Abstract

We measured the equivalent widths (\(EW\)s) of interstellar Ti II absorption lines at \(\lambda\) 3383.759 for about 250 reddened objects and found a good correlation of the \(EW\)s with distances to the background stars, estimated using Gaia DR3 parallaxes. Hipparcos trigonometric parallaxes were used for very bright objects which were not observed by Gaia. The Ti II based distance estimation procedure is similar to the well known Ca II-method (Megier et al., 2005, 2009). However, there are at least 3 advantages of the Ti II method: in contrast to interstellar Ca II H and K lines, blending of Ti II with stellar lines is not an issue even for late B stars; Ti II is to a much less extent influenced by the saturation effect; only a single line must be measured, i.e. there is only a single measurement error to be taken into account. The relation of between Ti II \(EW\) and distance is given by simple equation \(d\approx 30EW\), where \(d\) is the distance in pc and \(EW\) is the equivalent width of the Ti II \(\lambda\) 3383.759 line in mÅ.

中文翻译：

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星际 Ti II 距离量表

摘要

我们测量了约 250 个变红天体在\(\lambda\) 3383.759 处的星际 Ti II 吸收线的等效宽度 ( \(EW\) s) ，发现\(EW\) s 与到背景的距离具有良好的相关性恒星，使用 Gaia DR3 视差估计。依巴谷三角视差用于盖亚未观测到的非常明亮的物体。基于 Ti II 的距离估计过程类似于众所周知的 Ca II 方法（Megier 等人，2005 年，2009 年）。然而，Ti II 方法至少有 3 个优点：与星际 Ca II H 线和 K 线相比，Ti II 与恒星线的混合即使对于晚期 B 星也不是问题；Ti II 受饱和效应的影响要小得多；仅需测量单条线，即仅需要考虑单个测量误差。Ti II \(EW\)和距离之间的关系由简单方程\(d\approx 30EW\)给出，其中\(d\)是 pc 中的距离，\(EW\)是等效宽度Ti II \(\lambda\) 3383.759 线，单位为 mÅ。