TSD: An Inverse Problem Approach for Recovering the Exoplanetary Atmosphere Transmission Spectrum from High-resolution Spectroscopy
- 1Uppsala University
- 2Pontificia Universidad Católica de Chile
Abstract
Our ability to observe, detect, and characterize exoplanetary atmospheres has grown by leaps and bounds over the last 20 yr, aided largely by developments in astronomical instrumentation, improvements in data analysis techniques, and an increase in the sophistication and availability of spectroscopic models. Over this time, detections have been made for a number of important molecular species across a range of wavelengths and spectral resolutions. Ground-based observations at high resolution are particularly valuable due to the high contrast achievable between the stellar spectral continuum and the cores of resolved exoplanet absorption features. However, recovering such features without relying on a theoretical or empirical model of the exoplanet atmosphere remains a major hurdle in data analysis, with traditional methods being limited by both the choice of algorithm used to remove the nonexoplanetary components of the signal, as well as the accuracy of model template spectra used for cross-correlation. Here we present a new algorithm Transmission Spectroscopy Decomposition (TSD) formulated as an inverse problem that reconstructs the planetary transmission spectrum without recourse to an exoplanet-atmosphere template, minimizing the number of assumed and theoretically modelled components. Instead of cross-correlation with precomputed template exoplanet spectra, we rely on high spectral resolution and instrument stability to distinguish between the stellar, exoplanetary, and telluric components and velocity frames in the sequence of absorption spectra taken during multiple transits. We demonstrate the performance of our new method using both simulated and real K -band observations from ESO’s VLT/CRIRES+ instrument and present results obtained from two transits of the highly inflated super-Neptune WASP-107 b, which orbits a nearby K7V star.
Related
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- The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems VIII: patchy forsterite and enstatite clouds in the atmosphere of VHS 1256 b, retrieval lessons learned and outlook to the future
- High-resolution transmission spectroscopy of KELT-18b Metastable helium detection at 1083 nm
- Recovering the Morning and Evening Limbs of WASP-94Ab from Its Limb-Averaged JWST Transmission Spectrum
BibTeX
@article{piskunov2026inverse,
title = {{TSD: An Inverse Problem Approach for Recovering the Exoplanetary Atmosphere Transmission Spectrum from High-resolution Spectroscopy}},
author = {Nikolai Piskunov and Adam D. Rains and Linn Boldt-Christmas},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea6b2},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea6b2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - TSD: An Inverse Problem Approach for Recovering the Exoplanetary Atmosphere Transmission Spectrum from High-resolution Spectroscopy
AU - Nikolai Piskunov
AU - Adam D. Rains
AU - Linn Boldt-Christmas
PY - 2026
DA - 2026/10/12
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea6b2
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea6b2
AB - Our ability to observe, detect, and characterize exoplanetary atmospheres has grown by leaps and bounds over the last 20 yr, aided largely by developments in astronomical instrumentation, improvements in data analysis techniques, and an increase in the sophistication and availability of spectroscopic models. Over this time, detections have been made for a number of important molecular species across a range of wavelengths and spectral resolutions. Ground-based observations at high resolution are particularly valuable due to the high contrast achievable between the stellar spectral continuum and the cores of resolved exoplanet absorption features. However, recovering such features without relying on a theoretical or empirical model of the exoplanet atmosphere remains a major hurdle in data analysis, with traditional methods being limited by both the choice of algorithm used to remove the nonexoplanetary components of the signal, as well as the accuracy of model template spectra used for cross-correlation. Here we present a new algorithm Transmission Spectroscopy Decomposition (TSD) formulated as an inverse problem that reconstructs the planetary transmission spectrum without recourse to an exoplanet-atmosphere template, minimizing the number of assumed and theoretically modelled components. Instead of cross-correlation with precomputed template exoplanet spectra, we rely on high spectral resolution and instrument stability to distinguish between the stellar, exoplanetary, and telluric components and velocity frames in the sequence of absorption spectra taken during multiple transits. We demonstrate the performance of our new method using both simulated and real K -band observations from ESO’s VLT/CRIRES+ instrument and present results obtained from two transits of the highly inflated super-Neptune WASP-107 b, which orbits a nearby K7V star.
SN - 0004-637X
SN - 1538-4357
ER -