Date: 05.02.2019., 15:00
1. Report by Dr. Slusarev I.G. ” Jupiter Trojans and Hilda group: physical properties and origin “
The work is devoted to investigation of the physical properties of Jupiter Trojans and Hilda group by photometric observations and to the analysis of predictions hypotheses about the origin of these two groups and verifying the their consistency with the accumulated data on their physical and dynamic properties. During 167 nights, observations were made of 23 members of two studied resonance groups: 12 from the Hilda group and 11 from Jupiter Trojans. For the first time measured of well-sampled magnitude phase curves of Jupiter Trojans. They have almost identical linear phase dependences with an absence of noticeable nonlinear opposition surge at small phase angles similar with P and D type Hilda asteroids. Such magnitude phase angle behaviour is different from majority small Solar system bodies showing non-linear phase curve behaviour close to opposition. An absence of opposition surge can be explained by very dark surfaces of these objects for which only single light scattering is important. The linearity of the magnitude phase dependence up to extremely low phase angles suggests the assumption of the shadowing mechanism as dominant. For the first time was found that Trojans, moving around L4 is firmly distinguished from Trojans, moving around L5 in orbital inclination distribution. The available amount of data on the physical and dynamical properties of Hilda group asteroids and Jupiter Trojans is consistent with assumption that these two resonant populations of small bodies of the Solar System are primordial.
2. Report by Dr. Slusarev I.G. ” Verification of homogeneity of large main belt asteroid families from joint analysis of albedo and colors “
Families of asteroids are the result of the collisional disruption (partial or complete) of the impactor and the target. Thus, studying the physical properties of family members, we have the only one opportunity to study the internal structure of asteroids. Using a database of asteroid families from Nesvorny et al., 2015, which includes more than 120 families, 56 large and numerous families from main belt were selected. Color indexes were taken from SDSS MOC4 and radiometric albedo were obtained from WISE database. For all 56 families, the distribution of members color and albedo was plotted and analyzed. Three groups of points were distinguished on such graphs (color index – albedo), which correspond to low-albedo bodies, medium-albedo bodies and bodies with high albedo. The analysis showed that out of 56 families 37 are homogeneous in their optical properties, bimodal distribution of color and albedo is typical for 13 families. The Flora and Vesta families contain asteroids of all three subgroups. And four more families do not fit into this classification scheme.