The hierarchical triple nature of the former red nova precursor candidate KIC 9832227

Abstract

We revisit the issue of period variation of the recently claimed red nova precursor candidate KIC 9832227. By using the data gathered during the main mission of the Kepler satellite, and data collected by ground-based wide-field surveys and other monitoring programs (such as ASAS-SN), we find that the currently available timing data strongly support a model consisting of the known W UMa binary and a distant low-mass companion with an orbital period of ∼13.5 years. The period of the W UMa component exhibits a linear period decrease at a rate of (1.10 ± 0.05) × 10−6 days per year, within the range of many other similar systems. This rate of decrease is several orders of magnitude lower than that of V1309 Sco, the first (and so far the only) well-established binary precursor of a nova observed a few years before the outburst. The high-fidelity fit of the timing data and the conformity of the derived minimum mass of (0.38 ± 0.02) M⊙ of the outer companion from these data with the limit posed by the spectroscopic non-detection of this component are in agreement with the suggested hierarchical nature of this system.