arXiv subjects

J. Ehrhardt

Publications and source records attributed to J. Ehrhardt.

3 recordsLinked to original sources

arXiv2026

Peering through the disc of HD 98800 BaBb. Precise timing predictions for the HD 98800 AaAb occultation

HD 98800 is a young hierarchical quadruple system composed of the tight binaries AaAb and BaBb on a wide, highly inclined outer orbit. The B subsystem hosts a circumbinary disc in a polar configuration, and the geometry of the system offers a rare opportunity to observe the passage of the disc around BaBb in front of AaAb. We aim to update the overall orbital solution to offer precise time windows of the main occultation features by combining the orbit with the state-of-the-art knowledge of the disc's structure. We combine new and published radial-velocity measurements and multi-wavelength astrometry for the outer AB orbit and both inner subsystems, AaAb and BaBb, in a joint orbital fit. The revised solution is consistent with previous dynamical masses and improved the outer orbit, reducing the uncertainties in the period and periastron epoch by about a factor of two. It also narrows the predicted crossing-phase windows to 5--15 days at the 1{\sigma} level, improving the timing of ingress, egress, and the first cavity-crossing predictions. These results provide a more accurate timing framework for future observations of the occultation, although the predicted epochs remain model-dependent because of uncertainties in the disc structure.

astro-ph.EP↗

arXiv2026

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) I: Motivation, sample, data reduction, and results overview

The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity, and that some belts contain CO gas, whose origin and implications are uncertain. Most of this progress, however, has been limited by low-resolution observations. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to constrain their detailed radial and vertical structure, and to characterise the gas content. We constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models. The first ARKS results are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits multiple dusty rings. For highly inclined belts, we found that non-Gaussian vertical distributions are common and are indicative of multiple dynamical populations. We also found that 10 of the 24 belts present asymmetries. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas rich systems. ARKS has revealed a great diversity of structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products.

astro-ph.EP↗

arXiv2024

Small but mighty: High-resolution spectroscopy of ultra-hot Jupiter atmospheres with compact telescopes. KELT-9 b's transmission spectrum with Wendelstein's FOCES Spectrograph

When observing transmission spectra produced by atmospheres of ultra-hot Jupiters, large telescopes are typically the instrument of choice due to the very weak signal of the planet's atmosphere. This study aims to alleviate the desire for large telescopes by illustrating that the same science is possible with smaller telescope classes. We use the cross-correlation technique to showcase the potential of the high-resolution spectrograph FOCES at Wendelstein Observatory and demonstrate its potential to resolve the atmosphere of the ultra-hot Jupiter, KELT-9 b. A performance comparison is conducted between FOCES and HARPS-N spectrographs, considering both single transit and combined observations over three nights. With FOCES, we have detected seven species in KELT-9 b's atmosphere: Ti II, Fe I, Fe II, Na I, Mg I, Na II, Cr II, Sc II. Although HARPS-N surpasses FOCES in performance, our results reveal that smaller telescope classes are capable of resolving ultra-hot Jupiter atmospheres. This broadens the scope of potential studies, allowing for investigations into phenomena like temporal variations in atmospheric signals and the atmospheric loss characteristics of these close-in planets.

astro-ph.EP↗