Refined Rotational Period, Pole Solution & Shape Model for (3200) Phaethon

TL;DR

This study refines the rotational period, pole orientation, and shape model of asteroid-comet hybrid (3200) Phaethon through extensive photometry, providing insights into its physical properties and origin.

Contribution

The paper presents a detailed light curve inversion analysis that refines Phaethon's rotational and shape parameters, enhancing understanding of its transitional nature.

Findings

Refined rotational period to 3.6032 hours

Estimated pole orientation at lambda=+85°, beta=-20°

Derived a shape model and phase curve slope G~0.06

Abstract

(3200) Phaethon exhibits both comet- and asteroid-like properties, suggesting it could be a rare transitional object such as a dormant comet or previously volatile-rich asteroid. This justifies detailed study of (3200) Phaethon's physical properties, as a better understanding of asteroid-comet transition objects can provide insight into minor body evolution. We therefore acquired time-series photometry of (3200) Phaethon over 15 nights from 1994 to 2013, primarily using the Tektronix 2048x2048 pixel CCD on the University of Hawaii 2.2-m telescope. We utilized light curve inversion to: (1) refine (3200) Phaethon's rotational period to P=3.6032+/-0.0008 h; (2) estimate a rotational pole orientation of lambda=+85+/-13 degrees and beta=-20+/-10 degrees; and (3) derive a shape model. We also used our extensive light curve dataset to estimate the slope parameter of (3200) Phaethon's phase curve as G~0.06, consistent with C-type asteroids. We discuss how this highly oblique pole orientation with a negative ecliptic latitude supports previous evidence for (3200) Phaethon's origin in the inner main asteroid belt as well as the potential for deeply buried volatiles fueling impulsive yet rare cometary outbursts.