Context. The distinct formation pathways proposed for directly imaged exoplanets and isolated brown dwarfs might leave imprints in the inherited chemical composition. Elemental and isotopic tracers could help inform the suspected histories, but this requires a careful characterisation of the sub-stellar atmospheres. In particular, objects at the L-T transition exhibit signs of dynamics that can drive their atmospheres out of chemical equilibrium.
\nAims. In this work, we studied the nearest L-T brown dwarfs, Luhman 16A and B, to assess the chemical disequilibrium in their atmospheres. We also investigated the elemental and isotopic compositions in the context of their probable formation history within the Oceanus moving group.
\nMethods. As part of the ESO SupJup Survey, we obtained spatially resolved CRIRES+ K-band spectra of the binary. These high-resolution observations were analysed using an atmospheric retrieval framework that couples the radiative transfer code petitRADTRANS to the MultiNest sampling algorithm.
\nResults. We detect and retrieve the abundances of 12CO, H2O, CH4, NH3, H2S, HF, and the 13CO isotopologue. We find that both atmospheres are in chemical disequilibrium with somewhat stronger vertical mixing in Luhman 16A compared to B (Kzz,A ~ 108.7 vs Kzz,B ~ 108.2 cm2 s−1). The tested chemical models, free-equilibrium and disequilibrium chemistry, yield consistent mixing ratios and agree with earlier work at shorter wavelengths. The free-chemistry gaseous C/O ratios show evidence of oxygen trapping in silicate-oxide clouds. While the C/O ratios are consistent with the solar composition, the metallicities are modestly enhanced with [C/H] ~ 0.15. The carbon isotope ratios are measured at 12C/13CA = 74−2+2 and 2C/13CB = 74−3+3.
\nConclusions. The coincident constraints of metallicities and isotopes across the binary provide further evidence in favour of a common formation. The 12C/13C ratios are aligned with the present-day interstellar medium but lower than the Solar System value. This suggests a recent inheritance and corroborates the relatively young age (~500 Myr) of Luhman 16A and B as members of the Oceanus moving group.
", "doi": "10.1051/0004-6361/202558089", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy & Astrophysics", "publication_date": "2026-03", "volume": "707", "pages": "A210" }, { "id": "authors:xppkv-cy151", "collection": "authors", "collection_id": "xppkv-cy151", "cite_using_url": "https://authors.library.caltech.edu/records/xppkv-cy151", "type": "article", "title": "Extreme Winds on the Emerging Dayside of an Ultrahot Jupiter", "author": [ { "family_name": "Zhang", "given_name": "Yapeng", "orcid": "0000-0003-0097-4414", "clpid": "Zhang-Yapeng" }, { "family_name": "Wardenier", "given_name": "Joost P.", "orcid": "0000-0003-3191-2486" }, { "family_name": "Householder", "given_name": "Aaron", "orcid": "0000-0002-5812-3236" }, { "family_name": "Komacek", "given_name": "Thaddeus D.", "orcid": "0000-0002-9258-5311" }, { "family_name": "Kesseli", "given_name": "Aurora Y.", "orcid": "0000-0002-3239-5989", "clpid": "Kesseli-Aurora-Y" }, { "family_name": "Dai", "given_name": "Fei", "orcid": "0000-0002-8958-0683" }, { "family_name": "Howard", "given_name": "Andrew W.", "orcid": "0000-0001-8638-0320", "clpid": "Howard-A-W" }, { "family_name": "Inglis", "given_name": "Julie", "orcid": "0000-0001-9164-7966", "clpid": "Inglis-Julie" }, { "family_name": "Isaacson", "given_name": "Howard", "orcid": "0000-0002-0531-1073" }, { "family_name": "Knutson", "given_name": "Heather