On the Evolution of Rotational Modulation Amplitude in Solar-mass Main-sequence Stars
On the Evolution of Rotational Modulation Amplitude in Solar-mass Main-sequence Stars
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DOI：
10.3847/1538-4357/ac7527
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发表时间：
2022-06
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影响因子：
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通讯作者：
K. Masuda
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作者：
K. Masuda
利用McQuillan等人的Prot和Rper，研究了开普勒观测到的4000颗类日主序星的自转周期Prot和光度调制幅度Rper之间的关系，来自LAMOST DR 6的有效温度T eff和来自Gaia EDR 3的视差数据。正如在以前的工作中所建议的，我们发现由对流周转时间τ c或Rossby数Ro标度的P rot可以很好地预测R per：R per plateaus，在相对通量为0.2 <$Ro/Ro <$$> 0.4的情况下约为1%，并且在0.4 <$Ro/Ro <$$> 0.8的情况下随着Ro的增加而急剧衰减，其中Ro <$代表太阳的Ro。在后一种情况下，我们发现dlnRper/dlnRo为−4.5至−2.5，尽管该值对弱调制的检测偏差敏感，并且可能取决于其他参数，包括T eff和表面金属度。现有的X射线和Ca ii H和K通量数据也显示了Ro/Ro = 0.4的跃迁，表明所有这些跃迁都有相同的物理起源。我们还发现，随着Ro的增加，Rper的快速减小导致Ro/Ro = 0.6的较暗开普勒星的旋转调制被掩盖在光度噪声之下。这种效应使McQuillan等人的样品中检测到的最长P rot成为T eff的函数，并模糊了被提议在Ro/Ro = 1附近设置的失速降旋的特征。
We investigate the relation between rotation periods P rot and photometric modulation amplitudes R per for ≈4000 Sun-like main-sequence stars observed by Kepler, using P rot and R per from McQuillan et al., effective temperature T eff from LAMOST DR6, and parallax data from Gaia EDR3. As has been suggested in previous works, we find that P rot scaled by the convective turnover time τ c, or the Rossby number Ro, serves as a good predictor of R per: R per plateaus at around 1% in relative flux for 0.2 ≲ Ro/Ro⊙ ≲ 0.4, and decays steeply with increasing Ro for 0.4 ≲ Ro/Ro⊙ ≲ 0.8, where Ro⊙ denotes Ro of the Sun. In the latter regime we find dlnRper/dlnRo ∼ −4.5 to −2.5, although the value is sensitive to detection bias against weak modulation and may depend on other parameters including T eff and surface metallicity. The existing X-ray and Ca ii H and K flux data also show transitions at Ro/Ro⊙ ∼ 0.4, suggesting that all these transitions share the same physical origin. We also find that the rapid decrease of R per with increasing Ro causes rotational modulation of fainter Kepler stars with Ro/Ro⊙ ≳ 0.6 to be buried under the photometric noise. This effect sets the longest P rot detected in the McQuillan et al. sample as a function of T eff and obscures the signature of stalled spin down that has been proposed to set in around Ro/Ro⊙ ∼ 1.