scholarly journals Atmospheric characterization of hot Jupiters using hierarchical models of Spitzer observations

2021 ◽  
Author(s):  
Dylan Keating ◽  
Nicolas B Cowan
Keyword(s):  
Hierarchical Model ◽  
Information Criterion ◽  
Phase Curve ◽  
Bayesian Hierarchical ◽  
Hot Jupiters ◽  
Hierarchical Modelling ◽  
Brightness Temperatures ◽  
Eclipse Observations ◽  
The Individual

Abstract The field of exoplanet atmospheric characterization is trending towards comparative studies involving many planetary systems, and using Bayesian hierarchical modelling is a natural next step. Here we demonstrate two use cases. We first use hierarchical modelling to quantify variability in repeated observations by reanalyzing a suite of ten Spitzer secondary eclipse observations of the hot Jupiter XO-3b. We compare three models: one where we fit ten separate eclipse depths, one where we use a single eclipse depth for all ten observations, and a hierarchical model. By comparing the Widely Applicable Information Criterion of each model, we show that the hierarchical model is preferred over the others. The hierarchical model yields less scatter across the suite of eclipse depths—and higher precision on the individual eclipse depths—than does fitting the observations separately. We find that the hierarchical eclipse depth uncertainty is larger than the uncertainties on the individual eclipse depths, which suggests either slight astrophysical variability or that single eclipse observations underestimate the true eclipse depth uncertainty. Finally, we fit a suite of published dayside brightness measurements for 37 planets using a hierarchical model of brightness temperature versus irradiation temperature. The hierarchical model gives tighter constraints on the individual brightness temperatures than the non-hierarchical model. Although we tested hierarchical modelling on Spitzer eclipse data of hot Jupiters, it is applicable to observations of smaller planets like hot neptunes and super earths, as well as for photometric and spectroscopic transit or phase curve observations.

scholarly journals TESS unveils the phase curve of WASP-33b

2020 ◽  
Vol 639 ◽  
pp. A34 ◽  
Author(s):  
C. von Essen ◽  
M. Mallonn ◽  
C. C. Borre ◽  
V. Antoci ◽  
K. G. Stassun ◽  
...  
Keyword(s):  
Light Curve ◽  
Signal To Noise Ratio ◽  
Phase Curve ◽  
Hot Jupiters ◽  
Brightness Temperatures ◽  
Pulsation Spectrum ◽  
Stellar Pulsations ◽  
Detailed Determination

We present the detection and characterization of the full-orbit phase curve and secondary eclipse of the ultra-hot Jupiter WASP-33b at optical wavelengths, along with the pulsation spectrum of the host star. We analyzed data collected by the Transiting Exoplanet Survey Satellite (TESS) in sector 18. WASP-33b belongs to a very short list of highly irradiated exoplanets that were discovered from the ground and were later visited by TESS. The host star of WASP-33b is of δ Scuti-type and shows nonradial pulsations in the millimagnitude regime, with periods comparable to the period of the primary transit. These completely deform the photometric light curve, which hinders our interpretations. By carrying out a detailed determination of the pulsation spectrum of the host star, we find 29 pulsation frequencies with a signal-to-noise ratio higher than 4. After cleaning the light curve from the stellar pulsations, we confidently report a secondary eclipse depth of 305.8 ± 35.5 parts-per-million (ppm), along with an amplitude of the phase curve of 100.4 ± 13.1 ppm and a corresponding westward offset between the region of maximum brightness and the substellar point of 28.7 ± 7.1 degrees, making WASP-33b one of the few planets with such an offset found so far. Our derived Bond albedo, AB = 0.369 ± 0.050, and heat recirculation efficiency, ɛ = 0.189 ± 0.014, confirm again that he behavior of WASP-33b is similar to that of other hot Jupiters, despite the high irradiation received from its host star. By connecting the amplitude of the phase curve to the primary transit and depths of the secondary eclipse, we determine that the day- and nightside brightness temperatures of WASP-33b are 3014 ± 60 K and 1605 ± 45 K, respectively. From the detection of photometric variations due to gravitational interactions, we estimate a planet mass of MP = 2.81 ± 0.53 MJ. Based on analyzing the stellar pulsations in the frame of the planetary orbit, we find no signals of star-planet interactions.

scholarly journals Bayesian Hierarchical Modeling of the Individual Hypoglycaemic Symptoms’ Reporting Consistency

2020 ◽  
Vol 8 (5) ◽  
pp. 5319-5324
Keyword(s):  
Predictive Model ◽  
Hierarchical Model ◽  
Hierarchical Modeling ◽  
Patient Specific ◽  
Bayesian Hierarchical Modeling ◽  
Serum Angiotensin Converting Enzyme ◽  
Bayesian Hierarchical ◽  
Factors Affecting ◽  
The Individual ◽  
Gender Type

