2006ApJ...638L..97T

We have detected absorption lines from the high-velocity cloud (HVC) complex WB in the spectrum of the star HE 1048+0231. This detection sets an upper limit on the distance to the cloud of 8.8^+2.3_–1.3kpc. Nondetection (at greater than 3 σ confidence) in the star HE 1138-1303 at 7.7±0.2 kpc sets a probable lower limit. The equivalent width of the Ca II K line due to the HVC [W_λ(Ca II K)=114.6±4.4 mÅ] corresponds to a column density of N(Ca II)=(1.32±0.05)x10¹²/cm2. Using an H I spectrum from the Leiden/Argentine/Bonn survey, we calculate N(Ca II)/N(H I) = (81±16)x10^–9. These distance limits imply an H I mass limit of 3.8x10⁵ M_☉<M_H I_<4.9x10⁵ M_☉. The upper distance limit imposed by these observations shows that this HVC complex has a probable Galactic or circumgalactic origin. Future metallicity measurements will be able to confirm or refute this interpretation.