Lightcurve analysis of asteroid (39420) Elizabethgaskell and the possible excess of long-period non-principal-axis rotators in the Hungaria population

We obtained observations and performed rotation period, pole orientation and convex shape model analysis for the slowly rotating Hungaria asteroid (39420) Elizabethgaskell as a follow-up to the Thousand Asteroid Light Curve Survey (TALCS, Masiero et al., 2009). The TALCS observations combined with our follow-up observations did not allow for an unambiguous spin and shape solution. To reject the possibility of a methodological failure in the analysis, we simulated a lightcurve of an elongated object by generating synthetic detections with the same cadence as in the real observations and added random noise. The same period, pole and shape analysis was then successfully performed for a simulated object. Thus, we conclude that (39420) Elizabethgaskell is either a binary or, more likely, a non-principal-axis rotator. Being one of only two Hungarias observed in an untargeted survey, the properties of (39420) Elizabethgaskell suggest that binaries and/or non-principal-axis rotators are common in the Hungaria population.