HELIOS-K 2.0 Opacity Calculator and Open-source Opacity Database for Exoplanetary Atmospheres

Grimm, Simon L; Malik, Matej; Kitzmann, Daniel; Guzmán-Mesa, Andrea; Hoeijmakers, H. Jens; Fisher, Chloe; Mendonça, João M.; Yurchenko, Sergey N.; Tennyson, Jonathan; Alesina, Fabien; Buchschacher, Nicolas; Burnier, Julien; Segransan, Damien; Kurucz, Robert L.; Heng, Kevin (2021). HELIOS-K 2.0 Opacity Calculator and Open-source Opacity Database for Exoplanetary Atmospheres. Astrophysical journal - supplement series, 253(1), p. 30. Institute of Physics Publishing IOP 10.3847/1538-4365/abd773

Grimm_2021_ApJS_253_30.pdf - Published Version
Available under License Publisher holds Copyright.

Download (4MB) | Preview

Computing and using opacities is a key part of modeling and interpreting data of exoplanetary atmospheres. Since the underlying spectroscopic line lists are constantly expanding and currently include up to ∼1010–1011 transition lines, the opacity calculator codes need to become more powerful. Here we present major upgrades to the HELIOS-K GPU-accelerated opacity calculator and describe the necessary steps to process large line lists within a reasonable amount of time. Besides performance improvements, we include more capabilities and present a toolbox for handling different atomic and molecular data sets, from downloading and preprocessing the data to performing the opacity calculations in a user-friendly way. HELIOS-K supports line lists from ExoMol, HITRAN, HITEMP, NIST, Kurucz, and VALD3. By matching the resolution of 0.1 cm−1 and cutting length of 25 cm−1 used by the ExoCross code for timing performance (251 s excluding data read-in time), HELIOS-K can process the ExoMol BT2 water line list in 12.5 s. Using a resolution of 0.01 cm−1, it takes 45 s, equivalent to about 107 lines s−1. As a wavenumber resolution of 0.01 cm−1 suffices for most exoplanetary atmosphere spectroscopic calculations, we adopt this resolution in calculating opacity functions for several hundred atomic and molecular species and make them freely available on the open-access DACE database. For the opacity calculations of the database, we use a cutting length of 100 cm−1 for molecules and no cutting length for atoms. Our opacities are available for downloading from https://dace.unige.ch/opacityDatabase and may be visualized using https://dace.unige.ch/opacity.

Item Type:

Journal Article (Original Article)


10 Strategic Research Centers > Center for Space and Habitability (CSH)
13 Central Units > Administrative Director's Office > IT Section
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Grimm, Simon Lukas, Kitzmann, Daniel, Fisher, Chloe Elizabeth, Heng, Kevin


500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services




Institute of Physics Publishing IOP




Danielle Zemp

Date Deposited:

18 May 2022 09:24

Last Modified:

05 Dec 2022 16:19

Publisher DOI:






Actions (login required)

Edit item Edit item
Provide Feedback