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We report the results of intensive monitoring of the variability in theH$\alpha$ line for two F-type stars, $\tau$ Boo and $\upsilon$ And, during thelast four years 2019-2022, in order to investigate their stellar magneticactivity. The 4-year H$\alpha$ line intensity data taken with the 1.88-mreflector at Okayama Branch Office, Subaru Telescope, shows the existence of apossible $\sim$ 123-day magnetic activity cycle of $\tau$ Boo. The result ofthe H$\alpha$ variability as another tracer of the magnetic activity on thechromosphere is consistent with previous studies of the Ca II H&K line andsuggests that the magnetic activity cycle is persisted in $\tau$ Boo. For$\upsilon$ And, we suggest a quadratic long-term trend in the H$\alpha$variability. Meanwhile, the short-term monitoring shows no significant periodcorresponding to specific variations likely induced by their hot-Jupiter inboth cases ($\approx$ 3.31 and 4.62 days, respectively). In this H$\alpha$observation, we could not find any signature of the Star-Planet MagneticInteraction. It is speculated that the detected magnetic activity variabilityof the two F-type stars is related to the stellar intrinsic dynamo.

publications of the astronomical society of japan

Magnetic activity variability from H$\alpha$ line intensive monitoring  for two F-type stars having a hot-Jupiter, $\tau$ Bootis A and $\upsilon$  Andromedae A