We report the discovery of HATS-71b, a transiting gas giant planet on a P = 3.7955 day orbit around a G = 15.35 mag M3 dwarf star. HATS-71 is the coolest M dwarf star known to host a hot Jupiter. The loss of light during transits is 4.7%, more than any other confirmed transiting planet system. The planet was identified as a candidate by the ground-based HATSouth transit survey. It was confirmed using ground-based photometry, spectroscopy, and imaging, as well as space-based photometry from the NASA TESS mission (TIC 234523599). Combining all of these data, and utilizing Gaia DR2, we find that the planet has a radius of $1.080 \pm 0.016 R_J$ and mass of $0.45 \pm 0.24 M_J$ (95% confidence upper limit of $0.81 M_J$ ), while the star has a mass of $0.569 \pm^{0.042}_{0.069}\,M_\odot$ and a radius of $0.5161\pm^{0.0053}_{0.0099}\,R_\odot$. The Gaia DR2 data show that HATS-71 lies near the binary main sequence in the Hertzsprung-Russell diagram, suggesting that there may be an unresolved stellar binary companion. All of the available data is well fitted by a model in which there is a secondary star of mass $0.24 M_\odot$, although we caution that at present there is no direct spectroscopic or imaging evidence for such a companion. Even if there does exist such a stellar companion, the radius and mass of the planet would be only marginally different from the values we have calculated under the assumption that the star is single.

中文翻译：

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HATS-71b：一颗巨大的行星在 TESS 扇区 1 中穿过 M3 矮星

我们报告了 HATS-71b 的发现，这是一颗在 P = 3.7955 天轨道上围绕 G = 15.35 mag M3 矮星运行的凌日气态巨行星。HATS-71 是已知拥有热木星的最酷的 M 矮星。凌日期间的光损失为 4.7%，比任何其他已确认的凌日行星系统都要多。这颗行星被基于地面的 HATSouth 过境调查确定为候选者。使用地面光度法、光谱学和成像以及 NASA TESS 任务 (TIC 234523599) 的天基光度法证实了这一点。结合所有这些数据，并利用 Gaia DR2，我们发现这颗行星的半径为 $1.080 \pm 0.016 R_J$，质量为 $0.45 \pm 0.24 M_J$（95% 置信上限为 $0.81 M_J$），而恒星质量为 $0.569 \pm^{0.042}_{0.069}\,M_\odot$，半径为 $0.5161\pm^{0.0053}_{0.0099}\,R_\odot$。Gaia DR2 数据显示 HATS-71 位于 Hertzsprung-Russell 图中的双星主序带附近，表明可能存在未解析的双星伴星。所有可用数据都被一个模型拟合得很好，其中有一颗质量为 $0.24 M_\odot$ 的次生星，尽管我们警告说，目前没有直接的光谱或成像证据表明这样的伴星。即使确实存在这样的恒星伴星，行星的半径和质量也与我们在假设恒星是单颗的情况下计算出的值略有不同。所有可用数据都被一个模型拟合得很好，其中有一颗质量为 $0.24 M_\odot$ 的次生星，尽管我们警告说，目前没有直接的光谱或成像证据表明这样的伴星。即使确实存在这样的恒星伴星，行星的半径和质量也与我们在假设恒星是单颗的情况下计算出的值略有不同。所有可用数据都被一个模型拟合得很好，其中有一颗质量为 $0.24 M_\odot$ 的次生星，尽管我们警告说，目前没有直接的光谱或成像证据表明这样的伴星。即使确实存在这样的恒星伴星，行星的半径和质量也与我们在假设恒星是单颗的情况下计算出的值略有不同。