The Mg II and Lyα lines of nearby K dwarfs: interstellar medium components and flux measurements.
WOOD B.E., AMBRUSTER C.W., BROWN A. and LINSKY J.L.
Abstract (from CDS):
We analyze local interstellar medium (LISM) absorption observed in the Lyα and Mg II h and k lines of six nearby K dwarf stars, using UV spectra of these stars obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. For four of the six stars, we detect an absorption component with a velocity and column density consistent with the Local Interstellar Cloud (LIC). For HD 197890, there is no observed component at the expected LIC velocity or at the projected velocity of the G cloud, which is a nearby cloud in the general direction of the Galactic center. It also seems doubtful that either of the two components seen toward HD 82558 are LIC or G cloud absorption. The total H I column density toward HD 82558 (d=18.3 pc) is extremely high (logNH=19.05±0.15), representing the largest average H I density detected for any line of sight through the nearby LISM (nH~0.2 cm–3). This is particularly remarkable considering that this star is only 39° from the ``interstellar tunnel'' toward ε CMa, where column densities are an order of magnitude lower than this toward stars that are an order of magnitude farther away.