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High-resolution spectroscopy has proven to be a powerful avenue for atmospheric remote sensing of exoplanets. Recently, ESO commissioned the CRIRES+ high-resolution infrared spectrograph at VLT. CRIRES+ is a cross-dispersed spectrograph with high throughput and wide wavelength coverage across the near-infrared (0.95-5.3 $\mu$m), designed to be particularly suited for atmospheric characterisation of exoplanets. In this work, we report early insights into the performance of CRIRES+ for exoplanet spectroscopy and conduct a detailed assessment of the data reduction procedure. Because of the novelty of the instrument, we perform two independent data reduction strategies, using the official CR2RES pipeline and our new custom-built ExoRES pipeline. Using science verification observations we find that the spectral resolving power of CRIRES+ can reach $R \gtrsim 100,000$ for optimal observing conditions. Similarly, we find the signal-to-noise ratio (S/N) to be consistent with expected and empirical estimates for the observations considered. As a case study, we perform the first application of CRIRES+ to the atmospheric characterisation of an exoplanet - the ultra-hot Jupiter MASCARA-1 b. We detect CO and H$_2$O in the atmosphere of MASCARA-1 b at a S/N of 12.9 and 5.3, respectively, and a temperature inversion revealed through the CO and H$_2$O emission lines, the first for an exoplanet. We find a combined S/N of 13.8 for CO and H$_2$O together, with a preference for lower H$_2$O abundance compared to CO. Our findings demonstrate the scientific potential of CRIRES+ and highlight the excellent opportunity for high-resolution atmospheric spectroscopy of diverse exoplanets., Comment: Accepted version updated with proof edits

Atmospheric retrievals of exoplanet transmission spectra allow constraints on the composition and structure of the day-night terminator region. Such retrievals in the past have typically assumed one-dimensional temperature structures which were adequate to explain extant observations. However, the increasing data quality expected from exoplanet spectroscopy with JWST motivates considerations of multidimensional atmospheric retrievals. We present AURA-3D, a three-dimensional atmospheric retrieval framework for exoplanet transmission spectra. AURA-3D includes a forward model that enables rapid computation of transmission spectra in 3D geometry for a given atmospheric structure and can, therefore, be used for atmospheric retrievals as well as for computing spectra from General Circulation Models (GCMs). In order to efficiently explore the space of possible 3D temperature structures in retrievals, we develop a parametric 3D pressure-temperature profile which can accurately represent azimuthally-averaged temperature structures of a range of hot Jupiter GCMs. We apply our retrieval framework to simulated JWST observations of hot Jupiter transmission spectra, obtaining accurate estimates of the day-night temperature variation across the terminator as well as the abundances of chemical species. We demonstrate an example of a model hot Jupiter transmission spectrum for which a traditional 1D retrieval of JWST-quality data returns biased abundance estimates, whereas a retrieval including a day-night temperature gradient can accurately retrieve the true abundances. Our forward model also has the capability to include inhomogeneous chemistry as well as variable clouds/hazes. This new retrieval framework opens the field to detailed multidimensional atmospheric characterisation using transmission spectra of exoplanets in the JWST era., 27 pages, 16 figures. Accepted for publication in ApJ

Plasma technology is actively used for nanoparticle synthesis and modification. All plasma techniques share the ambition of providing high quality, nanostructured materials with full control over their crystalline state and functional properties. Pulsed-DC physical/chemical vapour deposition, high power impulse magnetron sputtering, and pulsed cathodic arc are consolidated low-temperature plasma processes for the synthesis of high-quality nanocomposite films in vacuum environment. However, atmospheric arc discharge stands out thanks to the high throughput, wide variety, and excellent quality of obtained stand-alone nanomaterials, mainly core–shell nanoparticles, transition metal dichalcogenide monolayers, and carbon-based nanostructures, like graphene and carbon nanotubes. Unique capabilities of this arc technique are due to its flexibility and wide range of plasma parameters achievable by modulation of the frequency, duty cycle, and amplitude of pulse waveform. The many possibilities offered by pulsed arc discharges applied on synthesis of low-dimensional materials are reviewed here. Periodical variations in temperature and density of the pulsing arc plasma enable nanosynthesis with a more rational use of the supplied power. Parameters such as plasma composition, consumed power, process stability, material properties, and economical aspects, are discussed. Finally, a brief outlook towards future tendencies of nanomaterial preparation is proposed. Atmospheric pulsed arcs constitute promising, clean processes providing ecological and sustainable development in the production of nanomaterials both in industry and research laboratories.

