Secular and Rotational Light Curves of 6478 Gault

TL;DR

This study presents detailed light curves of asteroid 6478 Gault, revealing its rotational period, possible binary nature, and suggesting it is a dormant comet undergoing surface dust expulsion due to rotational disruption.

Contribution

First comprehensive light curve analysis of 6478 Gault, identifying its rotational period, binary evidence, and evolutionary status as a dormant comet.

Findings

Rotational period of 3.360 hours with evidence of binarity.

No phase effect observed, indicating an optically thick dust cloud.

Derived absolute magnitude of 16.11+-0.05.

Abstract

We obtained 877 images of active asteroid 6478 Gault on 41 nights from January 10th to June 8th, 2019, using several telescopes. We created the phase, secular and rotational light curves of Gault, from which several physical parameters can be derived. From the phase plot we find that no phase effect was evident. This implies that an optically thick cloud of dust surrounded the nucleus hiding the surface. The secular light curve (SLC) shows several zones of activity the origin of which is speculative. From the SLC plots a robust absolute magnitude can be derived and we find mV(1,1,alpha) = 16.11+-0.05. We also found a rotational period Prot = 3.360+-0.005 h and show evidence that 6478 might be a binary. The parameters of the pair are derived. Previous works have concluded that 6478 is in a state of rotational disruption and the above rotational period supports this result. Our conclusion is that 6478 Gault is a suffocated comet getting rid of its suffocation by expelling surface dust into space using the centrifugal force. This is an evolutionary stage in the lifetime of some comets. Besides being a main belt comet (MBC) the object is classified as a dormant Methuselah Lazarus comet.