A.", "orcid": "0000-0002-5375-4725", "clpid": "Knutson-H-A" }, { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" }, { "family_name": "Pino", "given_name": "Lorenzo", "orcid": "0000-0002-1321-8856" }, { "family_name": "Wallack", "given_name": "Nicole", "orcid": "0000-0003-0354-0187", "clpid": "Wallack-N-L" }, { "family_name": "Xuan", "given_name": "Jerry W.", "orcid": "0000-0002-6618-1137", "clpid": "Xuan-Jerry-W" }, { "family_name": "Carmichael", "given_name": "Theron W.", "orcid": "0000-0001-6416-1274" }, { "family_name": "Huber", "given_name": "Daniel", "orcid": "0000-0001-8832-4488" }, { "family_name": "Lee", "given_name": "Rena A.", "orcid": "0000-0001-7058-4134" }, { "family_name": "Saunders", "given_name": "Nicholas", "orcid": "0000-0003-2657-3889" }, { "family_name": "Weiss", "given_name": "Lauren", "orcid": "0000-0002-3725-3058" }, { "family_name": "Zhang", "given_name": "Jingwen", "orcid": "0000-0002-2696-2406" } ], "abstract": "High-resolution spectroscopy provides a unique opportunity to directly probe atmospheric dynamics by resolving Doppler shifts of planetary signals as a function of orbital phase. Using the optical spectrometer the Keck Planet Finder, we carry out a pilot study on high-resolution phase-curve spectra of the ultrahot Jupiter KELT-9 b. We spectrally and temporally resolve its dayside emission from posttransit to preeclipse (orbital phase \u03d5 = 0.1–0.45). The signal strength and width increase with orbital phase as the dayside rotates into view. The net Doppler shift varies progressively from −13.4 ± 0.6 to −0.4 ± 1.0 km s−1, the extent of which exceeds its rotation velocity of 6.4 ± 0.1 km s−1, providing unambiguous evidence of atmospheric winds. We devise a retrieval framework to fit the full time-series spectra, accounting for the variation of the line profiles due to the rotation and winds. We retrieve a supersonic day-to-night wind speed up to 11.7 ± 0.6 km s−1 on the emerging dayside, representing the most extreme atmospheric winds in hot Jupiters to date. Comparison to 3D circulation models reveals weak atmospheric drag, consistent with relatively efficient heat recirculation, as also supported by space-based phase-curve measurements. Additionally, we retrieve the dayside chemistry (including Fe i, Fe ii, Ti i, Ti ii, Ca i, Ca ii, Mg i, and Si i) and temperature structure, and we place constraints on the nightside thermal profile. Our high-resolution phase-curve spectra and the measured supersonic winds provide excellent benchmarks for extreme physics in circulation models, demonstrating the power of this technique in understanding the climates of hot Jupiters.
\nWe carried out the first high-resolution transit observations of the exoplanet WASP-49 Ab with Keck/HIRES. Upon custom wavelength calibration we achieve a Doppler RV precision of < 60 m s\u207b¹\u2060. This is an improvement in RV stability of roughly 240 m s\u207b¹ with respect to the instrument standard. We report an average sodium flux residual of ΔF_(NaD)/F*(λ) ~3.2 ± 0.4 per cent (8.0σ\u2060) comparable to previous studies. Interestingly, an average Doppler shift of −6.2 ± 0.5 km s\u207b¹ (12.4σ\u2060) is identified offset from the exoplanet rest frame. The velocity residuals in time trace a blueshift (vΓ,ingress ~ −10.3 ± 1.9 km s\u207b¹\u2060\u2060) to redshift (vΓ,egress ~ + 4.1 ± 1.5 \u2060km s\u207b¹) suggesting the origin of the observed sodium is unlikely from the atmosphere of the planet. The average Na light curves indicate a depth of ΔF_(NaD)/F*(t) ~0.47 ± 0.04 per cent (11.7σ\u2060) enduring ≤ 90 min with a half-max duration of ~40.1 min. Frequent high-resolution spectroscopic observations will be able to characterize the periodicity of the observed Doppler shifts. Considering the origin of the transient sodium gas is of unknown geometry, a co-orbiting natural satellite may be a likely source.
