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Abstract KELT-20b is a well-studied (T_eq = 2262 K) ultrahot Jupiter, but its multidimensional atmospheric structure remains unconstrained. We performed high-resolution cross-correlation transmission spectroscopy (HRCCTS) on a single-transit time series of KELT-20b, observed with the Potsdam Echelle Polarimetric and Spectroscopic Instrument on the Large Binocular Telescope. Upon combining nineteen in-transit exposures, we detect FeI(11.9σ) and FeII(23.7σ) and tentatively detect NaI(3.4σ) and CrI(3.3σ). The full-transit velocity offsets of the strongest absorbers are ΔV_FeI = −1.0 ± 0.7 km s⁻¹and ΔV_FeII = 0.0 ± 0.5 km s⁻¹, which are mostly inconsistent with previously published values for KELT-20b, although the previous measurements are mostly inconsistent with each other. By correcting for discrepant systemic velocity solutions of up to 1.7 km s⁻¹between studies, our FeIIoffset becomes consistent with previous measurements (≤1.7σ), while FeIremains significantly less blueshifted than in earlier studies (≥2.2−4.5σ). We propose a set of detection criteria to improve future reproducibility in HRCCTS work. Phase-resolving the FeIand FeIIabsorption signatures into eight orbital phase bins reveals distinct dynamical regimes: FeIIexhibits a strong phase-dependent blueshift from ingress to egress along with significant limb asymmetry, while FeIshows weaker signals and a more modest blueshift with phase. These patterns indicate day-to-night winds and suggest scale height differences are a significant driver of limb asymmetry in KELT-20b. 

ABSTRACT Ultra-hot Jupiters (UHJs) orbit close to their host stars and experience extreme conditions, making them important laboratories to explore atmospheric composition and dynamics. Transmission spectroscopy is a useful tool to reveal chemical species and their vertical and longitudinal distribution in the atmosphere. We use transmission spectra from the PEPSI (Potsdam Echelle Polarimetric and Spectroscopic Instrument) spectrograph on the Large Binocular Telescope to search for species and measure their time-resolved wind velocities in the atmosphere of TOI-1518 b. We detect Fe i at 7.8$$\sigma$$ and Fe ii at 8.9$$\sigma$$, and tentatively detect Cr i at 4.4$$\sigma$$ and Ni i at 4.0$$\sigma$$. The time-resolved wind velocities of Fe i show a velocity pattern that is consistent with the velocity pattern of Fe ii. TOI-1518 b joins a small sample of UHJs for which time-resolved wind velocities have been measured. 

Abstract We present five datasets of high-resolution optical emission spectra of the ultra-hot-Jupiter KELT-20 b with the PEPSI spectrograph. Using a Bayesian retrieval framework, we constrain its dayside pressure–temperature profile and abundances of Fe, Ni, and Ca, providing the first measurements for Ni and Ca for KELT-20 b in emission. We retrieve the preeclipse and posteclipse datasets separately (corresponding to the evening and morning sides, respectively), and compare the constraints on their thermal structures and chemical abundances. We constrain lower abundances in the pre-eclipse datasets compared to the posteclipse datasets. We interpret these results with an equilibrium chemistry model which suggests ∼10–30× supersolar refractory abundances. Due to the well-known degeneracy between absolute abundances and continuum opacities, the abundance ratios are more precise probes of the planetary abundances. Therefore we measure the abundance ratios [Ni/Fe] and [Ca/Fe] across these datasets and find they agree within 1σ. We constrain [Ni/Fe] to be consistent with solar within 2σ, and [Ca/Fe] to be 0.001–0.01× solar, not accounting for ionization. We compare these abundance ratios with literature results for KELT-20 b in transmission, and find they agree within 2σ, suggesting that even though the abundances vary significantly as a function of phase, the abundance ratios of these species remain relatively constant. We find a ∼100 K difference in temperature at the top of the thermal inversion, suggesting a hotter evening side than morning side and underscoring the importance of considering 3D effects when studying ultrahot Jupiters. 

