Spitzer thermal phase curve of WASP-121 b

Abstract

Aims. We analyse unpublished Spitzer observations of the thermal phase-curve of WASP-121 b, a benchmark ultra-hot Jupiter. Methods. We adopted the wavelet pixel-independent component analysis technique to remove challenging instrumental systematic effects in these datasets and we fit them simultaneously with parametric light-curve models. We also performed phase-curve retrievals to better understand the horizontal and vertical thermal structure of the planetary atmosphere. Results. We measured planetary brightness temperatures of $\sim$2700\,K (dayside) and $\sim$700--1100\,K (nightside), along with modest peak offsets of 5.9${}^{\circ }\pm$1.6 (3.6\,$\mu$m) and 5.0${}^{\circ }$${}_{-3.1}^{+3.4}$ (4.5\,$\mu$m) after mid-eclipse. These results suggest inefficient heat redistribution in the atmosphere of WASP-121 b. The inferred atmospheric Bond albedo and circulation efficiency align well with observed trends for hot giant exoplanets. Interestingly, the measured peak offsets correspond to a westward hot spot, which has rarely been observed. We also report consistent transit depths at 3.6 and 4.5\,$\mu$m, along with updated geometric and orbital parameters. Finally, we compared our Spitzer results with previous measurements, including recent JWST observations. Conclusions. We extracted new information on the thermal properties and dynamics of an exoplanet atmosphere from an especially problematic dataset. This study probes the reliability of exoplanet phase-curve parameters obtained from Spitzer observations when state-of-the-art pipelines are adopted to remove the instrumental systematic effects. It demonstrates that Spitzer phase-curve observations provide a useful baseline for comparison with JWST observations, and shows the increase in parameters precision achieved with the newer telescope.

14 pages, 10 figures

References in corpus (44)

• Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
• emcee v3: A Python ensemble sampling toolkit for affine-invariant MCMC
• Towards Chemical Constraints on Hot Jupiter Migration
• Tau-REx I: A next generation retrieval code for exoplanetary atmospheres
• An ultrahot gas-giant exoplanet with a stratosphere
• Spitzer Phase Curve Constraints for WASP-43b at 3.6 and 4.5 microns
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b
• High temperature condensate clouds in super-hot Jupiter atmospheres
• Balancing the Energy Budget of Short-Period Giant Planets: Evidence for Reflective Clouds and Optical Absorbers
• Atmospheric Rossiter-McLaughlin effect and transmission spectroscopy of WASP-121b with ESPRESSO
• Magnetic Effects in Hot Jupiter Atmospheres
• Variability in the Atmosphere of the Hot Giant Planet HAT-P-7 b
• Climate of an Ultra hot Jupiter: Spectroscopic phase curve of WASP-18b with HST/WFC3
• Properties of analytic transit light curve models
• Five key exoplanet questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse
• An emission spectrum for WASP-121b measured across the 0.8-1.1 micron wavelength range using the Hubble Space Telescope
• Detection of a Westward Hotspot Offset in the Atmosphere of a Hot Gas Giant CoRoT-2b
• Evidence for H${}_2$ Dissociation and Recombination Heat Transport in the Atmosphere of KELT-9b
• Diurnal variations in the stratosphere of the ultrahot giant exoplanet WASP-121b
• An inventory of atomic species in the atmosphere of WASP-121b using UVES high-resolution spectroscopy
• Confirmation of water emission in the dayside spectrum of the ultrahot Jupiter WASP-121b
• THOR: A New and Flexible Global Circulation Model to Explore Planetary Atmospheres
• TESS unveils the phase curve of WASP-33b. Characterization of the planetary atmosphere and the pulsations from the star
• A comparison of chemical models of exoplanet atmospheres enabled by TauREx 3.1
• Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b
• Neutral Cr and V in the atmosphere of ultra hot jupiter WASP-121 b
• Revisiting Spitzer transit observations with Independent Component Analysis: new results for the GJ436 system
• Revisiting the Energy Budget of WASP-43b: Enhanced day-night heat transport
• Shallow-water Magnetohydrodynamics for Westward Hotspots on Hot Jupiters
• Swift UVOT near-UV transit observations of WASP-121 b
• A JWST NIRSpec Phase Curve for WASP-121b: Dayside Emission Strongest Eastward of the Substellar Point and Nightside Conditions Conducive to Cloud Formation
• Low albedos of hot to ultra-hot Jupiters in the optical to near-infrared transition regime
• Detectability of shape deformation in short-period exoplanets
• A new look at Spitzer primary transit observations of the exoplanet HD189733b
• Phase curve pollution of exoplanet transmission spectra
• Modons on Tidally Synchronised Extrasolar Planets
• TauREx3 PhaseCurve: A 1.5D model for phase curve description
• On spectroscopic phase-curve retrievals: H2 dissociation and thermal inversion in the atmosphere of the ultra-hot Jupiter WASP-103 b
• A Lack of Variability Between Repeated Spitzer Phase Curves of WASP-43b
• The secondary transit of the hot Jupiter WASP-121b at 2 $\mu$m
• Inside-Out Planet Formation. VII. Astrochemical Models of Protoplanetary Disks and Implications for Planetary Compositions
• Thermal Phase Curves of XO-3b: an Eccentric Hot Jupiter at the Deuterium Burning Limit
• HST/STIS capability for Love number measurement of WASP-121b
• Is binning always sinning? The impact of time-averaging for exoplanet phase curves

Cited by in corpus (5)

• Is the atmosphere of the ultra-hot Jupiter WASP-121b variable?
• Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode
• Retrieving day- and nightside atmospheric properties of the ultra-hot Jupiter TOI-2109b. Detection of Fe and CO emission lines and evidence for inefficient heat transport
• Reflected-light Phase Curves with PICASO: A Kepler-7b Case Study
• Precise Constraints on the Energy Budget of WASP-121 b from its JWST NIRISS/SOSS Phase Curve