Helios-r2 : A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres

Kitzmann, Daniel; Heng, Kevin; Oreshenko, Maria; Grimm, Simon; Apai, Dániel; Bowler, Brendan P.; Burgasser, Adam J.; Marley, Mark S. (2020). Helios-r2 : A New Bayesian, Open-source Retrieval Model for Brown Dwarfs and Exoplanet Atmospheres. Astrophysical journal, 890(2), p. 174. Institute of Physics Publishing IOP 10.3847/1538-4357/ab6d71

[img]
Preview
Text
1910.01070.pdf - Draft Version
Available under License Publisher holds Copyright.

Download (8MB) | Preview
[img]
Preview
Text
Kitzmann_2020_ApJ_890_174.pdf - Published Version
Available under License Publisher holds Copyright.

Download (7MB) | Preview

We present an improved, hybrid CPU-GPU atmospheric retrieval code, Helios-r2, which is applicable to medium-resolution emission spectra of brown dwarfs, in preparation for precision atmospheric spectroscopy in the era of the James Webb Space Telescope. The model is available as open-source code on the Exoclimes Simulation Platform. We subject Helios-r2 to a battery of tests of varying difficulty. The simplest test involves a mock retrieval on a forward model generated using the same radiative transfer technique, the same implementation of opacities, and the same chemistry model. The least trivial test involves a mock retrieval on synthetic spectra from the Sonora model grid, which uses a different radiative transfer technique, a different implementation of opacities, and a different chemistry model. A calibration factor, which is included to capture uncertainties in the brown dwarf radius, distance to the brown dwarf and flux calibration of the spectrum, may compensate, sometimes erroneously, for discrepancies in modeling choices and implementation. We analyze spectra of the benchmark brown dwarf GJ 570 D and the binary brown dwarf companions in the Epsilon Indi system. The retrieved surface gravities are consistent with previous studies and/or values inferred from dynamical masses (for Epsilon Indi Ba and Bb only). There remains no clear criterion on how to reject unphysical values of the retrieved brown dwarf radii. The inferred radii and corresponding masses should be taken with great caution. The retrieved carbon-to-oxygen ratios and metallicity depend on whether chemical equilibrium is assumed.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Center for Space and Habitability (CSH)

UniBE Contributor:

Kitzmann, Daniel; Heng, Kevin; Oreshenko, Maria and Grimm, Simon

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

0004-637X

Publisher:

Institute of Physics Publishing IOP

Language:

English

Submitter:

Danielle Zemp

Date Deposited:

06 May 2020 12:02

Last Modified:

10 May 2020 02:44

Publisher DOI:

10.3847/1538-4357/ab6d71

BORIS DOI:

10.7892/boris.142576

URI:

https://boris.unibe.ch/id/eprint/142576

Actions (login required)

Edit item Edit item
Provide Feedback