2023PASJ...75..446L

We report the results of intensive monitoring of the variability in the Hα line for two F-type stars, τ Boo and υ And, over the last four years 2019-2022, in order to investigate their stellar magnetic activity. The 4 yr Hα line intensity data taken with the 1.88 m reflector at the Okayama Branch Office, Subaru Telescope, shows the existence of a possible ∼123 d magnetic activity cycle for τ Boo. The result of the Hα variability as another tracer of the magnetic activity on the chromosphere is consistent with previous studies of the Ca II H&K line and suggests that the magnetic activity cycle persists in τ Boo. For υ And, we suggest a quadratic long-term trend in the Hα variability. Meanwhile, the short-term monitoring shows no significant period corresponding to specific variations likely induced by their hot Jupiter in both cases (≈3.31 and 4.62 d, respectively). In this Hα observation, we could not find any signature of the star-planet magnetic interaction. It is speculated that the detected magnetic activity variability of the two F-type stars is related to the stellar intrinsic dynamo.