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.

Planets and satellites: Fundamental parameters

Planets and satellites: Detection

Stars: Fundamental parameters

Ephemerides

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

Department of Physics

V. Van Grootel

Universite de Liège

J. Cabrera

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Valerio Nascimbeni

Osservatorio Astronomico di Padova

P. Maxted

Keele University

S.C.C. Barros

Universidade do Porto

N. Billot

Université de Genève

X. Bonfils

Université Grenoble Alpes

L. Borsato

Osservatorio Astronomico di Padova

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

Osservatorio Astronomico di Padova

M. Lendl

Université de Genève

C. M. Persson

N. C. Santos

Universidade do Porto

Gaetano Scandariato

Osservatorio Astrofisico di Catania

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 Astrofisico 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

Osservatorio Astronomico di Padova

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

Osservatorio Astronomico di Padova

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

Osservatorio Astronomico di Padova

L. Malvasio

Universität Bern

L. Marafatto

Osservatorio Astronomico di Padova

H. Michaelis

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

M. Munari

Osservatorio Astrofisico di Catania

G. Olofsson

Stockholms universitet

H. Ottacher

Institut fur Weltraumforschung

R. Ottensamer

Universität Wien

I. Pagano

Osservatorio Astrofisico di Catania

E. Palle

Instituto Astrofisico de Canarias

G. Peter

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

D. Piazza

Universität Bern

Giampaolo P. Piotto

Osservatorio Astronomico di Padova

Don L. Pollacco

The University of Warwick

Roberto Ragazzoni

Osservatorio Astronomico di Padova

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

Osservatorio Astronomico di Padova

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 A157

Ämneskategorier

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik

Reglerteknik

DOI

10.1051/0004-6361/202039608

Mer information

Senast uppdaterat

2021-07-08