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Paper: Variable Interstellar Absorption toward HD 219188
Volume: 365, SINS — Small Ionized and Neutral Structures in the Diffuse Interstellar Medium
Page: 86
Authors: Welty, D.E.
Abstract: We discuss the results of continued optical/UV monitoring of the variable intermediate-velocity absorption toward the low halo star HD 219188. Comparisons between HST/STIS echelle spectra obtained in 2001, 2003, and 2004 and HST/GHRS echelle spectra obtained in 19941995 indicate that the total N(H) and the (mild) depletions showed no significant changes over that whole period. Both nH and ne, however, increased by factors of 24 between 1995 and 2001, then remained roughly constant thereafter. The observed variations thus appear to be due to modest differences in density and/or ionization (and not total column density), over scales of tens of AU.
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