Interstellar and Circumstellar Optical & Ultraviolet Lines Towards SN 1998 S 1

We have observed SN 1998S which exploded in NGC 3877, with the Utrecht Echelle Spectrograph (6 − 7 km s FWHM) at the William Herschel Telescope and with the E230M echelle of the Space Telescope Imaging Spectrograph (8 km s FWHM) aboard the Hubble Space Telescope. Both data sets were obtained at two epochs, separated by 19 (optical) and seven days (UV data). From our own Galaxy we detect interstellar absorption lines of Ca II K, Fe II λλ2600, 2586, 2374, 2344, Mg I λ2852, and probably Mn II λ2576, at vLSR = −95 km s −1 arising from the outer edge of the High Velocity Cloud Complex M. We derive gas-phase abundances of [Fe/H] = −1.4 and [Mn/H] = −1.0, values which are very similar to warm disk clouds found in the local ISM. This is the first detection of manganese from a Galactic HVC, and we believe that the derived gas-phase abundances argue against the HVC material having an extragalactic origin. At the velocity of NGC 3877 we detect interstellar Mg I λ2852, Mn II λλ2576, 2594, 2606, Ca II K and Na I D2,D1 absorption lines, spanning a velocity range of −102 to +9 km s from the systemic velocity of the galaxy (910 km s). Surprisingly, the component at −102 km s is seen to increase by a factor of ∼ 1 dex in N(Na I) between 20-March-1998 and 8-April-1998, and in N(Mg I) between 4-April-1998 and 11-April-1998. Unusually, our data also show narrow Balmer, He I, and metastable UV Fe II P-Cygni profiles, with a narrow absorption component superimposed on the bottom of the profile’s absorption trough. Both the broad and narrow components of the optical