Publications (75)
Titanium oxide and chemical inhomogeneity in the atmosphere of the exoplanet WASP-189b
Bibiana Prinoth, H. Jens Hoeijmakers, Daniel Kitzmann +21
The temperature of an atmosphere decreases with increasing altitude, unless a shortwave absorber exists that causes a temperature inversion. Ozone plays this role in the Earth`s at…
Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations
Dan J. Bower, Daniel Kitzmann, Aaron S. Wolf +3
A terrestrial planet is molten during formation and may remain so if subject to intense insolation or tidal forces. Observations continue to favour the detection and characterisati…
Analytical Models of Exoplanetary Atmospheres. IV. Improved Two-stream Radiative Transfer for the Treatment of Aerosols
Kevin Heng, Daniel Kitzmann
We present a novel generalization of the two-stream method of radiative transfer, which allows for the accurate treatment of radiative transfer in the presence of strong infrared s…
A population view of transiting hot giant exoplanets: Tracing Fe and Ti chemistry with ESPRESSO and MAROON-X
Bibiana Prinoth, Vivien Parmentier, Stefan Pelletier +9
Hot and ultra-hot Jupiters offer a unique laboratory to study atmospheric chemistry at the population level using ground-based high-resolution spectroscopy. Fe and Ti are key trace…
Supervised Machine Learning for Intercomparison of Model Grids of Brown Dwarfs: Application to GJ 570D and the Epsilon Indi B Binary System
Maria Oreshenko, Daniel Kitzmann, Pablo Marquez-Neila +6
Self-consistent model grids of brown dwarfs involve complex physics and chemistry, and are often computed using proprietary computer codes, making it challenging to identify the re…
NCCR PlanetS: Observational and computational characterization of exoplanet atmospheres
Daniel Kitzmann, Elspeth K. H. Lee, Jens Hoeijmakers +1
This chapter reviews the current state of observational and theoretical efforts in the characterization of exoplanet atmospheres, with a focus on developments enabled through the S…
Hunt for Starspots in HARPS Spectra of G and K Stars
Brett M. Morris, H. Jens Hoeijmakers, Daniel Kitzmann +1
We present a method for detecting starspots on cool stars using the cross-correlation function (CCF) of high resolution molecular spectral templates applied to archival high-resolu…
The potassium absorption on HD189733b and HD209458b
Engin Keles, Matthias Mallonn, Carolina von Essen +9
In this work, we investigate the potassium excess absorption around 7699A of the exoplanets HD189733b and HD209458b. For this purpose, we used high spectral resolution transit obse…
Retrieval study of cool, directly imaged exoplanet 51 Eri b
Niall Whiteford, Alistair Glasse, Katy L. Chubb +12
Retrieval methods are a powerful analysis technique for modelling exoplanetary atmospheres by estimating the bulk physical and chemical properties that combine in a forward model t…
Competing chemical signatures in the atmosphere of TOI-270 d: Inference of sulfur and carbon chemistry
Lukas Felix, Daniel Kitzmann, Brice-Olivier Demory +1
Recent JWST measurements allow access to the near-infrared spectrum of the sub-Neptune TOI-270 d, for which two different interpretations, a high-metallicity miscible envelope and…
Exploring the atmospheric dynamics of the extreme ultra-hot Jupiter KELT-9b using TESS photometry
Ian Wong, Avi Shporer, Daniel Kitzmann +24
We carry out a phase-curve analysis of the KELT-9 system using photometric observations from NASA's Transiting Exoplanet Survey Satellite (TESS). The measured secondary eclipse dep…
The PEPSI Exoplanet Transit Survey (PETS) I: Investigating the presence of a silicate atmosphere on the super-Earth 55 Cnc e
Engin Keles, Matthias Mallonn, Daniel Kitzmann +26
The study of exoplanets and especially their atmospheres can reveal key insights on their evolution by identifying specific atmospheric species. For such atmospheric investigations…
A Comparative Study of Atmospheric Chemistry with VULCAN
