arXiv subjects

Macarena Zanardi

Publications and source records attributed to Macarena Zanardi.

6 recordsLinked to original sources

arXiv2026

Relativistic Effects on Circumbinary Orbit Stability

With n-body simulations and analytic approximations we study the dynamics and stability of low eccentricity misaligned test particles around binary systems with varying mass fraction and eccentricity. General relativity (GR) plays a primary role in determining the motion of an outer particle since it drives apsidal precession of the binary orbit. The effects of GR can drive particle instability close to the binary orbit, depending upon the binary parameters and the initial inclination of the particle. For the binary parameters we consider, we find instability up to a semimajor axis of about 8 ab, where ab is the binary semimajor axis. In particular, we identify and analyse three different regions of instability that are driven by GR in the phase plane of the initial semimajor axis and the initial inclination of the particle. The results have implications for circumbinary orbits and circumbinary disks on all scales, but are particularly important around supermassive black hole binaries where the effects of GR can be strong.

astro-ph.HE↗

arXiv2025

Flipping particles with nodal circulations by general relativity under the presence of an inner perturber

From a secular Hamiltonian up to the quadrupole level with general relativity (GR), we study nodal circulations with orbital flips of test particles of the Habitable Zone (HZ) around a solar-mass star, which are perturbed by an inner planetary-mass companion. Nodal circulations with orbital flips of an HZ test particle with eccentricity e2 are possible for any mass m1 and eccentricity e1 of the inner perturber and a suitable inclination i2. In particular, the greater the values of m1 and e2 , the smaller the minimum extreme inclination i2 capable of producing nodal circulations with orbital flips for each e1. As long as nodal librations with orbital flips are not possible for any i2, the greater the values of m1, e1, and e2, the larger the region of the plane (Ω2, i2) associated with nodal circulations with orbital flips. If nodal librations with orbital flips occur, the region of the plane (Ω2, i2) referred to nodal circulations with orbital flips increases with a decrease in m1 and e2, and with an increase in e1. We observe very good agreements between the analytical criteria and the N-body experiments for m1 ranging from Earth-mass planets to super-Jupiters, and small and moderate e2. The main discrepancies are found for high e2, which are more evident with an increase in m1 and e1.

astro-ph.EP↗

arXiv2019

The inverse Lidov-Kozai resonance for an outer test particle due to an eccentric perturber

We analyze the behavior of the argument of pericenter $ω_2$ of an outer particle in the elliptical restricted three-body problem, focusing on the inverse Lidov-Kozai resonance. First, we calculate the contribution of the terms of quadrupole, octupole, and hexadecapolar order of the secular approximation of the potential to the outer particle's $ω_2$ precession rate $(dω_2/dτ)$. Then, we derive analytical criteria that determine the vanishing of the $ω_2$ quadrupole precession rate $(dω_2/dτ)_{\text{quad}}$ for different values of the inner perturber's eccentricity $e_1$. Finally, we use such analytical considerations and describe the behavior of $ω_2$ of outer particles extracted from N-body simulations. Our analytical study indicates that the values of the inclination $i_2$ and the ascending node longitude $Ω_2$ associated with the outer particle that vanish $(dω_2/dτ)_{\text{quad}}$ strongly depend on the eccentricity $e_1$ of the inner perturber. In fact, if $e_1 <$ 0.25 ($>$ 0.40825), $(dω_2/dτ)_{\text{quad}}$ is only vanished for particles whose $Ω_2$ circulates (librates). For $e_1$ between 0.25 and 0.40825, $(dω_2/dτ)_{\text{quad}}$ can be vanished for any particle for a suitable selection of pairs ($Ω_2$, $i_2$). Our analysis of the N-body simulations shows that the inverse Lidov-Kozai resonance is possible for small, moderate and high values of $e_1$. Moreover, such a resonance produces distinctive features in the evolution of a particle in the ($Ω_2$, $i_2$) plane. In fact, if $ω_2$ librates and $Ω_2$ circulates, the extremes of $i_2$ at $Ω_2 =$ 90$^{\circ}$ and 270$^{\circ}$ do not reach the same value, while if $ω_2$ and $Ω_2$ librate, the evolutionary trajectory of the particle in the ($Ω_2$, $i_2$) plane evidences an asymmetry respect to $i_2 =$ 90$^{\circ}$.

