Detection of CaI and CH absorption at the velocity of the variable interstellar component towards Velorum

I report the detection of interstellar CaI and CH at the velocity of the previously reported variable absorption component towards κ Velorum (HD 81188). The very high spectral resolution (R≈ 900 000) has resolved the intrinsic line profiles, yielding a kinetic temperature of Tk= 190+170−150 K, and a line-of-sight tubulent velocity of vt= 0.26+0.08−0.13 km s−1, for the densest material. The CaI/Caii ratio implies a spatial density of nH≳ 103 cm−3, although this may considerably underestimate the density in the variable region itself. The CH column density suggests a path-length of ∼102 to 103 au, supporting suggestions that variable interstellar components such as this are formed in extended structures (sheets or filaments) aligned with the line of sight.