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Three planets transiting the evolved star EPIC 249893012 : A hot 8.8-M super-Earth and two warm 14.7 and 10.2-M sub-Neptunes

Hidalgo, D. ; Pallé, E. ; Alonso, R. ; Gandolfi, D. ; Nowak, G. ; Luque, R. ; Hirano, T. ; Justesen, A. B. ; Cochran, W. D. and Barragán, O. , et al. (2020) In Astronomy and Astrophysics 636.
Abstract

We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC 249893012, a G8 IV-V evolved star (M = 1.05 ± 0.05 M, R = 1.71 ± 0.04 R, Teff = 5430 ± 85 K). The star is just leaving the main sequence. We combined K2 photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES high-precision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of 3.5949-0.0007+0.0007 days, a mass of 8.75-1.08+1.09 M, and a radius of 1.95-0.08+0.09 R, the inner... (More)

We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC 249893012, a G8 IV-V evolved star (M = 1.05 ± 0.05 M, R = 1.71 ± 0.04 R, Teff = 5430 ± 85 K). The star is just leaving the main sequence. We combined K2 photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES high-precision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of 3.5949-0.0007+0.0007 days, a mass of 8.75-1.08+1.09 M, and a radius of 1.95-0.08+0.09 R, the inner planet b is compatible with nickel-iron core and a silicate mantle (ρb = 6.39-1.04+1.19 g cm-3). Planets c and d with orbital periods of 15.624-0.001+0.001 and 35.747-0.005+0.005 days, respectively, have masses and radii of 14.67-1.89+1,84 M and 3.67-0.14+0.17 R and 10.18-2.42+2.46 M and 3.94-0.12+0.13 R, respectively, yielding a mean density of 1.62-0.29+0.30 and 0.91-0.23+0.25 g cm-3, respectively. The radius of planet b lies in the transition region between rocky and gaseous planets, but its density is consistent with a rocky composition. Its semimajor axis and the corresponding photoevaporation levels to which the planet has been exposed might explain its measured density today. In contrast, the densities and semimajor axes of planets c and d suggest a very thick atmosphere. The singularity of this system, which orbits a slightly evolved star that is just leaving the main sequence, makes it a good candidate for a deeper study from a dynamical point of view.

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publishing date
type
Contribution to journal
publication status
published
keywords
Planetary systems, Planets and satellites: detection, Planets and satellites: fundamental parameters, Techniques: photometric, Techniques: radial velocities
in
Astronomy and Astrophysics
volume
636
article number
A89
publisher
EDP Sciences
external identifiers
  • scopus:85084414220
ISSN
0004-6361
DOI
10.1051/0004-6361/201937080
language
English
LU publication?
no
additional info
Publisher Copyright: © ESO 2020.
id
963e5391-1c47-4b86-a9b6-2d9b79b4033c
date added to LUP
2023-02-02 09:54:49
date last changed
2023-02-21 10:37:10
@article{963e5391-1c47-4b86-a9b6-2d9b79b4033c,
  abstract     = {{<p>We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC 249893012, a G8 IV-V evolved star (M = 1.05 ± 0.05 M, R = 1.71 ± 0.04 R, T<sub>eff</sub> = 5430 ± 85 K). The star is just leaving the main sequence. We combined K2 photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES high-precision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of 3.5949<sub>-0.0007</sub><sup>+0.0007</sup> days, a mass of 8.75<sub>-1.08</sub><sup>+1.09</sup> M, and a radius of 1.95<sub>-0.08</sub><sup>+0.09</sup> R, the inner planet b is compatible with nickel-iron core and a silicate mantle (ρ<sub>b</sub> = 6.39<sub>-1.04</sub><sup>+1.19</sup> g cm<sup>-3</sup>). Planets c and d with orbital periods of 15.624<sub>-0.001</sub><sup>+0.001</sup> and 35.747<sub>-0.005</sub><sup>+0.005</sup> days, respectively, have masses and radii of 14.67<sub>-1.89</sub><sup>+1,84</sup> M and 3.67<sub>-0.14</sub><sup>+0.17</sup> R and 10.18<sub>-2.42</sub><sup>+2.46</sup> M and 3.94<sub>-0.12</sub><sup>+0.13</sup> R, respectively, yielding a mean density of 1.62<sub>-0.29</sub><sup>+0.30</sup> and 0.91<sub>-0.23</sub><sup>+0.25</sup> g cm<sup>-3</sup>, respectively. The radius of planet b lies in the transition region between rocky and gaseous planets, but its density is consistent with a rocky composition. Its semimajor axis and the corresponding photoevaporation levels to which the planet has been exposed might explain its measured density today. In contrast, the densities and semimajor axes of planets c and d suggest a very thick atmosphere. The singularity of this system, which orbits a slightly evolved star that is just leaving the main sequence, makes it a good candidate for a deeper study from a dynamical point of view.</p>}},
  author       = {{Hidalgo, D. and Pallé, E. and Alonso, R. and Gandolfi, D. and Nowak, G. and Luque, R. and Hirano, T. and Justesen, A. B. and Cochran, W. D. and Barragán, O. and Spina, L. and Rodler, F. and Albrecht, S. and Anderson, D. and Amado, P. and Bryant, E. and Caballero, J. A. and Cabrera, J. and Csizmadia, Sz and Dai, F. and Deeg, H. J. and Eigmuller, Ph and Endl, M. and Erikson, A. and Esposito, M. and Figueira, P. and Georgieva, I. and Grziwa, S. and Guenther, E. and Hatzes, A. P. and Hjorth, M. and Hoeijmakers, H. J. and Kabath, P. and Korth, J. and Kuzuhara, M. and Lafarga, M. and Lampon, M. and Leão, I. C. and Livingston, J. and Mathur, S. and Montañes-Rodriguez, P. and Morales, J. C. and Murgas, F. and Nagel, E. and Narita, N. and Nielsen, L. D. and Patzold, M. and Persson, C. M. and Prieto-Arranz, J. and Quirrenbach, A. and Rauer, H. and Redfield, S. and Reiners, A. and Ribas, I. and Smith, A. M.S. and Šubjak, J. and Van Eylen, V. and Wilson, P. A.}},
  issn         = {{0004-6361}},
  keywords     = {{Planetary systems; Planets and satellites: detection; Planets and satellites: fundamental parameters; Techniques: photometric; Techniques: radial velocities}},
  language     = {{eng}},
  month        = {{04}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Three planets transiting the evolved star EPIC 249893012 : A hot 8.8-M super-Earth and two warm 14.7 and 10.2-M sub-Neptunes}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201937080}},
  doi          = {{10.1051/0004-6361/201937080}},
  volume       = {{636}},
  year         = {{2020}},
}