Analysis of Early Science observations with the CHaracterising ExOPlanets Satellite (CHEOPS) using pycheops

Maxted, P. F. L.; Ehrenreich, D.; Wilson, T. G.; Alibert, Y.; Cameron, A. Collier; Hoyer, S.; Sousa, S. G.; Olofsson, G.; Bekkelien, A.; Deline, A.; Delrez, L.; Bonfanti, A.; Borsato, L.; Alonso, R.; Escudé, G. Anglada; Barrado, D.; Barros, S. C. C.; Baumjohann, W.; Beck, M.; Beck, T.; Benz, W.; Billot, N.; Biondi, F.; Bonfils, X.; Brandeker, A.; Broeg, C.; Bárczy, T.; Cabrera, J.; Charnoz, S.; Van Damme, C. Corral; Csizmadia, Sz.; Davies, M. B.; Deleuil, M.; Demangeon, O. D. S.; Demory, B. -O.; Erikson, A.; Florén, H. G.; Fortier, A.; Fossati, L.; Fridlund, M.; Futyan, D.; Gandolfi, D.; Gillon, M.; Guedel, M.; Guterman, P.; Heng, K.; Isaak, K. G.; Kiss, L.; Laskar, J.; Etangs, A. Lecavelier des; Lendl, M.; Lovis, C.; Magrin, D.; Nascimbeni, V.; Ottensamer, R.; Pagano, I.; Pallé, E.; Peter, G.; Piotto, G.; Pollacco, D.; Pozuelos, F. J.; Queloz, D.; Ragazzoni, R.; Rando, N.; Rauer, H.; Reimers, C.; Ribas, I.; Salmon, S.; Santos, N. C.; Scandariato, G.; Simon, A. E.; Smith, A. M. S.; Steller, M.; Swayne, M. I.; Szabó, Gy. M.; Ségransan, D.; Thomas, N.; Udry, S.; Van Grootel, V.; Walton, N. A.

doi:10.48550/arxiv.2111.08828

Cited by 9 publications

(17 citation statements)

References 17 publications

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“…To avoid the large number of fitted parameters, pycheops has implemented a technique (Luger et al 2017) to perform an implicit decorrelation of several light curves using a GP. A detailed description of pycheops and example applications to CHEOPS data are given in Maxted et al (2021). The derived transit times with pycheops are closer than 1 σ to the ones derived with the multidimensional GP.…”

Section: Pycheopsmentioning

confidence: 61%

“…For WASP-103, this corresponds to ∼ 3.4 CHEOPS orbits (∼ 7.8 hours). However, for observations with an efficiency of less than 88%, we do not have the recommended three CHEOPS orbits of data to be able to detrend the systematic noise (Maxted et al 2021). Hence, we increased the duration of the observations which resulted in a much better detrending of the systematic noise (see Section 2.2).…”

Section: Cheops Observations Of Wasp-103bmentioning

confidence: 99%

“…The first one is based on multi-dimensional Gaussian processes (GPs) (Rasmussen & Williams 2006) coupled with the batman transit model (Kreidberg 2015a). The second method is based on linear decorrelation using a combination of sinusoidal functions implemented in pycheops (Maxted et al 2021).…”

Section: Cheops Data Analysismentioning

confidence: 99%

“…For comparison, we also analysed the OPTIMAL extracted light curves with pycheops (Maxted et al 2021), a custom python package developed specially for CHEOPS data. First we used the single visit analysis to determine the best parameters to use as decorrelation instrumental parameters.…”

Section: Pycheopsmentioning

confidence: 99%

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Detection of the tidal deformation of WASP-103b at $3\,σ$ with CHEOPS

