Tau: A 1D radiative transfer code for transmission spectroscopy of extrasolar planet atmospheres

Abstract

The tau code is a 1D line-by-line radiative transfer code, which is generally applicable for modelling transmission spectra of close-in extrasolar planets. The inputs are the assumed pressure–temperature profile of the planetary atmosphere, the continuum absorption coefficients and the absorption cross-sections for the trace molecular absorbers present in the model, as well as the fundamental system parameters taken from the published literature. The program then calculates the optical path through the planetary atmosphere of the radiation from the host star, and quantifies the absorption due to the modelled composition in a transmission spectrum of transit depth as a function of wavelength. The code is written in C++, parallelised using OpenMP, and is available for public download and use from http://www.ucl.ac.uk/exoplanets/. Program summaryProgram title: tauCatalogue identifier: AEPN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEPN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 56728No. of bytes in distributed program, including test data, etc.: 1907711Distribution format: tar.gzProgramming language: C++.Computer: non-specific.Operating system: Linux, Mac.Has the code been vectorised or parallelized?: YesRAM: 300 MBClassification: 1.3.External routines: OpenMP (http://openmp.org/wp/)Nature of problem:Calculation of molecular absorption, and hence transit depths, as a function of wavelength for stellar radiation passing through planetary atmospheres.Solution method:Line-by-line calculation of wavelength-dependent optical depths using absorption cross-sections for various trace molecular absorbers.Additional comments:The distribution file contains, •./doc/: readme and User Guide.•./run/: sample input data files•./out/sample_tau_output.dat: sample output file for Run Mode 9 (H2O at χ=10−5 for HD189733b at Tatm=1500K).Running time:From 0:5 to 500 s, depending on run parameters