Long-term Study of Changes in the Orbital Periods of 18 Eclipsing SW Sextantis Stars

TL;DR

This study analyzes 17 years of eclipse timing data for 18 SW Sextantis stars, revealing diverse long-term orbital period behaviors and recent rapid period decreases in two systems, highlighting the complexity of their orbital evolution.

Contribution

It provides the first extensive long-term eclipse timing analysis of multiple SW Sex stars, identifying varied period change behaviors and recent rapid period decreases.

Findings

Systems show increasing, decreasing, or oscillating orbital periods.

Rapid period decreases observed in SW Sex and RW Tri during 2017-2018.

Long-term data insufficient for definitive trend conclusions.

Abstract

SW Sex stars are an informal sub-class of eclipsing nova-like cataclysmic variables. We report 934 new eclipse times measured over the past 17 years for HS 0728+6738 (V482 Cam), SW Sex, DW UMa, HS 0129+2933 (TT Tri), V1315 Aql, PX And, HS 0455+8315, HS 0220+0603, BP Lyn, BH Lyn, LX Ser, UU Aqr, V1776 Cyg, RW Tri, 1RXS J064434.5+334451, AC Cnc, V363 Aur, and BT Mon. When combined with published eclipse times going back in some cases many decades, we show that these binary systems exhibit a range of behaviors, including increasing, decreasing, and possibly oscillating orbital periods. Nevertheless, the duration of these observations is still not long enough to be able to make reliable quantitative statements about their long term behaviors. In addition to these long term trends, we also observed rapid and unusual decreases in the orbital periods of SW Sex and RW Tri during 2017 and 2018, respectively.