Spin vectors in the Koronis family II: additional clustered spins, and one stray

"We recorded 101 new rotation lightcurves of five Koronis family members, and then combined the new observations with previous data to determine the objects' sidereal rotation periods, spin vector orientations, and model shape solutions. The observing program was tailored specifically for spin vector analyses by determining single-apparition Lumme-Bowell solar phase coefficients, and by measuring synodic rotation periods precisely enough to unambiguously count the rotations between two consecutive oppositions, which is a prerequisite for identifying the correct sidereal period. The new data make possible first pole and shape determinations for (263) Dresda, (462) Eriphyla, and (1289) Kutafssi, and they improve the models for (277) Elvira and (534) Nassovia, two objects previously studied by Slivan et aL [Slivan, S.M., Binzel, R.P., Crespo da Silva, L.D., Kaasalainen, M., Lynclaker, M.M., Krco, M., 2003. Icarus 162, 285-3071. Our results increase the number of Koronis family spin vectors reported in the literature to fourteen, a sample which now includes the seven largest family members. The spin properties of Eriphyla (rotation period P = 8.66 h, spin vector obliquity epsilon = 51 degrees) and Kutaissi (P = 3.62 h, epsilon = 165 degrees) are consistent with the markedly nonrandom distribution reported by Slivan [Slivan, S.M., 2002. Nature 419, 49-51], and explained by Vokrouhlicky et al. [Vokrouhlicky, D., Nesvomg, D., Bottke, W.F., 2003. Nature 425, 147-151] as the result of the effects of thermal ""YORP"" torques combined with solar and planetary gravitational torques. Dresda (P = 16.81 h, epsilon = 16 degrees) is the first prograde Koronis member whose spin obliquity and spin rate significantly differ from the clustered spin properties previously found for other prograde Koromis members; nevertheless, its spin vector is consistent with several of the spin evolution possibilities that were identified in the YORP modeling. (C) 2008 Elsevier Inc. All rights reserved."