Thomas Marquart

Ultrahot Neptunes reside in the most extreme irradiation regime of the hot Neptune desert and remain challenging targets for atmospheric characterization because of their intrinsically low planet-to-star flux ratios. We present high-resolution transit and dayside thermal emission spectroscopy of the ultrahot Neptune LTT 9779 b obtained with CRIRES ⁺ , aimed at probing both atmospheric escape and dayside molecular emission. No significant absorption is detected in the metastable He I λ1083 nm triplet during transit, yielding a 3 σ upper limit of 0.45% on the excess helium absorption depth and supporting previous non-detections that suggest weak ongoing atmospheric escape. For the dayside emission spectra in the K band, our cross-correlation analysis reveals an H ₂ O absorption signal and a tentative CO feature, with the combined signal reaching a detection significance of 4.8 σ . Both the CRIRES ⁺ and previous JWST data favor a non-inverted temperature structure, providing no evidence of a thermal inversion on the planetary day-side. We further perform a joint atmospheric retrieval combining the CRIRES ⁺ high-resolution spectra with JWST/NIRISS SOSS secondary-eclipse observations. The joint retrieval yields a low H ₂ O abundance, while the CO abundance remains weakly constrained. The inferred planetary equatorial rotational velocity, v _eq = 4.9 _−3.0 ^+4.4 km s ⁻¹ , is consistent within 1 σ with the synchronous rotation velocity expected for a tidally locked planet (~2.8 km s ⁻¹ ). However, the large uncertainties prevent us from placing strong constraints on the planet’s rotation state. Future phase-resolved CRIRES ⁺ observations with broader orbital-phase coverage and higher signal-to-noise ratios would improve the abundance constraints and probe the atmospheric dynamics of this rare ultrahot Neptune.

We introduce the data reduction pipeline for the Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES). TOFES is installed in the Coudé room and will be connected to the 1.5 m Tartu Observatory AZT-12 telescope through a four-channel instrument adapter to be mounted at the Cassegrain focus of the telescope. The spectrograph has an average spectral resolution of ∼30,000 and covers the 390–900 nm wavelength band in a single exposure. The data reduction pipeline, based on the PyReduce package, was tested on spectra of the Sun. We also present the Spectroscopy-Toolbox package, which was developed to provide additional tools for diagnostics and spectral line identification for radial velocity measurements. The spectrograph will address a range of scientific questions, including the stellar characterisation of Herbig Ae/Be stars to measure accretion contamination from their protoplanetary disks, the stellar characterisation of exoplanet host-stars including the Ariel space mission targets, and radial velocity monitoring of large-scale atmospheric variability in massive stars.

So far, the majority of high-resolution spectroscopy studies on exoplanet atmospheres have focused on transiting planetary systems. Consequently, the atmospheres of non-transiting exoplanets remain poorly explored, and the potential of high-resolution spectroscopy for determining key planetary parameters beyond their atmospheric properties has not been fully exploited. We obtained high-resolution emission spectra of the non-transiting hot Jupiter 51 Peg b in the K band with VLT/CRIRES ⁺ to study its atmospheric thermochemical and dynamical structure and derive additional planetary parameters from the Doppler shift of its spectral lines. Using the cross-correlation technique, we confirmed the spectral signature of H ₂ O in the planetary emission spectrum and a non-inverted atmospheric temperature profile. An indication was also found for the presence of atmospheric CO, although with a signal strength below the threshold for significant detection. The atmospheric chemical and thermal conditions were quantitatively constrained by use of a Bayesian retrieval framework, which yielded a high metallicity value (2.63 _+0.93 ^−1.00 dex) suggestive of chemical quenching, a solar C/O ratio (0.54 _−0.23 ^+0.18 ), and a temperature profile in the upper atmosphere in line with the expected planetary equilibrium temperature. Moreover, we measured an excess of spectral line broadening, which suggests the presence of atmospheric dynamics in the atmosphere of 51 Peg b. The planetary signal was recovered at an orbital semi-amplitude of 102.8 _−9.1 ^+8.3 km s ⁻¹ , differing from previous high-resolution measurements. From the obtained orbital semi-amplitude, we further derived the surface gravity (3.15 ± 0.12 log cgs), mass (0.61 _−0.05 ^+0.06 M _Jup ), and orbital inclination (49.8 _−5.7 ^+5.8 deg) of 51 Peg b. The mass and inclination values differ from those reported in earlier works. Overall, this study provides new constraints on the thermochemical and dynamical properties of 51 Peg b’s atmosphere and demonstrates the potential of high-resolution emission spectroscopy for measuring parameters related to the planetary orbital motion.

