Extrasolar Planets

A Super-Earth Orbiting Near The Inner Edge Of The Habitable Zone Around The M4.5-dwarf Ross 508

By Keith Cowing
astro-ph.EP
May 24, 2022
Filed under
A Super-Earth Orbiting Near The Inner Edge Of The Habitable Zone Around The M4.5-dwarf Ross 508
Planets with masses below 10 M⊕ around stars with 2800 K ≤ Teff ≤ 4000 K. Ross 508 b is located near the runaway greenhouse limit as the inner edge of a habitable zone for an Earth-sized aquaplanet around M dwarfs (Kopparapu et al. 2017). The error bar of Ross 508’s insolation is based on the 3σ limit on its eccentricity.

We report the near-infrared radial-velocity (RV) discovery of a super-Earth planet on a 10.77-day orbit around the M4.5 dwarf Ross 508 (Jmag=9.1).

Using precision RVs from the Subaru Telescope IRD (InfraRed Doppler) instrument, we derive a semi-amplitude of 3.92+0.60−0.58 ms−1, corresponding to a planet with a minimum mass msini=4.00+0.53−0.55 M⊕. We find no evidence of significant signals at the detected period in spectroscopic stellar activity indicators or MEarth photometry. The planet, Ross 508 b, has a semimajor-axis of 0.05366+0.00056−0.00049 au.

This gives an orbit-averaged insolation of ≈1.4 times the Earth’s value, placing Ross 508 b near the inner edge of its star’s habitable zone. We have explored the possibility that the planet has a high eccentricity and its host is accompanied by an additional unconfirmed companion on a wide orbit. Our discovery demonstrates that the near-infrared RV search can play a crucial role to find a low-mass planet around cool M dwarfs like Ross 508.

Hiroki Harakawa, Takuya Takarada, Yui Kasagi, Teruyuki Hirano, Takayuki Kotani, Masayuki Kuzuhara, Masashi Omiya, Hajime Kawahara, Akihiko Fukui, Yasunori Hori, Hiroyuki Tako Ishikawa, Masahiro Ogihara, John Livingston, Timothy D. Brandt, Thayne Currie, Wako Aoki, Charles A. Beichman, Thomas Henning, Klaus Hodapp, Masato Ishizuka, Hideyuki Izumiura, Shane Jacobson, Markus Janson, Eiji Kambe, Takanori Kodama, Eiichiro Kokubo, Mihoko Konishi, Vigneshwaran Krishnamurthy, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Jungmi Kwon, Yuji Matsumoto, Michael W. McElwain, Koyu Mitsui, Takao Nakagawa, Norio Narita, Jun Nishikawa, Stevanus K. Nugroho, Eugene Serabyn, Takuma Serizawa, Aoi Takahashi, Akitoshi Ueda, Taichi Uyama, Sébastien Vievard, Ji Wang, John Wisniewski, Motohide Tamura, Bun’ei Sato

Comments: Accepted for publication in PASJ (May 23, 2022)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2205.11986 [astro-ph.EP] (or arXiv:2205.11986v1 [astro-ph.EP] for this version)
Submission history
From: Takayuki Kotani
[v1] Tue, 24 May 2022 11:34:00 UTC (14,675 KB)
https://arxiv.org/abs/2205.11986
Astrobiology

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