", "doi": "10.1093/mnrasl/slaf031", "issn": "1745-3925", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society: Letters", "publication_date": "2025-06", "series_number": "1", "volume": "540", "issue": "1", "pages": "L48-L53" }, { "id": "authors:vbx04-jkh58", "collection": "authors", "collection_id": "vbx04-jkh58", "cite_using_url": "https://authors.library.caltech.edu/records/vbx04-jkh58", "type": "article", "title": "The ESO SupJup Survey. VI. \u00b9\u00b2C/\u00b9\u00b3C isotope ratio comparison of three L-type brown dwarfs", "author": [ { "family_name": "Mulder", "given_name": "W.", "orcid": "0000-0001-5762-9385" }, { "family_name": "de Regt", "given_name": "S.", "orcid": "0000-0003-4760-6168" }, { "family_name": "Landman", "given_name": "R.", "orcid": "0000-0002-7261-8083" }, { "family_name": "Picos", "given_name": "D. Gonz\u00e1lez", "orcid": "0000-0001-9282-9462" }, { "family_name": "Snellen", "given_name": "I. A. G.", "orcid": "0000-0003-1624-3667" }, { "family_name": "Zhang", "given_name": "Y.", "clpid": "Zhang-Y" }, { "family_name": "Gandhi", "given_name": "S.", "orcid": "0000-0001-9552-3709", "clpid": "Gandhi-Siddharth" }, { "family_name": "Ginski", "given_name": "C.", "orcid": "0000-0002-4438-1971" }, { "family_name": "Kesseli", "given_name": "A. Y.", "orcid": "0000-0002-3239-5989", "clpid": "Kesseli-Aurora-Y" }, { "family_name": "Nasedkin", "given_name": "E.", "orcid": "0000-0002-9792-3121" }, { "family_name": "Stolker", "given_name": "T.", "orcid": "0000-0002-5823-3072" } ], "abstract": "Context. Recent research suggests that the distinct formation processes of exoplanets and brown dwarfs may have an influence on the chemical and isotopic composition of their atmospheres. Variations in the carbon 12C/13C isotope ratio have been observed and tentatively linked to the top-down formation of brown dwarfs and the core accretion pathway of super-Jupiters. The ESO SupJup Survey, conducted with CRIRES+ on the Very Large Telescope, aims to characterise the atmospheres of young brown dwarfs and super-Jupiters, specifically by investigating the 12C/13C ratio as a tracer of their formation pathways.
\nAims. We present the atmospheric characterisation of three isolated L-type brown dwarfs (2MASS J08354256-0819237, 2MASS J05012406-0010452, and 2MASS J05002100+0330501) included in the ESO SupJup Survey. We aim to constrain the C/O and 12C/13C ratios, and investigate whether the oxygen 16O/18O isotope ratio can be probed.
\nMethods. We analysed the CRIRES+ K-band spectra of the three targets using our atmospheric retrieval framework. This framework couples the radiative transfer code petitRADTRANS with the sampling algorithm MultiNest.
\nResults. We report 12C/13C ratios of 89−11+11 and 117−17+20 for J0835 and J0500 with strong 13CO significance (>6.5σ) and a tentative (3σ) detection of 13CO for J0501, resulting in a carbon isotope ratio of 155−53+56. Only a weak detection of the H218O isotope was found in J0835. The C/O ratios are found to be in the range 0.65 to 0.71 for the three targets, and all exhibit strong detections of HF.
\nConclusions. The 12C/13C ratios appear to be higher than that of the interstellar medium.
