Studying cool star magnetic activity gives an important insight into the stellar dynamo and its relationship with stellar properties, as well as allowing us to place the Sun's magnetism in the context of other stars. Only 61 Cyg A (K5V) and $\tau$ Boo (F8V) are currently known to have magnetic cycles like the Sun's, where the large-scale magnetic field polarity reverses in phase with the star's chromospheric activity cycles. ${\tau}$ Boo has a rapid $\sim$240 d magnetic cycle, and it is not yet clear whether this is related to the star's thin convection zone or if the dynamo is accelerated by interactions between ${\tau}$ Boo and its hot Jupiter. To shed light on this, we studied the magnetic activity of HD75332 (F7V) which has similar physical properties to ${\tau}$ Boo and does not appear to host a hot Jupiter. We characterized its long term chromospheric activity variability over 53 yrs and used Zeeman Doppler Imaging to reconstruct the large-scale surface magnetic field for 12 epochs between 2007 and 2019. Although we observe only one reversal of the large-scale magnetic dipole, our results suggest that HD75332 has a rapid $\sim$1.06 yr solar-like magnetic cycle where the magnetic field evolves in phase with its chromospheric activity. If a solar-like cycle is present, reversals of the large-scale radial field polarity are expected to occur at around activity cycle maxima. This would be similar to the rapid magnetic cycle observed for ${\tau}$ Boo, suggesting that rapid magnetic cycles may be intrinsic to late-F stars and related to their shallow convection zones.

中文翻译：

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HD 75332 的磁场和色球活动演化：在没有热木星的 F 星中的快速磁循环

研究冷恒星的磁活动可以深入了解恒星发电机及其与恒星特性的关系，并使我们能够将太阳的磁力置于其他恒星的背景中。目前已知只有 61 Cyg A (K5V) 和 $\tau$ Boo (F8V) 具有类似于太阳的磁循环，其中大规模磁场极性与恒星的色球活动循环同相反转。${\tau}$ Boo 有一个快速的 $\sim$240 d 磁循环，目前尚不清楚这是否与恒星的薄对流区有关，或者发电机是否因 ${\tau}$ Boo 之间的相互作用而加速还有它炽热的木星。为了阐明这一点，我们研究了 HD75332 (F7V) 的磁活动，它具有与 ${\tau}$ Boo 相似的物理特性，并且似乎没有承载热木星。我们表征了其 53 年来的长期色球活动变化，并使用塞曼多普勒成像重建了 2007 年至 2019 年间 12 个时期的大尺度表面磁场。虽然我们只观察到大尺度磁偶极子的一次逆转，但我们的结果表明HD75332 具有 1.06 年 1.06 美元的快速类似太阳的磁循环，其中磁场与其色球活动同相演变。如果存在类似太阳的周期，则预计在活动周期最大值附近会发生大规模径向场极性的逆转。这与观察到的 ${\tau}$ Boo 的快速磁循环相似，表明快速磁循环可能是晚 F 星所固有的，并且与它们的浅对流区有关。