Abstract Despite the wide range of planet–star (mis)alignments in the mature population of transiting exoplanets, the small number of known young transiting planets are nearly all aligned with the rotation axes of their host stars, as determined by the sky-projected obliquity angle. The small number of young systems with measured obliquities limits statistical conclusions. Here we determine the sky-projected obliquity (λ) of the 3 Myr transiting planet with a misaligned outer protoplanetary disk, TIDYE-1 b (IRAS 04125+2902b), using the Rossiter–McLaughlin (RM) effect. Our dataset lacks a pretransit baseline and ingress, complicating a blind RM fit. Instead, we use contemporaneous spectra and photometry from a mass-measurement campaign to model the stellar activity trend across the transit and provide an external prior on the velocity baseline. We determine $\mid \lambda \mid =11.8_{-5.0}^{+5.9}°$. Combined with the published rotational velocity of the star, we find a true three-dimensional obliquity of $\psi =15.2_{-5.7}^{+7.3}°$. Our result is consistent with an aligned orbit, suggesting the planet remains aligned to its star even though the outer disk is misaligned, though additional RM observations are needed to exclude the low-probability tail of misaligned (>30°) scenarios present in our posterior. 

ABSTRACT WASP-12 b is an ultra-hot Jupiter of special interest for atmospheric studies since it is on an inspiraling orbit in an extreme environment of intense radiation and circumstellar gas. Previously claimed detections of active mass-loss from this planet are controversial across the literature. To address this controversy, we obtain two new transit observations of WASP-12 b with the optical high-resolution PEPSI spectrograph on the Large Binocular Telescope. Contrary to previous work, we do not observe planetary H$$\alpha$$ absorption and rule out the amplitude of previously reported detections. Our non-detection may be limited by the sensitivity of our data or could indicate weaker mass-loss than suggested by previous studies. We conduct injection-recovery experiments to place constraints on the radial extent of WASP-12 b’s escaping atmosphere as probed by Balmer lines, but find that our data do not have the sensitivity to probe down to the planet’s Roche lobe. Using physically motivated models of atmospheric escape, we explore upper limit constraints on the planet’s mass-loss rate and deem the data quality in the wavelength regime of Balmer lines insufficient to determine a physically meaningful constraint. We also conduct a spectral survey of other optical absorbers to trace atmospheric circulation but detect no additional absorption. We conclude that previous claims of H$$\alpha$$ absorption from the atmosphere of WASP-12 b should be reevaluated. Given the anticipated line strength of Balmer/optical features, observing the atmosphere of this faint target will require stacking more observations even with the largest telescope facilities available. 

Diffraction-limited radial-velocity instruments offer a pathway towards improved precision and stability, and the exploration of new parameter spaces at high spatial and spectral resolution. However, achieving the necessary performance requires careful instrument design and considerable on-sky testing. We describe the design and construction of ‘Little iLocater’ (Lili), a compact spectrograph that has been used to validate the performance of the front-end fibre-injection system of the iLocater spectrograph. We present the design, assembly, and performance using on-sky data obtained at the Large Binocular Telescope (LBT), including extraction of spectra from standard stars, testing of the atmospheric dispersion corrector to elevations of 40°, and spatially resolved spectra from close companion systems. These results show the front-end fibre-injection system is performing as expected and is indicative of iLocater’s capabilities once installed at the LBT. 

ABSTRACT Most ultra-hot Jupiters (UHJs) show evidence of temperature inversions, in which temperature increases with altitude over a range of pressures. Temperature inversions can occur when there is a species that absorbs the stellar irradiation at a relatively high level of the atmospheres. However, the species responsible for this absorption remains unidentified. In particular, the UHJ KELT-20b is known to have a temperature inversion. Using high resolution emission spectroscopy from LBT/PEPSI we investigate the atomic and molecular opacity sources that may cause the inversion in KELT-20b, as well as explore its atmospheric chemistry. We confirm the presence of Fe i with a significance of 17σ. We also report a tentative 4.3σ detection of Ni i. A nominally 4.5σ detection of Mg i emission in the PEPSI blue arm is likely in fact due to aliasing between the Mg i cross-correlation template and the Fe i lines present in the spectrum. We cannot reproduce a recent detection of Cr i, while we do not have the wavelength coverage to robustly test past detections of Fe ii and Si i. Together with non-detections of molecular species like TiO, this suggests that Fe i is likely to be the dominant optical opacity source in the dayside atmosphere of KELT-20b and may be responsible for the temperature inversion. We explore ways to reconcile the differences between our results and those in literature and point to future paths to understand atmospheric variability. 