Ground-based and airborne instrumentation for astronomy IX (2022), Montreal, JUL 17-22, 2022.--Proceedings of SPIE - The International Society for Optical Engineering vol. 12184 Article number 1218424.-- Complete list of authors: Marconi, A.; Abreu, M.; Adibekyan, V.; Alberti, V.; Albrecht, S.; Alcaniz, J.; Aliverti, M.; Allende Prieto, C.; Gomez, J. D. Alvarado; Amado, P. J.; Amate, M.; Andersen, M. I.; Artigau, E.; Baker, C.; Baldini, V.; Balestra, A.; Barnes, S. A.; Baron, F.; Barros, S. C. C.; Bauer, S. M.; Beaulieu, M.; Bellido-Tirado, O.; Benneke, B.; Bensby, T.; Bergin, E. A.; Biazzo, K.; Bik, A.; Birkby, J. L.; Blind, N.; Boisse, I.; Bolmont, E.; Bonaglia, M.; Bonfils, X.; Borsa, F.; Brandeker, A.; Brandner, W.; Broeg, C. H.; Brogi, M.; Brousseau, D.; Brucalassi, A.; Brynnel, J.; Buchhave, L. A.; Buscher, D. F.; Cabral, A.; Calderone, G.; Calvo-Ortega, R.; Cantalloube, F.; Canto Martins, B. L.; Carbonaro, L.; Chauvin, G.; Chazelas, B.; Cheffot, A. -L.; Cheng, Y. S.; Chiavassa, A.; Christensen, L.; Cirami, R.; Cook, N. J.; Cooke, R. J.; Coretti, I.; Covino, S.; Cowan, N.; Cresci, G.; Cristiani, S.; Cunha Parro, V.; Cupani, G.; D'Odorico, V.; de Castro Leao, I.; De Cia, A.; De Medeiros, J. R.; Debras, F.; Debus, M.; Demangeon, O.; Dessauges-Zavadsky, M.; Di Marcantonio, P.; Dionies, F.; Doyon, R.; Dunn, J.; Ehrenreich, D.; Faria, J. P.; Feruglio, C.; Fisher, M.; Fontana, A.; Fumagalli, M.; Fusco, T.; Fynbo, J.; Gabella, O.; Gaessler, W.; Gallo, E.; Gao, X.; Genolet, L.; Genoni, M.; Giacobbe, P.; Giro, E.; Goncalves, R. S.; Gonzalez, O. A.; Gonzalez Hernandez, J. I.; Gracia Temich, F.; Haehnelt, M. G.; Haniff, C.; Hatzes, A.; Helled, R.; Hoeijmakers, H. J.; Huke, P.; Jaervinen, A. S.; Jaervinen, S. P.; Kaminski, A.; Korn, A. J.; Kouach, D.; Kowzan, G.; Kreidberg, L.; Landoni, M.; Lanotte, A.; Lavail, A.; Li, J.; Liske, J.; Lovis, C.; Lucatello, S.; Lunney, D.; MacIntosh, M. J.; Madhusudhan, N.; Magrini, L.; Maiolino, R.; Malo, L.; Man, A. W. S.; Marquart, T.; Marques, E. L.; Martins, C. J. A. P.; Martins, A. M.; Maslowski, P.; Mason, E.; Mason, C. A.; McCracken, R. A.; Mergo, P.; Micela, G.; Mitchell, T.; Molliere, P.; Monteiro, M. A.; Montgomery, D.; Mordasini, C.; Morin, J.; Mucciarelli, A.; Murphy, M. T.; N'Diaye, M.; Neichel, B.; Niedzielski, A. T.; Niemczura, E.; Nortmann, L.; Noterdaeme, P.; Nunes, N. J.; Oggioni, L.; Oliva, E.; Onel, H.; Origlia, L.; Ostlin, G.; Palle, E.; Papaderos, P.; Pariani, G.; Penate Castro, J.; Pepe, F.; Levasseur, L. Perreault; Petit, P.; Pino, L.; Piqueras, J.; Pollo, A.; Poppenhaeger, K.; Quirrenbach, A.; Rauscher, E.; Rebolo, R.; Redaelli, E. M. A.; Reffert, S.; Reid, D. T.; Reiners, A.; Richter, P.; Riva, M.; Rivoire, S.; Rodriguez-Lopez, C.; Roederer, I. U.; Romano, D.; Rousseau, S.; Rowe, J.; Salvadori, S.; Sanna, N.; Santos, N. C.; Diaz, P. Santos; Sanz-Forcada, J.; Sarajlic, M.; Sauvage, J. -F.; Schaefer, S.; Schiavon, R. P.; Schmidt, T. M.; Selmi, C.; Sivanandam, S.; Sordet, M.; Sordo, R.; Sortino, F.; Sosnowska, D.; Sousa, S. G.; Stempels, E.; Strassmeier, K. G.; Suarez Mascareno, A.; Sulich, A.; Sun, X.; Tanvir, N. R.; Tenegi-Sangines, F.; Thibault, S.; Thompson, S. J.; Tozzi, A.; Turbet, M.; Vallee, P.; Varas, R.; Venn, K. A.; Veran, J. -P.; Verma, A.; Viel, M.; Wade, G.; Waring, C.; Weber, M.; Weder, J.; Wehbe, B.; Weingrill, J.; Woche, M.; Xompero, M.; Zackrisson, E.; Zanutta, A.; Zapatero Osorio, M. R.; Zechmeister, M.; Zimara, J., The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of similar to 100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 mu m with the goal of extending it to 0.35-2.4 mu m with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coude room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states., The Italian effort for ANDES is supported by the Italian National Institute for Astrophysics (INAF). The Portuguese participation is supported by FCT -Fundacao para a Ciencia e a Tecnologia through national funds and by FEDER through COMPETE2020 -Programa Operacional Competitividade e Internacionalizacao by these grants: UID/FIS/04434/2019, UIDB/04434/2020 & UIDP/04434/2020; POCI-01-0145-FEDER-032113 & PTDC/FIS-AST/32113/2017. Swedish participation in the ANDES project is made possible through the national Swedish ELT Instrumentation Consortium (SELTIC), suppored by the Swedish Research Council (VR). CJM acknowledges FCT and POCH/FSE (EC) support through Investigador FCT Contract 2021.01214.CEECIND/CP1658/CT0001. JLB acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program under grant agreement No 805445. MTM acknowledges the support of the Australian Research Council through Future Fellowship grant FT180100194 SS acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program under grant agreement No 804240. TMS acknowledgment the support from the SNF synergia grant CRSII5-193689 (BLUVES), With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709

