Long-term, orbital, and rapid variations of the Be star V923 Aql = HD 183656

TL;DR

This study analyzes long-term cyclic variations, binary nature, and rapid changes in the Be star V923 Aql, supporting the one-armed disk oscillation model and confirming its binary system properties.

Contribution

It provides a comprehensive long-term observational analysis of V923 Aql, confirming its binary nature and supporting the one-armed disk oscillation model with detailed cycle characterization.

Findings

Cyclic variations with 1800-3000 day periods observed over seven cycles.

Binary system confirmed with a 214.716-day period.

Presence of rapid light and spectral changes, nature uncertain.

Abstract

We present the latest results of a long-term observational project aimed at observing, collecting from the literature, and homogenising the light, colour, and spectral variations of the well-known emission-line Be star V923 Aql. Our analysis of these parameters confirms that all of the observables exhibit cyclic changes with variable cycle length between about 1800 and 3000 days, so far documented for seven consecutive cycles. We show that these variations can be qualitatively understood within the framework of the model of one-armed oscillation of the circumstellar disk, with a wave of increased density and prograde revolution in space. We confirm the binary nature of the object with a 214.716 day period and estimate the probable system properties. We also confirm the presence of rapid light, and likely also spectral changes. However, we cannot provide any firm conclusions regarding their nature. A quantitative modelling study of long-term changes is planned as a follow-up to this work.