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Astron. Astrophys. 338, 200-208 (1998)

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Westerbork HI observations of two High-Velocity Clouds

P.S. Stoppelenburg, U.J. Schwarz and Hugo van Woerden *

Kapteyn Astronomical Institute, Groningen University, Postbus 800, 9700 AV Groningen, The Netherlands

Received 22 January 1998 / Accepted 18 February 1998


Westerbork HI synthesis observations are presented for the directions of the stars 4 Lac and HD 135485. Interstellar absorption lines at high velocities had been reported in the UV spectrum of 4 Lac, setting an upper limit of 1.2 kpc on the distance of the associated, small HI cloud (Bates et al. 1990, 1991). The Westerbork observations show that this cloud ([FORMULA], [FORMULA], [FORMULA] km s-1), which must have a high velocity relative to the surrounding disk gas, consists of two small condensations; the observations provide constraints on their mass and density, and indicate that the metallicity of this cloud is close to solar. For HD 135485, Albert et al. (1993) had found high-velocity absorption lines in optical spectra, but later reports indicate that these lines are probably circumstellar. The Westerbork observations around HD 135485 show that the HI found here is part of a larger HVC complex, Complex L, described by Wakker & van Woerden (1991). For both objects, the Westerbork results are compared with Jodrell Bank single-dish observations.

Key words: ISM: clouds – Radio lines: ISM – ISM: individual objects: HVC 100 – 7+100, HVC 347+35 – 112

* hugo@astro.rug.nl

Send offprint requests to: H. van Woerden

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© European Southern Observatory (ESO) 1998

Online publication: September 8, 1998