Abstract
I report the detection of interstellar Ca I and CH at the velocity of the previously reported variable absorption component towards K Velorum (HD 81188). The very high spectral resolution (R 900 000) has resolved the intrinsic line profiles, yielding a kinetic temperature of T k = 190 + 1 7 0 - 1 5 0 K, and a line-of-sight tubulent velocity of ν t = 0.26 + 0 . 0 8 - 0 . 1 3 km s - 1 , for the densest material. The Ca I/Ca II ratio implies a spatial density of n H ≥ 10 3 cm - 3 , although this may considerably underestimate the density in the variable region itself. The CH column density suggests a path-length of ∼10 2 to 10 3 au, supporting suggestions that variable interstellar components such as this are formed in extended structures (sheets or filaments) aligned with the line of sight.
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