New Insights Into the Nature of the Eclipsing System V609 Aquilae

TL;DR

This study provides detailed photometric analysis of the V609 Aquilae system, revealing its extreme brightness variations, orbital parameters, and evidence of period decrease due to mass transfer, challenging previous classifications of the system.

Contribution

It offers the first detailed photometric and period analysis of V609 Aquilae, showing its primary overfills its Roche lobe and exhibits a long-term period decrease, unlike earlier studies.

Findings

Deep primary eclipses of 1.04 magnitudes observed

Long-term period decrease of 7.75e-8 days/year detected

Primary star overfills its Roche lobe, contrary to NCB classification

Abstract

A photometric study of the Near Contact Binary (NCB) system V609 Aql reveals it to be the westernmost star of a close double, with brightness variations and implied parameters more extreme than those derived in an earlier photographic study, in which images of the variable and companion were almost certainly blended. The system's brightness variations exhibit deep primary eclipses ($\delta$ V = 1.04) and secondary eclipses ($\delta$ V = 0.44) matched to a model fit with a derived orbital inclination of i = 84.8$\pm$0.2 degrees and estimated component spectral types of F8-F9 and K2-K3. The primary overfills its Roche lobe in the optimum eclipse solution, inconsistent with the definition of NCBs. Period changes in the system are studied from 23 published times of light minimum and 21 newly-established values: 18 from examination of archival Harvard plates, and 3 from ASAS data and new CCD observations. O-C variations from 1891 to 2007 exhibit a long-term parabolic trend indicative of a period decrease, dP/dt = -(7.75$\pm$1.39) x 10^-8 d/yr, corresponding to mass transfer to the secondary of (6.5$pm$1.2) x 10^-8 SM/yr. Superposed variations may indicate fluctuations in the mass flow. The system is estimated to be ~513 pc distant.