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

Abstract

ABSTRACT 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, Hβ and Hα 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.