An investigation of the magnetic activity of HD 134319 based on TESS photometry and ground-based spectroscopy

We present an analysis of the starspot properties and chromospheric activity on HD 134319 using high-precision photometry by Transiting Exoplanet Survey Satellite (TESS) in sectors 14-16 (T1) and 21-23 (T2) and high-resolution spectroscopy by the ELODIE spectrograph on 1.93-m telescope of Observatoire de Haute-Provence (OHP/ELODIE) and the High Resolution Echelle Spectrometer on Keck 10-m telescope of W. M. Keck Observatory (Keck/HIRES) during the years 1995-2013. We applied a two-spot model with generalized Lomb-Scargle (GLS) periodogram determined period of P = 4.436391 +/- 0.00137 d to model chunks sliding over TESS light curve. We also measured the relative equivalent widths of Ca ii H and K, H beta and H alpha emissions by subtracting the overall spectrum from individual spectra. It was found that a two-spot configuration, namely a primary, slowly evolving and long-lasting spot (P) plus a secondary, rapidly evolving spot (S), was capable of explaining the data, although the actual starspot distribution cannot be derived from the collected data. Despite the spot radius-latitude degeneracy revealed in the best-fitting solutions, a sudden alternation between P and S radii followed by a gradual decrease of S in T1 and a decrease of both P and S from T1 to T2 were significant, corresponding to the evolution of magnetic activity. In addition, S revealed rotation and an oscillatory longitude migration synchronized to P in T1, but had a much larger migration than P in T2. This might indicate the evolution of the internal magnetic configuration. Chromospheric activity indicators were found to be tightly correlated with each other and revealed rotational modulation as well as a long-term decrease of emissions, implying the existence and evolution of magnetic activity on HD 134319.

Automated summary

In this study, the starspot properties and chromospheric activity on HD 134319 were analyzed using TESS photometry data, ELODIE spectroscopy data, and Keck/HIRES spectroscopy data. The results revealed the presence of a slowly evolving and long-lasting primary spot and a rapidly evolving secondary spot, with decreasing radii over time, corresponding to the evolution of magnetic activity. Additionally, the chromospheric activity indicators showed tight correlations, indicating the existence and evolution of magnetic activity on HD 134319.