(50000)创神星的双环
The two rings of (50000) Quaoar
AI总结：
本研究通过2022年掩星观测，确定了创神星的大小、形状，并发现了其第二个环，该环位于洛希极限之外，对理解环系统形成具有重要意义。
摘要：
创神星是一颗经典的海王星外天体（TNO），其面积等效直径为1,100公里，轨道半长轴为43.3天文单位。基于2018年至2021年间观测到的恒星掩星，在该天体周围探测到一个不均匀的环（Q1R，创神星的第一环）。目的：2022年8月9日观测到一次新的创神星星掩星，旨在改进创神星的形状模型和Q1R的物理参数，同时搜索该天体周围的额外物质。方法：这次掩星提供了横跨创神星的九条有效弦，确定了其大小、形状和天体测量位置。大型设施，如双子座北望远镜和加拿大-法国-夏威夷望远镜（CFHT），被用于获得高采集速率和高信噪比。光变曲线也被用于表征Q1R环（径向轮廓和轨道要素）。结果：对掩星弦的椭圆拟合给出了创神星的边缘，其视半长轴为579.5±4.0公里，视扁率为0.12±0.01，面积等效半径为543±2公里。创神星的边缘方向与Q1R和Weywot在创神星赤道平面内运行一致。Q1R的轨道半径被修正为4,057±6公里。更不透明环的径向不透明度轮廓遵循洛伦兹形状，延伸超过60公里，半高全宽（FWHM）约为5公里，峰值法向光学深度为0.4。除了与已报道的环相关的次级事件外，在2022年8月掩星期间在三个不同数据集中探测到的新次级事件与围绕创神星的另一个环一致，该环半径为2,520±20公里，假设该环是圆形的且与Q1R共面。这个新环的典型宽度为10公里，法向光学深度约为0.004。与Q1R一样，它也位于创神星的经典洛希极限之外。
英文摘要：
Quaoar is a classical Trans-Neptunian Object (TNO) with an area equivalent diameter of 1,100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations observed between 2018 and 2021, an inhomogeneous ring (Q1R, Quaoar's first ring) was detected around this body. Aims. A new stellar occultation by Quaoar was observed on August 9th, 2022 aiming to improve Quaoar's shape models and the physical parameters of Q1R while searching for additional material around the body. Methods. The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements). Results. Quaoar's elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of $579.5\pm4.0$ km, apparent oblateness of $0.12\pm0.01$, and area-equivalent radius of $543\pm2$ km. Quaoar's limb orientation is consistent with Q1R and Weywot orbiting in Quaoar's equatorial plane. The orbital radius of Q1R is refined to a value of $4,057\pm6$ km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of $\sim5$ km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of $2,520\pm20$ km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10 km and a normal optical depth of $\sim$0.004. Like Q1R, it also lies outside Quaoar's classical Roche limit.
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