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Vertical instabilities, buckling, in stellar bars weaken and shorten the bar. This can interrupt the bar-induced gas inflow into the central kpc of a galaxy for ˜ 1 Gyr. The subsequent bar growth in length and in amplitude can lead to a recurrent buckling. The first buckling results in the formation of a peanut/boxy-shaped bulge when viewed edge-on

Photometric and spectroscopic parameters for sigma Ori very low-mass stars and brown dwarfs candidates. (1 data file).

The activities related to the preparation of the asteroseismic, photometric space mission COROT are described. Photoelectric observations, wide-field CCD photometry, uvbyβ calibrations, and further time series have been obtained at different observatories and telescopes. They have been planned to complete the COROT program in the direction of the

A new method for absolute polarimetric calibration of large telescopes is presented. The proposed method is highly accurate and is based on the calibration of a small subaperture, which is then extended to the full system by means of actual observations of an astronomical source. The calibration procedure is described in detail along with numerical

We report an outburst of a black hole X-ray binary, V4641 Sgr in 2004 July. We succeeded in performing time-series photometry during the outburst, which showed repetitive short flares having a timescale of 10 min. Even after the outburst, it remained active for 17 d, as observed after an outburst in 2002. In conjunction with a low X-ray flux, we