", "doi": "10.1051/0004-6361/202452859", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2025-02", "volume": "694", "pages": "A164" }, { "id": "authors:xf5rb-2a224", "collection": "authors", "collection_id": "xf5rb-2a224", "cite_using_url": "https://authors.library.caltech.edu/records/xf5rb-2a224", "type": "article", "title": "Vanadium oxide and a sharp onset of cold-trapping on a giant exoplanet", "author": [ { "family_name": "Pelletier", "given_name": "Stefan", "orcid": "0000-0002-8573-805X", "clpid": "Pelletier-Stefan" }, { "family_name": "Benneke", "given_name": "Bj\u00f6rn", "orcid": "0000-0001-5578-1498", "clpid": "Benneke-Bj\u00f6rn" }, { "family_name": "Ali-Dib", "given_name": "Mohamad", "orcid": "0000-0002-6633-376X", "clpid": "Ali-Dib-Mohamad" }, { "family_name": "Prinoth", "given_name": "Bibiana", "orcid": "0000-0001-7216-4846", "clpid": "Prinoth-Bibiana" }, { "family_name": "Kasper", "given_name": "David", "orcid": "0000-0003-0534-6388", "clpid": "Kasper-David" }, { "family_name": "Seifahrt", "given_name": "Andreas", "orcid": "0000-0003-4526-3747", "clpid": "Seifahrt-Andreas" }, { "family_name": "Bean", "given_name": "Jacob L.", "orcid": "0000-0003-4733-6532", "clpid": "Bean-Jacob-L" }, { "family_name": "Debras", "given_name": "Florian", "orcid": "0000-0002-3113-4840", "clpid": "Debras-Florian" }, { "family_name": "Klein", "given_name": "Baptiste", "orcid": "0000-0003-0637-5236", "clpid": "Klein-Baptiste" }, { "family_name": "Bazinet", "given_name": "Luc", "orcid": "0000-0003-3181-5264", "clpid": "Bazinet-Luc" }, { "family_name": "Hoeijmakers", "given_name": "H. Jens", "orcid": "0000-0001-8981-6759", "clpid": "Hoeijmakers-H-Jens" }, { "family_name": "Kesseli", "given_name": "Aurora Y.", "orcid": "0000-0002-3239-5989", "clpid": "Kesseli-Aurora-Y" }, { "family_name": "Lim", "given_name": "Olivia", "orcid": "0000-0003-4676-0622", "clpid": "Lim-Olivia" }, { "family_name": "Carmona", "given_name": "Andres", "orcid": "0000-0003-2471-1299", "clpid": "Carmona-Andr\u00e9s" }, { "family_name": "Pino", "given_name": "Lorenzo", "orcid": "0000-0002-1321-8856", "clpid": "Pino-Lorenzo" }, { "family_name": "Casasayas-Barris", "given_name": "N\u00faria", "orcid": "0000-0002-2891-8222", "clpid": "Casasayas-Barris-N\u00faria" }, { "family_name": "Hood", "given_name": "Thea", "orcid": "0000-0003-1857-7230", "clpid": "Hood-Thea" }, { "family_name": "St\u00fcrmer", "given_name": "Julian", "orcid": "0000-0002-4410-4712", "clpid": "St\u00fcrmer-Julian" } ], "abstract": "The abundance of refractory elements in giant planets can provide key insights into their formation histories. Owing to the low temperatures of the Solar System giants, refractory elements condense below the cloud deck, limiting sensing capabilities to only highly volatile elements. Recently, ultra-hot giant exoplanets have allowed for some refractory elements to be measured, showing abundances broadly consistent with the solar nebula with titanium probably condensed out of the photosphere. Here we report precise abundance constraints of 14 major refractory elements on the ultra-hot giant planet WASP-76b that show distinct deviations from proto-solar and a sharp onset in condensation temperature. In particular, we find nickel to be enriched, a possible sign of the accretion of the core of a differentiated object during the evolution of the planet. Elements with condensation temperatures below 1,550\u2009K otherwise closely match those of the Sun before sharply transitioning to being strongly depleted above 1,550\u2009K, which is well explained by nightside cold-trapping. We further unambiguously detect vanadium oxide on WASP-76b, a molecule long suggested to drive atmospheric thermal inversions, and