Our paper on KIC 2831097 has been published in Astronomy & Astrophysics
The professional–amateur collaboration led by GEOS investigated the RR Lyrae variable KIC 2831097, once considered a strong candidate for belonging to a binary system.
Using spectroscopic observations with the FIES instrument at the Nordic Optical Telescope and complementary photometry from Gaia, TESS, and ground-based campaigns, researchers aimed to confirm binarity through radial velocity measurements.
The results, however, ruled out the light-time travel effect hypothesis: both quadrature observations showed the same mean radial velocity of –203 km/s. Instead, the study revealed that KIC 2831097 is a single, high-velocity, metal-poor RRc star in the Galactic halo, exhibiting a weak Blazhko effect and intriguing period changes that suggest evolutionary processes rather than orbital motion.
Lessons Learned and Future Work
This research underscores that regular oscillations in O–C diagrams do not necessarily indicate light-time travel effects. The Blazhko effect in KIC 2831097 is extremely small (0.004 d), and amateur observations proved invaluable for disentangling long-term variations.
The study also highlights subtle contamination issues in TESS photometry and sudden period changes in RRc variables, advancing theoretical understanding of why binary RR Lyrae stars are so rare.
The chase for such systems continues, and new maxima of KIC 2831097 are urgently needed to track its evolving period—avoiding large observational gaps to prevent ambiguity in cycle counts.