Shang-Min Tsai, Matej Malik, Daniel Kitzmann +4
We present an update of the open-source photochemical kinetics code VULCAN (Tsai et al. 2017; https://github.com/exoclime/VULCAN) to include C-H-N-O-S networks and photochemistry.…
Climates of Terrestrial Exoplanets and Biosignatures
Siddharth Bhatnagar, Emeline Bolmont, Nikita J. Boeren +18
Understanding the climates of terrestrial exoplanets and the detectability of biosignatures is an inherently interdisciplinary challenge, requiring the integration of insights from…
Parameter degeneracies associated with interpreting HST WFC3 transmission spectra of exoplanetary atmospheres
Aline Novais, Chloe Fisher, Luan Ghezzi +3
The Wide Field Camera 3 (WFC3) instrument on the Hubble Space Telescope has provided an abundance of exoplanet spectra over the years. These spectra have enabled analysis studies u…
Simulating gas giant exoplanet atmospheres with Exo-FMS: Comparing semi-grey, picket fence and correlated-k radiative-transfer schemes
Elspeth K. H. Lee, Vivien Parmentier, Mark Hammond +5
Radiative-transfer (RT) is a fundamental part of modelling exoplanet atmospheres with general circulation models (GCMs). An accurate RT scheme is required for estimates of the atmo…
Atmospheric characterization of terrestrial exoplanets in the mid-infrared: biosignatures, habitability & diversity
Sascha P. Quanz, Olivier Absil, Daniel Angerhausen +45
Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to…
HELIOS: An Open-source, GPU-accelerated Radiative Transfer Code For Self-consistent Exoplanetary Atmospheres
Matej Malik, Luc Grosheintz, João M. Mendonça +10
We present the open-source radiative transfer code named HELIOS, which is constructed for studying exoplanetary atmospheres. In its initial version, the model atmospheres of HELIOS…
FastChem Cond: Equilibrium chemistry with condensation and rainout for cool planetary and stellar environments
Daniel Kitzmann, Joachim W. Stock, A. Beate C. Patzer
Cool astrophysical objects, such as (exo)planets, brown dwarfs, or asymptotic giant branch stars, can be strongly affected by condensation. Condensation does not only directly affe…
Observations of scattered light from exoplanet atmospheres
Brett M. Morris, Kevin Heng, Daniel Kitzmann
Optical phase curves of hot Jupiters can reveal global scattering properties. We implement a Bayesian inference framework for optical phase curves with flux contributions from: ref…
JWST NIRSpec finds no clear signs of an atmosphere on TOI-1685 b
Chloe E. Fisher, Matthew J. Hooton, Amélie Gressier +21
Determining the prevalence of atmospheres on terrestrial planets is a core objective in exoplanetary science. While M dwarf systems offer a promising opportunity, conclusive observ…
Retrieval Study of Brown Dwarfs Across the L-T Sequence
Anna Lueber, Daniel Kitzmann, Brendan P. Bowler +2
A large suite of 228 atmospheric retrievals is performed on a curated sample of 19 brown dwarfs spanning the L0 to T8 spectral types using the open-source Helios-r2 retrieval code,…
A roadmap for the atmospheric characterization of terrestrial exoplanets with JWST
TRAPPIST-1 JWST Community Initiative, :, Julien de Wit +80
Ultra-cool dwarf stars are abundant, long-lived, and uniquely suited to enable the atmospheric study of transiting terrestrial companions with JWST. Amongst them, the most prominen…
An Ultra-Short Period Super-Earth and a Sub-Neptune Orbiting the K dwarf TOI-4311
Yoshi Nike Emilia Eschen, Thomas G. Wilson, Andrew Collier Cameron +95
We report the discovery and characterisation of the multi-planetary system around TOI-4311, a K dwarf kinematically between the Galactic thick disk and Hercules stream. TOI-4311 ho…
Helios-r2 -- A new Bayesian, open-source retrieval model for brown dwarfs and exoplanet atmospheres
Daniel Kitzmann, Kevin Heng, Maria Oreshenko +5
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 precisio…
