分类： 天文学 >> 天文学 提交时间： 2023-02-19
Billy Edwards
Quentin Changeat
Angelos Tsiaras
Kai Hou Yip
Ahmed F. Al-Refaie
Lara Anisman
Michelle F. Bieger
Amelie Gressier
Sho Shibata
Nour Skaf
Jeroen Bouwman
James Y-K. Cho
Masahiro Ikoma
Olivia Venot
Ingo Waldmann
Pierre-Olivier Lagage
Giovanna Tinetti
摘要： We present the analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation which our retrievals attribute to molecular species. Among these, we use Bayesian Hierarchical Modelling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet's mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass-metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H$^-$ opacity. We suggest that the general lack of trends seen across this population study could be due to i) the insufficient spectral coverage offered by HST WFC3 G141, ii) the lack of a simple trend across the whole population, iii) the essentially random nature of the target selection for this study or iv) a combination of all the above. We set out how we can learn from this vast dataset going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as JWST, Twinkle and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection.
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.
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