J/A+A/625/A136 WASP-18b HST/WFC3 spectroscopic phase curves (Arcangeli+, 2019)
Climate of an ultra hot Jupiter.
Spectroscopic phase curve of WASP-18b with HST/WFC3.
Arcangeli J., Desert J.-M., Parmentier V., Stevenson K.B., Bean J.L.,
Line M.R., Kreidberg L., Fortney J.J., Showman A.P.
<Astron. Astrophys. 625, A136 (2019)>
=2019A&A...625A.136A 2019A&A...625A.136A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Spectra, infrared
Keywords: planets and satellites: atmospheres
Abstract:
We present the analysis of a full-orbit, spectroscopic phase curve of
the ultra hot Jupiter (UHJ) WASP-18b, obtained with the Wide Field
Camera 3 aboard the Hubble Space Telescope. We measured the normalised
day-night contrast of the planet as >0.96 in luminosity: the
disc-integrated dayside emission from the planet is at 964±25ppm,
corresponding to 2894±30K, and we place an upper limit on the
nightside emission of <32ppm or 1430K at the 3σlevel. We also
find that the peak of the phase curve exhibits a small, but
significant oset in brightness of 4.5±0.5 degrees eastward. We
compare the extracted phase curve and phase-resolved spectra to 3D
global circulation models and find that broadly the data can be well
reproduced by some of these models. We find from this comparison
several constraints on the atmospheric properties of the planet.
Firstly we find that we need ecient drag to explain the very inefficient
day-night recirculation observed.We demonstrate that this drag could
be due to Lorentz-force drag by a magnetic field as weak as 10 gauss.
Secondly, we show that a high metallicity is not required to match the
large day-night temperature contrast. In fact, the effect of metallicity
on the phase curve is different from cooler gas-giant counterparts
because of the high-temperature chemistry in the atmosphere of
WASP-18b. Additionally, we compared the current UHJ spectroscopic
phase curves, WASP-18b and WASP-103b, and show that these two planets
provide a consistent picture with remarkable similarities in their
measured and inferred properties. However, key differences in these
properties, such as their brightness osets and radius anomalies,
suggest that UHJ could be used to separate between competing theories
for the inflation of gas-giant planets.
Description:
Wavelength-dependent phase curves of the ultra hot Jupiter WASP-18b
taken with HST/WFC3 with the G141 grism. These phase curves have had
instrumental systematics and stellar ellipsoidal variations removed.
The data are normalised so that the in-eclipse flux is 1,
corresponding to the star alone.
Objects:
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RA (2000) DE Designation(s)
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01 37 25.03 -45 40 40.4 WASP-18b = WASP-18b
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
w114_117.dat 49 306 Phase curve between 1.14-1.17 micron
w117_121.dat 49 306 Phase curve between 1.17-1.21 micron
w121_124.dat 49 306 Phase curve between 1.21-1.24 micron
w124_127.dat 49 306 Phase curve between 1.24-1.27 micron
w127_130.dat 49 306 Phase curve between 1.27-1.30 micron
w130_134.dat 49 306 Phase curve between 1.30-1.34 micron
w134_137.dat 49 306 Phase curve between 1.34-1.37 micron
w137_140.dat 49 306 Phase curve between 1.37-1.40 micron
w140_144.dat 49 306 Phase curve between 1.40-1.44 micron
w144_147.dat 49 306 Phase curve between 1.44-1.47 micron
w147_150.dat 49 306 Phase curve between 1.47-1.50 micron
w150_153.dat 49 306 Phase curve between 1.50-1.53 micron
w153_157.dat 49 306 Phase curve between 1.53-1.57 micron
w157_160.dat 49 306 Phase curve between 1.57-1.60 micron
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Byte-by-byte Description of file: w*.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d BJD Time at which each exposure was taken
17- 30 F14.12 --- Flux Normalised flux of the system
33- 50 F18.16 --- e_Flux Uncertainty on the measured flux
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Acknowledgements:
Jacob Arcangeli, jarcangeli92(at)gmail.com
(End) Patricia Vannier [CDS] 26-Apr-2019