Towards Consistent Modeling of Atmospheric Chemistry and Dynamics in Exoplanets: Validation and Generalization of Chemical Relaxation Method
Shang-Min Tsai, Daniel Kitzmann, James R. Lyons +3
Motivated by the work of Cooper & Showman, we revisit the chemical relaxation method, which seeks to enhance the computational efficiency of chemical-kinetics calculations by repla…
Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3
Michaël Gillon, Peter P. Pedersen, Benjamin V. Rackham +81
Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary p…
Analytical Models of Exoplanetary Atmospheres. VI. Full Solutions for Improved Two-stream Radiative Transfer Including Direct Stellar Beam
Kevin Heng, Matej Malik, Daniel Kitzmann
Two-stream radiative transfer is a workhorse in the Earth, planetary and exoplanetary sciences due to its simplicity and ease of implementation. However, a longstanding limitation…
3D radiative-transfer for exoplanet atmospheres. gCMCRT: a GPU accelerated MCRT code
Elspeth K. H. Lee, Joost P. Wardenier, Bibiana Prinoth +10
Radiative-transfer (RT) is a key component for investigating atmospheres of planetary bodies. With the 3D nature of exoplanet atmospheres being important in giving rise to their ob…
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems V: Do Self-Consistent Atmospheric Models Represent JWST Spectra? A Showcase With VHS 1256 b
Simon Petrus, Niall Whiteford, Polychronis Patapis +119
The unprecedented medium-resolution (R~1500-3500) near- and mid-infrared (1-18um) spectrum provided by JWST for the young (140+/-20Myr) low-mass (12-20MJup) L-T transition (L7) com…
High-resolution Transmission Spectroscopy of MASCARA-2 b with EXPRES
H. Jens Hoeijmakers, Samuel H. C. Cabot, Lily Zhao +10
We report detections of atomic species in the atmosphere of MASCARA-2 b, using the first transit observations obtained with the newly commissioned EXPRES spectrograph. EXPRES is a…
The Mantis Network I: A standard grid of templates and masks for cross-correlation analyses of ultra-hot Jupiter transmission spectra
Daniel Kitzmann, Jens H. Hoeijmakers, Simon L. Grimm +3
The atmospheres of ultra-hot Jupiters are highly interesting and unique chemical laboratories. Due to the very high atmospheric temperatures, their chemical composition is dominate…
The Mantis Network II: Examining the 3D high-resolution observable properties of the UHJs WASP-121b and WASP-189b through GCM modelling
Elspeth K. H. Lee, Bibiana Prinoth, Daniel Kitzmann +4
The atmospheres of ultra hot Jupiters (UHJs) are prime targets for the detection of molecules and atoms at both low and high spectral resolution. We study the atmospheres of the UH…
Atmospheric Characterization via Broadband Color Filters on the PLAnetary Transits and Oscillations of stars (PLATO) Mission
John Lee Grenfell, Mareike Godolt, Juan Cabrera +5
We assess broadband color filters for the two fast cameras on the PLAnetary Transits and Oscillations (PLATO) of stars space mission with respect to exoplanetary atmospheric charac…
Modelling the 3D atmospheric structure of the cold Jupiter WD1856+534b orbiting a white dwarf
Pascal A. Noti, Elspeth K. H. Lee, Daniel Kitzmann +5
WD-1856b+534b (WD-1856b) is to date the only detected cold Jupiter outside of our Solar System. This cold Jupiter can provide useful information about the cold giants in our Solar…
The Retrieved Atmospheric Properties of the Sub-stellar Object VHS 1256 b from Analyzing HST, VLT and JWST Spectra
Anna Lueber, Kevin Heng, Brendan P. Bowler +3
Motivated by the observed ~30% variations in flux from the L7 dwarf VHS 1256 b, we subjected its time-resolved Hubble Space Telescope (HST) WFC3 spectra (measured in two epochs in…
Hot Rocks Survey III: A deep eclipse for LHS 1140c and a new Gaussian process method to account for correlated noise in individual pixels
Mark Fortune, Neale P. Gibson, Hannah Diamond-Lowe +14
Time-series photometry at mid-infrared wavelengths is becoming a common technique to search for atmospheres around rocky exoplanets. This method constrains the brightness temperatu…
