BO Pegasi: A candidate on the breaking stage of the TRO cycle

Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, PR China National Astronomical Observatories, Chinese Academy of Science (NAOCAS) United Laboratory of Optical Astronomy, Chinese Academy of Science (ULOAC)

Corresponding author: qsb@netease.com

Received: 5 June 2001
Accepted: 28 January 2002

Abstract

A detailed period study of the short-period () close binary system, BO Peg, is presented based on the analysis of its O–C curve. It is found that the orbital period shows a continuous decrease with a rate dP/dt  days/year while it undergoes a possible small-amplitude oscillation. If the period oscillation is cyclic, it can be explained either by the light-time effect via the presence of an unseen third body or by the magnetic activity cycle of the secondary component. The continuous period decrease suggests a secular mass transfer from the more massive to the less massive component, which is in agreement with the near-contact configuration with a lobe-filling primary (Yamasaki & Okazaki [CITE]). These observations, as seen in RT Scl, FT Lup, TT Her, RS Ind, and V388 Cyg, are consistent with the Thermal Relaxation Oscillation (TRO) theory in that the primary component is transferring mass to the secondary in the broken-contact phase. To satisfy such a decrease in the orbital period, a conservative mass transfer rate (with no magnetic effect) would be of the order of dM/dt .