Light curves of transneptunian objects from the K2 mission of the Kepler Space Telescope

TL;DR

This study analyzes light curves of 66 transneptunian objects from the K2 mission, revealing many are slow rotators with higher amplitudes at large sizes, providing new insights into their rotational properties.

Contribution

First comprehensive analysis of transneptunian object light curves from K2, identifying many slow rotators and amplitude characteristics at large sizes.

Findings

56% detectability rate for light curve periods

37 targets with acceptable period confidence, mostly new

Large TNOs show higher light curve amplitudes than main belt asteroids

Abstract

The K2 mission of the Kepler Space Telescope allowed the observations of light curves of small solar system bodies throughout the whole Solar system. In this paper we present the results of a collection of K2 transneptunian object observations, between Campaigns C03 (November 2014 -- February 2015) to C19 (August -- September, 2018), which includes 66 targets. Due to the faintness of our targets the detectability rate of a light curve period is $\sim$56%, notably lower than in the case of other small body populations, like Hildas or Jovian trojans. We managed to obtain light curve periods with an acceptable confidence for 37 targets; the majority of these cases are new identifications. We were able to give light curve amplitude upper limits for the other 29 targets. Several of the newly detected light curve periods are longer than $\sim$24 h, in many cases close to $\sim$80 h, i.e., these targets are slow rotators. This relative abundance of slowly rotating objects is similar to that observed among Hildas, Jovian trojans and Centaurs in the K2 mission, and also among main belt asteroids measured with the TESS Space Telescope. Transneptunian objects show notably higher light curve amplitudes at large (D $\gtrsim$ 300 km) sizes than that found among large main belt asteroids, in contrast to the general expectation that due to their lower compressive strength they reach hydrostatic equlibrium at smaller sizes than their inner solar system counterparts.