Secular dynamics and family identification among highly inclined asteroids in the Euphrosyne region

Abstract

Among highly inclined asteroids the external region of the main belt beyond the 5J:2A mean‐motion resonance with Jupiter has long been known to host the Euphrosyne and Alauda families. The region is confined in semimajor axis between the 5J:‐2A and 2J:‐1A mean‐motion resonances with Jupiter, and is characterized by the presence of the ν6, ν5 and ν16 linear secular resonances, as well as by the z1, z2, z3 and other non‐linear secular resonances. In this work we employed the frequency modified Fourier transform method to obtain synthetic proper elements for 6841 numbered and 4034 multi‐opposition objects in the region of the Euphrosyne family, and used this data to obtain families and clumps in the domain of proper elements and frequencies. With respect to other works on family identification in the area, here we focused our investigation on the effect that the complicated local web of secular resonances has had on the dynamical evolutions of families and clumps. We detected all main linear and non‐linear secular resonances, up to order six, in the region and identified for the first time new populations of objects in ν6 anti‐aligned librating and ν5 anti‐aligned and aligned librating resonant states. We identified two new clumps among ν6 anti‐aligned librating objects, making them the second and the third groups in this resonant configuration ever found after the discovery of the Tina family. Once the local dynamics was fully understood, we then obtained dynamical groups in the domain of proper elements and in the domain of proper frequencies most apt to study the secular resonance present in each region, and computed ν6 resonant proper elements to study groups in regions affected by the ν6 secular resonance. We identified 18 families and 39 clumps in the Euphrosyne region, of which 12 families and five clumps were in frequency domains. Of particular interest was the group around (69559) (1997 UG5), found in both proper element and frequency domains, characterized by its interaction with five secular resonances. It is the first time that a group of asteroids is found in such an interesting resonant configuration. More importantly, we introduced new techniques for asteroid family identification in presence of secular resonances, which could in principle be used for other areas of the asteroid belt.

Asteroid Family Associations of Active Asteroids

“…It is bounded above in proper inclination space by the Euphrosyne family and below by the Luthera family, and is also adjacent to the Danae and Erminia families in proper semimajor axis space, separated by the 9J:4A MMR. Some exchange of objects may be possible between the Alauda family and surrounding families via the ν 6 secular resonance (which connects it to the Danae region), and various three-body MMRs (which connect it to the Euphrosyne and Luthera families) (Machuca & Carruba 2012). Several sub-families and clumps within this region have been identified (Machuca & Carruba 2012), but 324P is not linked to any of them at δ c val-ues smaller than the δ c value at which it is linked to the main Alauda family.…”

The resonant population of asteroids in librating states of the ν6 linear secular resonance

“…Here, we consider a list of 195 known asteroid families and clumps in the main asteroid belt that have been reported by different authors (Mothe-Diniz, Roig & Carvano 2005;Gil-Hutton 2006;Carruba & Machuca 2011b;Machuca & Carruba 2012;Carruba et al 2014;Milani et al 2014;Nesvorný, Brož & Carruba 2015;Spoto, Milani & Knežević 2015;Milani et al 2016), and from this list, we select 25 families that are located in the neighbourhood of the ν 6 resonance domain. The distribution of these families is shown in Fig.…”

“…The dynamical influence of this resonance on some asteroid families has been recently addressed by Carruba & Morbidelli (2011a), who identified the family of Tina with all of its members in anti-aligned libration. Besides, Machuca & Carruba (2012) and Carruba, Aljbaae & Souami (2014) found 19 members of the family of Euphrosyne also in anti-aligned libration. These bodies may represent a transient population that is temporarily captured in the resonance, or they may be members of a long-lasting group of resonant bodies.…”

The Rafita asteroid family

“…The swift rmvsy integrator allows to integrate a set of massless test particles (that do not interact among themselves) under the gravitational influence of all planets, considering the diurnal and seasonal versions of the Yarkovsky effect. Using the method outlined in Machuca & Carruba (2012), two spin axis obliquities forming angles of 0 • and 180…”