Rotational properties of the Haumea family members and candidates: Short-term variability

TL;DR

This study investigates the rotational properties of Haumea family members and candidates, revealing they tend to rotate faster than other transneptunian objects, with some objects exhibiting very rapid rotation and high density.

Contribution

It provides the most comprehensive short-term variability analysis of Haumea family members and candidates based on five years of observations, highlighting their distinct rotational characteristics.

Findings

Haumea family members have mean rotational periods around 6.3 hours.

Family members tend to rotate faster than other TNOs.

Object 2002 GH32 has a rotational period of about 3.98 hours and high density.

Abstract

Haumea is one of the most interesting and intriguing transneptunian objects (TNOs). It is a large, bright, fast rotator, and its spectrum indicates nearly pure water ice on the surface. It has at least two satellites and a dynamically related family of more than ten TNOs with very similar proper orbital parameters and similar surface properties. The Haumean family is the only one currently known in the transneptunian belt. Various models have been proposed but the formation of the family remains poorly understood. In this work, we have investigated the rotational properties of the family members and unconfirmed family candidates with short-term variability studies, and report the most complete review to date. We present results based on five years of observations and report the short-term variability of five family members, and seven candidates. The mean rotational periods, from Maxwellian fits to the frequency distributions, are 6.27+/-1.19 h for the confirmed family members, 6.44+/-1.16 h for the candidates, and 7.65+/-0.54 h for other TNOs (without relation to the family). According to our study, there is a suggestion that Haumea family members rotate faster than other TNOs, however, the sample of family member is still too limited for a secure conclusion. We also highlight the fast rotation of 2002 GH32. This object has a 0.36+/-0.02 mag amplitude lightcurve and a rotational period of about 3.98 h. Assuming 2002 GH32 is a triaxial object in hydrostatic equilibrium, we derive a lower limit to the density of 2.56 g cm^-3. This density is similar to Haumea's and much more dense than other small TNO densities.