The Transiting Exoplanet Survey Satellite mission was designed to find transiting planets around bright, nearby stars. Here we present the detection and mass measurement of a small, short-period ($\approx\,4$\,days) transiting planet around the bright ($V=7.9$), solar-type star HD 86226 (TOI-652, TIC 22221375), previously known to host a long-period ($\sim$1600 days) giant planet. HD 86226c (TOI-652.01) has a radius of $2.16\pm0.08$ $R_{\oplus}$ and a mass of 7.25$^{+1.19}_{-1.12}$ $M_{\oplus}$ based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is $3.97$ g cm$^{-3}$, which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well-constrained. Given the host star brightness, planet period, and location of the planet near both the ``radius gap'' and the ``hot Neptune desert'', HD 86226c is an interesting candidate for transmission spectroscopy to further refine its composition.

中文翻译：

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苔丝揭示了一颗已知的长周期巨行星的短周期亚海王星同胞 (HD 86226c)

过境系外行星勘测卫星任务旨在寻找附近明亮恒星周围的过境行星。在这里，我们展示了一颗小型、短周期（$\approx\,4$\,days）在明亮（$V=7.9$）太阳型恒星 HD 86226（TOI-652 , TIC 22221375)，以前已知拥有一颗长期（$\sim$1600 天）的巨行星。HD 86226c (TOI-652.01) 的半径为 $2.16\pm0.08$ $R_{\oplus}$，质量为 7.25$^{+1.19}_{-1.12}$ $M_{\oplus}$存档和新的径向速度数据。我们还更新了周期较长、未知的凌日行星的参数，发现它不像之前报告的那样偏心和质量较小。凌日行星的密度为 $3.97$ g cm$^{-3}$，这足以表明该行星至少有一个小的挥发性包层，但岩石、铁和水的质量分数并没有得到很好的约束。考虑到宿主恒星的亮度、行星周期以及行星在“半径间隙”和“热海王星沙漠”附近的位置，HD 86226c 是一个有趣的透射光谱候选者，可以进一步完善其组成。