RR Lyrae stars in the Milky Way are good tracers to study the kinematic behaviour and spatial distribution of older stellar populations. A recently established well documented sample of 217 RR Lyr stars with V < 12.5 mag, for which accurate distances and radial velocities as well as proper motions from the Hipparcos and Tycho-2 catalogues are available, has been used to reinvestigate these structural parameters. The kinematic parameters allowed to calculate the orbits of the stars. Nearly 1/3 of the stars of our sample have orbits staying near the Milky Way plane. Of the 217 stars, 163 have halo-like orbits fulfilling one of the following criteria: Θ < 100 km s −1 , orbit eccentricity > 0.4, and normalized maximum orbital z-distance > 0.45. Of these stars roughly half have retrograde orbits. The z-distance probability distribution of this sample shows scale heights of 1.3 ± 0.1 kpc for the disk component and 4.6 ± 0.3 kpc for the halo component. With our orbit statistics method we found a (vertical) spatial distribution which, out to z = 20 kpc, is similar to that found with other methods. This distribution is also compatible with the ones found for blue (HBA and sdB) halo stars. The circular velocity Θ, the orbit eccentricity, orbit z-extent and [Fe/H] are employed to look for possible correlations. If any, it is that the metal poor stars with [Fe/H] < 1.0 have a wide symmetric distribution about Θ = 0, thus for this subsample on average a motion independent of disk rotation. We conclude that the Milky Way possesses a halo component of old and metal poor stars with a scale height of 4-5 kpc having random orbits. The presence in our sample of a few metal poor stars (thus part of the halo population) with thin disk-like orbits is statistically not surprising. The midplane density ratio of halo to disk stars is found to be 0.16, a value very dependent on proper sample statistics.

RR Lyrae stars are of great importance for investigations of Galactic structure. However, a complete compendium of all RR-Lyraes in the solar neighbourhood with accurate classifications and coordinates does not exist to this day. Here we present a catalogue of 561 local RR-Lyrae stars (V max ≤ 12.5 mag) according to the magnitudes given in the Combined General Catalogue of Variable Stars (GCVS) and 16 fainter ones. The Tycho2 catalogue contains 100 RR Lyr stars. However, many objects have inaccurate coordinates in the GCVS, the primary source of variable star information, so that a reliable cross-identification is difficult. We identified RR Lyrae from both catalogues based on an intensive literature search. In dubious cases we carried out photometry of fields to identify the variable. Mennessier & Colome (2002, A&A, 390, 173) have published a paper with Tyc2-GCVS identifications, but we found that many of their identifications are wrong.

Abstract. We present the first results of a photometric and astrometric investigation of stars in the region of the globular cluster M 71 (NGC 6838). Using wide field CCD observations we determined B and V magnitudes of 4450 stars up to a limiting magnitude of V ≤ 18.5 mag. Relative proper motions were used to derive membership probabilities for stars with R < 3 around the centre of M 71. Our colour-magnitude diagram (CMD) of 320 probable cluster members reaches down to V = 18. A well defined red giant bump -for the first time seen in M 71 -could be detected in our CMD. From isochrone fitting we find M 71 metal poorer and older than previously assumed. Four faint variable stars were confirmed to be members of M 71. Moreover, we detected 13 blue stragglers among our cluster members.

Abstract. -The astrometric accuracy of triple image Carte du Ciel plates has been analysed using plates of the open cluster NGC 1647. A new multithreshold technique was used for the treatment of the triple image plates. Accuracies ranging from 100 mas to 200 mas were found. We determined proper motions with a median accuracy of 1.6 mas/a for 2220 stars in the field of NGC 1647. The membership probabilities of stars in the cluster region agree very well with the data of Francic (1989). Due to a significant difference of the proper motions of SZ Tau and the cluster members, SZ Tau seems not to be a member of NGC 1647.

Aims. RR Lyrae stars have been observed to improve the insight into processes at work in their atmospheres. Methods. Simultaneous Strömgren-photometry allows to obtain a rapid sequence of measurements in which photometric indices are unaffected by non-optimum observing conditions. The indices y, b − y, and c 1 are used with an established calibration to derive T eff and to determine the gravity, log g BJ from the Balmer jump, throughout the pulsation cycle. By employing the equations for stellar structure, additional parameters can be derived. Results. Strömgren photometry and its calibration in terms of T eff and log g can be used to determine the run of R and the atmosphere pulsation velocity. We find that the Balmer-line strengths are correlated with T eff and that the strength of the Ca ii K line correlates well with the radius of the star and thus the pulsation-dependent density of the atmosphere. The density in the stellar atmosphere fluctuates as indicated by the changes in the gravity log g BJ , derived from c 1 , between 2.3 and 4.5 dex. Also the Strömgren metal index, m 1 , fluctuates. We find a disagreement between log g(T, L, M), the gravity calculated from T eff , L, and the mass M, and the gravity log g BJ . This can be used to reassess the mass and the absolute magnitude of an individual star. The curves derived for the pulsational velocity V pul differ from curves obtained from spectra needed to apply the Baade-Wesselink method; we think these differences are due to phase dependent differences in the optical depth levels sampled in continuum photometry and in spectroscopy. We find an atmospheric oscillation in these fundamental mode RR Lyrae stars of periodicity P/7. Conclusions. Carefully conducted Strömgren-photometry allows to derive a large number of parameters for RR Lyrae stars. It provides a means of deriving masses and absolute magnitudes. When comparing photometry results with spectroscopic analyses it appears that optical depth effects affect all interpretations.