Opacity distribution functions for stellar spectra synthesis

Abstract

Contex. Stellar spectra synthesis is essential for the characterization of potential planetary hosts. In addition, comprehensive stellar variability calculations with fast radiative transfer are needed to disentangle planetary transits from stellar magnetically-driven variability. The planet-hunting space telescopes, such as CoRoT, Kepler, and TESS will bring vast quantities of data, rekindling the interest in fast calculations of the radiative transfer. Aims. We revisit the Opacity Distribution Functions (ODF) approach routinely applied to speedup stellar spectral synthesis. To achieve a considerable speedup relative to the current state-of-the-art, we further optimize the approach and search for the best ODF configuration. Furthermore, we generalize the ODF approach for fast calculations of flux in various filters often used in stellar observations. Methods. In a parameter-sweep-fashion, we generated ODF in the spectral range from UV to IR with different setups. The most accurate ODF configuration for each spectral interval was determined. For calculations of the radiative fluxes through filters we adapted the wavelength grid based on the transmission curve, whereafter the normal ODF procedure was performed. Results. Our optimum ODF configuration allows for a three fold speedup, compared to the previously used ODF configurations. The ODF generalization to calculate fluxes through filters results in a speedup of more than two orders of magnitude.

8 pages, 11 figures

References in corpus (13)

• The Gaia mission
• The Solar Optical Telescope for the Hinode Mission: An Overview
• Solar Irradiance Variability and Climate
• Recent variability of the solar spectral irradiance and its impact on climate modelling
• The second flight of the SUNRISE balloon-borne solar observatory: overview of instrument updates, the flight, the data and first results
• RH 1.5D: a massively parallel code for multi-level radiative transfer with partial frequency redistribution and Zeeman polarisation
• NLTE solar irradiance modeling with the COSI code
• Three-dimensional simulations of near-surface convection in main-sequence stars. III. The structure of small-scale magnetic flux concentrations
• Comparison of solar photospheric bright points between SUNRISE observations and MHD simulations
• 3-D non-LTE radiative transfer effects in Fe I lines: II. Line formation in 3-D radiation hydrodynamic simulations
• Spectral variability of photospheric radiation due to faculae I: The Sun and Sun-like stars
• Three-dimensional non-LTE radiative transfer effects in Fe I lines I. Flux sheet and flux tube geometries
• Three-dimensional simulations of near-surface convection in main-sequence stars. IV. Effect of small-scale magnetic flux concentrations on centre-to-limb variation and spectral lines

Cited by in corpus (6)

• MPS-ATLAS: A fast all-in-one code for synthesising stellar spectra
• Stellar limb darkening. A new MPS-ATLAS library for Kepler, TESS, CHEOPS, and PLATO passbands
• Can 1D radiative equilibrium models of faculae be used for calculating contamination of transmission spectra?
• Power spectrum of turbulent convection in the solar photosphere
• Opacity for realistic 3D MHD simulations of cool stellar atmospheres
• Radiative transfer with opacity distribution functions: Application to narrow band filters