基于北欧观测的双小行星(163693) Atira揭示含水CM碳质球粒陨石成分
Nordic-based observations of binary asteroid (163693) Atira reveal a hydrated CM chondrite composition
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- University of Helsinki（赫尔辛基大学）
- Finnish Centre for Astronomy with ESO, University of Turku（图尔库大学芬兰ESO天文学中心）
- Luleå University of Technology（吕勒奥理工大学）
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中文总结 AI 辅助
本研究通过北欧观测数据揭示双小行星(163693) Atira具有含水CM碳质球粒陨石成分，采用光度、光谱和偏振方法，为Atira群体地面物理特征研究提供重要参考。
中文摘要 AI 辅助
我们展示了于2024年3月5日夜间收集的(163693) Atira的光度、光谱和偏振观测数据。使用芬兰Kirkkonummi的Metsähovi天文台(L08)在V和R_C滤光片下获取的双波段光变曲线跨越近8小时。根据这些测量，我们估算出V-R_C = 0.43 ± 0.07星等。使用位于西班牙La Palma的北欧光学望远镜获得了可见光谱和线性偏振测量。我们采用半经验模型来恢复因光谱狭缝未对准而丢失的光谱通量。校正后的模型反射光谱表明其原始Cgh分类类型，在0.60至0.85微米范围内具有明显的吸收特征，深度约为7.4%。与陨石实验室光谱的直接比较表明，其与CM碳质球粒陨石高度匹配。我们在83度相位角下检测到较大程度的线性偏振，这与(3200) Phaethon和(155140) 2005 UD一致，但低于(162173) Ryugu和(152679) 1998 KU2。我们使用CM碳质球粒陨石密度，根据先前估算的体积密度估算出其整体孔隙率为51 ± 31%。体积密度和整体孔隙率的不确定性主要由主天体的体积主导。未来的近红外光谱和热红外观测可用于细化成分和体积密度。最后，我们讨论了对Atira群体地面物理特征研究的意义。
英文摘要
We present photometric, spectroscopic, and polarimetric observations of (163693) Atira collected on the night of 05 March 2024. A dual-band lightcurve acquired in the V and R_C filters using the Metsähovi Observatory (L08) in Kirkkonummi, Finland spans nearly 8~hours. From these measurements we estimate a V-R_C = 0.43 +/- 0.07 mag. A visible spectrum and linear polarisation measurement were obtained with the Nordic Optical Telescope in La Palma, Spain. We employ a semi-empirical model to recover the spectral flux that was lost due to a mis-aligned spectroscopic slit. The corrected model reflectance spectrum indicates a primitive Cgh taxonomic type with a distinct absorption feature from 0.60 to 0.85 um with a depth of ~7.4 %. Direct comparison with laboratory spectra of meteorites indicates close matches with CM carbonaceous chondrites. We detect a large degree of linear polarisation at a phase angle of 83 degrees which is consistent with (3200) Phaethon and (155140) 2005 UD, but lower than (162173) Ryugu and (152679) 1998 KU2. We use a CM carbonaceous chondrite density to estimate its bulk porosity of 51 +/- 31 % from previously estimated bulk density. The uncertainty in bulk density and bulk porosity is dominated by the volume of the primary. Future near-infrared spectroscopic and thermal infrared observations can be used to refine the composition and bulk density. Finally, we discuss implications for ground-based physical characterisation studies of the Atira population.
