J/A+A/700/A5 CHEOPS and TESS photometry of KELT-7 (Garai+, 2025)
The KELT-7b atmospheric thermal-inversion conundrum revisited with
CHEOPS, TESS, and additional data.
Garai Z., Krenn A., Cubillos P.E., Bruno G., Smith A.M.S., Wilson T.G.,
Brandeker A., Guenther M.N., Heitzmann A., Carone L., Singh V., Lendl M.,
Demangeon O.D.S., Alibert Y., Alonso R., Asquier J., Barczy T., Barrado D.,
Barros S.C.C., Baumjohann W., Benz W., Billot N., Borsato L., Broeg C.,
Collier Cameron A., Correia A.C.M., Csizmadia Sz., Davies M.B., Deleuil M.,
Deline A., Demory B.-O., Derekas A., Edwards B., Egger J.A., Ehrenreich D.,
Erikson A., Farinato J., Fortier A., Fossati L., Fridlund M., Gandolfi D.,
Gazeas K., Gillon M., Guedel M., Helling C., Isaak K.G., Kerschbaum F.,
Kiss L.L., Korth J., Lam K.W.F., Laskar J., Lecavelier des Etangs A.,
Magrin D., Maxted P.F.L., Merin B., Mordasini C., Nascimbeni V.,
Olofsson G., Ottensamer R., Pagano I., Palle E., Peter G., Piazza D.,
Piotto G., Pollacco D., Queloz D., Ragazzoni R., Rando N., Rauer H.,
Ribas I., Santos N.C., Scandariato G., Segransan D., Simon A.E., Sousa S.G.,
Stalport M., Sulis S., Szabo Gy.M., Udry S., Ulmer-Moll S., Van Grootel V.,
Venturini J., Villaver E., Walton N.A., Wolf S., Wolter D., Zingales T.
<Astron. Astrophys. 700, A5 (2025)>
=2025A&A...700A...5G 2025A&A...700A...5G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Space observations ;
Photometry ; Optical
Keywords: methods: observational - techniques: photometric -
planets and satellites: atmospheres -
planets and satellites: fundamental parameters -
planets and satellites: individual: KELT-7b
Abstract:
Early theoretical works suggested that ultrahot Jupiters have inverted
temperature-pressure (T-P) profiles in the presence of optical
absorbers, such as TiO and VO. Recently, an inverted T-P profile of
KELT-7b was detected, in agreement with the predictions. However, the
diagnosis of T-P inversions has always been recognized to be a
model-dependent process.
We used the Characterising Exoplanet Satellite (CHEOPS), the
Transiting Exoplanet Survey Satellite (TESS), and additional
literature data to characterize the atmosphere of KELT-7b, rederive
the T-P profile, provide a precise measurement of the albedo of
KELT-7b, and search for a possible distortion in the precise CHEOPS
transit light curve of the planet.
We first jointly fitted the CHEOPS and TESS data and measured the
occultation depths in these passbands. The CHEOPS transits were also
fitted with a model including the gravity-darkening effect. Emission
and absorption retrievals were performed to characterize the
atmosphere of KELT-7b. The albedo of the planet was calculated in the
CHEOPS and TESS passbands.
When adopting a thermochemical-equilibrium atmospheric composition,
the emission retrievals return a non-inverted T-P profile, in contrast
with previous results. When adopting a free-chemistry atmospheric
parameterization, the emission retrievals return an inverted T-P
profile with -- likely unphysically -- high concentrations of TiO and
VO. The 3D general circulation model (GCM) supports a TiO-induced
temperature inversion. We report for KELT-7b a very low geometric
albedo of Ag=0.05±0.06, which is consistent with the heat
distribution ε being close to zero and also consistent with a
3D GCM simulation, using magnetic drag (τdrag=104s). Based on
the CHEOPS photometry, we are unable to place any meaningful
constraint on the sky-projected orbital obliquity.
The choice of a free-chemistry approach or a
thermochemical-equilibrium chemistry is the main factor determining
the retrieval results. Free-chemistry retrievals generally yield
better fits; however, assuming free chemistry risks adopting
unphysical scenarios for ultrahot Jupiters, such as KELT-7b. We
applied a coherent stellar variability treatment on TESS and CHEOPS
observations, commensurate with the known stellar activity of the host
star. Other observations of KELT-7b would also benefit from a coherent
stellar variability treatment.
Description:
We present here the non-detrended CHEOPS secondary eclipse photometry
of KELT-7 with the full model, the detrended CHEOPS secondary eclipse
photometry of KELT-7 with the occultation model, the non-detrended
CHEOPS transit photometry of KELT-7 with the full model, the detrended
CHEOPS transit photometry of KELT-7 with the transit model, the
non-detrended TESS photometry of KELT-7 with the full model, and the
detrended TESS photometry of KELT-7 with the transit and occultation
model.
Objects:
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RA (2000) DE Designation(s)
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05 13 10.92 +33 19 05.4 HD 33643 = KELT-7
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tess.dat 88 109739 TESS photometry of KELT-7
ch-trans.dat 88 1722 CHEOPS transit photometry of KELT-7
ch-occ.dat 88 10849 CHEOPS occultation photometry of KELT-7
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See also:
J/A+A/692/A129 : WASP-3 b CHEOPS light curves (Scandariato+, 2024)
Byte-by-byte Description of file: tess.dat ch-trans.dat ch-occ.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d BJD Barycentric Julian date (BJD-2457000.0)
15- 22 F8.6 --- Flux Non-detrended normalized flux
26- 33 F8.6 --- e_Flux rms uncertainty on Flux
37- 44 F8.6 --- Full Full model
48- 55 F8.6 --- GP Gaussian process baseline
59- 66 F8.6 --- Tra Transit/occultation model
70- 77 F8.6 --- FluxDet Detrended normalized flux
80- 88 F9.6 --- Phase Orbital phase
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Acknowledgements:
Zoltan Garai, zgarai(at)ta3.sk
(End) Patricia Vannier [CDS] 29-May-2025