论文题目：Detecting exoplanet transits with the next generation of X-ray telescopes

摘要：在x射线波段探测系外行星的掩食信号能够提供一个深入了解高能辐射对行星上层大气有何影响的窗口。然而，在x波段，恒星的亮度相对比较暗，这使得当前的x射线望远镜很难探测到系外行星的掩食信号。截至目前，只有一颗系外行星（HD~189733~b）具有x射线波段的掩食信号。在本研究中，我们评估了未来的x射线天文台对于探测更多系外行星的能力，主要集中在NewAthena-WFI和计划中的先进x射线成像卫星（proposed Advanced X-ray Imaging Satellite (AXIS)），这两个望远镜能够比当前的设备收集到更多的光子。我们检查了NASA系外行星档案库中所有的掩食系外行星系统，并且搜集了每一颗宿主恒星x射线波段的流量的观测值或计算值。然后，我们预测了这两颗x射线望远镜的恒星计数率，且给出了仿真的光变曲线，利用null-hypothesis的检验辨认了前15颗掩食行星通过潜在的探测显著性。我们也评估了掩食信号探测的几率，当视x射线半径被放大，由于大气的逃逸，发现会有超过5个系外行星系统在4西格玛的水平下被探测到。最后，我们注意到宿主恒星的日冕温度（影响x射线掩食信号的形状）也会显著影响到我们探测到行星的能力。

摘要英文：Detecting exoplanet transits at X-ray wavelengths would provide a window into the effects of high energy irradiation on the upper atmospheres of planets. However, stars are relatively dim in the X-ray, making exoplanet transit detections difficult with current X-ray telescopes. To date, only one exoplanet (HD~189733~b) has an X-ray transit detection. In this study, we investigate the capability of future X-ray observatories to detect more exoplanet transits, focusing on both the NewAthena-WFI instrument and the proposed Advanced X-ray Imaging Satellite (AXIS), which provide more light-collecting power than current instruments. We examined all the transiting exoplanet systems in the NASA Exoplanet Archive and gathered X-ray flux measurements or estimates for each host star. We then predicted the stellar count rates for both AXIS and NewAthena and simulated light curves, using null-hypothesis testing to identify the top 15 transiting planets ranked by potential detection significance. We also evaluate transit detection probabilities when the apparent X-ray radius is enlarged due to atmospheric escape, finding that ≥5 of these planetary systems may be detectable on the >4σ level in this scenario. Finally, we note that the assumed host star coronal temperature, which affects the shape of an X-ray transit, can also significantly affect our ability to detect the planet.

链接：2408.06417 (arxiv.org)