Eclipse depths¶

Although PLATON began life as a transmission spectrum calculator, we have also written an eclipse depth calculator and retriever.

To use the eclipse depth calculator, first create a temperature-pressure profile:

from platon.TP_profile import Profile
p = Profile()
p.set_from_radiative_solution(T_star, Rs, a, Mp, Rp, beta, log_k_th, log_gamma, log_gamma2, alpha, T_int)

This creates a parametric T-P profile according to Line et al 2013, which is an extension of the Guillot et al 2010 parameterization. We recommend the use of this profile.

Alternatively:

from platon.TP_profile import Profile
p = Profile()
p.set_parametric(1200, 500, 0.5, 0.6, 1e6, 1900)

This creates a parametric T-P profile according to Madhusudhan & Seager 2009. The parameters are: T₀, P₁, α₁, α₂, P₃, T₃. P₀ is set to 10^-4 Pa, while P₂ and T₂ are derived from the six specified parameters.

Then, call the eclipse depth calculator:

from platon.eclipse_depth_calculator import EclipseDepthCalculator
calc = EclipseDepthCalculator(method="xsec") #"ktables" for correlated k
wavelengths, depths = calc.compute_depths(p, Rs, Mp, Rp, Tstar)

Most of the same parameters accepted by the transit depth calculator are also accepted by the eclipse depth calculator.

It is also possible to retrieve on combined transit and eclipse depths:

from platon.combined_retriever import CombinedRetriever

retriever = CombinedRetriever()
fit_info = retriever.get_default_fit_info(Rs, Mp, Rp, T_limb,
               T0=1200, P1=500, alpha1=0.5, alpha2=0.6, P3=1e6, T3=1900)

fit_info.add_uniform_fit_param(...)
fit_info.add_uniform_fit_param(...)

result = retriever.run_multinest(transit_bins, transit_depths, transit_errors,
                                 eclipse_bins, eclipse_depths, eclipse_errors,
                                 fit_info,
                                 rad_method="xsec") #"ktables" for corr-k

Here, T_limb is the temperature at the planetary limb (used for transit depths), while the T-P profile parameters are for the dayside (used for eclipse depths).

To do an eclipse-only retrieval, set transit_bins, transit_depths, and transit_errors to None, and likewise to do a transit-only retrieval.