2001A&A...373..625P

λ Bootis stars comprise only a small number of all A-type stars and are characterized as nonmagnetic, Populationi, late B to early F-type dwarfs which show significant underabundances of metals whereas the light elements (C, N, O and S) are almost normal abundant compared to the Sun. In the second paper on a spectroscopic survey for λ Bootis stars, we present the spectral classifications of all program stars observed. These stars were selected on the basis of their Stroemgren uvbyβ colors as λ Bootis candidates. In total, 708 objects in six open clusters, the Orion OB1 association and the Galactic field were classified. In addition, 9 serendipity non-candidates in the vicinity of our program stars as well as 15 Guide Star Catalogue stars were observed resulting in a total of 732 classified stars. The 15 objects from the Guide Star Catalogue are part of a program for the classification of apparent variable stars from the Fine Guidance Sensors of the Hubble Space Telescope. A grid of 105 MK standard as well as ``pathological'' stars guarantees a precise classification. A comparison of our spectral classification with the extensive work of Abt & Morrell (1995) shows no significant differences. The derived types are 0.23±0.09 (rms error per measurement) subclasses later and 0.30±0.08 luminosity classes more luminous than those of Abt & Morrell (1995) based on a sample of 160 objects in common. The estimated errors of the means are ±0.1 subclasses. The characteristics of our sample are discussed in respect to the distribution on the sky, apparent visual magnitudes and Stroemgren uvbyβ colors.