On the apsidal motion of BP Vulpeculae

TL;DR

This study analyzes the long-term apsidal motion of BP Vulpeculae, resolving previous contradictions by extending observational data over five decades, confirming prograde motion consistent with theoretical models.

Contribution

It provides the first BV light curve and a long-term analysis, demonstrating that BP Vulpeculae's apsidal motion is prograde and aligns with theoretical predictions.

Findings

Apsidal motion period is approximately 365 years.

The internal structure constant matches theoretical expectations.

Apsidal motion is confirmed to be prograde.

Abstract

BP Vulpeculae is a bright eclipsing binary system showing apsidal motion. It was found in an earlier study that it shows retrograde apsidal motion which contradicts theory. In this paper we present the first $BV$ light curve of the system and its light curve solution as well as seven new times of the minima from the years 1959-1963. This way we could expanded the baseline of the investigation to five decades. Based on this longer baseline we concluded that the apsidal motion is prograde agreeing with the theoretical expectations and its period is about 365 years and the determined internal structure constant is close to the theoretically expected one.