arXiv subjects

Matthew Beaudoin

Publications and source records attributed to Matthew Beaudoin.

4 recordsLinked to original sources

arXiv2026

Extending the infrastructure of the BAM code towards resistive general-relativistic magnetohydrodynamics: tests and first applications

Many astrophysical phenomena, including pulsars and short gamma-ray bursts, are associated with the extremely strong magnetic fields present in neutron stars and neutron star mergers. While the ideal magnetohydrodynamic approximation, which assumes infinite conductivity, provides an excellent description of the neutron-star interior, it cannot capture non-ideal processes such as Ohmic dissipation and magnetic reconnection. To overcome this limitation, we present an extension of the numerical-relativity code BAM incorporating a resistive general-relativistic magnetohydrodynamic (GRMHD) description. We validate the new implementation through an extensive suite of special-relativistic magnetohydrodynamic benchmark tests and by performing stable simulations of isolated and binary neutron star systems. For the latter, we investigate the impact of finite conductivity on magnetic-field amplification, mass ejection, and non-ideal GRMHD effects. In particular, we find that the component of the electric field parallel to the magnetic field, which is zero in the ideal case, can reach up to 10% of the total electric field strength. This highlights the potential importance of non-ideal effects for accurately modeling the long-term evolution of post-merger remnants, particularly in low-density regions. Although the present study is restricted to simplified piecewise-polytropic equations of state, it demonstrates the capabilities of the new resistive GRMHD framework and paves the way for future investigations employing more realistic microphysics.

astro-ph.HE↗

arXiv2023

OSSOS. XXIX. The Population and Perihelion Distribution of the Detached Kuiper Belt

The detached transneptunian objects (TNOs) are those with semimajor axes beyond the 2:1 resonance with Neptune, which are neither resonant nor scattering. Using the detached sample from the OSSOS telescopic survey, we produce the first studies of their orbital distribution based on matching the orbits and numbers of the known TNOs after accounting for survey biases. We show that the detached TNO perihelion ($q$) distribution cannot be uniform, but is instead better matched by two uniform components with a break near $q\approx40$ au. We produce parametric two-component models that are not rejectable by the OSSOS data set, and estimate that there are $36,\!000^{+12,000}_{-9,000}$ detached TNOs with absolute magnitudes $H_r < 8.66$ ($D \gtrsim 100$ km) and semimajor axes $48 < a < 250$ au (95% confidence limits). Although we believe these heuristic two-parameter models yield a correct population estimate, we then use the same methods to show that the perihelion distribution of a detached disk created by a simulated rogue planet matches the $q$ distribution even better, suggesting that the temporary presence of other planets in the early Solar System is a promising model to create today's large semimajor axis TNO population. This numerical model results in a detached TNO population estimate of $48,\!000^{+15,000}_{-12,000}$. Because this illustrates how difficult-to-detect $q>50$ au objects are likely present, we conclude that there are $(5 \pm 2)\times10^4$ dynamically detached TNOs, which are thus roughly twice as numerous as the entire transneptunian hot main belt.

astro-ph.EP↗

arXiv2022

A Rogue Planet Helps Populate the Distant Kuiper Belt

The orbital distribution of transneptunian objects (TNOs) in the distant Kuiper Belt (with semimajor axes beyond the 2:1 resonance, roughly $a$=50-100 au) provides constraints on the dynamical history of the outer solar system. Recent studies show two striking features of this region: 1) a very large population of objects in distant mean-motion resonances with Neptune, and 2) the existence of a substantial detached population (non-resonant objects largely decoupled from Neptune). Neptune migration models are able to implant some resonant and detached objects during the planet migration era, but many fail to match a variety of aspects of the orbital distribution. In this work, we report simulations carried out using an improved version of the GPU-based code GLISSE, following 100,000 test particles per simulation in parallel while handling their planetary close encounters. We demonstrate for the first time that a 2 Earth-mass rogue planet temporarily present during planet formation can abundantly populate both the distant resonances and the detached populations, surprisingly even without planetary migration. We show how weak encounters with the rogue greatly increase the efficiency of filling the resonances, while also dislodging TNOs out of resonance once they reach high perihelia. The rogue's secular gravitational influence simultaneously generates numerous detached objects observed at all semimajor axes. These results suggest that the early presence of additional planet(s) reproduces the observed TNO orbital structure in the distant Kuiper Belt.

astro-ph.EP↗

arXiv2020

The Population of Kilometer-scale Retrograde Jovian Irregular Moons

We have searched a 2010 archival data set from the Canada-France-Hawaii Telescope for very small (km-scale) irregular moons of Jupiter in order to constrain the size distribution of these moons down to radii of $\sim 400$~m, discovering 52 objects which are moving with Jupiter-like on-sky rates and are nearly certainly irregular moons. The four brightest detections, and seven in total, were all then linked to known jovian moons. Extrapolating our characterized detections (those down to magnitude $m_r=25.7$) to the entire retrograde circum-jovian population, we estimate the population of radius $>0.4$~km moons to be 600 (within a factor of 2). At the faintest magnitudes we find a relatively shallow luminosity function of exponential index $\alpha= 0.29 \pm 0.15$, corresponding to a differential diameter power law of index $q\simeq 2.5$.

astro-ph.EP↗