Postperihelion Cometary Activity on the Outer Main-belt Asteroid 2005 XR132

We report comet-like activity on the outer main-belt asteroid 2005 XR _132 discovered by the Lulin One-meter Telescope in early 2021 April. A series of follow-up observations were triggered to characterize the morphology and brightness variation of 2005 XR _132 . Long-term photometric data of the 2020 perihelion return reveal a 2 mag fading in 120 days, starting 20 days postperihelion, attributed to decreased cometary activity. Even though no variation indicative of the rotational period can be found in our data, we infer an a / b axial ratio of 1.32, given that the lower limit of rotational amplitude is 0.3 mag. A visible spectrum and broadband color support that 2005 XR _132 has a reflectance feature similar to a BR-type Centaur object. The syndyne and synchrone simulations reveal a low-speed dust ejecta consisting of millimeter-sized dust grains released shortly after the perihelion passage. We demonstrate that 2005 XR _132 has a short dynamical lifetime of 0.12 Myr, with