We present the first planet mass measurement obtained with CRIRES ⁺ radial velocity (RV) observations using the K -band gas cell. Our target, LHS 3844 b (TOI-136), is a transiting super-Earth with radius R _b = 1.286 _−0.044 ^+0.043 R _⊕ and an orbital period of P _b = 0.462929709 _{−0.000000042} ^+0.000000044 d, placing it in the class of ultra-short-period (USP) planets. The host star LHS 3844 is an old (7.8 ± 1.6 Gyr), slowly rotating ( P _rot = 130.0 _−13.4 ^+16.9 ) M5.0 dwarf with M _⋆ = 0.151 ± 0.014 M _⊙ at a distance of 15 pc ( V = 15.2 mag, K = 9.2 mag). Combining our CRIRES ⁺ RVs with archival ESPRESSO spectra, and confirming the signal in each dataset independently, we detected periodic RV variations with a semi-amplitude K _b = 6.95 _−0.60 ^+0.55 m s ⁻¹ , implying a planetary mass of m _b = 2.37 ± 0.25 M _⊕ and a bulk density of ρ _b = 6.15 _−0.61 ^+0.60 g cm ⁻³ cm ⁻³ , consistent with a predominantly rocky composition. We further found excess RV variability that may be attributed to stellar jitter or to an additional planetary signal, for which we identified a tentative super-Earth candidate with a period of ≈6.88 d. Owing to its proximity to its M-dwarf host, LHS 3844 b experiences intense irradiation and is unlikely to retain a substantial H/He envelope. Interior modeling places an upper limit on the iron-core mass fraction, which is consistent with an Earth-like rocky composition. With an emission spectroscopy metric (ESM) of 28, LHS 3844 b is a prime JWST target for atmospheric and surface characterization and the most promising surface-characterization target known. Phase-curve spectroscopy may reveal its surface mineralogy and enable the first robust detection of exoplanet surface spectral features. Our results demonstrate that near-infrared RVs obtained with CRIRES ⁺ enable robust mass measurements of super-Earths orbiting late M dwarfs.

The atmospheres of transiting exoplanets can be studied spectroscopically using space-based or ground-based observations. Each has its own set of strengths and weaknesses, so there are benefits to both approaches. This is especially true for more challenging targets such as cooler, smaller exoplanets whose atmospheres most likely contain many molecular species and cloud decks. We aim to study the atmosphere of the warm Neptune-like exoplanet WASP-107 b (T_ ≈ 740 K). Several molecular species have been detected in this exoplanet in studies using the space-based JWST, and we aim to confirm and expand upon these detections by using the ground-based VLT and evaluating how well our findings agree with previously retrieved atmospheric parameters. eq We observed two transits of with VLT/ŗiresp and created cross-correlation templates of the target atmosphere based on results from previous studies. We created different templates to investigate the impact of varying volume mixing ratios of species and the inclusion or exclusion of clouds. Considering this target's observational challenges, we created simulated observations prior to evaluating our real data in order to assess our expected detection significances with the cross-correlation technique. We of two molecular species, CO ( ( . This previous space-based detections and demonstrates, for the first time, the capability of VLT/ŗiresp to detect species in targets cooler than hot Jupiters using transmission spectroscopy. We show that our analysis is sensitive to the inclusion of clouds but less so to different volume mixing ratios. Interestingly, our deviates , and we speculate on the possible reasons for this effect. We demonstrate that the error budget for these relatively cool exoplanets is severely reduced in comparison to hotter exoplanets and emphasise the need for further work in the context of high-resolution spectroscopy. report cross-correlation signals and H2O in our ̨pvsys maps supports signal maximum notably but consistently from its expected location in the ̨p direction of our maps

