Table 3
Parameter values for the WASP-18 b system.
Fitted parameter | Symbol | Value | Prior | Unit |
---|---|---|---|---|
Time of inferior conjunction | T 0 | 375.169847 ± 0.000019 |
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BJDTDB - 2 458 000 |
Orbital period | P | 0.941452379 ± 0.000000016 | – | days |
Planet-to-star radii ratio | Rp/R★ |
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– | – |
Normalised semi-major axis | a/R★ | 3.493 ± 0.011 | – | – |
Orbital inclination | i | 84.08 ± 0.17 |
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deg |
Eccentricity / argument of periastron | e cos ω | 0* | fixed | – |
e sin ω | 0* | fixed | – | |
Stellar radius | R★ | 1.2561 ± 0.0079 |
![]() |
R⊙ |
CHEOPS | ||||
Dayside flux† |
![]() |
![]() |
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ppm |
EV amplitude |
![]() |
![]() |
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ppm |
DB amplitude |
![]() |
![]() |
![]() |
ppm |
LDC |
![]() |
0.357 ± 0.018 | – | – |
![]() |
![]() |
– | – | |
TESS | ||||
Dayside flux† |
![]() |
340.4 ± 7.0 |
![]() |
ppm |
EV amplitude |
![]() |
![]() |
![]() |
ppm |
DB amplitude |
![]() |
![]() |
![]() |
ppm |
LDC |
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0.293 ± 0.018 | – | – |
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0.168 ± 0.031 | – | – | |
Spitzer/IRAC | ||||
Channel 1 dayside flux† |
![]() |
![]() |
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ppm |
Channel 2 dayside flux† |
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3935 ± 25 |
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ppm |
Channel 3 dayside flux† |
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4090 ± 230 |
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ppm |
Channel 4 dayside flux† |
![]() |
![]() |
![]() |
ppm |
Derived parameters | ||||
Optimal time of inferior conjunction |
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1251.662013 ± 0.000011 | BJDTDB - 2 458 000 | |
Planetary radius | Rp | 1.1926 ± 0.0077 | RJ | |
Semi-major axis | a |
![]() |
au | |
Impact parameter | b |
![]() |
R ★ | |
Eccentricity | e | 0* | – | |
CHEOPS occultation depth |
![]() |
211.3 ± 7.5 | ppm | |
TESS occultation depth |
![]() |
![]() |
ppm | |
Spitzer/IRAC Ch. 1 occ. depth |
![]() |
3098 ± 111 | ppm | |
Spitzer/IRAC Ch. 2 occ. depth |
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3925 ± 25 | ppm | |
Spitzer/IRAC Ch. 3 occ. depth |
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4080 ± 230 | ppm | |
Spitzer/IRAC Ch. 4 occ. depth |
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ppm | |
Transit duration | T 14 | 2.1790 ± 0.0017 | hours | |
Max. equilibrium dayside temperature | T day, max | 3061 ± 29‡ | K |
Notes. The top part of the table lists the fitted parameters with their corresponding prior probabilities. Uniform prior probabilities are represented with U(x
min, x
max), where x
min and x
max are the minimum and maximum allowed values, respectively. Normal (Gaussian) prior probabilities are written as N(μ, σ), where μ and σ are the mean and standard deviation of the normal distribution, respectively. The lower part of the table shows the values of parameters derived from the sampled parameter space. (*)We fixed the eccentricity to 0 despite the non-zero values reported in the literature (Hellier et al. 2009; Triaud et al. 2010; Nymeyer et al. 2011; Csizmadia et al. 2019) because of the small eccentricity value and the possible tidal origin of the eccentric radial-velocity signal (see discussion in Section 4.3). (†)The maximum values of the phase curve F
max are equal to the dayside fluxes because the phase offset Δφ was fixed to 0. (‡)Equilibrium dayside temperature assuming full absorption of the incoming radiation (AB
= 0), no heat redistribution (ε = 0, i.e. immediate re-radiation) and black-body spectral energy distributions for both the planet and the star, i.e. .
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