We report comet-like activity on the outer main-belt asteroid 2005 XR₁₃₂ 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 XR₁₃₂. 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 XR₁₃₂ 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 XR₁₃₂ has a short dynamical lifetime of 0.12 Myr, with <5% of it in the near-Earth space. Due to the strong gravitational influence from Jupiter and Saturn, the asteroid has followed a random walk orbital migrating process. We also find that since 1550 CE, the perihelion distance of 2005 XR₁₃₂ has gradually decreased from 2.8 to 2.0 au, likely due to the Kozai–Lidov effect, which potentially reactivated the dormant nucleus. All these dynamical properties support a cometary origin for 2005 XR₁₃₂ rather than an ice-rich main-belt object kicked out from a stable orbit, although current observational evidence has yet to confirm repeating cometary activities.

中文翻译：

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外主带小行星 2005 XR132 的近日点后彗星活动

我们报告了鲁林一米望远镜于 2021 年 4 月上旬发现的外主带小行星 2005 XR ₁₃₂上的彗星活动。一系列后续观测被触发，以表征 2005 XR ₁₃₂的形态和亮度变化。 2020 年近日点回归的长期光度数据显示，从近日点后 20 天开始，120 天内出现 2 星等的衰落，原因是彗星活动减少。尽管在我们的数据中找不到表明自转周期的变化，但我们推断A/乙考虑到旋转幅度的下限为 0.3 mag，轴比为 1.32。可见光谱和宽带颜色支持 2005 XR ₁₃₂具有类似于 BR 型半人马天体的反射率特征。同步和同步模拟揭示了低速尘埃喷射物，由在近日点通过后不久释放的毫米大小的尘埃颗粒组成。我们证明 2005 XR ₁₃₂的动态寿命很短，为 0.12 Myr，其中 <5% 在近地空间。由于受到木星和土星的强烈引力影响，小行星经历了随机游走的轨道迁移过程。我们还发现，自公元1550年以来，2005 XR ₁₃₂的近日点距离逐渐从2.8天文单位减少到2.0天文单位，这可能是由于科扎伊-利多夫效应，该效应可能重新激活了休眠核。所有这些动力学特性都支持 2005 XR ₁₃₂的彗星起源，而不是从稳定轨道中踢出的富含冰的主带天体，尽管目前的观测证据尚未证实重复的彗星活动。