The ultra-hot Jupiter (UHJ) TOI-2109b marks the lower edge of the equilibrium temperature gap between 3500 and 4500 K, an unexplored thermal regime that separates KELT-9b, the hottest planet yet discovered, from all other currently known gas giants. To study the thermochemical structure of TOI-2109b’s atmosphere, we obtained high-resolution emission spectra of both the planetary day- and nightsides with CAHA/CARMENES and VLT/CRIRES⁺. By applying the cross-correlation technique to the high-resolution spectra, we identified the emission signatures of Fe I (S/N = 4.3) and CO (S/N = 6.3), as well as a thermal inversion layer in the dayside atmo-sphere; no significant H₂O signal was detected from the dayside. None of the analyzed species were detectable from the nightside atmosphere. We applied a Bayesian retrieval framework that combines high-resolution spectroscopy with photometric measurements to constrain the dayside atmospheric parameters and derive upper limits for the nightside hemisphere. The dayside thermal inversion extends from approximately 3200 to 4600 K, with an atmospheric metallicity consistent with that of the host star (0.36 dex). Only weak constraints could be placed on the C/O ratio, with a lower limit of 0.15. The retrieved spectral line broadening is consistent with tidally locked rotation, indicating the absence of strong dynamical processes in the atmosphere. An upper temperature limit of approximately 2400 K and a maximum atmospheric temperature gradient of about 700 K/log bar could be derived for the planetary nightside. Comparison of the retrieved dayside temperature-pressure profile with theoretical models, the absence of strong atmospheric dynamics, and significant differences in the thermal constraints between the day- and nightside hemispheres suggest a limited heat transport efficiency across the planetary atmosphere. Overall, our results place TOI-2109b in a transitional regime between the UHJs below the thermal gap, which show both CO and H₂O emission lines, and KELT-9b, where molecular features are largely absent.

Context. High-precision radial velocity (RV) measurements with slit spectrographs require the instrument profile (IP) and Earth’s atmospheric spectrum to be known and to be incorporated into the RV calculation. Aims. We developed an RV pipeline, called Velocity and IP EstimatoR (viper), to achieve high-precision RVs in the near-infrared (NIR). The code is able to process observations taken with a gas cell and includes modelling of the IP and telluric lines. Methods. We utilised least-square fitting and telluric forward modelling to account for instrument instabilities and atmospheric absorption lines. As part of this process, we demonstrate the creation of telluric-free stellar spectra. Results. By applying viper to observations obtained with the upgraded CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES⁺) and a gas absorption cell in the K band, we are able to reach an RV precision of around 3 m/s over a time span of 2.5 years. For observations using telluric lines for the wavelength reference, an RV precision of 10 m/s is achieved. Conclusions. We demonstrate that despite telluric contamination, a high RV precision is possible at NIR wavelengths, even for a slit spectrograph with varying IP. Furthermore, we show that CRIRES⁺ performs well and is an excellent choice for science studies requiring precise stellar RV measurements in the infrared.