also observe a global east\u2013west asymmetry in its absorption signals. Overall, our findings indicate that giant planets have a mostly stellar-like refractory elemental content and suggest that temperature sequences of hot Jupiter spectra can show abrupt transitions wherein a mineral species is either present or completely absent if a cold trap exists below its condensation temperature.", "doi": "10.1038/s41586-023-06134-0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2023-07-20", "volume": "619", "pages": "491-494" }, { "id": "authors:xx6hv-0pw86", "collection": "authors", "collection_id": "xx6hv-0pw86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230530-441768000.56", "type": "article", "title": "Retrieval Survey of Metals in Six Ultrahot Jupiters: Trends in Chemistry, Rain-out, Ionization, and Atmospheric Dynamics", "author": [ { "family_name": "Gandhi", "given_name": "Siddharth", "orcid": "0000-0001-9552-3709", "clpid": "Gandhi-Siddharth" }, { "family_name": "Kesseli", "given_name": "Aurora", "orcid": "0000-0002-3239-5989", "clpid": "Kesseli-Aurora-Y" }, { "family_name": "Zhang", "given_name": "Yapeng", "orcid": "0000-0003-0097-4414", "clpid": "Zhang-Yapeng" }, { "family_name": "Louca", "given_name": "Amy", "orcid": "0000-0002-3191-2200", "clpid": "Louca-Amy" }, { "family_name": "Snellen", "given_name": "Ignas", "orcid": "0000-0003-1624-3667", "clpid": "Snellen-Ignas-A-G" }, { "family_name": "Brogi", "given_name": "Matteo", "orcid": "0000-0002-7704-0153", "clpid": "Brogi-Matteo" }, { "family_name": "Miguel", "given_name": "Yamila", "orcid": "0000-0002-0747-8862", "clpid": "Miguel-Yamila" }, { "family_name": "Casasayas-Barris", "given_name": "N\u00faria", "orcid": "0000-0002-2891-8222", "clpid": "Casasayas-Barris-N\u00faria" }, { "family_name": "Pelletier", "given_name": "Stefan", "orcid": "0000-0002-8573-805X", "clpid": "Pelletier-Stefan" }, { "family_name": "Landman", "given_name": "Rico", "orcid": "0000-0002-7261-8083", "clpid": "Landman-Rico" }, { "family_name": "Maguire", "given_name": "Cathal", "orcid": "0000-0002-9061-780X", "clpid": "Maguire-Cathal" }, { "family_name": "Gibson", "given_name": "Neale P.", "orcid": "0000-0002-9308-2353", "clpid": "Gibson-Neale-P" } ], "abstract": "Ground-based high-resolution spectroscopy (HRS) has detected numerous chemical species and atmospheric dynamics in exoplanets, most notably ultrahot Jupiters (UHJs). However, quantitative estimates on abundances have been challenging but are essential for accurate comparative characterization and to determine formation scenarios. In this work, we retrieve the atmospheres of six UHJs (WASP-76 b, MASCARA-4 b, MASCARA-2 b, WASP-121 b, HAT-P-70 b, and WASP-189 b) with ESPRESSO and HARPS-N/HARPS observations, exploring trends in eleven neutral species and dynamics. While Fe abundances agree well with stellar values, Mg, Ni, Cr, Mn, and V show more variation, highlighting the difficulty in using a single species as a proxy for metallicity. We find that Ca, Na, Ti, and TiO are underabundant, potentially due to ionization and/or nightside rain-out. Our retrievals also show that relative abundances between species are more robust, consistent with previous works. We perform spatially resolved and phase-resolved retrievals for WASP-76 b and WASP-121 b given their high signal-to-noise observations, and find the chemical abundances in each of the terminator regions are broadly consistent. We additionally constrain dynamics for our sample through Doppler shifts and broadening of the planetary signals during the primary eclipse, with median blueshifts between \u223c0.9 and 9.0 km s\u207b\u00b9 due to day\u2013night winds. Furthermore, we constrain spectroscopic masses