J/A+A/684/A27 WASP-76 CHEOPS light curves (Demangeon+, 2024)
Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b.
Demangeon O.D.S., Cubillos P.E., Singh V., Wilson T.G., Carone L.,
Bekkelien A., Deline A., Ehrenreich D., Maxted P.F.L., Demory B.-O.,
Zingales T., Lendl M., Bonfanti A., Sousa S.G., Brandeker A., Alibert Y.,
Alonso R.; Asquier J., Barczy T., Barrado Navascues D., Barros S.C.C.,
Baumjohann W., Beck M., Beck T., Benz W., Billot N., Biondi F., Borsato L.,
Broeg C., Buder M., Collier Cameron A., Csizmadia Sz., Davies M.B.,
Deleuil M., Delrez L., Erikson A., Fortier A., Fossati L., Fridlund M.,
Gandolfi D., Gillon M., Guedel M., Guenther M. N., Heitzmann A., Helling C.,
Hoyer S., Isaak K.G., Kiss L.L., Lam K.W.F., Laskar J.,
Lecavelier des Etangs A., Magrin D., Mecina M., Mordasini C.,
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., Rieder M., Salmon S., Santos N.C., Scandariato G., Segransan D.,
Simon A.E., Smith A.M.S., Stalport M., Szabo Gy.M., Thomas N., Udry S.,
Van Grootel V., Venturini J., Villaver E., Walton N.A.
<Astron. Astrophys. 684, A27 (2024)>
=2024A&A...684A..27D 2024A&A...684A..27D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ; Optical
Keywords: techniques: photometric - planets and satellites: atmospheres -
planets and satellites: composition
Abstract:
WASP-76 b has been a recurrent subject of study since the detection of
a signature in high-resolution transit spectroscopy data indicating an
asymmetry between the two limbs of the planet. The existence of this
asymmetric signature has been confirmed by multiple studies, but its
physical origin is still under debate. In addition, it contrasts with
the absence of asymmetry reported in the infrared (IR) phase curve.
We provide a more comprehensive dataset of WASP-76 b with the goal of
drawing a complete view of the physical processes at work in this
atmosphere. In particular, we attempt to reconcile visible
high-resolution transit spectroscopy data and IR broadband phase
curves.
We gathered 3 phase curves, 20 occultations, and 6 transits for
WASP-76 b in the visible with the cheops space telescope. We also
report the analysis of three unpublished sectors observed by the tess
space telescope (also in the visible), which represents 34 phase
curves. Results: WASP-76 b displays an occultation of 260±11 and
152±10ppm in tess and cheops bandpasses respectively. Depending
on the composition assumed for the atmosphere and the data reduction
used for the IR data, we derived geometric albedo estimates that range
from 0.05±0.023 to 0.146±0.013 and from <0.13 to 0.189±0.017 in
the cheops and tess bandpasses, respectively. As expected from the IR
phase curves, a low-order model of the phase curves does not yield any
detectable asymmetry in the visible either. However, an empirical
model allowing for sharper phase curve variations offers a hint of a
flux excess before the occultation, with an amplitude of ∼40 ppm, an
orbital offset of ~-30 degrees, and a width of ∼20 degrees. We also
constrained the orbital eccentricity of WASP-76 b to a value lower
than 0.0067, with a 99.7% confidence level. This result contradicts
earlier proposed scenarios aimed at explaining the asymmetry observed
in high-resolution transit spectroscopy.
In light of these findings, we hypothesise that WASP-76 b could have
night-side clouds that extend predominantly towards its eastern limb.
At this limb, the clouds would be associated with spherical droplets
or spherically shaped aerosols of an unknown species, which would be
responsible for a glory effect in the visible phase curves.
Description:
We present the result a study of the broadband photometric data
available on WASP-76 b (CHEOPS, TESS, HST and Spitzer) focusing on the
occultation and phase curves. In particular, we observed WASP-76 b
with CHEOPS during 29 separate visits spread over 3 consecutives
observability periods (3 years). We observed 2 full PC, 15
occultations, and 2 transits between 2020-09-09 and 2020-12-16. One
year later, we observed 1 additional PC, 5 more occultations and 3
transits from 2021-09-05 to 2021-12-07. Finally, a year later, on
2022-09-18, we observed 1 additional transit. In this catalogue
we provide the raw and reduced data of this observation campaign.
Objects:
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RA (2000) DE Designation(s)
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01 46 31.85 +02 42 02.0 WASP-76 = TIC 293435336
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 101 13452 Raw and detrended CHEOPS light curves
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See also:
https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html : TESS data
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 18 F18.13 d Time Time of the measurement in BTJD (BJD-2457000)
(Time)
20- 37 F18.10 ppm NFluxRaw Raw normalized flux as provided by the CHEOPS
data reduction pipeline for the DEFAULT
aperture (RawNormalisedFlux) (1)
39- 63 F25.18 ppm DFluxVar Flux variation corrected from instrumental
systematics (DetrendedFluxVariations)
65- 82 F18.14 ppm e_Flux Error on the flux, applies to both the raw and
detrended fluxes (Flux_error)
84-101 F18.14 --- eFluxJitt Error on the flux including the jitter
parameter, applies to both the raw and
detrended fluxes (Fluxerrorwith_Jitter)
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Note (1): 1 should correspond to the stellar flux level.
Nore (2): 0 corresponds to the stellar flux level.
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Acknowledgements:
Olivier Demangeon, olivier.demangeon(at)astro.up.pt
(End) Patricia Vannier [CDS] 21-Feb-2024