Asteroseismology of KIC 8263801: Is It a Member of NGC 6866 and a Red Clump Star?

• Published in: The Astrophysical journal Vol. 866; no. 1; pp. 59 - 67
• Main Authors: Tang, Yanke, Basu, Sarbani, Davies, Guy R., Bellinger, Earl P., Gai, Ning
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 10.10.2018; IOP Publishing
• Subjects: Astrophysics; Diagnostic systems; Giant stars; Helium; Light curve; Quadrupoles; Red giant stars; Star clusters; Stars & galaxies; stars: evolution; stars: oscillations; stars: solar-type; Stellar age; Stellar evolution; Stellar seismology
• DOI: 10.3847/1538-4357/aadcf2
• ISSN: 0004-637X

We present an asteroseismic analysis of the Kepler light curve of KIC 8263801, a red-giant star in the open cluster NGC 6866 that has previously been reported to be a helium-burning red-clump (RC) star. We extracted the frequencies of the radial and quadrupole modes from its frequency power spectrum and determined its properties using a grid of evolutionary models constructed with MESA. The oscillation frequencies were calculated using the GYRE code and the surface term was corrected using the Ball & Gizon prescription. We find that the star has a mass of M/M = 1.793 0.072, age t = 1.48 0.21 Gyr, and radius R/R = 10.53 0.28. By analyzing the internal structure of the best-fitting model, we infer the evolutionary status of the star KIC 8263801 as being on the ascending part of the red-giant branch, and not on the RC. This result is verified using a purely asteroseismic diagnostic, the ϵc − Δ c diagram which can distinguish red-giant branch stars from red-clump stars. Finally, by comparing its age with NGC 6866 (t = 0.65 0.1 Gyr), we conclude that KIC 8263801 is not a member of this open cluster.