J/A+A/659/L4 Geometric albedo of HD 209458 b (Brandeker+, 2022)
CHEOPS geometric albedo of the hot Jupiter HD 209458b.
Brandeker A., Heng K., Lendl M., Patel J.A., Morris B.M., Broeg C.,
Guterman P., Beck M., Maxted P.F.L., Demangeon O., Delrez L., Demory B.-O.,
Kitzmann D., Santos N.C., Singh V., Alibert Y., Alonso R., Anglada G.,
Barczy T., Barrado y Navascues D., Barros S.C.C., Baumjohann W., Beck T.,
Benz W., Billot N., Bonfils X., Bruno G., Cabrera J., Charnoz S.,
Collier Cameron A., Corral van Damme C., Csizmadia Sz., Davies M.B.,
Deleuil M., Deline A., Ehrenreich D., Erikson A., Farinato J., Fortier A.,
Fossati L., Fridlund M., Gandolfi D., Gillon M., Guedel M., Hoyer S.,
Isaak K.G., Kiss L., Laskar J., Lecavelier des Etangs A., Lovis C.,
Luntzer A., Magrin D., Nascimbeni V., Olofsson G., Ottensamer R., Pagano I.,
Palle E., Peter G., Piotto G., Pollacco D., Queloz D., Ragazzoni R.,
Rando N., Rauer H., Ribas I., Scandariato G., Segransan D., Simon A.E.,
Smith A.M.S., Sousa S.G., Steller M., Szabo G.M., Thomas N., Udry S.,
Van Grootel V., Walton N., Wolter D.
<Astron. Astrophys. 659, L4 (2022)>
=2022A&A...659L...4B 2022A&A...659L...4B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry
Keywords: techniques: photometric - planetary systems -
planets and satellites: atmosphere -
planets and satellites: individual: HD 209458 b
Abstract:
We report the detection of the secondary eclipse of the hot Jupiter HD
209458 b in optical/visible light using the CHEOPS space telescope.
Our measurement of 20.4+3.23.3 parts per million (ppm)
translates into a geometric albedo of Ag=0.096±0.016. The
previously estimated dayside temperature of about 1500K implies that
our geometric albedo measurement consists predominantly of reflected
starlight and is largely uncontaminated by thermal emission. This
makes the present result one of the most robust measurements of Ag for
any exoplanet, critical for understanding the atmosphere. Our
calculations of the bandpass-integrated geometric albedo demonstrate
that the measured value of Ag is consistent with a cloud-free
atmosphere, where starlight is reflected via Rayleigh scattering by
hydrogen molecules, with water and sodium abundances consistent with
stellar metallicity. We predict that the bandpass-integrated TESS
geometric albedo is too faint to detect and that a phase curve of HD
209458 b observed by CHEOPS would have a distinct shape associated
with Rayleigh scattering if the atmosphere is indeed cloud-free.
Description:
We present CHEOPS photometry of HD 209458 containing ten occultations.
table.dat contains the raw photometric time series with auxiliary
detrending vectors. table1.dat contains the detrended and phase-folded
light curve. Raw data can be obtained from the CHEOPS data archive:
https://cheops-archive.astro.unige.ch/archive_browser/
Objects:
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RA (2000) DE Designation(s)
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22 03 10.77 +18 53 03.55 HD 209458 = BD+18 4917
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 100 24989 Raw photometric time series with auxiliary
detrending vectors
table1.dat 39 24687 Detrended and phase-folded light curve
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 18 F18.10 d JD [2459422.96/2459479.83] Julian date of
observation
20- 31 F12.10 --- NFlux [0.99/1.01] Normalised raw flux
33- 44 F12.10 --- e_NFlux [0.0/0.01] 1-sigma uncertainty in NFluX
46- 59 F14.10 deg RollAngle [0.03/360.0] Roll angle
61- 73 F13.10 --- CenX [27.44/30.98] x-centroid position
75- 87 F13.10 --- CenY [29.42/32.65] y-centroid position
89-100 F12.10 --- BG [0.0/0.01] Background
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.10 d Time [-0.28/0.24] Time from eclipse center
15- 26 F12.10 --- NFlux [0.99/1.01] Normalised flux, after detrending and
correcting for systematics and other trends
28- 39 F12.10 --- e_NFlux [0.0/0.01] 1-sigma uncertainty in NFlux
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Acknowledgements:
Jayshil A. Patel, jayshil.patel(at)astro.su.se
Alexis Brandeker, alexis(at)astro.su.se
(End) Patricia Vannier [CDS] 18-Feb-2022