[论文解读] The GAPS Programme with HARPS-N at TNG XVI: Measurement of the Rossiter-McLaughlin effect of the transiting planetary systems HAT-P-3, HAT-P-12, HAT-P-22, WASP-39 and WASP-60

L. Mancini, M. Esposito+44 more|arXiv (Cornell University)|Feb 12, 2018

Stellar, planetary, and galactic studies参考文献 94被引用 10

一句话总结

本研究利用TNG望远镜上的HARPS-N获得的高精度径向速度数据，测量了五个凌星系外行星系统（HAT-P-3b、HAT-P-12b、HAT-P-22b、WASP-39b和WASP-60b）中的罗斯特-麦克劳林效应，以确定天空投影轨道倾角。研究发现WASP-60b处于逆行轨道（$\lambda = -129^\circ \pm 17^\circ$），而HAT-P-22b的真实错位角为$\psi = 24^\circ \pm 18^\circ$；此外，对WASP-60系统的重新评估表明，其恒星质量更大、年龄更轻，行星也更大、更热，与以往认知不同。

ABSTRACT

We characterised five transiting planetary systems (HAT-P-3, HAT-P-12, HAT-P-22, WASP-39 and WASP-60) and determined their sky-projected planet orbital obliquity through the measurement of the RM effect. We used HARPS-N high-precision radial velocity measurements, gathered during transit events, to measure the RM effect in the target systems and determine the sky-projected angle between the planetary orbital plane and the stellar equator. The characterisation of stellar atmospheric parameters was performed exploiting the HARPS-N spectra, using line equivalent width ratios, and spectral synthesis methods. Photometric parameters of the five transiting exoplanets were re-analysed through 17 new light curves, obtained with an array of medium-class telescopes, and other light curves from the literature. Survey-time-series photometric data were analysed for determining the rotation periods of the five stars and their spin inclination. From the analysis of the RM effect we derived a sky-projected obliquity of 21.2 degree, -54 degree, -2.1 degree, 0 degree and -129 degree for HAT-P-3b, HAT-P-12b, HAT-P-22b, WASP-39b and WASP-60b, respectively. The latter value indicates that WASP-60b is moving on a retrograde orbit. These values represent the first measurements of λfor the five exoplanetary systems under study. The stellar activity of HAT-P-22 indicates a rotation period of 28.7 days, which allowed us to estimate the true misalignment angle of HAT-P-22b, ψ=24 degree. The revision of the physical parameters of the five exoplanetary systems returned values that are fully compatible with those existing in the literature. The exception to this is the WASP-60 system, for which, based on higher quality spectroscopic and photometric data, we found a more massive and younger star and a larger and hotter planet.

研究动机与目标

• 利用罗斯特-麦克劳林效应，测量五个凌星系外行星系统的天空投影倾角（$\lambda$）。
• 研究行星轨道角动量与恒星自转矢量之间的对齐情况，以探究行星系统的形成与迁移机制。
• 利用高精度的光度与光谱数据，重新评估宿主恒星与行星的物理参数。
• 对于可测量恒星自转周期的系统，确定真实错位角（$\psi$）。
• 评估不完整光曲线对凌星参数估计的影响，特别是对WASP-60b的影响。

提出的方法

• 在凌星事件期间，利用HARPS-N的高精度径向速度测量检测罗斯特-麦克劳林效应。
• 通过HARPS-N光谱中的谱线等效宽度比值与光谱合成法，推导恒星大气参数。
• 结合文献数据，利用中型望远镜获得17条新的光度光曲线，重新分析凌星参数。
• 通过光度时间序列分析，测定恒星自转周期与自转倾角。
• 利用HAT-P-22的自转周期，从天空投影倾角（$\lambda$）计算真实错位角（$\psi$）。
• 采用Southworth（2012）方法对行星与恒星参数进行统一重新分析，以确保一致性。

实验结果

研究问题

• RQ1 HAT-P-3、HAT-P-12、HAT-P-22、WASP-39与WASP-60行星系统的天空投影倾角（$\lambda$）是多少？
• RQ2 WASP-60b的行星轨道是否为逆行？这对其形成历史有何含义？
• RQ3 HAT-P-22b的真实错位角（$\psi$）是多少？与天空投影倾角相比如何？
• RQ4 修订后的光度与光谱数据如何影响WASP-60系统物理参数的估计？
• RQ5 不完整的凌星光曲线在多大程度上会偏差行星与恒星参数的估计？

主要发现

• HAT-P-3b的天空投影倾角为$\lambda = 21.2^\circ \pm 8.7^\circ$，表明其与恒星自转方向近乎对齐。
• HAT-P-12b的天空投影倾角为$\lambda = -54^\circ{}^{+41^\circ}_{-13^\circ}$，表明存在显著的错位。
• HAT-P-22b的天空投影倾角为$\lambda = -2.1^\circ \pm 3.0^\circ$，与对齐一致，其真实错位角$\psi = 24^\circ \pm 18^\circ$由28.7 ± 0.4天的自转周期推导得出。
• WASP-39b的天空投影倾角为$\lambda = 0^\circ \pm 11^\circ$，表明近乎对齐。
• WASP-60b处于逆行轨道，$\lambda = -129^\circ \pm 17^\circ$；修订后的参数显示其恒星质量更大、年龄更轻，行星也更大、更热，与先前报告不同。
• WASP-60b的凌星深度比发现论文中深约33%，表明不完整光曲线可能导致光度参数估计出现显著误差。