however, there are significant departures. In order to accommodate the new eclipse times, the two-planet model requires that one or both of the planets require highly eccentric orbits, that is, e ≥ 0.4. Such multiple planet orbits are considered to be unstable. Whilst our new observations are consistent with two cyclic variations as previously predicted, significant residuals remain. We conclude that either additional cyclic terms, possibly associated with more planets, or other mechanisms, such as the Applegate mechanism are contributing to the eclipse time variations. Further long-term monitoring is required.