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The stable climate of KELT-9b

Jones, K; Morris, BM; Demory, B-O; Ehrenreich, D; Hoyer, S; Simon, AE; Lendl, M; Demangeon, ODS; Sousa, SG; Bonfanti, A; Wilson, TG; Salmon, S; Csizmadia, S; Parviainen /, H; Bruno, G; Alibert, Y; Alonso, R; Anglada, G; Barczy, T; Barrado, D; Barros, SCC; Baumjohann, W; Beck, M; Beck, T; Benz, W; Bonfils, X; Brandeker, A; Broeg, C; Cabrera, J; Charnoz, S; Cameron, AC; Davies, MB; Deleuil, M; Deline, A; Isaak, KG; Kiss, LL; Laskar, J; des Etangs, AL; Lovis, C; Magrin, D; Maxted, PFL; Nascimbeni, V; Olofsson, G; Ottensamer, R; Pagano, I; Palle, E; Peter, G; Van Grootel, V; Piotto, G; Pollacco, D; Queloz, D; Ragazzoni, R; Rando, N; Ratti, F; Rauer, H; Reimers, C; Ribas, I; Santos, NC; Scandariato, G; Segransan, D; Smith, AMS; Steller, M; Szabo, GM; Thomas, N; Udry, S; Heng, K; Hooton, MJ; Billot, N; Delrez, L; Erikson, A; Fortier, A; Fossati, L; Fridlund, M; Gandolfi, D; Gillon, M; Gudel, M; Walter, I; Walton, NA; Jungo, WW

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K Jones

BM Morris

B-O Demory

D Ehrenreich

S Hoyer

AE Simon

M Lendl

ODS Demangeon

SG Sousa

A Bonfanti

TG Wilson

S Salmon

S Csizmadia

H Parviainen /

G Bruno

Y Alibert

R Alonso

G Anglada

T Barczy

D Barrado

SCC Barros

W Baumjohann

M Beck

T Beck

W Benz

X Bonfils

A Brandeker

C Broeg

J Cabrera

S Charnoz

AC Cameron

MB Davies

M Deleuil

A Deline

KG Isaak

LL Kiss

J Laskar

AL des Etangs

C Lovis

D Magrin

V Nascimbeni

G Olofsson

R Ottensamer

I Pagano

E Palle

G Peter

V Van Grootel

G Piotto

D Pollacco

D Queloz

R Ragazzoni

N Rando

F Ratti

H Rauer

C Reimers

I Ribas

NC Santos

G Scandariato

D Segransan

AMS Smith

M Steller

GM Szabo

N Thomas

S Udry

K Heng

MJ Hooton

N Billot

L Delrez

A Erikson

A Fortier

L Fossati

M Fridlund

D Gandolfi

M Gillon

M Gudel

I Walter

NA Walton

WW Jungo


Even among the most irradiated gas giants, so-called ultra-hot Jupiters, KELT-9b stands out as the hottest planet thus far discovered with a dayside temperature of over 4500 K. At these extreme irradiation levels, we expect an increase in heat redistribution efficiency and a low Bond albedo owed to an extended atmosphere with molecular hydrogen dissociation occurring on the planetary dayside. We present new photometric observations of the KELT-9 system throughout 4 full orbits and 9 separate occultations obtained by the 30 cm space telescope CHEOPS. The CHEOPS bandpass, located at optical wavelengths, captures the peak of the thermal emission spectrum of KELT-9b. In this work we simultaneously analyse CHEOPS phase curves along with public phase curves from TESS and Spitzer to infer joint constraints on the phase curve variation, gravity-darkened transits, and occultation depth in three bandpasses, as well as derive 2D temperature maps of the atmosphere at three different depths. We find a day-night heat redistribution efficiency of ~0.3 which confirms expectations of enhanced energy transfer to the planetary nightside due to dissociation and recombination of molecular hydrogen. We also calculate a Bond albedo consistent with zero. We find no evidence of variability of the brightness temperature of the planet, excluding variability greater than 1%

Journal Article Type Article
Acceptance Date Aug 8, 2022
Online Publication Date Oct 19, 2022
Publication Date Oct 19, 2022
Journal Astronomy & Astrophysics
Print ISSN 0004-6361
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 666
Article Number A118
Keywords techniques: photometric / instrumentation: photometers / planets and satellites: atmospheres / planets and satellites: gaseous planets / eclipses / occultations
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