HD 207897 b: A dense sub-Neptune transiting a nearby and bright K-type star

N. Heidari (1, 2, 3) , I. Boisse (3) , J. Orell-Miquel (4, 5) , G. Hébrard (6, 7) , L. Acuña (3) , N. C. Hara (8) , J. Lillo-Box (9) , J. D. Eastman (10) , L. Arnold (7, 11) , N. Astudillo-Defru (12) , V. Adibekyan (13, 14) , A. Bieryla (10) , X. Bonfils (15) , F. Bouchy (3) , T. Barclay (16, 17) , C. E. Brasseur (18) , S. Borgniet (19) , V. Bourrier (20) , L. Buchhave (21) , A. Behmard (22) , C. Beard (23) , N. M. Batalha (24) , B. Courcol (3) , P. Cortés-Zuleta (3) , K. Collins (10) , A. Carmona (15) , I. J. M. Crossfield (25) , A. Chontos (26) , X. Delfosse (15) , S. Dalal (6) , M. Deleuil (3) , O. D. S. Demangeon (27, 14) , R. F. Díaz (28) , X. Dumusque (29) , T. Daylan (30) , D. Dragomir (31) , E. Delgado Mena (27) , C. Dressing (32) , F. Dai (33) , P. A. Dalba (34) , D. Ehrenreich (20) , T. Forveille (15) , B. Fulton (35) , T. Fetherolf (34) , G. Gaisné (15) , S. Giacalone (32) , N. Riazi (1) , S. Hoyer (3) , M. J. Hobson (3) , A. W. Howard (22) , D. Huber (26) , M. L. Hill (34) , L. A. Hirsch (36) , H. Isaacson (32, 37) , J. Jenkins (38) , S. R. Kane (34) , F. Kiefer (6) , R. Luque (4, 5) , D. W. Latham (10) , J. Lubin (23) , T. Lopez (3) , O. Mousis (3) , C. Moutou (39) , G. Montagnier (7) , L. Mignon (15) , A. Mayo (32) , T. Močnik (40) , J. M. A. Murphy (24) , E. Palle (4, 5) , F. Pepe (20) , E. A. Petigura (41) , J. Rey (42) , G. Ricker (30) , P. Robertson (23) , A. Roy (18, 43) , R. A. Rubenzahl (22) , L. J. Rosenthal (22) , A. Santerne (3) , N. C. Santos (27, 14) , S. G. Sousa (27) , K. G. Stassun (27) , M. Stalport (29) , N. Scarsdale (24) , P. A. Strøm (6, 44) , S. Seager (30) , D. Segransan (29) , P. Tenenbaum (38) , R. Tronsgaard (45) , S. Udry (20) , R. Vanderspek (30) , F. Vakili (30) , J. Winn (46) , L. M. Weiss (26)

1 Shahid Beheshti University
2 OCA - Observatoire de la Côte d'Azur
3 LAM - Laboratoire d'Astrophysique de Marseille
4 IAC - Instituto de Astrofisica de Canarias
5 Departamento de Astrofísica [La laguna]
6 IAP - Institut d'Astrophysique de Paris
7 OHP - Observatoire de Haute-Provence
8 Geneva Observatory
9 ESAC - European Space Astronomy Centre
10 CfA - Harvard-Smithsonian Center for Astrophysics
11 CFHT - Canada-France-Hawaii Telescope Corporation
12 UCSC - Universidad Católica de la Santísima Concepción
13 CAUP - Centro de Astrofísica da Universidade do Porto
14 DFA/FCUP - Departamento de Física e Astronomia [Porto]
15 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
16 ARC-CREST - NASA Ames Research Center Cooperative for Research in Earth Science in Technology
17 UMBC - University of Maryland [Baltimore County]
18 NASA
19 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
20 UNIGE - Université de Genève = University of Geneva
21 DTU Space - National Space Institute [Lyngby]
22 CALTECH - California Institute of Technology
23 UC Irvine - University of California [Irvine]
24 UC Santa Cruz - University of California [Santa Cruz]
25 KU - University of Kansas [Lawrence]
26 UH - University of Hawai'i [Honolulu]
27 IASTRO - Instituto de Astrofísica e Ciências do Espaço
28 ECyT - Escuela de Ciencia y Tecnología [San Martín]
29 ObsGE - Observatoire Astronomique de l'Université de Genève
30 MIT - Massachusetts Institute of Technology
31 The University of New Mexico [Albuquerque]
32 UC Berkeley - University of California [Berkeley]
33 Division of Geological and Planetary Sciences [Pasadena]
34 UC Riverside - University of California [Riverside]
35 NExScI - NASA ExoPlanet Science Institute
36 Stanford University
37 USQ - University of Southern Queensland
38 ARC - NASA Ames Research Center
39 IRAP - Institut de recherche en astrophysique et planétologie
40 NOIRLab - NSF’s National Optical-Infrared Astronomy Research Laboratory
41 UCLA - University of California [Los Angeles]
42 Las Campanas Observatory, Carnegie Observatories
43 JHU - Johns Hopkins University
44 University of Warwick [Coventry]
45 DTU - Danmarks Tekniske Universitet = Technical University of Denmark
46 Princeton University

We present the discovery and characterization of a transiting sub-Neptune that orbits the nearby (28 pc) and bright (V = 8.37) K0V star HD 207897 (TOI-1611) with a 16.20-day period. This discovery is based on photometric measurements from the Transiting Exoplanet Survey Satellite mission and radial velocity (RV) observations from the SOPHIE, Automated Planet Finder, and HIRES high-precision spectrographs. We used EXOFASTv2 to model the parameters of the planet and its host star simultaneously, combining photometric and RV data to determine the planetary system parameters. We show that the planet has a radius of 2.50 ± 0.08 RE and a mass of either 14.4 ± 1.6 ME or 15.9 ± 1.6 ME with nearly equal probability. The two solutions correspond to two possibilities for the stellar activity period. The density accordingly is either 5.1 ± 0.7 g cm−3 or 5.5−0.7+0.8 g cm−3, making it one of the relatively rare dense sub-Neptunes. The existence of this dense planet at only 0.12 AU from its host star is unusual in the currently observed sub-Neptune (2 < RE < 4) population. The most likely scenario is that this planet has migrated to its current position.

Domaines: Astrophysique [astro-ph]

N. Heidari, I. Boisse, J. Orell-Miquel, G. Hébrard, L. Acuña, et al.. HD 207897 b: A dense sub-Neptune transiting a nearby and bright K-type star. Astronomy and Astrophysics - A&A, 2022, 658, pp.A176. ⟨10.1051/0004-6361/202141429⟩. ⟨hal-03580996⟩