论文标题
罗斯比数量的全部和部分对流的星星
Rossby numbers of fully and partially convective stars
论文作者
论文摘要
我们通过使用恒星进化模型来研究理论对流周转时间（$τ_ {\ rm c} $）和Rossby数字（$ {\ rm ro} $）来研究恒星磁性活动，以获取前序列和主要序列。问题在于，通常确定$τ_ {\ rm c} $的规范场所（对流区基底以上的一半混合长度）失败了完全对流的恒星，并且在文献中对此无需一致。我们的计算是使用Aton Stellar Evolution Code进行的。我们将分析集中在完全和部分对流的恒星上，这些星星最近观察到缓慢旋转完全对流的恒星，其X射线排放与它们的Rossby数字相关，其方式与太阳能恒星相同，这表明磁场产生不需要速度线。我们调查了$τ_ {\ rm c} $在恒星半径上的行为，用于不同质量和年龄的星星。由于$ {\ rm ro} $取决于$τ_ {\ rm c} $，该$随着恒星半径的变化很大，我们使用理论结果来确定更好的径向位置，以便在该位置上计算完全对流的星星。使用我们的替代位置，我们在旋转 - 活动图中拟合了847星的样品（$ l _ {\ rm x}/l _ {\ rm bol} $ vers $ {\ rm ro} $）和两部分的powerlaw函数。我们的拟合参数与以前的工作相一致，表明具有$ {\ rm ro} $$ \ leq $$ {\ rm ro_ {sat}} $的星星分布在$ l _ {\ rm x}/lm _ {\ rm bol} $的饱和度附近，适用于$ rm rm rm rm rm rm rm rm rm rm rm rm rm rm rm rm rm rm rm rm rom} ro_ {sat}} $，$ l _ {\ rm x}/l _ {\ rm bol} $清楚地用$ {\ rm ro} $腐烂，指数为$ -2.4 \！\！\ pm \！0.1 $。
We investigate stellar magnetic activity from the theoretical point of view, by using stellar evolution models to calculate theoretical convective turnover times ($τ_{\rm c}$) and Rossby numbers (${\rm Ro}$) for pre-main-sequence and main-sequence stars. The problem is that the canonical place where $τ_{\rm c}$ is usually determined (half a mixing length above the base of the convective zone) fails for fully convective stars and there is no agreement on this in the literature. Our calculations were performed with the ATON stellar evolution code. We concentrated our analysis on fully and partially convective stars motivated by recent observations of slowly rotating fully convective stars, whose X-ray emissions correlate with their Rossby numbers in the same way as in solar-like stars, suggesting that the presence of a tachocline is not required for magnetic field generation. We investigate the behaviour of $τ_{\rm c}$ over the stellar radius for stars of different masses and ages. As ${\rm Ro}$ depends on $τ_{\rm c}$, which varies strongly with the stellar radius, we use our theoretical results to determine a better radial position at which to calculate it for fully convective stars. Using our alternative locations, we fit a sample of 847 stars in the rotation-activity diagram ($L_{\rm X}/L_{\rm bol}$ versus ${\rm Ro}$) with a two-part power-law function. Our fit parameters are consistent with previous work, showing that stars with ${\rm Ro}$$\leq$${\rm Ro_{sat}}$ are distributed around a saturation level in $L_{\rm X}/L_{\rm bol}$ and, for stars with ${\rm Ro}$$>$${\rm Ro_{sat}}$, $L_{\rm X}/L_{\rm bol}$ clearly decays with ${\rm Ro}$ with an exponent of $-2.4\!\pm\!0.1$.
