arXiv subjects

David Cont

Publications and source records attributed to David Cont.

3 recordsLinked to original sources

arXiv2026

The future of high-resolution UV spectroscopy: Science with a UV \'Echelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission

High-resolution UV spectroscopy serves a diversity of science cases, from small bodies to planets, stars, and galaxies, but is currently limited to the Hubble Space Telescope and bright targets. Major advances require increasing sensitivity by at least one order of magnitude. Here we present the UV science cases for PEGASUS (Planets, Earths, Galaxies, And Stars UV Spectrograph), a UV \'Echelle high-resolution spectrograph concept, with $R = \lambda/\delta\lambda \sim 100\,000$ (full range 10 000-140 000) and covering 90--400 nm, with a foreseen extension to at least 800 nm. PEGASUS is ideally suited for the Habitable Worlds Observatory (HWO), enabling transformative science across the UV/optical wavelength ranges. PEGASUS will be unique in high sensitivity (effective area) and high spectral resolution -- an uncharted territory -- as well as robustness, thanks to the simplicity of its design. Its UV science cases include: I) Formation and evolution of planets and their habitability: properties of exoplanets and atmospheres, protoplanetary disks, Solar System bodies; II) Stellar lives and deaths at their extremes: the first stars and the origin of the elements, compact and massive stars, Supernovae; III) Gas and metals in the baryon cycle of galaxies: the interstellar, circumgalactic, and intergalactic medium and their roles in galaxy growth. These are essential for the Astro Decadal 2020 Survey, Voyage 2050, and HWO. While this paper focuses on high-impact science enabled by UV high-resolution spectroscopy, PEGASUS will extend into the optical regime and lower spectral resolution, making it a multi-purpose, widely used, workhorse spectrograph for HWO.

astro-ph.IM↗

arXiv2025

Revisiting the atmosphere of HAT-P-70b with CARMENES high-resolution transmission spectroscopy

Owing to hot and inflated envelopes that facilitate atmospheric studies, ultra-hot Jupiters (UHJs) have attracted much attention. Significant progress has been achieved, from enlarging the sample size to broadening the studies to encompass diverse stellar types and ages. Here, we present a transmission spectroscopy study of HAT-P-70b, an UHJ orbiting a young A-type star, through high-resolution observations with CARMENES at the 3.5m Calar Alto telescope. By using the line-by-line technique, we confirm the previous detections of Ha, Na I, and Ca II, report a new tentative detection of K I, and impose an upper limit on the He triplet absorption. Through cross-correlation analysis, we identify the Ca II and Fe I absorptions, both blue-shifted by approximately 5 km/s, indicating a day-to-night side atmospheric wind. Additionally, we find a new tentative detection of K I. We do not see any significant atmospheric molecular signal in the near-infrared data. Putting HAT-P-70b in the context of UHJs from the literature, it turns out that (1) Ha absorption is more common on gas giants orbiting stars younger than 1 Gyr, with a relative detection probability of $P_{\rm Age<1\,Gyr}({\rm Ha})/P_{\rm Age\geq1\,Gyr}({\rm Ha})\sim 3$; (2) any UHJ is likely to exhibit Fe I absorption if it has Ca II.

astro-ph.EP↗

arXiv2025

VLT/CRIRES+ observations of warm Neptune WASP-107 b: Challenges in detecting molecules with ground-based transmission spectroscopy of cooler and cloudy exoplanets

Atmospheres of transiting exoplanets can be studied spectroscopically using space-based or ground-based observations. Each has its own strengths and weaknesses, so there are benefits to both approaches. This is especially true for challenging targets such as cooler, smaller exoplanets whose atmospheres likely contain many molecular species and cloud decks. We aim to study the atmosphere of the warm Neptune-like exoplanet WASP-107 b (Teq~740 K). Several molecular species have been detected in this exoplanet in recent space-based JWST studies, and we aim to confirm and expand upon these detections using ground-based VLT, evaluating how well our findings agree with previously retrieved atmospheric parameters. We observe two transits of WASP-107 b with VLT/CRIRES+ and create cross-correlation templates of the target atmosphere based on retrieval results from JWST studies. We create different templates to investigate the impact of varying volume mixing ratios of species and inclusion or exclusion of clouds. Considering this target's observational challenges, we create simulated observations prior to evaluating real data to assess expected detection significances. We report detections of two molecular species, CO (~6 S/N) and H2O (~4.5 S/N). This confirms previous space-based detections and demonstrates, for the first time, the capability of VLT/CRIRES+ to detect species in targets cooler than hot Jupiters using transmission spectroscopy. We show our analysis is sensitive to cloud inclusion, but less so to different volume mixing ratios. Interestingly, our detection deviates from its expected location in our Kp-vsys diagrams, and we speculate on possible reasons for this. We demonstrate that the error budget for relatively cooler exoplanets is severely reduced in comparison to hotter exoplanets, and underline need for further work in context of high-resolution spectroscopy.

astro-ph.EP↗