Secular and rotational light curves of 6478 Gault

Abstract

We obtained 877 images of active asteroid 6478 Gault on 41 nights from 2019 January 10 to June 8, 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,α) = 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, meaning Gault is both highly evolved and has a decaying perihelion distance.