Discovery of main-belt comet P/2006 VW₁₃₉ by Pan-STARRS1

The main-belt asteroid (300163) 2006 VW₁₃₉ (later designated P/2006 VW₁₃₉) was discovered to exhibit comet-like activity by the Pan-STARRS1 (PS1) 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 (MBC), 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 30days provides further evidence for this object's cometary nature, suggesting it is in fact an MBC, 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 × 10²⁴mols^-1, from which we infer a water production rate of mols^-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 >100Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68ms^-1. At 70ms^-1, this cluster merges with the Themis family, suggesting that it could be similar to the Beagle family to which another MBC, 133P/Elst-Pizarro, belongs.