NEOMOD 2：基于卡塔利娜巡天十年观测的近地天体更新模型
NEOMOD 2: An Updated Model of Near-Earth Objects from a Decade of Catalina Sky Survey Observations
AI总结：
本研究利用升级后G96望远镜2013-2022年的观测数据更新近地天体模型NEOMOD，修正了大天体种群偏差，揭示小天体轨道分布特征并提出潮汐瓦解补充机制，使撞击通量估算与火流星数据更一致。
摘要：
卡塔利娜巡天（Catalina Sky Survey, CSS）是一项重要的近地天体（Near-Earth Objects, NEOs）巡天项目。在近期的研究中，我们利用2005-2012年的CSS观测数据建立了新的近地天体种群模型NEOMOD。CSS的G96望远镜于2016年完成升级，此后已探测到超过10000个不同的近地天体。\n本研究表征了G96望远镜的近地天体探测效率，并利用2013-2022年G96的近地天体探测数据更新了NEOMOD模型，解决了此前模型中与大尺寸近地天体种群相关的不一致性问题。我们估算，绝对星等H<17.75（对应参考反照率p_V=0.14下直径D>1 km）的近地天体数量为936±29个。H=25-28区间的近地天体尺寸分布斜率相对较缓（累积指数为2.6），H<28的近地天体（D>9 m）数量确定为(1.20±0.04)×10^7个。\n小尺寸近地天体的轨道分布与大尺寸天体不同，撞击概率更高。我们估算，H<28的近地天体每年撞击地球的次数为0.034±0.002次，处于大气火流星观测推断的撞击通量范围的下限附近。与所有近地天体均直接来自主带的模型相比，G96探测到的小尺寸近地天体中，半长轴a=1–1.6 au的低偏心率轨道天体存在过剩，且该过剩程度随H值增大而升高。我们认为，极小型近地天体的种群数量因大尺寸近地天体在与类地行星近距离交会时发生潮汐瓦解而得到补充。当模型中（近似）纳入潮汐瓦解效应后，我们估算H<28的近地天体每年撞击地球的次数为0.06±0.01次，这一结果与火流星观测数据更为吻合。
英文摘要：
Catalina Sky Survey (CSS) is a major survey of Near-Earth Objects (NEOs). In a recent work, we used CSS observations from 2005-2012 to develop a new population model of NEOs (NEOMOD). CSS's G96 telescope was upgraded in 2016 and detected over 10,000 unique NEOs since then. Here we characterize the NEO detection efficiency of G96 and use G96's NEO detections from 2013-2022 to update NEOMOD. This resolves previous model inconsistencies related to the population of large NEOs. We estimate there are 936+/-29 NEOs with absolute magnitude H<17.75 (diameter D>1 km for the reference albedo p_V=0.14). The slope of the NEO size distribution for H=25-28 is found to be relatively shallow (cumulative index 2.6) and the number of H<28 NEOs (D>9 m) is determined to be (1.20+/-0.04)x10^7. Small NEOs have a different orbital distribution and higher impact probabilities than large NEOs. We estimate 0.034+/-0.002 impacts of H<28 NEOs on the Earth per year, which is near the low end of the impact flux range inferred from atmospheric bolide observations. Relative to a model where all NEOs are delivered directly from the main belt, the population of small NEOs detected by G96 shows an excess of low-eccentricity orbits with a=1--1.6 au that appears to increase with H. We suggest that the population of very small NEOs is boosted by tidal disruption of large NEOs during close encounters to the terrestrial planets. When the effect of tidal disruption is (approximately) accounted for in the model, we estimate 0.06+/-0.01 impacts of H<28 NEOs on the Earth per year, which is more in line with the bolide data.
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