The alkali metal sodium (Na) is one of the most commonly detected chemical species in the upper atmospheres of giant exoplanets. In this work we conducted a homogeneous survey of Na in a diverse sample of ten highly irradiated giant exoplanets using high-resolution transmission spectroscopy. Our sample includes nine planets with previous Na detections and one new detection. We confirm previous detections and assess multiple approaches for deriving Na line properties from high-resolution transmission spectra. The homogeneously measured sodium line depths were used to constrain the atmospheric heights ($H_{\text{Na}}$) with respect to the planetary radii ($R_{\text{p}}$). We assess an empirical trend describing the relative atmospheric height ($H_{\text{Na}}/R_{\text{p}}$) as a function of planetary equilibrium temperature ($T_{\text{eq}}$) and surface gravity ($g$), in which $H_{\text{Na}}/R_{\text{p}}$ decreases exponentially with $\xi \propto gT_{\text{eq}}$, approaching a constant at large $\xi$. We also report the sodium D2/D1 line ratios across our sample and find that seven targets have line ratios that are consistent with unity. Finally, we measured net blueshifted offsets of the sodium absorption lines from their rest frame wavelengths for all ten planets, corresponding to day-night wind velocities of a few km s$^{-1}$. This suggests that the broad sample of exoplanets share common underlying processes that govern atmospheric dynamics. Our study highlights a promising avenue for using high-resolution transmission spectroscopy to further our understanding of how atmospheric characteristics vary over a diverse sample of exoplanets.

TOI-270d is a temperate sub-Neptune discovered by the Transiting Exoplanet Survey Satellite (TESS) around a bright (J=9.1mag) M3V host star. With an approximate radius of 2RE and equilibrium temperature of 350K, TOI-270d is one of the most promising small exoplanets for atmospheric characterisation using transit spectroscopy. Here we present a primary transit observation of TOI-270d made with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) spectrograph across the 1.126-1.644 micron wavelength range, and a 95% credible upper limit of $8.2 \times 10^{-14}$ erg s$^{-1}$ cm$^{-2}$ A$^{-1}$ arcsec$^{-2}$ for the stellar Ly-alpha emission obtained using the Space Telescope Imaging Spectrograph (STIS). The transmission spectrum derived from the TESS and WFC3 data provides evidence for molecular absorption by a hydrogen-rich atmosphere at 4-sigma significance relative to a featureless spectrum. The strongest evidence for any individual absorber is obtained for H2O, which is favoured at 3-sigma significance. When retrieving on the WFC3 data alone and allowing for the possibility of a heterogeneous stellar brightness profile, the detection significance of H2O is reduced to 2.8-sigma. Further observations are therefore required to robustly determine the atmospheric composition of TOI-270d and assess the impact of stellar heterogeneity. If confirmed, our findings would make TOI-270d one of the smallest and coolest exoplanets to date with detected atmospheric spectral features., Comment: Accepted for publication in AAS journals on November 22, 2022 (received July 5, 2022; revised October 30, 2022)

