CHEOPS observations of KELT-20 b/MASCARA-2 b: An aligned orbit and signs of variability from a reflective day side
Journal article, 2024

Context. Occultations are windows of opportunity to indirectly peek into the dayside atmosphere of exoplanets. High-precision transit events provide information on the spin-orbit alignment of exoplanets around fast-rotating hosts. Aims. We aim to precisely measure the planetary radius and geometric albedo of the ultra-hot Jupiter (UHJ) KELT-20 b along with the spin-orbit alignment of the system. Methods. We obtained optical high-precision transits and occultations of KELT-20 b using CHEOPS observations in conjunction with simultaneous TESS observations. We interpreted the occultation measurements together with archival infrared observations to measure the planetary geometric albedo and dayside temperatures. We further used the host star's gravity-darkened nature to measure the system's obliquity. Results. We present a time-averaged precise occultation depth of 82 ± 6 ppm measured with seven CHEOPS visits and 131-7+8 from the analysis of all available TESS photometry. Using these measurements, we precisely constrain the geometric albedo of KELT-20 b to 0.26 ± 0.04 and the brightness temperature of the dayside hemisphere to 2566-80+77 K. Assuming Lambertian scattering law, we constrain the Bond albedo to 0.36-0.05+0.04 along with a minimal heat transfer to the night side (Ïμ = 0.14-0.10+0.13). Furthermore, using five transit observations we provide stricter constraints of 3 9 ± 1 1 deg on the sky-projected obliquity of the system. Conclusions. The aligned orbit of KELT-20 b is in contrast to previous CHEOPS studies that have found strongly inclined orbits for planets orbiting other A-type stars. The comparably high planetary geometric albedo of KELT-20 b corroborates a known trend of strongly irradiated planets being more reflective. Finally, we tentatively detect signs of temporal variability in the occultation depths, which might indicate variable cloud cover advecting onto the planetary day side.

Planets and satellites: gaseous planets

Planets and satellites: individual: KELT-20 b

Techniques: photometric

Planets and satellites: individual: MASCARA-2 b

Planets and satellites: atmospheres

Author

V. Singh

Istituto nazionale di astrofisica (INAF)

Gaetano Scandariato

Istituto nazionale di astrofisica (INAF)

A. M.S. Smith

German Aerospace Center (DLR)

P. E. Cubillos

Institut fur Weltraumforschung

Istituto nazionale di astrofisica (INAF)

M. Lendl

University of Geneva

N. Billot

University of Geneva

A. Fortier

University of Bern

D. Queloz

University of Cambridge

Swiss Federal Institute of Technology in Zürich (ETH)

S. G. Sousa

University of Porto

Szilard Csizmadia

German Aerospace Center (DLR)

A. Brandeker

Stockholm University

L. Carone

Institut fur Weltraumforschung

T.G. Wilson

The University of Warwick

B. Akinsanmi

University of Geneva

J. A. Patel

Stockholm University

A. Krenn

Institut fur Weltraumforschung

O. Demangeon

University of Porto

G. Bruno

Istituto nazionale di astrofisica (INAF)

I. Pagano

Istituto nazionale di astrofisica (INAF)

M.J. Hooton

University of Cambridge

J. Cabrera

German Aerospace Center (DLR)

N. C. Santos

University of Porto

Y. Alibert

University of Bern

R. Alonso

University of La Laguna

Instituto de Astrofísica de Canarias

J. Asquier

European Space Research and Technology Centre (ESA ESTEC)

T. Bárczy

Admatis

D. Barrado Navascues

Centro de Astrobiologia (CAB)

S.C.C. Barros

University of Porto

W. Baumjohann

Institut fur Weltraumforschung

M. Beck

University of Geneva

T. Beck

University of Bern

W. Benz

University of Bern

M. Bergomi

Istituto nazionale di astrofisica (INAF)

A. Bonfanti

Institut fur Weltraumforschung

X. Bonfils

Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)

L. Borsato

Istituto nazionale di astrofisica (INAF)

C. Broeg

University of Bern

S. Charnoz

Institut de Physique du Globe de Paris

A. Collier Cameron

University of St Andrews

M. B. Davies

Lund University

M. Deleuil

Laboratoire d'Astrophysique de Marseille

A. Deline

University of Geneva

L. Delrez

University of Liège

B.O. Demory

University of Bern

D. Ehrenreich

University of Geneva

Anders Erikson

German Aerospace Center (DLR)

L. Fossati

Institut fur Weltraumforschung

Malcolm Fridlund

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Leiden University

D. Gandolfi

University of Turin

Michaël Gillon

University of Liège

M. Gudel

University of Vienna

Maximilian N. Günther

European Space Research and Technology Centre (ESA ESTEC)

J. V. Harre

German Aerospace Center (DLR)

A. Heitzmann

University of Geneva

Ch. Helling

Institut fur Weltraumforschung

Technische Universität Graz

S. Hoyer

Laboratoire d'Astrophysique de Marseille

K. Isaak

European Space Research and Technology Centre (ESA ESTEC)

L. L. Kiss

Eötvös Loránd University (ELTE)

Hungarian Academy of Sciences

K. W.F. Lam

German Aerospace Center (DLR)

J. Laskar

Paris Observatory

A. L. des Etangs

Centre national de la recherche scientifique (CNRS)

D. Magrin

Istituto nazionale di astrofisica (INAF)

P. Maxted

Keele University

H. Mischler

University of Bern

C. Mordasini

University of Bern

Valerio Nascimbeni

Istituto nazionale di astrofisica (INAF)

G. Olofsson

Stockholm University

R. Ottensamer

University of Vienna

Enric Palle

Instituto de Astrofísica de Canarias

University of La Laguna

G. Peter

German Aerospace Center (DLR)

Giampaolo P. Piotto

University of Padua

Istituto nazionale di astrofisica (INAF)

D. Pollacco

The University of Warwick

R. Ragazzoni

University of Padua

Istituto nazionale di astrofisica (INAF)

N. Rando

European Space Research and Technology Centre (ESA ESTEC)

H. Rauer

German Aerospace Center (DLR)

Technische Universität Berlin

Freie Universität Berlin

I. Ribas

Institute of Space Sciences (ICE) - CSIC

Institute of Space Studies of Catalonia (IEEC)

S. Salmon

University of Geneva

D. Segransan

University of Geneva

A.E. Simon

University of Bern

M. Stalport

University of Liège

M. Steinberger

Institut fur Weltraumforschung

G.M. Szabó

Eötvös Loránd University (ELTE)

Nicolas Thomas

University of Bern

S. Udry

University of Geneva

B. Ulmer

German Aerospace Center (DLR)

V. Van Grootel

University of Liège

J. Venturini

University of Geneva

E. Villaver

University of La Laguna

Instituto de Astrofísica de Canarias

N. A. Walton

University of Cambridge

Tiziano Zingales

University of Padua

Istituto nazionale di astrofisica (INAF)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 683 A1

Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects

Swedish National Space Board (174/18), 2017-01-01 -- 2022-12-31.

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

Infrastructure

Onsala Space Observatory

DOI

10.1051/0004-6361/202347533

More information

Latest update

8/8/2024 2