分类： 天文学 >> 天文学 提交时间： 2023-02-19
Teruyuki Hirano
Fei Dai
John H. Livingston
Yui Kasagi
Norio Narita
Hiroyuki Tako Ishikawa
Sascha Grziwa
Kristine W. F. Lam
Kohei Miyakawa
Luisa M. Serrano
Yuji Matsumoto
Eiichiro Kokubo
Tadahiro Kimura
Masahiro Ikoma
Joshua N. Winn
John P. Wisniewski
Hiroki Harakawa
Huan-Yu Teng
William D. Cochran
Akihiko Fukui
摘要： We report on the discovery of an Earth-sized transiting planet ($R_p=1.015\pm0.051\,R_\oplus$) in a $P=4.02$ day orbit around K2-415 (EPIC 211414619), an M5V star at 22 pc. The planet candidate was first identified by analyzing the light curve data by the K2 mission, and is here shown to exist in the most recent data from TESS. Combining the light curves with the data secured by our follow-up observations including high-resolution imaging and near infrared spectroscopy with IRD, we rule out false positive scenarios, finding a low false positive probability of $2\times 10^{-4}$. Based on IRD's radial velocities of K2-415, which were sparsely taken over three years, we obtain the planet mass of $3.0\pm 2.7\,M_\oplus$ ($M_p<7.5\,M_\oplus$ at $95\,\%$ confidence) for K2-415b. Being one of the lowest mass stars ($\approx 0.16\,M_\odot$) known to host an Earth-sized transiting planet, K2-415 will be an interesting target for further follow-up observations, including additional radial velocity monitoring and transit spectroscopy.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Emil Knudstrup
Simon H. Albrecht
Davide Gandolfi
Marcus L. Marcussen
Elisa Goffo
Luisa M. Serrano
Fei Dai
Seth Redfield
Teruyuki Hirano
Szilárd Csizmadia
William D. Cochran
Hans J. Deeg
Malcolm Fridlund
Kristine W. F. Lam
John H. Livingston
Rafael Luque
Norio Narita
Enric Palle
Carina M. Persson
Vincent Van Eylen
摘要： TOI-640 b is a hot, puffy Jupiter with a mass of $0.57 \pm 0.02$ M$_{\rm J}$ and radius of $1.72 \pm 0.05$ R$_{\rm J}$, orbiting a slightly evolved F-type star with a separation of $6.33^{+0.07}_{-0.06}$ R$_\star$. Through spectroscopic in-transit observations made with the HARPS spectrograph, we measured the Rossiter-McLaughlin effect, analysing both in-transit radial velocities and the distortion of the stellar spectral lines. From these observations, we find the host star to have a projected obliquity of $\lambda=184\pm3^\circ$. From the TESS light curve, we measured the stellar rotation period, allowing us to determine the stellar inclination, $i_\star=23^{+3\circ}_{-2}$, meaning we are viewing the star pole-on. Combining this with the orbital inclination allowed us to calculate the host star obliquity, $\psi=104\pm2^\circ$. TOI-640 b joins a group of planets orbiting over stellar poles within the range $80^\circ-125^\circ$. The origin of this orbital configuration is not well understood.
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