We have entered the era of the James Webb Space Telescope (JWST). We use the first JWST transmission spectrum of the hot Saturn-mass exoplanet, WASP-39 b, obtained with the NIRSpec instrument in the 3-5 $\mu$m range to investigate (a) what atmospheric constraints are possible with JWST-quality data in this spectral range, (b) requirements for atmospheric models used in retrievals, (c) effect of differences between data reduction pipelines on retrieved atmospheric properties, and (d) complementarity between JWST data in the 3-5 $\mu$m range and HST observations at shorter wavelengths. JWST spectra in the 3-5 $\mu$m range provide a promising avenue for chemical detections while encompassing a window in cloud opacity for several prominent aerosols. We confirm recent inferences of CO$_2$, SO$_2$, H$_2$O, and CO in WASP-39 b, report tentative evidence for H$_2$S, and retrieve elemental abundances consistent with Saturn's metallicity. We retrieve molecular abundances with $\sim$0.3-0.6 dex precision with this relatively limited spectral range. When considering the 3-5 $\mu$m data alone, reported differences in spectra with different reduction pipelines can affect abundance estimates by up to $\sim$1 dex and the detectability of less prominent species. Complementing with data at shorter wavelengths, e.g. with other JWST instruments or HST WFC3 ($\sim$0.8-1.7 $\mu$m), can significantly improve the accuracy and precision of the abundance estimates. The high data quality enables constraints on aerosol properties, including their composition, modal size and extent, motivating their consideration in retrievals. Our results highlight the promise of JWST exoplanet spectroscopy, while underscoring the importance of robust data reduction and atmospheric retrieval approaches in the JWST era., Comment: Accepted for publication in ApJ Letters

The complexity of atmospheric retrieval models is largely data-driven and one-dimensional models have generally been considered adequate with current data quality. However, recent studies have suggested that using 1D models in retrievals can result in anomalously cool terminator temperatures and biased abundance estimates even with existing transmission spectra of hot Jupiters. Motivated by these claims and upcoming high-quality transmission spectra we systematically explore the limitations of 1D models using synthetic and current observations. We use 1D models of varying complexity, both analytic and numerical, to revisit claims of biases when interpreting transmission spectra of hot Jupiters with inhomogeneous terminator compositions. Overall, we find the reported biases to be resulting from specific model assumptions rather than intrinsic limitations of 1D atmospheric models in retrieving current observations of asymmetric terminators. Additionally, we revise atmospheric retrievals of the hot Jupiter WASP-43b ($T_{\rm eq}=1440$ K) and the ultra-hot Jupiter WASP-103b ($T_{\rm eq}=2484$ K ) for which previous studies inferred abnormally cool atmospheric temperatures. We retrieve temperatures consistent with expectations. We note, however, that in the limit of extreme terminator inhomogeneities and high data quality some atmospheric inferences may conceivably be biased, although to a lesser extent than previously claimed. To address such cases, we implement a 2D retrieval framework for transmission spectra which allows accurate constraints on average atmospheric properties and provides insights into the spectral ranges where the imprints of atmospheric inhomogeneities are strongest. Our study highlights the need for careful considerations of model assumptions and data quality before attributing biases in retrieved estimates to unaccounted atmospheric inhomogeneities., Replaced with version accepted for publication in The Astrophysical Journal

Understanding the internal structures of planets with a large H$_2$O component is important for the characterisation of sub-Neptune planets. The finding that the mini-Neptune K2-18b could host a liquid water ocean beneath a mostly hydrogen envelope motivates a detailed examination of the phase structures of water-rich planets. To this end, we present new internal structure models for super-Earths and mini-Neptunes that enable detailed characterisation of a planet's water component. We use our models to explore the possible phase structures of water worlds and find that a diverse range of interiors are possible, from oceans sandwiched between two layers of ice to supercritical interiors beneath steam atmospheres. We determine how the bulk properties and surface conditions of a water world affect its ocean depth, finding that oceans can be up to hundreds of times deeper than on Earth. For example, a planet with a 300 K surface can possess H$_2$O oceans with depths from 30-500 km, depending on its mass and composition. We also constrain the region of mass-radius space in which planets with H/He envelopes could host liquid H$_2$O, noting that the liquid phase can persist at temperatures up to 647 K at high pressures of $218$-$7\times10^4$ bar. Such H/He envelopes could contribute significantly to the planet radius while retaining liquid water at the surface, depending on the planet mass and temperature profile. Our findings highlight the exciting possibility that habitable conditions may be present on planets much larger than Earth., Comment: 19 pages, 15 figures. Accepted for publication in MNRAS