用HST/STIS测量两艘旅行者号飞船视线上的局部ISM
Measuring the Local ISM along the Sight Lines of the Two Voyager Spacecraft with HST/STIS
摘要：
2012年，旅行者1号穿越太阳风层顶，成为第一个离开太阳系的人造物体。这一里程碑标志着本地星际介质（LISM）探索的重要新时代的开始。我们目前的测量的结构和组成的LISM在旅行者号航天器的直接路径，通过使用高分辨率的哈勃太空望远镜（HST）光谱附近的恒星，位于沿同一视线。我们提供了近紫外（2600-2800埃）和远紫外（1200-1500埃）LISM吸收的全面清单。LISM吸收曲线用于在每对紧密间隔（<15度）的视线之间进行比较。通过对几条吸收线的拟合，我们对LISM的物理性质进行了测量。我们估计沿着旅行者2视线的电子密度，我们的值与旅行者1号最近的测量结果一致。HI Ly-alpha线的过量吸收显示出GJ 780周围存在日光层和天体层。这只是第14次探测到天体层，大质量损失率（$\dot{M} = 10\dot{M}_\odot$）与其他亚巨星一致。日光层吸收与预测的逆风方向58度视线强度相匹配。随着HST和旅行者号的寿命结束，我们有机会综合它们各自的观测结果，将现场测量与最短的视线测量相结合，以研究围绕太阳的银河ISM。
英文摘要：
In 2012, Voyager 1 crossed the heliopause, becoming the first human-made object to exit the solar system. This milestone signifies the beginning of an important new era for local interstellar medium (LISM) exploration. We present measurements of the structure and composition of the LISM in the immediate path of the Voyager spacecraft by using high-resolution Hubble Space Telescope (HST) spectra of nearby stars that lie along the same lines of sight. We provide a comprehensive inventory of LISM absorption in the near-ultraviolet (2600-2800 Angstroms) and far-ultraviolet (1200-1500 Angstroms). The LISM absorption profiles are used to make comparisons between each pair of closely spaced (<15 deg) sight lines. With fits to several absorption lines, we make measurements of the physical properties of the LISM. We estimate electron density along the Voyager 2 sight line, and our values are consistent with recent measurements by Voyager 1. Excess absorption in the HI Ly-alpha line displays the presence of both the heliosphere and an astrosphere around GJ 780. This is only the 14th detection of an astrosphere, and the large mass-loss rate ($\dot{M} = 10\dot{M}_\odot$) is consistent with other subgiant stars. The heliospheric absorption matches the predicted strength for a sight line 58 deg from the upwind direction. As both HST and Voyager reach the end of their lifetimes, we have the opportunity to synthesize their respective observations, combining in situ measurements with the shortest possible line-of-sight measurements to study the Galactic ISM surrounding the Sun.
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