HD 4915: A Maunder Minimum Candidate

Abstract

We study the magnetic activity cycle of HD 4915 using the Ca ii HK emission line strengths measured by Keck I/High Resolution Echelle Spectrometer (HIRES) spectrograph. The star has been observed as a part of California Planet Search Program from 2006 to present. We note decreasing amplitude in the magnetic activity cycle, a pattern suggesting the star’s entry into a Magnetic Grand Minimum state, reminiscent of the Sun’s Maunder and Dalton Minima. We recommend further monitoring of the star to confirm the grand minimum nature of the dynamo, which would provide insight into the state of the Sun’s chromosphere and the global magnetic field during its grand minima. We also recommend continued observations of HK emission lines, and ground- or space-based photometric observations to estimate the sunspot coverage.