KIC 2831097 - A 2-year orbital-period RR Lyrae binary candidate

Abstract

We report the discovery of a new Kepler first-overtone RR Lyrae pulsator, KIC 2831097. The pulsation shows large, 0.1 d amplitude, systematic phase variations that can be interpreted as light travel-time effect caused by orbital motion in a binary system, superimposed on a linear pulsation-period decrease. The assumed eccentric (e=0.47) orbit with the period of approximately 2 yr is the shortest among the non-eclipsing RR Lyrae binary candidates. The binary model gives a lowest estimate for the mass of the companion of 8.4 M_Sun, that places it among black hole candidates. Beside the first-overtone pulsation, numerous additional non-radial pulsation frequencies were also identified. We detected an ~47-d Blazhko-like irregular light-curve modulation.

arXiv commentAccepted for publication in MNRAS Letters. 5 pages, 5 figures, 2 tables

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• First results on RR Lyrae stars with the TESS space telescope: untangling the connections between mode content, colors and distances
• A Bayesian Analysis of Physical Parameters for 783 Kepler (Near-)Contact Binaries: Extreme-Mass-Ratio Systems and a New Mass Ratio versus Period Lower Limit
• Studies of RR Lyrae Variables in Binary Systems. I.: Evidence of a Trimodal Companion Mass Distribution
• The contact binary VW Cephei revisited: surface activity and period variation
• A cautionary tale of interpreting O-C diagrams: period instability in a classical RR Lyr Star Z CVn mimicking as a distant companion
• A Radial Velocity Search for Binary RR Lyrae Variables
• Time series analysis of bright TESS RRc stars: Additional modes, phase variations and more
• Large amplitude change in spot-induced rotational modulation of the Kepler Ap star KIC 2569073
• Spectroscopic and photometric time series of the bright RRc star T Sex
• To Grow Old and Peculiar: A Survey of Anomalous Variable Stars in M80 and Age Determination using K2 and Gaia
• The elusive chase for the first RR Lyr star in a binary system: the case of KIC 2831097
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• IY Lyr: A Thick-Disk first-overtone RR Lyrae Star with a Possible Neutron Star Companion