J/A+A/683/A1 KELT-20b/MASCARA-2b CHEOPS light curve (Singh+, 2024)
CHEOPS observations of KELT-20b/MASCARA-2b:
An aligned orbit and signs of variability from a reflective dayside.
Singh V., Scandariato G., Smith A.M.S., Cubillos P.E., Lendl M., Billot N.,
Fortier A., Queloz D., Sousa S.G., Csizmadia Sz., Brandeker A., Carone L.,
Wilson T.G., Akinsanmi B., Patel J.A., Krenn A., Demangeon O.D.S., Bruno G.,
Pagano I., Hooton M.J., Cabrera J., Santos N.C., Alibert Y., Alonso R.,
Asquier J., Barczy T., Barrado Navascues D., Barros S.C.C., Baumjohann W.,
Beck M., Beck T., Benz W., Bergomi M., Bonfanti A., Bonfils X., Borsato L.,
Broeg C., Charnoz S., Collier Cameron A., Davies M.B., Deleuil M.,
Deline A., Delrez L., Demory B.-O., Ehrenreich D., Erikson A., Fossati L.,
Fridlund M., Gandolfi D., Gillon M., Guedel M., Guenther M.N., Harre J.-V.,
Heitzmann A., Helling C., Hoyer S., Isaak K.G., Kiss L.L., Lam K.W.F.,
Laskar J., Lecavelier des Etangs A., Magrin D., Maxted P.F.L., Mischler H.,
Mordasini C., Nascimbeni V., Olofsson G., Ottensamer R., Palle E., Peter G.,
Piotto G., Pollacco D., Ragazzoni R., Rando N., Rauer H., Ribas I.,
Salmon S., Segransan D., Simon A.E., Stalport M., Steinberger M.,
Szabo Gy.M., Thomas N., Udry S., Ulmer B., Van Grootel V., Venturini J.,
Villaver E., Walton N.A., Zingales T.
<Astron. Astrophys. 683, A1 (2024)>
=2024A&A...683A...1S 2024A&A...683A...1S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ; Optical
Keywords: techniques: photometric - planets and satellites: atmospheres -
planets and satellites: gaseous planets -
planets and satellites: individual: KELT-20 -
planets and satellites: individual: MASCARA-2 b
Abstract:
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.
We aim to precisely measure the planetary radius and geometric albedo
of the ultra-hot Jupiter(UHJ) KELT-20 b. We also aim to strongly
constrain the KELT-20 system's spin-orbit alignment.
We obtained optical high-precision transits and occultations of
KELT-20 b using the CHaracterising ExOPlanet Satellite (CHEOPS). We
analyzed them in conjunction with the simultaneous observations with
Transiting Exoplanet Survey Satellite (TESS). We interpret the
occultation measurements together with archival infrared observations
to measure the planetary geometric albedo and dayside temperatures. We
further use the host star's gravity-darkened nature to measure the
system's obliquity.
We present time-averaged precise occultation depth of 82±6ppm
measured with seven CHEOPS visits and 131+8-7 ppm 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+77-80K. Assuming Lambertian scattering law, we constrain
the Bond albedo to 0.36+0.04-0.05 along with a minimal heat
transfer to the nightside (≤0.14+0.13-0.10). Furthermore,
using five transit observations we provide stricter constraints of
3.9±1.1-degrees 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. KELT-20 b's comparably high planetary
geometric albedo 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 dayside.
Description:
Tablec1.dat contains the PIPE photometric extraction of the CHEOPS
light curve of KELT-20. The light curve includes 7 occultation and 5
transit observations. Table2.dat contains the detrended light curve.
Objects:
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RA (2000) DE Designation(s)
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19 38 38.73 31 13 09.22 KELT-20 = MASCARA-2 = HD 185603
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 182 8498 PIPE extracted CHEOPS light curve of KELT-20
lc_det.dat 44 662 Light curve detrended
(corrected version, 19-Aug-2024)
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See also:
J/A+A/612/A57 : MASCARA-2b (HD185603) light curves and spectra (Talens+, 2018)
J/A+A/616/A151 : MASCARA-2b NaI + Ha absorption lines (Casasayas-Barris+, 2018)
J/A+A/628/A9 : MASCARA-2b transmission spectra (Casasayas-Barris+, 2019)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d MJD MJD time of observation
20- 37 F18.10 d BJD BJD time of observation
39- 56 F18.9 ct Flux Flux counts
58- 76 F19.13 ct e_Flux Error flux counts
78- 97 F20.14 ct BG Background Flux
99-119 F21.17 deg Roll Roll angle
121-138 F18.14 --- Centx Centroid x
140-157 F18.14 --- Centy Centroid y
159-162 F4.1 --- Flag [0/25] Flag to designate bad data
164-182 F19.15 K T ThermFront2 thermistor readout
(Telescope temperature)
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Byte-by-byte Description of file: lc_det.dat
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Bytes Format Units Label Explanations
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1- 18 F18.10 d BJD BJD time of observation
20- 31 F12.10 --- Flux Relative flux
33- 44 E12.7 --- e_Flux Relative flux error
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Acknowledgements:
Vikash Singh, Vikash.Singh(at)inaf.it
History:
29-Feb-2024: on-line version
19-Aug-2024: corrected lc_det.dat file
(End) Vikash Singh [INAF-OACT], Patricia Vannier [CDS] 06-Nov-2023