与ESPRESSO一起重访Proxima
Revisiting Proxima with ESPRESSO
摘要：
我们的目标是使用新的ESTERO光谱仪获得的独立测量结果来确认Proxima b的存在，并利用其提高的精度来改进行星参数。我们分析了2019年期间对Proxima进行的63次光谱ESTO观测。我们获得了径向速度测量与一个典型的径向速度光子噪声为26厘米/秒。我们对径向速度和交叉关联函数的半高宽的时间序列进行了联合MCMC分析，以模拟数据中存在的行星和恒星信号，应用高斯过程回归处理恒星活动。我们证实了在ESTERO数据中独立存在Proxima b。ESTRO数据本身显示Proxima b的周期为11.218 $\pm$ 0.029天，最小质量为1.29 $\pm$ 0.13 Me。在合并的数据集中，我们测量到周期为11.18427 $\pm$ 0.00070天，最小质量为1.173 $\pm$ 0.086 Me。我们没有发现恒星活动作为潜在原因的证据11.2天的信号我们发现了第二个短周期信号存在的一些证据，在5.15天，半振幅仅为40厘米/秒。如果造成的行星的同伴，它将对应于0.29 $\pm$ 0.08 Me. We发现，CCF的半高宽可以作为一个代理的亮度变化，其随时间的梯度可以用来成功地去趋势的径向速度数据的恒星活动的影响的一部分。在ESTERO数据中，由活动引起的径向速度信号显示出振幅朝向较红波长的趋势。使用摄谱仪红端测量的速度受活动的影响较小，这表明恒星活动是以斑点为主的。收集的数据不包括在短于50天的时间内质量超过0.6 Me的额外同伴的存在。
英文摘要：
We aim to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision. We analysed 63 spectroscopic ESPRESSO observations of Proxima taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26 cm/s. We ran a joint MCMC analysis on the time series of the radial velocity and full-width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with stellar activity. We confirm the presence of Proxima b independently in the ESPRESSO data. The ESPRESSO data on its own shows Proxima b at a period of 11.218 $\pm$ 0.029 days, with a minimum mass of 1.29 $\pm$ 0.13 Me. In the combined dataset we measure a period of 11.18427 $\pm$ 0.00070 days with a minimum mass of 1.173 $\pm$ 0.086 Me. We find no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of merely 40 cm/s. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 $\pm$ 0.08 Me. We find that the FWHM of the CCF can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the radial velocity data from part of the influence of stellar activity. The activity-induced radial velocity signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot-dominated. The data collected excludes the presence of extra companions with masses above 0.6 Me at periods shorter than 50 days.
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