Hypoglycaemia symptoms vary between individual and across episodes making it difficult for the patients to realize if they are having a hypoglycaemia. Therefore, the ability to detect the onset of hypoglycaemia is important for quick corrective action. In this paper, we describe a Bayesian hierarchical model which is able to quantify the consistency of reporting symptoms by individual patient and simultaneously investigate patient-specific covariates affecting the consistency. The model is developed within a Bayesian framework using Markov chain Monte Carlo methodology where the consistency parameter is estimated via Gibbs sampling. The association between patient-specific covariates and consistency is investigated using generalized linear model before implementing the stepwise regression to identify the best predictive model. The results obtained show that symptoms classified as autonomic and neuroglycopenic are prominent in detecting the onset of hypoglycaemia. No patient-specific covariate appears to be significantly affecting patients reporting' consistency. However, the best predictive model obtained contains covariates gender, type of diabetes, retinopathy, serum angiotensin converting enzyme and C-peptide.The hierarchical model developed allows researchers to estimate patient’s consistency in reporting symptoms and identify factors affecting it under one setting.

scholarly journals Following the TraCS of exoplanets with Pan-Planets: Wendelstein-1b and Wendelstein-2b

2020 ◽  
Vol 639 ◽  
pp. A130
Author(s):  
C. Obermeier ◽  
J. Steuer ◽  
H. Kellermann ◽  
R. P. Saglia ◽  
Th. Henning ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Radial Velocity ◽  
Thermal Emission ◽  
Dwarf Star ◽  
Statistical Characterization ◽  
Hot Jupiters ◽  
Eclipse Observations ◽  
Short Period ◽  
Hot Jupiter

Hot Jupiters seem to get rarer with decreasing stellar mass. The goal of the Pan-Planets transit survey was the detection of such planets and a statistical characterization of their frequency. Here, we announce the discovery and validation of two planets found in that survey, Wendelstein-1b and Wendelstein-2b, which are two short-period hot Jupiters that orbit late K host stars. We validated them both by the traditional method of radial velocity measurements with the HIgh Resolution Echelle Spectrometer and the Habitable-zone Planet Finder instruments and then by their Transit Color Signature (TraCS). We observed the targets in the wavelength range of 4000−24 000 Å and performed a simultaneous multiband transit fit and additionally determined their thermal emission via secondary eclipse observations. Wendelstein-1b is a hot Jupiter with a radius of 1.0314−0.0061+0.0061 RJ and mass of 0.592−0.129+0.0165 MJ, orbiting a K7V dwarf star at a period of 2.66 d, and has an estimated surface temperature of about 1727−90+78 K. Wendelstein-2b is a hot Jupiter with a radius of 1.1592−0.0210+0.0204 RJ and a mass of 0.731−0.311+0.0541 MJ, orbiting a K6V dwarf star at a period of 1.75 d, and has an estimated surface temperature of about 1852−140+120 K. With this, we demonstrate that multiband photometry is an effective way of validating transiting exoplanets, in particular for fainter targets since radial velocity follow-up becomes more and more costly for those targets.

scholarly journals A transition between the hot and the ultra-hot Jupiter atmospheres

2020 ◽  
Vol 639 ◽  
pp. A36 ◽  
Author(s):  
Claire Baxter ◽  
Jean-Michel Désert ◽  
Vivien Parmentier ◽  
Mike Line ◽  
Jonathan Fortney ◽  
...  
Keyword(s):  
Near Infrared ◽  
Thermal Structure ◽  
Emission Spectra ◽  
Equilibrium Temperature ◽  
Hot Jupiters ◽  
Brightness Temperatures ◽  
Eclipse Observations ◽  
Theoretical Predictions ◽  
The Difference ◽  
Hot Jupiter

A key hypothesis in the field of exoplanet atmospheres is the trend of atmospheric thermal structure with planetary equilibrium temperature. We explore this trend and report here the first statistical detection of a transition in the near-infrared atmospheric emission between hot and ultra-hot Jupiters. We measure this transition using secondary eclipse observations and interpret this phenomenon as changes in atmospheric properties, and more specifically in terms of transition from non-inverted to inverted thermal profiles. We examine a sample of 78 hot Jupiters with secondary eclipse measurements at 3.6 and 4.5 μm measured with Spitzer Infrared Array Camera. We calculate the planetary brightness temperatures using PHOENIX models to correct for the stellar flux. We measure the deviation of the data from the blackbody, which we define as the difference between the observed 4.5 μm eclipse depth and that expected at this wavelength based on the brightness temperature measured at 3.6 μm. We study how the deviation between 3.6 and 4.5 μm changes with theoretical predictions with equilibrium temperature and incoming stellar irradiation. We reveal a clear transition in the observed emission spectra of the hot Jupiter population at 1660 ± 100 K in the zero albedo, full redistribution equilibrium temperature. We find the hotter exoplanets have even hotter daysides at 4.5 μm compared to 3.6 μm, which manifests as an exponential increase in the emitted power of the planets with stellar insolation. We propose that the measured transition is a result of seeing carbon monoxide in emission due to the formation of temperature inversions in the atmospheres of the hottest planets. These thermal inversions could be caused by the presence of atomic and molecular species with high opacities in the optical and/or the lack of cooling species. Our findings are in remarkable agreement with a new grid of 1D radiative and convective models varying metallicity, carbon to oxygen ratio (C/O), surface gravity, and stellar effective temperature. We find that the population of hot Jupiters statistically disfavors high C/O planets (C/O ≥ 0.85).

Sign in / Sign up

Export Citation Format

Share Document