CHEOPS observations of the HD 108236 planetary system: A fifth planet, improved ephemerides, and planetary radii
Artikel i vetenskaplig tidskrift, 2021
Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 mag) star HD 108236 (also known as TOI-1233) was recently reported on the basis of TESS and ground-based light curves. Aims. We perform a first characterisation of the HD 108236 planetary system through high-precision CHEOPS photometry and improve the transit ephemerides and system parameters. Methods. We characterise the host star through spectroscopic analysis and derive the radius with the infrared flux method. We constrain the stellar mass and age by combining the results obtained from two sets of stellar evolutionary tracks. We analyse the available TESS light curves and one CHEOPS transit light curve for each known planet in the system. Results. We find that HD 108236 is a Sun-like star with R? = 0.877 ± 0.008 R? , M? = 0.869-0.048+0.050 M? , and an age of 6.7-5.1+4.0 Gyr. We report the serendipitous detection of an additional planet, HD 108236 f, in one of the CHEOPS light curves. For this planet, the combined analysis of the TESS and CHEOPS light curves leads to a tentative orbital period of about 29.5 days. From the light curve analysis, we obtain radii of 1.615 ± 0.051, 2.071 ± 0.052, 2.539-0.065+0.062, 3.083 ± 0.052, and 2.017-0.057+0.052 R? for planets HD 108236 b to HD 108236 f, respectively. These values are in agreement with previous TESS-based estimates, but with an improved precision of about a factor of two. We perform a stability analysis of the system, concluding that the planetary orbits most likely have eccentricities smaller than 0.1. We also employ a planetary atmospheric evolution framework to constrain the masses of the five planets, concluding that HD 108236 b and HD 108236 c should have an Earth-like density, while the outer planets should host a low mean molecular weight envelope. Conclusions. The detection of the fifth planet makes HD 108236 the third system brighter than V = 10 mag to host more than four transiting planets. The longer time span enables us to significantly improve the orbital ephemerides such that the uncertainty on the transit times will be of the order of minutes for the years to come. A comparison of the results obtained from the TESS and CHEOPS light curves indicates that for a V - 9 mag solar-like star and a transit signal of -500 ppm, one CHEOPS transit light curve ensures the same level of photometric precision as eight TESS transits combined, although this conclusion depends on the length and position of the gaps in the light curve.
Stars: Fundamental parameters
Ephemerides
Planets and satellites: Detection
Planets and satellites: Fundamental parameters
Författare
A. Bonfanti
Institut fur Weltraumforschung
L. Delrez
Universite de Liège
M.J. Hooton
Universität Bern
T.G. Wilson
University of St Andrews
L. Fossati
Institut fur Weltraumforschung
Y. Alibert
Universität Bern
S. Hoyer
Laboratoire d'Astrophysique de Marseille
A. J. Mustill
Lunds universitet
H. P. Osborn
Universität Bern
V. Adibekyan
Universidade do Porto
D. Gandolfi
Istituto nazionale di astrofisica (INAF)
S. Salmon
Universite de Liège
S.G. Sousa
Universidade do Porto
A. Tuson
University of Cambridge
V. Van Grootel
Universite de Liège
J. Cabrera
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
P. Maxted
Keele University
S.C.C. Barros
Universidade do Porto
N. Billot
Université de Genève
X. Bonfils
Université Grenoble Alpes
L. Borsato
Istituto nazionale di astrofisica (INAF)
C. Broeg
Universität Bern
Melvyn B. Davies
Lunds universitet
M. Deleuil
Laboratoire d'Astrophysique de Marseille
O. Demangeon
Laboratoire d'Astrophysique de Marseille
Malcolm Fridlund
Universiteit Leiden
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
G. Lacedelli
Istituto nazionale di astrofisica (INAF)
M. Lendl
Université de Genève
C. M. Persson
N. C. Santos
Universidade do Porto
Gaetano Scandariato
Istituto nazionale di astrofisica (INAF)
G.M. Szabó
Eötvös Loránd University (ELTE)
A. Collier Cameron
University of St Andrews
S. Udry
Université de Genève
W. Benz
Universität Bern
M. Beck
Université de Genève
D. Ehrenreich
Université de Genève
A. Fortier
Universität Bern
K. Isaak
European Space Research and Technology Centre (ESA ESTEC)
D. Queloz
Université de Genève
R. Alonso
Instituto de Astrofísica de Canarias
J. Asquier
European Space Research and Technology Centre (ESA ESTEC)
T. Bandy
Universität Bern
T. Bárczy
Admatis
D. Barrado
Centro de Astrobiologia (CAB)
O. Barragán
University of Oxford
W. Baumjohann
Institut fur Weltraumforschung
T. Beck
Universität Bern
A. Bekkelien
Université de Genève
M. Bergomi
Istituto nazionale di astrofisica (INAF)
A. Brandeker
Stockholms universitet
M.-D. Busch
Universität Bern
V. Cessa
Universität Bern
S. Charnoz
Institut de Physique du Globe de Paris
B. Chazelas
Université de Genève
C. Corral Van Damme
European Space Research and Technology Centre (ESA ESTEC)
B.O. Demory
Universität Bern
Anders Erikson
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
J. Farinato
Istituto nazionale di astrofisica (INAF)
D. Futyan
Université de Genève
A. Garcia Munoz
Technische Universität Berlin
Michaël Gillon
Universite de Liège
M. Guedel
Universität Wien
P. Guterman
Laboratoire d'Astrophysique de Marseille
J. Hasiba
Institut fur Weltraumforschung
Kevin Heng
Universität Bern
E. Hernandez
Universität Bern
L. Kiss
Magyar Tudomanyos Akademia
T. Kuntzer
Université de Genève
J. Laskar
Observatoire de Paris
A. L. des Etangs
Institut d 'Astrophysique de Paris
C. Lovis
Université de Genève
D. Magrin
Istituto nazionale di astrofisica (INAF)
L. Malvasio
Universität Bern
L. Marafatto
Istituto nazionale di astrofisica (INAF)
H. Michaelis
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
M. Munari
Istituto nazionale di astrofisica (INAF)
G. Olofsson
Stockholms universitet
H. Ottacher
Institut fur Weltraumforschung
R. Ottensamer
Universität Wien
I. Pagano
Istituto nazionale di astrofisica (INAF)
E. Palle
Instituto de Astrofísica de Canarias
G. Peter
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
D. Piazza
Universität Bern
Giampaolo P. Piotto
Istituto nazionale di astrofisica (INAF)
Don L. Pollacco
The University of Warwick
Roberto Ragazzoni
Istituto nazionale di astrofisica (INAF)
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
F. Ratti
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
I. Ribas
Institut de Ciències de l'Espai (ICE) - CSIC
M. Rieder
Universität Bern
R. Rohlfs
Université de Genève
F. Safa
European Space Research and Technology Centre (ESA ESTEC)
M. Salatti
Agenzia Spaziale Italiana
D. Segransan
Université de Genève
A.E. Simon
Universität Bern
Alexis M. S. Smith
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
M. Sordet
Université de Genève
Manfred B. Steller
Institut fur Weltraumforschung
Nicolas Thomas
Universität Bern
M. Tschentscher
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Vincent Van Eylen
University College London (UCL)
V. Viotto
Istituto nazionale di astrofisica (INAF)
I. Walter
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
N. A. Walton
University of Cambridge
F. Wildi
Université de Genève
D. Wolter
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 646 A157Ämneskategorier
Astronomi, astrofysik och kosmologi
Atom- och molekylfysik och optik
Reglerteknik
DOI
10.1051/0004-6361/202039608