V432 Per, a close binary star in poor thermal contact

Abstract

In a program instigated to understand close, possibly contact binary stars which appear to be in poor thermal contact, we have re-observed V432 Per both photometrically and spectroscopically. We conclude that the mass ratio is likely in the range q = 0.30–0.38, and the system clearly has a transit primary eclipse. The face of the less massive secondary towards the primary seems to be significantly hotter than expected. It was hoped that spectral line profiles would allow determination of this spot’s radius (rspot), but the low mass of the secondary precluded this. With the existing observations, it is impossible to say whether this system is a true contact binary (rspot 30 ◦ –90 ◦ ), is semidetached (rspot 90 ◦ –120 ◦ ) or is marginally detached (rspot 120 ◦ –150 ◦ ). However, while it may be marginally in physical contact, it is clearly in poor thermal contact. With its short period and marginal contact, this system merits further attention as a potential transitional species in binary-star evolution.