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A sidereal rotation counting approach is demonstrated by resolving an ambiguity in the synodic rotation period of Koronis family member (3032) Evans, whose rotation lightcurves' features did not easily distinguish between doubly- and quadruply-periodic. It confirms that Evans's spin rate does not exceed the rubble-pile spin barrier and thus presents no inconsistency with being a ∼ 14-km reaccumulated object. The full spin vector solution for Evans is comparable to those for the known prograde low-obliquity comparably-fast rotators in the Koronis family, consistent with having been spun up by YORP thermal radiation torques. • Case study analysis using lightcurve epochs to resolve an ambiguous rotation period. • Sidereal rotation counting identifies the alias period even for symmetric lightcurves. • Spin rate of (3032) Evans does not exceed the rubble-pile spin barrier. • Spin vector of Evans is consistent with spin-up by YORP thermal radiation torques. [ABSTRACT FROM AUTHOR]

An observational study of Koronis family members' spin properties was undertaken with two primary objectives: to reduce selection biases for object rotation period and lightcurve amplitude in the sample of members' known spin vectors, and to better constrain future modeling of spin properties evolution. Here we report rotation lightcurves of nineteen Koronis family members, and derived results that increase the sample of determined spin vectors in the Koronis family to include 34 of the largest 36 family members, completing it to H ≈ 11. 3 (D ∼ 16 km) for the largest 32 members. The program observations were made during a total of 72 apparitions between 2005–2021, and are reported here along with several earlier unpublished lightcurves. All of the reported data were analyzed together with previously published lightcurves to determine the objects' sidereal rotation periods, spin vector orientations, and convex model shape solutions. The derived distributions of retrograde rotation rates and pole obliquities appear to be qualitatively consistent with outcomes of modification by thermal YORP torques. The distribution of spin rates for the prograde rotators remains narrower than that for the retrograde rotators; in particular, the absence of prograde rotators having periods longer than about 20 h is real, while among the retrograde rotators are several objects having longer periods up to about 65 h. None of the prograde objects newly added to the sample appear to be trapped in an s 6 spin–orbit resonance that is characteristic of most of the largest prograde objects (Vokrouhlický et al., 2003); these smaller objects either could have been trapped previously and have already evolved out, or have experienced spin evolution tracks that did not include the resonance. • Koronis family spin vector sample completed to largest 32 members (∼ 16 km diameter). • Removal of sample selection biases for interpreting and modeling spin evolution. • The absence of prograde spins having rotation periods longer than about 20 h is real. • Smaller prograde objects avoided or escaped the spin–orbit trapping of larger objects. • Epochs analysis combined with convex inversion is effective to determine spin vectors. [ABSTRACT FROM AUTHOR]

Abstract: Studies of asteroid families constrain models of asteroid collisions and evolution processes, and the Karin cluster within the Koronis family is among the youngest families known (Nesvorný, D., Bottke, Jr., W.F., Dones, L., Levison, H.F. [2002]. Nature 417, 720–722). (832) Karin itself is by far the largest member of the Karin cluster, thus knowledge of Karin’s spin vector is important to constrain family formation and evolution models that include spin, and to test whether its spin properties are consistent with the Karin cluster being a very young family. We observed rotation lightcurves of Karin during its four consecutive apparitions in 2006–2009, and combined the new observations with previously published lightcurves to determine its spin vector orientation and preliminary model shape. Karin is a prograde rotator with a period of (18.352±0.003) h, spin obliquity near (42±5)°, and pole ecliptic longitude near either (52±5)° or (230±5)°. The spin vector and shape results for Karin will constrain models of family formation that include spin properties; in the meantime we briefly discuss Karin’s own spin in the context of those of other members of the Karin cluster and the parent body’s siblings in the Koronis family. [Copyright &y& Elsevier]