Precision radial velocity spectrographs that use adaptive optics (AO) show promise to advance telescope observing capabilities beyond those of seeing-limited designs. We are building a spectrograph for the Large Binocular Telescope (LBT) named iLocater that uses AO to inject starlight directly into single mode fibers. iLocater's first acquisition camera system (the SX camera), which receives light from one of the 8.4 m diameter primary mirrors of the LBT, was initially installed in summer 2019 and has since been used for several commissioning runs. We present results from first-light observations that include on-sky measurements as part of commissioning activities. Imaging measurements of the bright B3IV star 2 Cygni (V= 4.98) resulted in the direct detection of a candidate companion star at an angular separation of onlyθ = 70 mas. Follow-up AO measurements using Keck/NIRC2 recover the candidate companion in multiple filters. AnR ≈ 1500 miniature spectrograph recently installed at the LBT named Lili provides spatially resolved spectra of each binary component, indicating similar spectral types and strengthening the case for companionship. Studying the multiplicity of young runaway star systems like 2 Cygni (36.6 ± 0.5 Myr) can help to understand formation mechanisms for stars that exhibit anomalous velocities through the Galaxy. This on-sky demonstration illustrates the spatial resolution of the iLocater SX acquisition camera working in tandem with the LBT AO system; it further derisks a number of technical hurdles involved in combining AO with Doppler spectroscopy. 

We report the discovery of TOI-4641b, a warm Jupiter transiting a rapidly rotating F-type star with a stellar effective temperature of 6560 K. The planet has a radius of 0.73 RJup, a mass smaller than 3.87 MJup(3σ), and a period of 22.09 d. It is orbiting a bright star (V=7.5 mag) on a circular orbit with a radius and mass of 1.73 R⊙ and 1.41 M⊙. Follow-up ground-based photometry was obtained using the Tierras Observatory. Two transits were also observed with the Tillinghast Reflector Echelle Spectrograph, revealing the star to have a low projected spin-orbit angle (λ=$$1.41^{+0.76}_{-0.76}$$°). Such obliquity measurements for stars with warm Jupiters are relatively few, and may shed light on the formation of warm Jupiters. Among the known planets orbiting hot and rapidly rotating stars, TOI-4641b is one of the longest period planets to be thoroughly characterized. Unlike hot Jupiters around hot stars which are more often misaligned, the warm Jupiter TOI-4641b is found in a well-aligned orbit. Future exploration of this parameter space can add one more dimension to the star–planet orbital obliquity distribution that has been well sampled for hot Jupiters. 

Abstract Recent observations have shown that the atmospheres of ultrahot Jupiters (UHJs) commonly possess temperature inversions, where the temperature increases with increasing altitude. Nonetheless, which opacity sources are responsible for the presence of these inversions remains largely observationally unconstrained. We used LBT/PEPSI to observe the atmosphere of the UHJ KELT-20 b in both transmission and emission in order to search for molecular agents which could be responsible for the temperature inversion. We validate our methodology by confirming a previous detection of Feiin emission at 16.9σ. Our search for the inversion agents TiO, VO, FeH, and CaH results in non-detections. Using injection-recovery testing we set 4σupper limits upon the volume mixing ratios for these constituents as low as ∼1 × 10⁻⁹for TiO. For TiO, VO, and CaH, our limits are much lower than expectations from an equilibrium chemical model, while we cannot set constraining limits on FeH with our data. We thus rule out TiO and CaH as the source of the temperature inversion in KELT-20 b, and VO only if the line lists are sufficiently accurate.