Pulsations and Period Variations of the $\delta$ Scuti Star AN Lyncis in a possible three-body system

Abstract

Observations for the $\delta$ Scuti star AN Lyn have been made between 2008 and 2016 with the 85-cm telescope at Xinglong station of National Astronomical Observatories of China, the 84-cm telescope at SPM Observatory of Mexico and the Nanshan One meter Wide field Telescope of Xinjiang Observatory of China. Data in $V$ in 50 nights and in $R$ in 34 nights are obtained in total. The bi-site observations from both Xinglong Station and SPM Observatory in 2014 are analyzed with Fourier Decomposition to detect pulsation frequencies. Two independent frequencies are resolved, including one non-radial mode. A number of stellar model tracks are constructed with the MESA code and the fit of frequencies leads to the best-fit model with the stellar mass of $M=1.70\pm 0.05{\mathrm{M}}_{\odot }$ , the metallicity abundance of $Z=0.020\pm 0.001$, the age of $1.33\pm 0.01$ billion years and the period change rate $1/P\cdot \mathrm{d}P/\mathrm{d}t=1.06\times 10^{-9}\mathrm{y}{\mathrm{r}}^{-1}$, locating the star at the evolutionary stage close to the terminal age main sequence (TAMS). The O-C diagram provides the period change rate of $1/P\cdot \mathrm{d}P/\mathrm{d}t=4.5(8)\times 10^{-7}\mathrm{y}{\mathrm{r}}^{-1}$. However, the period change rate calculated from the models is smaller in two orders than the one derived from the O-C diagram. Together with the sinusoidal function signature, the period variations are regarded to be dominated by the light-travel time effect of the orbital motion of a three-body system with two low-luminosity components, rather than the stellar evolutionary effect.

14 pages, 8 tables, 17 figures, accepted by mnras

References in corpus (4)

• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Gaia Data Release 1: Catalogue validation