Despite recent progress in the spectroscopic characterization of individual exoplanets, the atmospheres of key ultra-hot Jupiters (UHJs) still lack comprehensive investigations. These include WASP-178b, one of the most irradiated UHJs known to date. We observed the dayside emission signal of this planet with CRIRES⁺ in the spectral K band. By applying the cross-correlation technique and a Bayesian retrieval framework to the high-resolution spectra, we identified the emission signature of ¹²CO (S/N = 8.9) and H₂O (S/N = 4.9), and a strong atmospheric thermal inversion. A joint retrieval with space-based secondary eclipse measurements from TESS and CHEOPS allowed us to refine our results on the thermal profile and thus to constrain the atmospheric chemistry, yielding a solar to super-solar metallicity (1.4 ± 1.6 dex) and a solar C/O ratio (0.6 ± 0.2). We infer a significant excess of spectral line broadening and identify a slight Doppler-shift between the ¹²CO and H₂O signals. These findings provide strong evidence for a super-rotating atmospheric flow pattern and suggest the possible existence of chemical inhomogeneities across the planetary dayside hemisphere. In addition, the inclusion of photometric data in our retrieval allows us to account for stellar light reflected by the planetary atmosphere, resulting in an upper limit on the geometric albedo (0.23). The successful characterization of WASP-178b’s atmosphere through a joint analysis of CRIRES⁺, TESS, and CHEOPS observations highlights the potential of combined studies with space- and ground-based instruments and represents a promising avenue for advancing our understanding of exoplanet atmospheres.

Aims. We aim to characterise the small-scale magnetic fields of a sample of 16 Sun-like stars and investigate the capabilities of the newly upgraded near-infrared (NIR) instrument CRIRES⁺ at the Very Large Telescope in the context of small-scale magnetic field studies. Our targets also had their magnetic fields studied with optical spectra, which allowed us to compare magnetic field properties at different spatial scales on the stellar surface and to contrast small-scale magnetic field measurements at different wavelengths. Methods. We analysed the Zeeman broadening signature for six magnetically sensitive and insensitive Fe I lines in the H-band to measure small-scale magnetic fields on the stellar surfaces of our sample. We used polarised radiative transfer modelling and non-local thermodynamic equilibrium departure coefficients in combination with Markov chain Monte Carlo sampling to determine magnetic field characteristics and non-magnetic stellar parameters. We used two different approaches to describe the small-scale magnetic fields. The first is a two-component model with a single magnetic region and a free magnetic field strength. The second model contains multiple magnetic components with fixed magnetic field strengths. Results. We found average magnetic field strengths ranging from ∼0.4 kG down to < 0.1 kG. The results align closely with other results from high-resolution NIR spectrographs, such as SPIRou. It appears that the typical magnetic field strength in the magnetic region is slightly stronger than 1.3 kG, and for most stars in our sample, this strength is between 1 and 2 kG. We also found that the small-scale fields correlate with the large-scale fields and that the small-scale fields are at least ten times stronger than the large-scale fields inferred with Zeeman Doppler imaging. The two- and multi-component models produce systematically different results, as the strong fields from the multi-component model increase the obtained mean magnetic field strength. When comparing our results with the optical measurements of small-scale fields, we found a systematic offset two to three times stronger than fields in the optical results. This discrepancy cannot be explained by uncertainties in stellar parameters. Care should therefore be taken when comparing results obtained at different wavelengths until a clear cause can be established.

We present Lyα imaging of 45 low-redshift star-forming galaxies observed with the Hubble Space Telescope. The galaxies have been selected to have moderate to high star formation rates (SFRs) using far-ultraviolet (FUV) luminosity and Hα equivalent width criteria, but no constraints on Lyα luminosity. We employ a pixel stellar continuum fitting code to obtain accurate continuum-subtracted Lyα, Hα, and Hβ maps. We find that Lyα is less concentrated than FUV and optical line emission in almost all galaxies with significant Lyα emission. We present global measurements of Lyα and other quantities measured in apertures designed to capture all of the Lyα emission. We then show how the escape fraction of Lyα relates to a number of other measured quantities (mass, metallicity, star formation, ionization parameter, and extinction). We find that the escape fraction is strongly anticorrelated with nebular and stellar extinction, weakly anticorrelated with stellar mass, but no conclusive evidence for correlations with other quantities. We show that Lyα escape fractions are inconsistent with common dust extinction laws, and discuss how a combination of radiative transfer effects and clumpy dust models can help resolve the discrepancies. We present an SFR calibration based on Lyα luminosity, where the equivalent width of Lyα is used to correct for nonunity escape fraction, and show that this relation provides a reasonably accurate SFR estimate. We also show stacked growth curves of Lyα for the galaxies that can be used to find aperture loss fractions at a given physical radius.