V717 Andromedae: An Active Low Mass Ratio Contact Binary

TL;DR

V717 Andromedae is analyzed as an extreme low mass ratio contact binary with $q\approx0.197$ and high inclination $i\approx84.5^{\circ}$, showing a moderate fillout of $f\approx27\%$ and nearly equal component temperatures. Using multi-band photometry and the Wilson-Devinney model, the authors derive absolute parameters including $M_1\approx1.00\,M_{\odot}$ and $M_2\approx0.197\,M_{\odot}$, with a orbital separation $A\approx2.13\,R_{\odot}$ and a period $P\approx0.31736$ d; the period shows no significant long-term change over ~17 years. Spectroscopic indicators from LAMOST reveal Ca II infrared triplet line filling, signaling chromospheric activity, while theoretical orbital-stability analysis based on $q_{inst}$ suggests the system is dynamically stable and not a current merger candidate. The work highlights the coexistence of strong magnetic activity with long-term orbital stability in an extreme low mass ratio contact binary and emphasizes need for ongoing monitoring to catch potential future evolution.

Abstract

Multi-band photometric analysis of the contact binary V717 Andromedae (V717 And) is presented. The system is found to be an extreme low mass ratio system (q = 0.197) with high inclination (i = 84.5 deg), moderate degree of contact (27%) and near equal temperatures of the components. Period analysis of survey photometry spanning over 6300 days reveals no significant change. Although the system does not demonstrate a significant O'Connell effect there are a number of other markers strongly suggesting the system is chromospherically active. Orbital analysis indicates that the system is stable and not a merger candidate.

Figures (4)

• Figure 1: Period of V717 And spanning over 6300 days. Black line = Line of best fit. Estimates from various surveys as per colour coded data points.
• Figure 2: The critical portion of the mass ratio search grid from q=0.16 to q=0.22. The residual between the observed and fitted light curves has been normalised to the minimum residual at q=0.197
• Figure 3: Observed and modelled light curves for V 717 And. The blue curve shows $B$-band, green, $V$-band, and red, $R$-band; the purple curve shows the Check Star. Black lines represent the WD modelled light curves for each band. The curves have been shifted vertically for clarity.
• Figure 4: Filling of the two main ($\lambda$8542 and $\lambda$8663) CaII IRT lines. The orange lines represent the flux of V717 And and the purple lines represent the flux of the template star