for MASCARA-2 b and HAT-P-70 b consistent with their known upper limits, but we note that these may be biased due to degeneracies. This work highlights the importance of future HRS studies to further probe differences and trends between exoplanets.", "doi": "10.3847/1538-3881/accd65", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2023-06", "series_number": "6", "volume": "165", "issue": "6", "pages": "Art. No. 242" }, { "id": "authors:e4z1n-f4204", "collection": "authors", "collection_id": "e4z1n-f4204", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220804-249944000", "type": "article", "title": "Spatially resolving the terminator: variation of Fe, temperature, and winds in WASP-76\u00a0b across planetary limbs and orbital phase", "author": [ { "family_name": "Gandhi", "given_name": "Siddharth", "orcid": "0000-0001-9552-3709", "clpid": "Gandhi-Siddharth" }, { "family_name": "Kesseli", "given_name": "Aurora", "orcid": "0000-0002-3239-5989", "clpid": "Kesseli-Aurora-Y" }, { "family_name": "Snellen", "given_name": "Ignas", "orcid": "0000-0003-1624-3667", "clpid": "Snellen-Ignas-A-G" }, { "family_name": "Brogi", "given_name": "Matteo", "orcid": "0000-0002-7704-0153", "clpid": "Brogi-Matteo" }, { "family_name": "Wardenier", "given_name": "Joost P.", "orcid": "0000-0003-3191-2486", "clpid": "Wardenier-Joost-P" }, { "family_name": "Parmentier", "given_name": "Vivien", "orcid": "0000-0001-9521-6258", "clpid": "Parmentier-Vivien" }, { "family_name": "Welbanks", "given_name": "Luis", "orcid": "0000-0003-0156-4564", "clpid": "Welbanks-Luis" }, { "family_name": "Savel", "given_name": "Arjun B.", "orcid": "0000-0002-2454-768X", "clpid": "Savel-Arjun-B" } ], "abstract": "Exoplanet atmospheres are inherently three-dimensional systems in which thermal/chemical variation and winds can strongly influence spectra. Recently, the ultra-hot Jupiter WASP-76 b has shown evidence for condensation and asymmetric Fe absorption with time. However, it is currently unclear whether these asymmetries are driven by chemical or thermal differences between the two limbs, as precise constraints on variation in these have remained elusive due to the challenges of modelling these dynamics in a Bayesian framework. To address this, we develop a new model, HyDRA-2D, capable of simultaneously retrieving morning and evening terminators with day-night winds. We explore variations in Fe, temperature profile, winds, and opacity deck with limb and orbital phase using VLT/ESPRESSO observations of WASP-76 b. We find Fe is more prominent on the evening for the last quarter of the transit, with log(X_(Fe)) = \u22124.03^(+0.28)_(\u22120.31)\u2060, but the morning shows a lower abundance with a wider uncertainty, log(X_(Fe)) = \u22124.59^(+0.85)_(\u22121.0)\u2060, driven by degeneracy with the opacity deck and the stronger evening signal. We constrain 0.1-mbar temperatures ranging from 2950\u207a\u00b9\u00b9\u00b9\u208b\u2081\u2085\u2086 to 2615\u207a\u00b2\u2076\u2076\u208b\u2082\u2087\u2085 K, with a trend of higher temperatures for the more irradiated atmospheric regions. We also constrain a day-night wind speed of 9.8^(+1.2)_(\u22121.1) km\u2009s\u207b\u00b9 for the last quarter, higher than 5.9^(+1.5)_(\u22121.1) km\u2009s\u207b\u00b9 for the first, in line with general circulation models. We find our new spatially and phase-resolved treatment is statistically favoured by 4.9\u03c3 over traditional 1D-retrievals, and thus demonstrate the power of such modelling for robust constraints with current and future facilities.", "doi": "10.1093/mnras/stac1744", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2022-09", "series_number": "1", "volume": "515", "issue": "1", "pages": "749-766" } ]