Interpreting High-Resolution Spectroscopy of Exoplanets Using Cross-Correlations and Supervised Machine Learning
Chloe Fisher, H. Jens Hoeijmakers, Daniel Kitzmann +4
We present a new method for performing atmospheric retrieval on ground-based, high-resolution data of exoplanets. Our method combines cross-correlation functions with a random fore…
An Ultra-Short Period Super-Earth and Sub-Neptune Spanning the Radius Valley Orbiting the Kinematic Thick Disk Star TOI-2345
Yoshi Nike Emilia Eschen, Thomas G. Wilson, Andrea Bonfanti +94
A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Ther…
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems III: Aperture Masking Interferometric Observations of the star HIP 65426 at 3.8 um
Shrishmoy Ray, Steph Sallum, Sasha Hinkley +121
We present aperture masking interferometry (AMI) observations of the star HIP 65426 at as a part of the JWST Direct Imaging Early Release Science (ERS) program obta…
Optical properties of potential condensates in exoplanetary atmospheres
Daniel Kitzmann, Kevin Heng
The prevalence of clouds in currently observable exoplanetary atmospheres motivates the compilation and calculation of their optical properties. First, we present a new open-source…
VULCAN: an Open-Source, Validated Chemical Kinetics Python Code for Exoplanetary Atmospheres
Shang-Min Tsai, James R. Lyons, Luc Grosheintz +3
We present an open-source and validated chemical kinetics code for studying hot exoplanetary atmospheres, which we name VULCAN. It is constructed for gaseous chemistry from 500 to…
Differentiable Modeling of Planet and Substellar Atmosphere: High-Resolution Emission, Transmission, and Reflection Spectroscopy with ExoJAX2
Hajime Kawahara, Yui Kawashima, Shotaro Tada +11
Modeling based on differentiable programming holds great promise for astronomy, enabling advanced techniques such as gradient-based posterior sampling and optimization. This paradi…
The Peculiar Atmospheric Chemistry of KELT-9b
Daniel Kitzmann, Kevin Heng, Paul B. Rimmer +6
The atmospheric temperatures of the ultra-hot Jupiter KELT-9b straddle the transition between gas giants and stars, and therefore between two traditionally distinct regimes of atmo…
FastChem 2: An improved computer program to determine the gas-phase chemical equilibrium composition for arbitrary element distributions
Joachim W. Stock, Daniel Kitzmann, A. Beate C. Patzer
The computation of complex neutral/ionised chemical equilibrium compositions is invaluable to obtain scientific insights of, for example, the atmospheres of extrasolar planets and…
Exoplanet science with a space-based mid-infrared nulling interferometer
Sascha P. Quanz, Jens Kammerer, Denis Defrère +3
One of the long-term goals of exoplanet science is the (atmospheric) characterization of a large sample (>100) of terrestrial planets to assess their potential habitability and ove…
Hot Rocks Survey V: Secondary Eclipse Photometry of GJ 3473 b with JWST/MIRI
Måns Holmberg, Hannah Diamond-Lowe, João M. Mendonça +16
JWST is transforming our ability to characterise small exoplanets, from sub-Neptunes to rocky worlds. A key open question is whether highly irradiated rocky planets can retain atmo…
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems IV: NIRISS Aperture Masking Interferometry Performance and Lessons Learned
Steph Sallum, Shrishmoy Ray, Jens Kammerer +120
We present a performance analysis for the aperture masking interferometry (AMI) mode on board the James Webb Space Telescope Near Infrared Imager and Slitless Spectrograph (JWST/NI…
Clouds and Hazes in Exoplanet Atmospheres
Mark S. Marley, Andrew S. Ackerman, Jeffrey N. Cuzzi +1
Clouds and hazes are commonplace in the atmospheres of solar system planets and are likely ubiquitous in the atmospheres of extrasolar planets as well. Clouds affect every aspect o…
FastChem 4: New chemical elements and improved convergence behaviour
