Small Body Reservoirs in Planetary Scattering Events.

DI SISTO, ROMINA P.; GUILERA, O.M.; DE ELÍA, GONZALO CARLOS; LI, GONGJIE; ZANARDI, MACARENA; NAOZ, SMADAR

Montevideo

Congreso; Asteroid Comets Meteors 2017; 2017

Introduction: During the last years, an enormous diversity of planetary systems has been discovered around stars of different spectral types. In particular, low-mass stars are of relevant interest because they are the most common stars in our stellar neighborhood [1] [2]. Observational and theoretical studies suggest that planetary scattering events seem to be usual at systems that host gaseous giant planets [3]. In the present study, we analyze the process of planetary scattering involving three Jupiter-mass planets around M0-type stars. In particular, we study the orbital distribution of the surviving planets, as well as the dynamical properties of the remnant outer small body reservoirs. Numerical Methods: First, we use a semi-analytical model [4] to define the properties of theprotoplanetary disk that lead to the formation of three Jupiter-mass planets around an M0-type star. Once the disk parameters are determined,we carry out N-body simulations [5] assuming, three Jupiter-mass planets close to their instability limit together with an outer planetesimals disk. To model such a population, we use 1000 massless particles, which are distributed from 2 au to 30 au from the center star. In particular,the present work focuses on the analysis of Nbody simulations in which a single Jupiter-mass planet survives after the dynamical instability event. These numerical simulations are integrated for 100 Myr in order to study the dynamical evolution of the small body reservoirs resultingfrom the different systems. Results: The Jupiter-mass planet that survive to the planetary scattering event adopt values for the semimajor axis and eccentricity of 0.5 au to 10 au, and 0.01 to 0.94, respectively. As for the small body reservoirs, a very interesting result indicates that the surviving particles show different dynamical behaviours. In fact, our simulations produce particles on prograde and retrograde orbits, as well as particles whose orbital plane flips from prograde to retrograde and back again along their evolution [6]. Such particles are called "Type-F particles?. We find strong correlations between the inclination ?i? and the ascending node longitude ?Ω? of such particles (Fig.1). First, the Ω librates around 90° and/or 270°. This property is very important becauserepresent a necessary and sufficient condition for the flipping of an orbit. Moreover, the libration periods of i and Ω are equal and they are out to phase by a quarter period. We also remark that the larger the libration amplitude of i, the larger the libration amplitude of Ω. Finally, we analyzed the initial conditions of Type-F particles afall our simulations immediately after the dynamical instability event, when a single Jupiter-mass planet survives in the system. We carry out this study with the goal to determine the parameter space that lead to the flipping of an orbit. Our results suggest that the orbit of a test particle can flip for any value of its initial eccentricity, althougthwe do not find Type-F particles with initial inclination i < 18°. Moreover, our study indicates that the minimum value of the initial inclination of the Type-F particles in a given system seems to decrease with an increase in the eccentricity of the giant planet.