The changing rotational lightcurve of Varuna and evidence for a close-in satelite

From CCD observations carried out with different telescopes, we present short-term photometric measurements of the large trans-Neptunian object Varuna in 10 epochs, spanning around 19 years.

We observe that the amplitude of the rotational light curve has changed considerably during this period of time from 0.41 to 0.55 mag… We propose that these changes in the rotational light-curve shape are due to a large and close-in satellite whose rotation induces the additional periodicity. The peak-to-valley amplitude of this oscillation is in the order of 0.04 mag. We estimate that the satellite orbits Varuna with a period of 11.9819 hr (or 23.9638 hr).

The Astrophysical Journal Letters, 883:L21 (7pp), 2019 September 20 © 2019. The American Astronomical Society.

Download paper