CHEOPS and TESS view of the ultra-short-period super-Earth TOI-561 b
Journal article, 2023
Context. Ultra-short-period planets (USPs) are a unique class of super-Earths with an orbital period of less than a day, and hence they are subject to intense radiation from their host star. These planets cannot retain a primordial H/He atmosphere, and most of them are indeed consistent with being bare rocky cores. A few USPs, however, show evidence for a heavyweight envelope, which could be a water layer resilient to evaporation or a secondary metal-rich atmosphere sustained by outgassing of the molten volcanic surface. Much thus remains to be learned about the nature and formation of USPs. Aims. The prime goal of the present work is to refine the bulk planetary properties of the recently discovered TOI-561 b through the study of its transits and occultations. This is crucial in order to understand the internal structure of this USP and to assess the presence of an atmosphere. Methods. We obtained ultra-precise transit photometry of TOI-561 b with CHEOPS, and performed a joint analysis of these data along with three archival visits from CHEOPS and four TESS sectors. Results. Our analysis of TOI-561 b transit photometry put strong constraints on its properties. In particular, we restrict the uncertainties on the planetary radius at similar to 2% retrieving R-p = 1.42 +/- 0.02 R-circle plus. This result informs our internal structure modelling of the planet, which shows that the observations are consistent with a negligible H/He atmosphere; however, other lighter materials are required, in addition to a pure iron core and a silicate mantle, to explain the observed density. We find that this can be explained by the inclusion of a water layer in our model. Additionally, we ran a grid of forward models with a water-enriched atmosphere to explain the transit radius. We searched for variability in the measured R-p/R-star over time, which could trace changes in the structure of the planetary envelope. However, no temporal variations are recovered within the present data precision. In addition to the transit event, we tentatively detect an occultation signal in the TESS data with an eclipse depth L = 27.40(-11.35)(+10.87) ppm. We use models of outgassed atmospheres from the literature to explain this eclipse signal. We find that the thermal emission from the planet can mostly explain the observation. Based on this, we predict that near- to mid-infrared observations with the James Webb Space Telescope should be able to detect silicate species in the atmosphere of the planet. This could also reveal important clues about the planetary interior and help disentangle planet formation and evolution models.
planets and satellites: atmospheres
planets and satellites: composition
planets and satellites: individual: TOI-561 b
techniques: photometric
planets and satellites: terrestrial planets
Author
J. A. Patel
Stockholm University
J. A. Egger
University of Bern
T. G. Wilson
University of St Andrews
The University of Warwick
V. Bourrier
University of Geneva
L. Carone
Austrian Academy of Sciences
M. Beck
University of Geneva
D. Ehrenreich
University of Geneva
S. G. Sousa
University of Porto
W. Benz
University of Bern
A. Brandeker
Stockholm University
A. Deline
University of Geneva
Y. Alibert
University of Bern
K. W. F. Lam
German Aerospace Center (DLR)
M. Lendl
University of Geneva
R. Alonso
University of La Laguna
Instituto de Astrofísica de Canarias
G. Anglada
Institute of Space Studies of Catalonia (IEEC)
Spanish National Research Council (CSIC)
T. Barczy
Admatis
D. Barrado
Spanish National Research Council (CSIC)
S. C. C. Barros
University of Porto
W. Baumjohann
Austrian Academy of Sciences
T. Beck
University of Bern
N. Billot
University of Geneva
X. Bonfils
Grenoble Alpes University
C. Broeg
University of Bern
M. -d. Busch
University of Bern
J. Cabrera
German Aerospace Center (DLR)
S. Charnoz
Paris Descartes University
A. Collier Cameron
University of St Andrews
Sz. Csizmadia
German Aerospace Center (DLR)
M. B. Davies
Lund University
M. Deleuil
Aix Marseille University
L. Delrez
University of Liège
O. D. S. Demangeon
University of Porto
B. -o. Demory
University of Bern
A. Erikson
German Aerospace Center (DLR)
A. Fortier
University of Bern
L. Fossati
Austrian Academy of Sciences
Malcolm Fridlund
Leiden University
Chalmers, Space, Earth and Environment, Onsala Space Observatory
D. Gandolfi
University of Turin
M. Gillon
University of Liège
M. Guedel
University of Vienna
K. Heng
The University of Warwick
University of Bern
S. Hoyer
Aix Marseille University
K. G. Isaak
European Space Agency (ESA)
L. L. Kiss
Hungarian Academy of Sciences
Eötvös Loránd University (ELTE)
E. Kopp
German Aerospace Center (DLR)
J. Laskar
Sorbonne University
A. Lecavelier des Etangs
Pierre and Marie Curie University (UPMC)
C. Lovis
University of Geneva
D. Magrin
Istituto nazionale di astrofisica (INAF)
P. F. L. Maxted
Keele University
V. Nascimbeni
Istituto nazionale di astrofisica (INAF)
G. Olofsson
Stockholm University
R. Ottensamer
University of Vienna
I. Pagano
Istituto nazionale di astrofisica (INAF)
E. Palle
Instituto de Astrofísica de Canarias
G. Peter
German Aerospace Center (DLR)
G. 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
University of Padua
Istituto nazionale di astrofisica (INAF)
N. Rando
European Space Agency (ESA)
F. Ratti
European Space Agency (ESA)
H. Rauer
German Aerospace Center (DLR)
Freie Universität Berlin
Technische Universität Berlin
I. Ribas
Institute of Space Studies of Catalonia (IEEC)
Spanish National Research Council (CSIC)
N. C. Santos
University of Porto
G. Scandariato
Istituto nazionale di astrofisica (INAF)
D. Segransan
University of Geneva
A. E. Simon
University of Bern
A. M. S. Smith
German Aerospace Center (DLR)
M. Steller
Austrian Academy of Sciences
Gy. M. Szabo
Eötvös Loránd University (ELTE)
N. Thomas
University of Bern
S. Udry
University of Geneva
B. Ulmer
German Aerospace Center (DLR)
V. Van Grootel
University of Liège
V. Viotto
Istituto nazionale di astrofisica (INAF)
N. A. Walton
University of Cambridge
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 679 A92Exoplanet diversity with satellite studies
Swedish National Space Board (174/18), 2019-02-04 -- 2023-08-01.
Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)
Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.
Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.
Subject Categories
Astronomy, Astrophysics and Cosmology
Other Physics Topics
DOI
10.1051/0004-6361/202244946