The Galactic nature of high-velocity cloud complex WB

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(-1.3)(+2.3) kpc. Nondetection (at greater than 3 sigma 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-gimel (Ca-II K) = 114.6 +/- 4.4 m angstrom] corresponds to a column density of N(Ca (II))=p (1.32 +/- 0.05) x 10(12) cm(-2). Using an H (I) spectrum from the Leiden/Argentine/Bonn survey, we calculate N(Ca (II))/N(H (I)) = (81 +/- 16) x 10(-9). These distance limits imply an H (I) mass limit of 3.8 x 10(5) M-circle dot < M < 4.9 x 10(5) M-circle dot. 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.