Daniel Kitzmann, Joachim W. Stock, A. Beate C. Patzer
Chemical equilibrium calculations are a key ingredient for modelling and interpreting spectroscopic observations of (exo)planets, brown dwarfs, cool stars, and protoplanetary disks…
The Goldilocks problem for detecting water in terrestrial planets: Constraining water abundances in the mid-IR with LIFE
Sarah Rugheimer, Eleonora Alei, Björn S. Konrad +7
We investigate how well the Large Interferometer for Exoplanets (LIFE) mission concept can detect habitable conditions on exoplanets through the presence of atmospheric water vapor…
Kinetic and photochemical disequilibrium in the potentially carbon-rich atmosphere of the warm-Jupiter WASP-69b
Nidhi Bangera, Christiane Helling, Gloria Guilluy +5
High-resolution transmission spectroscopy of the warm gas-giant WASP-69b has revealed the presence of H2O, CO, CH4, NH3, and C2H2 in its atmosphere. This study investigates the imp…
Visible-light Phase Curves from the Second Year of the TESS Primary Mission
Ian Wong, Daniel Kitzmann, Avi Shporer +10
We carried out a systematic study of full-orbit phase curves for known transiting systems in the northern ecliptic sky that were observed during Year 2 of the TESS primary mission.…
JWST/NIRISS and HST: Exploring the improved ability to characterise exoplanet atmospheres in the JWST era
Chloe Fisher, Jake Taylor, Vivien Parmentier +6
The Hubble Space Telescope has been a pioneering instrument for studying the atmospheres of exoplanets, specifically its WFC3 and STIS instruments. With the launch of JWST, we are…
Clouds in the atmospheres of extrasolar planets. V. The impact of CO2 ice clouds on the outer boundary of the habitable zone
Daniel Kitzmann
Clouds have a strong impact on the climate of planetary atmospheres. The potential scattering greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar plane…
Information content of JWST-NIRSPEC transmission spectra of warm Neptunes
Andrea Guzmán-Mesa, Daniel Kitzmann, Chloe Fisher +7
Warm Neptunes offer a rich opportunity for understanding exo-atmospheric chemistry. With the upcoming James Webb Space Telescope (JWST), there is a need to elucidate the balance be…
Sunbathing under white light -- 3D modelling of brown dwarf - white dwarf atmospheres with strong UV irradiation
Elspeth K. H. Lee, Joshua D. Lothringer, Sarah L. Casewell +3
The atmospheres of brown dwarfs orbiting in close proximity to their parent white dwarf represent some of the most extreme irradiated environments known. Understanding their comple…
Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b
H. Jens Hoeijmakers, David Ehrenreich, Kevin Heng +10
The chemical composition of an exoplanet is a key ingredient in constraining its formation history. Iron is the most abundant transition metal, but has never been directly detected…
Ultra-hot Jupiter atmospheres at high spectral resolution
Stefan Pelletier, Daniel Kitzmann, Valentina Vaulato +3
Observations of ultra-hot Jupiters offer an unprecedented opportunity to study the physics of some of the most extreme planetary atmospheres known. With exceedingly high amounts of…
Intercomparison of Brown Dwarf Model Grids and Atmospheric Retrieval Using Machine Learning
Anna Lueber, Daniel Kitzmann, Chloe E. Fisher +4
Understanding differences between sub-stellar spectral data and models has proven to be a major challenge, especially for self-consistent model grids that are necessary for a thoro…
Astrometric Accelerations as Dynamical Beacons: Discovery and Characterization of HIP 21152 B, the First T-Dwarf Companion in the Hyades
Kyle Franson, Brendan P. Bowler, Mariangela Bonavita +28
Benchmark brown dwarf companions with well-determined ages and model-independent masses are powerful tools to test substellar evolutionary models and probe the formation of giant p…
Physically-motivated basis functions for temperature maps of exoplanets
Brett M. Morris, Kevin Heng, Kathryn Jones +4
