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Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)

Prieto-Arranz, J. ; Palle, E. ; Gandolfi, D. ; Barragán, O. ; Guenther, E. W. ; Dai, F. ; Fridlund, M. ; Hirano, T. ; Livingston, J. and Luque, R. , et al. (2018) In Astronomy and Astrophysics 618.
Abstract

Context. Multiplanet systems are excellent laboratories to test planet formation models as all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (~30 pc) detected by NASA's Kepler or K2 space mission. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with... (More)

Context. Multiplanet systems are excellent laboratories to test planet formation models as all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (~30 pc) detected by NASA's Kepler or K2 space mission. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with high-precision radial-velocity measurements gathered with the FIES, HARPS, and HARPS-N spectrographs we revised the system parameters and derive the masses of the three planets. Results. We find that GJ 9827 b has a mass of Mb = 3.69-0.46+0.48 M and a radius of Rb = 1.58-0.13+0.14 R, yielding a mean density of ρb = 5.11-1.27+1.74 g cm-3. GJ 9827 c has a mass of Mc = 1.45-0.57+0.58 M, radius of Rc = 1.24-0.11+0.11 R, and a mean density of ρc = 4.13-1.77+2.31 g cm-3. For GJ 9827 d, we derive Md = 1.45-0.57+0.58 M, Rd = 1.24-0.11+0.11 R, and ρd = 1.51-0.53+0.71 g cm-3. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and sub-Neptunes. The planetary bulk compositions are compatible with a scenario where all three planets formed with similar core and atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its primordial atmosphere, owing to the much lower stellarirradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmosphericescape can be studied in detail for all planets, helping us to understand how compact systems form and evolve.

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publishing date
type
Contribution to journal
publication status
published
keywords
Planetary systems, Stars: abundances, Stars: individual: GJ 9827, Techniques: high angular resolution, Techniques: photometric, Techniques: radial velocities
in
Astronomy and Astrophysics
volume
618
article number
A116
publisher
EDP Sciences
external identifiers
  • scopus:85056131311
ISSN
0004-6361
DOI
10.1051/0004-6361/201832872
language
English
LU publication?
no
additional info
Publisher Copyright: © ESO 2018.
id
08eb816a-4ae5-4098-803c-d870adc24d6e
date added to LUP
2023-02-02 11:14:58
date last changed
2023-02-20 14:30:02
@article{08eb816a-4ae5-4098-803c-d870adc24d6e,
  abstract     = {{<p>Context. Multiplanet systems are excellent laboratories to test planet formation models as all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (~30 pc) detected by NASA's Kepler or K2 space mission. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with high-precision radial-velocity measurements gathered with the FIES, HARPS, and HARPS-N spectrographs we revised the system parameters and derive the masses of the three planets. Results. We find that GJ 9827 b has a mass of M<sub>b</sub> = 3.69<sub>-0.46</sub><sup>+0.48</sup> M and a radius of R<sub>b</sub> = 1.58<sub>-0.13</sub><sup>+0.14</sup> R, yielding a mean density of ρ<sub>b</sub> = 5.11<sub>-1.27</sub><sup>+1.74</sup> g cm<sup>-3</sup>. GJ 9827 c has a mass of M<sub>c</sub> = 1.45<sub>-0.57</sub><sup>+0.58</sup> M, radius of R<sub>c</sub> = 1.24<sub>-0.11</sub><sup>+0.11</sup> R, and a mean density of ρ<sub>c</sub> = 4.13<sub>-1.77</sub><sup>+2.31</sup> g cm<sup>-3</sup>. For GJ 9827 d, we derive M<sub>d</sub> = 1.45<sub>-0.57</sub><sup>+0.58</sup> M, R<sub>d</sub> = 1.24<sub>-0.11</sub><sup>+0.11</sup> R, and ρ<sub>d</sub> = 1.51<sub>-0.53</sub><sup>+0.71</sup> g cm<sup>-3</sup>. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and sub-Neptunes. The planetary bulk compositions are compatible with a scenario where all three planets formed with similar core and atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its primordial atmosphere, owing to the much lower stellarirradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmosphericescape can be studied in detail for all planets, helping us to understand how compact systems form and evolve.</p>}},
  author       = {{Prieto-Arranz, J. and Palle, E. and Gandolfi, D. and Barragán, O. and Guenther, E. W. and Dai, F. and Fridlund, M. and Hirano, T. and Livingston, J. and Luque, R. and Niraula, P. and Persson, C. M. and Redfield, S. and Albrecht, S. and Alonso, R. and Antoniciello, G. and Cabrera, J. and Cochran, W. D. and Csizmadia, Sz and Deeg, H. and Eigmüller, Ph and Endl, M. and Erikson, A. and Everett, M. E. and Fukui, A. and Grziwa, S. and Hatzes, A. P. and Hidalgo, D. and Hjorth, M. and Korth, J. and Lorenzo-Oliveira, D. and Murgas, F. and Narita, N. and Nespral, D. and Nowak, G. and Pätzold, M. and Montañez Rodríguez, P. and Rauer, H. and Ribas, I. and Smith, A. M.S. and Trifonov, T. and Van Eylen, V. and Winn, J. N.}},
  issn         = {{0004-6361}},
  keywords     = {{Planetary systems; Stars: abundances; Stars: individual: GJ 9827; Techniques: high angular resolution; Techniques: photometric; Techniques: radial velocities}},
  language     = {{eng}},
  month        = {{10}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201832872}},
  doi          = {{10.1051/0004-6361/201832872}},
  volume       = {{618}},
  year         = {{2018}},
}