An ultra-short-period super-Earth with an extremely high density and an outer companion

John H Livingston; Davide Gandolfi; Alessandro A Trani; Mahesh Herath; Oscar Barragán; Artie Hatzes; Rafael Luque; Akihiko Fukui; Grzegorz Nowak; Enric Palle; Coel Hellier; Malcolm Fridlund; Jerome de Leon; Teruyuki Hirano; Norio Narita; Simon Albrecht; Fei Dai; Hans Deeg; Vincent Van Eylen; Judith Korth; Motohide Tamura

doi:10.1038/s41598-024-76490-y

An ultra-short-period super-Earth with an extremely high density and an outer companion

Sci Rep. 2024 Nov 8;14(1):27219. doi: 10.1038/s41598-024-76490-y.

Authors

John H Livingston^{1

2

3}, Davide Gandolfi⁴, Alessandro A Trani^{5

6

7}, Mahesh Herath^{8

9}, Oscar Barragán¹⁰, Artie Hatzes¹¹, Rafael Luque¹², Akihiko Fukui¹³, Grzegorz Nowak^{14

15

16}, Enric Palle^{15

16}, Coel Hellier¹⁷, Malcolm Fridlund¹⁸, Jerome de Leon¹³, Teruyuki Hirano^{19

20

21}, Norio Narita¹³, Simon Albrecht²², Fei Dai^{23

24

25}, Hans Deeg^{15

16}, Vincent Van Eylen²⁶, Judith Korth²⁷, Motohide Tamura^{19

20

28}

Affiliations

¹ Astrobiology Center, NINS, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan. [email protected].
² National Astronomical Observatory of Japan, NINS, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan. [email protected].
³ Astronomical Science Program, Graduate University for Advanced Studies, SOKENDAI, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588, Japan. [email protected].
⁴ Dipartimento di Fisica, Universitá di Torino, via P. Giuria 1, 10125, Turin, Italy.
⁵ Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, 2100, Copenhagen, Denmark.
⁶ School of Science, Research Center for the Early Universe, The University of Tokyo, Tokyo, 113-0033, Japan.
⁷ Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan.
⁸ Trottier Space Institute, McGill University, Montreal, QC, H3A 2A7, Canada.
⁹ Department of Earth and Planetary Science, McGill University, 3450 Rue University, Montreal, QC, H3A 0E8, Canada.
¹⁰ Department of Physics, Sub-department of Astrophysics, University of Oxford, Oxford, OX1 3RH, UK.
¹¹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778, Tautenberg, Germany.
¹² Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, 60637, USA.
¹³ Komaba Institute for Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902, Japan.
¹⁴ Faculty of Physics, Astronomy and Informatics, Institute of Astronomy, Nicolaus Copernicus University, Grudzia̧dzka 5, 87-100, Toruń, Poland.
¹⁵ Instituto de Astrofísica de Canarias, C. Vía Láctea S/N, 38205, La Laguna, Tenerife, Spain.
¹⁶ Dept. de Astrofísica, Universidad de La Laguna, 38206, La Laguna, Tenerife, Spain.
¹⁷ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK.
¹⁸ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92, Onsala, Sweden.
¹⁹ Astrobiology Center, NINS, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan.
²⁰ National Astronomical Observatory of Japan, NINS, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan.
²¹ Astronomical Science Program, Graduate University for Advanced Studies, SOKENDAI, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588, Japan.
²² Department of Physics and Astronomy, Stellar Astrophysics Centre, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark.
²³ Institute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA.
²⁴ Division of Geological and Planetary Sciences, 1200 E California Blvd, Pasadena, CA, 91125, USA.
²⁵ Department of Astronomy, California Institute of Technology, Pasadena, CA, 91125, USA.
²⁶ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK.
²⁷ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 118, 22100, Lund, Sweden.
²⁸ Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.

Abstract

We present the discovery and characterization of a new multi-planetary system around the Sun-like star K2-360 (EPIC 201595106). K2-360 was first identified in K2 photometry as the host of an ultra-short-period (USP) planet candidate with a period of 0.88 d. We obtained follow-up transit photometry, confirming the star as the host of the signal. High precision radial velocity measurements from HARPS and HARPS-N confirm the transiting USP planet and reveal the existence of an outer (non-transiting) planet with an orbital period of $\sim$ 10 d. We measure a mass of $7.67 \pm 0.75$ $M_{\oplus}$ and a radius of $1.57 \pm 0.08$ $R_{\oplus}$ for the transiting planet, yielding a high mean density of $11 \pm 2$ g ${cm}^{- 3}$ , making it the densest well-characterized USP super-Earth discovered to date. We measure a minimum mass of $15.2 \pm 1.8$ $M_{\oplus}$ for the outer planet, and explore a migration formation pathway via the von Zeipel-Kozai-Lidov (ZKL) mechanism and tidal dissipation.

Abstract

Grants and funding