Thermal phase curves of exoplanet atmospheres have revealed temperature maps as a function of planetary longitude, often by sinusoidal decomposition of the phase curve. We construc…
Stellar Contamination Correction Using Back-to-Back Transits of TRAPPIST-1 b and c
Alexander D. Rathcke, Lars A. Buchhave, Julien De Wit +8
Stellar surface heterogeneities, such as spots and faculae, often contaminate exoplanet transit spectra, hindering precise atmospheric characterization. We demonstrate a novel, epo…
HELIOS-K 2.0 Opacity Calculator and Open-source Opacity Database for Exoplanetary Atmospheres
Simon L. Grimm, Matej Malik, Daniel Kitzmann +12
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 an…
Lithologic Controls on Silicate Weathering Regimes of Temperate Planets
Kaustubh Hakim, Dan J. Bower, Meng Tian +6
Weathering of silicate rocks at a planetary surface can draw down CO from the atmosphere for eventual burial and long-term storage in the planetary interior. This process is th…
Revisiting the scattering greenhouse effect of CO2 ice clouds
Daniel Kitzmann
Carbon dioxide ice clouds are thought to play an important role for cold terrestrial planets with thick CO2 dominated atmospheres. Various previous studies showed that a scattering…
Self-luminous and irradiated exoplanetary atmospheres explored with HELIOS
Matej Malik, Daniel Kitzmann, João M. Mendonça +5
We present new methodological features and physical ingredients included in the 1D radiative transfer code HELIOS, improving the hemispheric two-stream formalism. We conduct a thor…
Time-resolved transmission spectroscopy of the ultra-hot Jupiter WASP-189 b
Bibiana Prinoth, H. Jens Hoeijmakers, Stefan Pelletier +14
Ultra-hot Jupiters are tidally locked with their host stars dividing their atmospheres into a hot dayside and a colder nightside. As the planet moves through transit, different reg…
A ground-based NUV secondary eclipse observation of KELT-9b
Matthew J. Hooton, Christopher A. Watson, Ernst J. W. de Mooij +2
KELT-9b is a recently discovered exoplanet with a 1.49 d orbit around a B9.5/A0-type star. The unparalleled levels of UV irradiation it receives from its host star put KELT-9b in i…
Closed-formed ab initio solutions of geometric albedos and reflected light phase curves of exoplanets
Kevin Heng, Brett M. Morris, Daniel Kitzmann
Studying the albedos of the planets and moons of the Solar System dates back at least a century. Of particular interest is the relationship between the albedo measured at superior…
Hot Rocks Survey I : A possible shallow eclipse for LHS 1478 b
Prune C. August, Lars A. Buchhave, Hannah Diamond-Lowe +18
M dwarf systems offer an opportunity to study terrestrial exoplanetary atmospheres due to their small size and cool temperatures. However, the extreme conditions imposed by these h…
The theory of transmission spectra revisited: a semi-analytical method for interpreting WFC3 data and an unresolved challenge
Kevin Heng, Daniel Kitzmann
The computation of transmission spectra is a central ingredient in the study of exoplanetary atmospheres. First, we revisit the theory of transmission spectra, unifying ideas from…
Hot Rocks Survey IV: Emission from LTT 3780 b is consistent with a bare rock
Natalie H. Allen, Néstor Espinoza, Hannah Diamond-Lowe +19
It is an open question whether small planets around M dwarfs are able to maintain atmospheres. The Hot Rocks Survey aims to address this question by observing 9 rocky exoplanets or…
Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b
Diana Powell, Adina D. Feinstein, Elspeth K. H. Lee +70
The recent inference of sulphur dioxide (SO) in the atmosphere of the hot (1100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations suggests that phot…
TOI-2109b: An Ultrahot Gas Giant on a 16 hr Orbit
Ian Wong, Avi Shporer, George Zhou +56
We report the discovery of an ultrahot Jupiter with an extremely short orbital period of days (16 hr). The plane…