arXiv subjects

Bruno Sicardy

Publications and source records attributed to Bruno Sicardy.

23 records · Page 2Linked to original sources

arXiv2017

Rings beyond the giant planets

Until 2013, only the giant planets were known to host ring systems. In June 2013, a stellar occulation revealed the presence of narrow and dense rings around Chariklo, a small Centaur object that orbits between Saturn and Uranus. Meanwhile, the Cassini spacecraft revealed evidence for the possible past presence of rings around the Saturnian satellites Rhea and Iapetus. Mars and Pluto are expected to have tenuous dusty rings, though they have so far evaded detection. More remotely, transit events observed around a star in 2007 may have revealed for the first time exoplanetary rings around a giant planet orbiting that star. So, evidence is building to show that rings are more common features in the universe than previously thought. Several interesting issues arising from the discovery (or suspicion) of new ring systems are described in this chapter.

astro-ph.EP↗

arXiv2016

Derivation of Capture Probabilities for the Corotation Eccentric Mean Motion Resonances

We study in this paper the capture of a massless particle into an isolated, first order Corotation Eccentric Resonance (CER), in the framework of the Planar, Eccentric and Restricted Three-Body problem near a m+1:m mean motion commensurability (m integer). While capture into Lindblad Eccentric Resonances (where the perturber's orbit is circular) has been investigated years ago, capture into CER (where the perturber's orbit is elliptic) has not yet been investigated in detail. Here, we derive the generic equations of motion near a CER in the general case where both the perturber and the test particle migrate. We derive the probability of capture in that context, and we examine more closely two particular cases: (i) if only the perturber is migrating, capture is possible only if the migration is outward from the primary. Notably, the probability of capture is independent of the way the perturber migrates outward; (ii) if only the test particle is migrating, then capture is possible only if the algebraic value of its migration rate is a decreasing function of orbital radius. In this case, the probability of capture is proportional to the radial gradient of migration. These results differ from the capture into Lindblad Eccentric Resonance (LER), where it is necessary that the orbits of the perturber and the test particle converge for capture to be possible. Possible applications for planetary satellites are discussed.

astro-ph.EP↗

arXiv2016

Results from the 2014 November 15th multi-chord stellar occultation by the TNO (229762) 2007 UK$_{126}$

We present results derived from the first multi-chord stellar occultation by the trans-Neptunian object (229762) 2007 UK$_{126}$, observed on 2014 November 15. The event was observed by the Research and Education Collaborative Occultation Network (RECON) project and International Occultation Timing Association (IOTA) collaborators throughout the United States. Use of two different data analysis methods obtain a satisfactory fit to seven chords, yelding an elliptical fit to the chords with an equatorial radius of $R=338_{-10} ^{+15}$ km and equivalent radius of $R_{eq}=319_{-7} ^{+14}$ km. A circular fit also gives a radius of $R=324_{-23} ^{+30}$ km. Assuming that the object is a Maclaurin spheroid with indeterminate aspect angle, and using two published absolute magnitudes for the body, we derive possible ranges for geometric albedo between $p_{V}=0.159_{-0.013} ^{+0.007}$ and $p_{R}=0.189_{-0.015}^{+0.009}$, and for the body oblateness between $ε=0.105_{-0.040} ^{+0.050}$ and $ε=0.118_{-0.048} ^{+0.055}$. For a nominal rotational period of 11.05 h, an upper limit for density of $ρ=1740$ kg~m$^{-3}$ is estimated for the body.

astro-ph.EP↗

arXiv2016

The Outer Solar System Origins Survey: I. Design and First-Quarter Discoveries

We report the discovery, tracking and detection circumstances for 85 trans-Neptunian objects (TNOs) from the first 42 deg$^{2}$ of the Outer Solar System Origins Survey (OSSOS). This ongoing $r$-band Solar System survey uses the 0.9 deg$^{2}$ field-of-view MegaPrime camera on the 3.6 m Canada-France-Hawaii Telescope. Our orbital elements for these TNOs are precise to a fractional semi-major axis uncertainty $<0.1\%$. We achieve this precision in just two oppositions, as compared to the normal 3-5 oppositions, via a dense observing cadence and innovative astrometric technique. These discoveries are free of ephemeris bias, a first for large trans-Neptunian surveys. We also provide the necessary information to enable models of TNO orbital distributions to be tested against our TNO sample. We confirm the existence of a cold "kernel" of objects within the main cold classical Kuiper belt, and infer the existence of an extension of the "stirred" cold classical Kuiper belt to at least several AU beyond the 2:1 mean motion resonance with Neptune. We find that the population model of Petit et al. (2011) remains a plausible representation of the Kuiper belt. The full survey, to be completed in 2017, will provide an exquisitely characterized sample of important resonant TNO populations, ideal for testing models of giant planet migration during the early history of the Solar System.

astro-ph.EP↗

arXiv2013

Coupling between corotation and Lindblad resonances in the elliptic planar three-body problem

We investigate the dynamics of two satellites with masses $μ_s$ and $μ'_s$ orbiting a massive central planet in a common plane, near a first order mean motion resonance $m$+1:$m$ ($m$ integer). We consider only the resonant terms of first order in eccentricity in the disturbing potential of the satellites, plus the secular terms causing the orbital apsidal precessions. We obtain a two-degree of freedom system, associated with the two critical resonant angles $ϕ= (m+1)λ' -mλ- \varpi$ and $ϕ'= (m+1)λ' -mλ- \varpi'$, where $λ$ and $\varpi$ are the mean longitude and longitude of periapsis of $μ_s$, respectively, and where the primed quantities apply to $μ'_s$. We consider the special case where $μ_s \rightarrow 0$ (restricted problem). The symmetry between the two angles $ϕ$ and $ϕ'$ is then broken, leading to two different kinds of resonances, classically referred to as Corotation Eccentric resonance (CER) and Lindblad Eccentric Resonance (LER), respectively. We write the four reduced equations of motion near the CER and LER, that form what we call the CoraLin model. This model depends upon only two dimensionless parameters that control the dynamics of the system: the distance $D$ between the CER and LER, and a forcing parameter $ε_L$ that includes both the mass and the orbital eccentricity of the disturbing satellite. Three regimes are found: for $D=0$ the system is integrable, for $D$ of order unity, it exhibits prominent chaotic regions, while for $D$ large compared to 2, the behavior of the system is regular and can be qualitatively described using simple adiabatic invariant arguments. We apply this model to three recently discovered small Saturnian satellites dynamically linked to Mimas through first order mean motion resonances : Aegaeon, Methone and Anthe.

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