Barros,

Akinsanm,

Boué

et al. 2022

Preprint

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Context. Ultra-short period planets undergo strong tidal interactions with their host star which lead to planet deformation and orbital tidal decay. Aims. WASP-103b is the exoplanet with the highest expected deformation signature in its transit light curve and one of the shortest expected spiral-in times. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet's internal structure. Moreover, measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics. Methods. We obtained 12 transit light curves of WASP-103b with the CHaracterising ExOplanet Satellite (CHEOPS) to estimate the tidal deformation and tidal decay of this extreme system. We modelled the high-precision CHEOPS transit light curves together with systematic instrumental noise using multi-dimensional Gaussian process regression informed by a set of instrumental parameters. To model the tidal deformation, we used a parametrisation model which allowed us to determine the second degree fluid Love number of the planet. We combined our light curves with previously observed transits of WASP-103b with the Hubble Space Telescope (HST) and Spitzer to increase the signal-to-noise of the light curve and better distinguish the minute signal expected from the planetary deformation. Results. We estimate the radial Love number of WASP-103b to be h f = 1.59 +0.45 −0.53 . This is the first time that the tidal deformation is directly detected (at 3 σ) from the transit light curve of an exoplanet. Combining the transit times derived from CHEOPS, HST, and Spitzer light curves with the other transit times available in the literature, we find no significant orbital period variation for WASP-103b. However, the data show a hint of an orbital period increase instead of a decrease, as is expected for tidal decay. This could be either due to a visual companion star if this star is bound, the Applegate effect, or a statistical artefact. Conclusions. The estimated Love number of WASP-103b is similar to Jupiter's. This will allow us to constrain the internal structure and composition of WASP-103b, which could provide clues on the inflation of hot Jupiters. Future observations with James Webb Space Telescope (JWST) can better constrain the radial Love number of WASP-103b due to their high signal-to-noise and the smaller signature of limb darkening in the infrared. A longer time baseline is needed to constrain the tidal decay in this system.

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Section: Pycheopsmentioning

confidence: 61%

Section: Cheops Observations Of Wasp-103bmentioning

confidence: 99%

Section: Cheops Data Analysismentioning

confidence: 99%

Section: Pycheopsmentioning

confidence: 99%

See 2 more Smart Citations

Detection of the tidal deformation of WASP-103b at $3\,σ$ with CHEOPS

Barros,

Akinsanm,

Boué

et al. 2022

Preprint

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“…After masking out the flares (as shown in Fig. A.1), we determined the transit parameters using the pycheops software module (Maxted et al 2021). pycheops uses the qpower2 transit model and the power-2 limb-darkening law (Maxted & Gill 2019); it calculates transit models of a spot-free star and a planet with a circular silhouette.…”

Section: The Transit Modelmentioning

confidence: 99%

Transit timing variations of AU Microscopii b and c

Szabó,

Garai,

Brandeker

et al. 2022

Preprint

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Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as detected in combined TESS (2018, 2020) and CHEOPS (2020, 2021) transit observations. AU Mic is a young planetary system with a debris disk and two transiting warm Neptunes. A TTV on the order of several minutes was previously reported for AU Mic b, which was suggested to be an outcome of mutual perturbations between the planets in the system. In 2021, we observed AU Mic b (five transits) and c (three transits) with the CHEOPS space telescope to follow-up the TTV of AU Mic b and possibly detect a TTV for AU Mic c. When analyzing TESS and CHEOPS 2020-2021 measurements together, we find that a prominent TTV emerges with a full span of ≥ 23 minutes between the two TTV extrema. Assuming that the period change results from a periodic process -such as mutual perturbations-we demonstrate that the times of transits in the summer of 2022 are expected to be 30-85 minutes later than predicted by the available linear ephemeris.

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The atmosphere and architecture of WASP-189 b probed by its CHEOPS phase curve

Deline

Hooton

Lendl

et al. 2022

A&A

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Context. Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These ‘ultra-hot Jupiters’ have atmospheres made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet’s atmospheric properties. Aims. We aim to analyse the photometric observations of WASP-189 acquired with the Characterising Exoplanet Satellite (CHEOPS) to derive constraints on the system architecture and the planetary atmosphere. Methods. We implemented a light-curve model suited for an asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also modelled the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity, and CHEOPS systematics. Results. From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189 b, Rp = 1.600−0.016+0.017 RJ, with a precision of 1%, and the true orbital obliquity of the planetary system, Ψp = 89.6 ± 1.2deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth of δecl = 96.5−5.0+4.5 ppm, from which we derive an upper limit on the geometric albedo: Ag < 0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope. Conclusions. Based on the derived system architecture, we predict the eclipse depth in the upcoming Transiting Exoplanet Survey Satellite (TESS) observations to be up to ~165 ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment J2 (oblateness).

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Analysis of Early Science observations with the CHaracterising ExOPlanets Satellite (CHEOPS) using pycheops

Cited by 9 publications

References 17 publications

Detection of the tidal deformation of WASP-103b at $3\,σ$ with CHEOPS

Detection of the tidal deformation of WASP-103b at $3\,σ$ with CHEOPS

Transit timing variations of AU Microscopii b and c

The atmosphere and architecture of WASP-189 b probed by its CHEOPS phase curve

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