Tentative Detection of the Rotation of Eris

TL;DR

This study uses space-based and ground-based photometry to investigate Eris's rotation period, finding marginal evidence for a ~1.08-day rotation, challenging previous claims of a much longer period.

Contribution

First multi-week space-based photometric study of Eris providing improved sampling and refined rotation period estimates.

Findings

No evidence for a slow rotation period of multiple days.

Detected rotation period of approximately 1.08 days with high confidence.

Combined data analysis increased confidence in the rotation period estimate.

Abstract

We report a multi-week sequence of B-band photometric measurements of the dwarf planet Eris using the {\it Swift} satellite. The use of an observatory in low-Earth orbit provides better temporal sampling than is available with a ground-based telescope. We find no compelling evidence for an unusually slow rotation period of multiple days, as has been suggested previously. A $\sim$1.08 day rotation period is marginally detected at a modest level of statistical confidence ($\sim$97%). Analysis of the combination of the $Swift$ data with the ground-based B-band measurements of \citet{2007AJ....133...26R} returns the same period ($\sim$1.08 day) at a slightly higher statistical confidence ($\sim$99%).