Discovery of Main-Belt Comet P/2006 VW139 by Pan-STARRS1

Main belt asteroid (300163) 2006 VW139 (later designated P/2006 VW139 ) was discovered to exhibit comet-like activity by the Pan-STARRS1 survey telescope using automated point-spread-function analyses performed by PS1’s Moving Object Processing System. Deep follow-up observations show both a short (∼10" ) antisolar dust tail and a longer (∼60" ) dust trail aligned with the object’s orbit plane, similar to the morphology observed for another main-belt comet, P/2010 R2 (La Sagra), and other well-established comets, implying the action of a long-lived, sublimation-driven emission event. Photometry showing the brightness of the near-nucleus coma remaining constant over ∼ 30 days provides further evidence for this  object’s cometary nature, suggesting it is in fact a main-belt comet, and not a disrupted asteroid. A spectroscopic search for CN emission was unsuccessful, though we find an upper limit CN production rate of Q_CN < 1.3 × 10²⁴ mol s⁻¹ , from which we infer a water production rate of Q_H2O < 10²⁶ mol s⁻¹ . We also find an approximately linear optical spectral slope of 7.2%/1000 ̊, similar to other cometary dust comae. Numerical simulations indicate that P/2006 VW139 is dynamically stable for > 100 Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68 m s⁻¹ . At 70 m s⁻¹ , this cluster merges with the Themis family, suggesting that it could be  similar to the Beagle family to which another main-belt comet, 133P/Elst-Pizarro, belongs.