Planets observed with CHEOPS: Two super-Earths orbiting the red dwarf star TOI-776
Journal article, 2024
Context. M-dwarf stars are the most common of potential exoplanet host stars in the Galaxy. It is therefore very important to understand planetary systems orbiting such stars and to determine the physical parameters of such planets with high precision. Also with the launch of the James Webb Space Telescope (JWST) the observation of atmospheric parameters of planets orbiting these stars has begun. It is therefore required to determine properties of potential targets. Aims. Two planets around the red dwarf TOI-776 were detected by TESS. The objective of our study was to use transit observations obtained by the CHEOPS space mission to improve the current precision of the planetary radii, as well as additional radial velocity (RV) data in order to improve mass estimates of the two planets. Using these quantities, we wanted to derive the bulk densities of those planets, improving the precision in earlier results, and use this information to put them in context of other exoplanetary systems involving very low mass stars. Methods. Utilizing new transit data from the CHEOPS satellite and its photometric telescope, we obtained very high precision planetary transit measurements. Interpretation of these provides updated planetary radii, along with other system parameters. A concurrent ESO large observing program using the high precision spectrograph HARPS has doubled the available radial velocity data. Calculating the power spectrum of a number of stellar activity indices we update the previously estimated stellar rotation period to a lower value. Results. The CHEOPS data provide precise transit depths of 909 and 1177 ppm translating into radii of Rb = 1.798-0.077+0.078 R⊕ and Rc = 2.047-0.078+0.081 R⊕, respectively. Our interpretation of the radial velocities and activity indicator time series data estimates a stellar rotation period for this early M dwarf of ~21.1 days. A further multi-dimensional Gaussian process approach confirm this new estimate. By performing a Skew-Normal (SN) fit onto the Cross Correlation Functions we extracted the RV data and the activity indicators to estimate the planetary masses, obtaining Mb = 5.0-1.6+1.6 M⊕ and Mc = 6.9-2.5+2.6 M⊕. Conclusions. We improve the precision in planetary radius for TOI-776 b and c by a factor of more than two. Our data and modelling give us parameters of both bodies consistent with mini-Neptunes, albeit with a relatively high density. The stellar activity of TOI-776 is found to have increased by a factor larger than 2 since the last set of observations.
techniques: photometric
techniques: spectroscopic
planets and satellites: individual: TOI-776 c
planets and satellites: individual: TOI-776 b
planets and satellites: detection
stars: individual: LP 961-53
Author
Malcolm Fridlund
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Leiden University
Iskra Georgieva
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
A. Bonfanti
Institut fur Weltraumforschung
Y. Alibert
University of Bern
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
D. Gandolfi
University of Turin
M. Beck
University of Geneva
A. Deline
University of Geneva
S. Hoyer
Laboratoire d'Astrophysique de Marseille
G. Olofsson
Stockholm University
T.G. Wilson
University of St Andrews
O. Barragán
University of Oxford
L. Fossati
Institut fur Weltraumforschung
A. J. Mustill
Lund University
A. Brandeker
Stockholm University
A. Hatzes
Thüringer Landessternwarte Tautenburg
H.-G. Florén
Stockholm University
Umberto Simola
4Pharma Ltd
M.J. Hooton
University of Bern
University of Cambridge
R. Luque
Institute of Astrophysics of Andalusia (IAA)
University of Chicago
S. G. Sousa
University of Porto
J. A. Egger
University of Bern
A. Antoniadis-Karnavas
University of Porto
S. Salmon
University of Geneva
V. Adibekyan
University of Porto
R. Alonso
Instituto de Astrofísica de Canarias
University of La Laguna
G. Anglada
Institute of Space Sciences (ICE) - CSIC
Institute of Space Studies of Catalonia (IEEC)
T. Bárczy
Admatis
D. Barrado Navascues
European Space Astronomy Centre (ESAC)
S.C.C. Barros
University of Porto
W. Baumjohann
Institut fur Weltraumforschung
T. Beck
University of Bern
W. Benz
University of Bern
X. Bonfils
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
C. Broeg
University of Bern
J. Cabrera
German Aerospace Center (DLR)
S. Charnoz
Institut de Physique du Globe de Paris
A. Collier Cameron
University of St Andrews
Szilard Csizmadia
German Aerospace Center (DLR)
M. B. Davies
Lund University
H. Deeg
University of La Laguna
Instituto de Astrofísica de Canarias
M. Deleuil
Laboratoire d'Astrophysique de Marseille
L. Delrez
University of Liège
O. Demangeon
University of Porto
B.O. Demory
University of Bern
D. Ehrenreich
University of Geneva
Anders Erikson
German Aerospace Center (DLR)
M. Esposito
Thüringer Landessternwarte Tautenburg
A. Fortier
University of Bern
Michaël Gillon
University of Liège
M. Gudel
University of Vienna
Kevin Heng
University Of Leicester
University of Bern
K. Isaak
European Space Research and Technology Centre (ESA ESTEC)
L. L. Kiss
Hungarian Academy of Sciences
Eötvös Loránd University (ELTE)
Judith Korth
Lund University
J. Laskar
Paris Observatory
A. L. des Etangs
Institut d 'Astrophysique de Paris
M. Lendl
University of Geneva
J.H. Livingston
The Graduate University for Advanced Studies (SOKENDAI)
National Institutes of Natural Sciences
National Astronomical Observatory of Japan
University of Tokyo
C. Lovis
University of Geneva
D. Magrin
Istituto nazionale di astrofisica (INAF)
P. Maxted
Keele University
A. Muresan
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
R. Ottensamer
University of Vienna
I. Pagano
Istituto nazionale di astrofisica (INAF)
Enric Palle
Instituto de Astrofísica de Canarias
G. Peter
German Aerospace Center (DLR)
Giampaolo P. Piotto
University of Padua
Istituto nazionale di astrofisica (INAF)
D. Pollacco
The University of Warwick
D. Queloz
University of Cambridge
Swiss Federal Institute of Technology in Zürich (ETH)
R. Ragazzoni
Istituto nazionale di astrofisica (INAF)
University of Padua
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
Freie Universität Berlin
Technische Universität Berlin
German Aerospace Center (DLR)
S. Redfield
Wesleyan University
I. Ribas
Institute of Space Studies of Catalonia (IEEC)
Institute of Space Sciences (ICE) - CSIC
N. C. Santos
University of Porto
Gaetano Scandariato
Istituto nazionale di astrofisica (INAF)
D. Segransan
University of Geneva
L. M. Serrano
University of Turin
A.E. Simon
University of Bern
A. M.S. Smith
German Aerospace Center (DLR)
Manfred B. Steller
Institut fur Weltraumforschung
G.M. Szabó
Eötvös Loránd University (ELTE)
Nicolas Thomas
University of Bern
S. Udry
University of Geneva
Vincent Van Eylen
University College London (UCL)
V. Van Grootel
University of Liège
N. A. Walton
University of Cambridge
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 684 A12Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202243838