Results from the 2014 November 15th multi-chord stellar occultation by the TNO (229762) 2007 UK$_{126}$

TL;DR

This paper reports the first multi-chord stellar occultation observation of TNO (229762) 2007 UK$_{126}$, providing size, shape, and albedo estimates, and constraining its density and oblateness.

Contribution

It presents the first multi-chord occultation data for this TNO, deriving its size, shape, albedo, and physical properties with multiple analysis methods.

Findings

Elliptical fit yields radius ~338 km

Albedo estimates range from 0.159 to 0.189

Density upper limit estimated at 1740 kg/m^3

Abstract

We present results derived from the first multi-chord stellar occultation by the trans-Neptunian object (229762) 2007 UK$_{126}$, observed on 2014 November 15. The event was observed by the Research and Education Collaborative Occultation Network (RECON) project and International Occultation Timing Association (IOTA) collaborators throughout the United States. Use of two different data analysis methods obtain a satisfactory fit to seven chords, yelding an elliptical fit to the chords with an equatorial radius of $R=338_{-10} ^{+15}$ km and equivalent radius of $R_{eq}=319_{-7} ^{+14}$ km. A circular fit also gives a radius of $R=324_{-23} ^{+30}$ km. Assuming that the object is a Maclaurin spheroid with indeterminate aspect angle, and using two published absolute magnitudes for the body, we derive possible ranges for geometric albedo between $p_{V}=0.159_{-0.013} ^{+0.007}$ and $p_{R}=0.189_{-0.015}^{+0.009}$, and for the body oblateness between $\epsilon=0.105_{-0.040} ^{+0.050}$ and $\epsilon=0.118_{-0.048} ^{+0.055}$. For a nominal rotational period of 11.05 h, an upper limit for density of $\rho=1740$ kg~m$^{-3}$ is estimated for the body.