arXiv subjects

Frank W. Wagner

Publications and source records attributed to Frank W. Wagner.

4 recordsLinked to original sources

arXiv2026

Trans-Neptunian Object dynamics even better explained by a stellar flyby after 4.5 Gyr of evolution

The Trans-Neptunian objects (TNOs) formed together with the planets from a flat disc of gas and dust but now orbit the Sun mostly on inclined, eccentric orbits. One explanation for the TNOs' orbits is a close flyby of another star. One with a mass of $M_p =$0.8 Msun at $q_p =$ 110 au and $i_p =$70° fits the observations. However, such close encounters were more frequent when the Sun was young and still part of its birth cluster. Assuming that the flyby happened then, we use numerical $N$-body simulations to model how the TNOs' orbits changed due to interactions with the planets over the 4.56 Gyr since the Sun formed. We find that the cold Kuiper belt region lost about 80% and the hot Kuiper belt population about 40% of its initial population. About 7% --8% of the TNOs were injected into the planet region, but almost all (99%) were ejected afterwards. By contrast, the orbital parameters of distant Sedna-like objects ($q >$60 au) remained basically unchanged. Surprisingly, in sum, these changes improve the fit to the observed TNO population even more, strengthening the argument for a close flyby to the Solar System. The remaining differences concern the location of the cold population and the inclination distribution of the Sedna population. We discuss possible reasons and steps to resolve these issues.

astro-ph.EP↗

arXiv2026

Disc lifetime distribution as a function of the mass of host star

The lifetime of protoplanetary discs is a critical factor for planet formation. Although the mean disc lifetime provides an estimate of the typical period available for planet formation, it does not capture the substantial variability in individual disc lifetimes or their dependence on host star mass. This study addresses these limitations by deriving the disc lifetime distribution as a function of stellar mass. Our results reveal a pronounced mass-dependence. Performing a phenomenological fit using a Weibull distribution, we find the maxima of the distributions at $t_{max}^H =$3.72 Myr for high-mass stars ($\approx$ 1.00--3.00 $M_{\odot}$) and $t_{max}^L =$ 7.20 Myr for low-mass stars ($\approx$ 0.01--0.20 $M_{\odot}$) assuming an initial disc fraction of $f_{init} = 0.8$. All distributions are broad (typically 3.2 Myr $< σ<$ 4.7 Myr), with the distribution for low-mass stars being somewhat broader. Our analysis indicates that not all stars are initially surrounded by a disc (60% $< f_{init} <$ 90% at cluster zero age), and that the initial disc fraction is even lower ($f_{init} \approx$ 40%) for higher-mass stars. The potential mechanisms responsible for the observed spread and mass-dependence of disc lifetime distributions and initial disc fractions are discussed. Our primary aim is to demonstrate the methodology; more robust constraints will require improved data on mass-dependent disc fractions. Nevertheless, the derived mass-dependent disc lifetime distributions can already serve as a valuable input or a benchmark for planet-formation synthesis models.

astro-ph.EP↗

arXiv2026

Towards FAIR Astrophysical Simulations

Reproducibility is a cornerstone of science. FAIR (findable, accessible, interoperable, and reusable) data is often a vital step towards testing the reproducibility of results. The implementation of FAIR principles in the astrophysical simulation community is still varied. We approach the discussion of this topic mainly from a high-performance computing (HPC) point of view. We identify the main obstacles to FAIR astrophysics simulations: First, the vast datasets created in simulations on HPC facilities complicate FAIR data management. Second, missing incentives to fully share codes, results, and diagnostic data. Third, a lack of workflows that include data publication and technical support. Therefore, particularly smaller research groups struggle due to the unavailability of dedicated personnel and time in their efforts towards FAIR and open simulations. We propose actionable steps towards achieving ``FAIRer'' data and open source publication standards in numerical astrophysics. Our suggestions include low-threshold methods to fulfil the basic FAIR requirements as well as basic tools for FAIR (meta-)data generation and data/code publication. This work is a high-level overview intended to initiate discussions within the community, offering initial solutions to these challenges.

astro-ph.IM↗

arXiv2025

TNO colours provide new evidence for a past close flyby of another star to the Solar System

Thousands of small bodies, known as trans-Neptunian objects (TNOs), orbit the Sun beyond Neptune. TNOs are remnants of the planets' formation from a disc of gas and dust, so it is puzzling that they move mostly on eccentric orbits inclined to the planetary plane and show a complex red-to-grey colour distribution. A close stellar flyby can account for the TNOs' dynamics, but it is unclear if this can also explain the correlation between their colours and orbital characteristics. Assuming an initial red-to-grey colour gradient in the disc, our numerical study finds that the spiral arms induced by the stellar flyby simultaneously lead to the observed TNOs' colour patterns and orbital dynamics. The combined explanation of these TNO properties strengthens the evidence for a close flyby of another star to the young Solar System. Our study predicts that (1) small TNOs beyond 60 au will mostly be grey, and (2) retrograde TNOs will lack the colour most common to high-inclination TNOs. The anticipated TNO discoveries by the Vera Rubin telescope will be able to test these predictions. A confirmed flyby would allow us to reveal the chemical composition of the Solar System's primordial disc.

astro-ph.EP↗