High amplitude δ Scuti star BO Lyn with evidence of a late A-type companion in an elliptical orbit

We present 145 times of light maximum for high amplitude δ Scuti star BO Lyn based on several sky surveys (CRTS, DASCH, NSVS, OMC and SuperWASP) and our photometric observations. Combining with the data in literature, a total of 179 times of light maximum are used to analyze the O − C diagram of BO Lyn. We find that it can be described by an upward parabolic component and a periodic variation with a period of 34.5 ± 0.1 yr. The latter could be caused by the light travel time effect as a result of an additional companion orbiting in a highly elliptical orbit ( e = 0.64 ± 0.03). Our study indicates that the companion’s luminosity cannot be ignored, and it should be a late A-type main-sequence star. The long-term period change of BO Lyn is also detected, and its value, 1.52 ± 0.26 × 10 −3 d Myr −1 , is consistent with evolutionary models. We suggest that more spectroscopic and photometric observations are needed in the future to confirm the nature of the BO Lyn system.