利用ESPRESSO开展GJ 570 A和GJ 783 A型K矮星的EPRV星震学研究：与三维对流模拟存在矛盾的经验模式振幅标度关系
EPRV Asteroseismology of the K dwarfs GJ 570 A and GJ 783 A with ESPRESSO. Empirical mode-amplitude scaling in tension with 3D convection simulations
AI总结：
本研究利用ESPRESSO开展GJ 570 A和GJ 783 A型K矮星的EPRV星震学研究，发现观测到的振荡振幅标度关系与三维对流模拟结果存在矛盾，揭示了对流-脉动耦合相关的缺失物理。
摘要：
K矮星中的类太阳振荡固有振幅较低，这使得在空间光度测量中难以探测。极高精度径向速度（EPRV）仪器的出现使得在中K型星 regime 中开展多普勒星震学研究成为可能，为检验模式激发与阻尼物理提供了新机遇。我们研究了振荡振幅随恒星参数的标度关系，并评估三维表面对流模拟是否能重现观测到的振幅行为。针对K矮星GJ 570 A（K4 V）和GJ 783 A（K2.5 V），我们分别获取了连续5个和6个夜晚的高 cadence ESPRESSO 径向速度时间序列。我们从加权功率谱中识别振荡模式，并在谱去卷积后通过正弦波拟合提取这些模式。峰值模式振幅通过高度平滑的功率谱测量得到。为了对比，我们开展了包含激发和阻尼率计算的三维辐射流体动力学模拟。我们为GJ 570 A测量了6个模式，为GJ 783 A测量了24个模式（$\ell=0$-$2$，以及GJ 783 A的$\ell=3$）。峰值径向模式振幅分别为$2.57 \pm 0.52\:{\rm cm\,s^{-1}}$和$4.90 \pm 0.81\:{\rm cm\,s^{-1}}$。这些结果支持从$\sim(L/M)^{0.7}$振幅标度向更陡峭的$\sim(L/M)^{1.5}$标度的转变，该转变发生在G/K矮星边界附近，朝向减小的$L/M$方向。相比之下，三维模拟预测K矮星的标度为$\sim(L/M)^{0.9}$，这揭示了观测与第一性原理对流模型之间的矛盾。EPRV星震学延伸至中K型星 regime，并揭示了我们的三维对流模拟无法重现的陡峭模式振幅标度。这种差异表明，我们在对流-脉动耦合的实现中存在缺失的物理机制，和/或所采用的建模假设存在局限性，这为进一步的理论研究提供了动力。
英文摘要：
Solar-like oscillations in K dwarfs have intrinsically low amplitudes, making them challenging to detect in space-based photometry. The advent of Extremely Precise Radial Velocity (EPRV) instrumentation enables Doppler asteroseismology in the mid-K regime, providing a new opportunity to test mode-excitation and damping physics. We investigate the scaling of oscillation amplitudes with stellar parameters and assess whether 3D surface convection simulations reproduce the observed amplitude behavior. High-cadence ESPRESSO radial-velocity time series were obtained over five and six consecutive nights for the K dwarfs GJ 570 A (K4 V) and GJ 783 A (K2.5 V), respectively. We identified oscillation modes from weighted power spectra and extracted them via sine-wave fitting following spectral deconvolution. Peak mode amplitudes were measured from heavily smoothed power spectra. For comparison, we performed 3D radiative-hydrodynamical simulations including excitation and damping-rate calculations. We measured 6 modes for GJ 570 A and 24 for GJ 783 A ($\ell=0$-$2$, and $\ell=3$ for GJ 783 A). The peak radial-mode amplitudes are $2.57 \pm 0.52\:{\rm cm\,s^{-1}}$ and $4.90 \pm 0.81\:{\rm cm\,s^{-1}}$, respectively. These results support a transition from an $\sim(L/M)^{0.7}$ amplitude scaling to a steeper $\sim(L/M)^{1.5}$ scaling, occurring near the G/K-dwarf boundary toward decreasing $L/M$. In contrast, 3D simulations predict an $\sim(L/M)^{0.9}$ scaling for K dwarfs, revealing tension between observations and first-principles convection models. EPRV asteroseismology extends into the mid-K regime and exposes a steep mode-amplitude scaling that our 3D convection simulations do not reproduce. This discrepancy points to missing physics in our implementation of convection-pulsation coupling and/or limitations in the adopted modeling assumptions, motivating further theoretical investigation.
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