astro-ph.EP↗

arXiv2018

The role of the general relativity on icy body reservoirs under the effects of an inner eccentric Jupiter

Recent studies have analyzed the dynamical evolution of outer small body populations under the effects of an eccentric inner massive perturber. Such outer reservoirs are composed of particles on prograde and retrograde orbits, as well as particles whose orbit flips from prograde to retrograde and back again showing a coupling between the inclination i and the ascending node longitude Ω(Type-F particles). We analyze the role of the General Relativity (GR) on the dynamics of outer particles under the influence of an inner eccentric Jupiter-mass planet produced by a planetary scattering event. In particular, we study how the GR affects the dynamical evolution of the outer Type-F particles, which experience an eccentric Lidov-Kozai mechanism. We carry out N-body simulations with and without GR effects. When the GR is included, the extreme values of Ωare obtained for retrograde inclinations, while the minimum and maximum inclinations allowed for Type-F particles increase in comparison with that derived without GR effects. According to this, if the GR is included in the simulations, the range of prograde (retrograde) inclinations of the libration region is reduced (increased) respect to that obtained in absence of GR. We find two new class of particles when the GR effects are included in the simulations. On the one hand, particles whose orbital plane flips from prograde to retrograde and back again without experiencing a coupling between i and Ω. On the other hand, retrograde particles that show a strong coupling between i and Ω. We infer that the GR may significantly modify the dynamical properties of the outer reservoirs that evolve under the effects of an eccentric inner perturber.

astro-ph.EP↗

arXiv2017

The Eccentric Kozai-Lidov mechanism for Outer Test Particle

The secular approximation of the hierarchical three body systems has been proven to be very useful in addressing many astrophysical systems, from planets, stars to black holes. In such a system two objects are on a tight orbit, and the tertiary is on a much wider orbit. Here we study the dynamics of a system by taking the tertiary mass to zero and solve the hierarchical three body system up to the octupole level of approximation. We find a rich dynamics that the outer orbit undergoes due to gravitational perturbations from the inner binary. The nominal result of the precession of the nodes is mostly limited for the lowest order of approximation, however, when the octupole-level of approximation is introduced the system becomes chaotic, as expected, and the tertiary oscillates below and above 90deg, similarly to the non-test particle flip behavior (e.g., Naoz 2016). We provide the Hamiltonian of the system and investigate the dynamics of the system from the quadrupole to the octupole level of approximations. We also analyze the chaotic and quasi-periodic orbital evolution by studying the surfaces of sections. Furthermore, including general relativity, we show case the long term evolution of individual debris disk particles under the influence of a far away interior eccentric planet. We show that this dynamics can naturally result in retrograde objects and a puffy disk after a long timescale evolution (few Gyr) for initially aligned configuration.

astro-ph.EP↗

arXiv2015

Surface ages of mid-size Saturnian satellites

The observations of the surfaces of the mid sized Saturnian satellites made by Cassini Huygens mission have shown a variety of features that allows study of the processes that took place and are taking place on those worlds. Research of the Saturnian satellite surfaces has clear implications for Saturn history and surroundings. In a recent paper, the production of craters on the mid sized Saturnian satellites by Centaur objects was calculated considering the current Solar System. We have compared our results with crater counts from Cassini images and we have noted that the number of observed small craters is less than our calculated number. In this paper we estimate the age of the surface for each observed terrain on each mid sized satellite of Saturn. We have noticed that since there are less observed small craters than calculated (except on Iapetus), this results in younger ages. This could be the result of efficient endogenous or exogenous process(es) for erasing small craters and or crater saturation at those sizes. The size limit from which the observed number of smaller craters is less than the calculated is different for each satellite, possibly indicating processes that are unique to each, but other potential common explanations would be crater saturation and or deposition of E ring particles. These processes are also suggested by the findings that the smaller craters are being preferentially removed, and the erasure process is gradual. On Enceladus, only mid and high latitude plains have remnants of old terrains; the other regions could be young; the regions near the South Polar Terrain could be as young as 50 Myr old. On the contrary for Iapetus, all the surface is old and it notably registers a primordial source of craters. As the crater size is decreased, it would be perceived to approach saturation until D less than 2 km craters, where saturation is complete.

astro-ph.EP↗