We report redshift measurements for 12 BL Lacertae objects from a program aimed at obtaining high signal-to-noise ratio (up to ~500) optical spectroscopy of a mixed sample of objects. The new observations, gathered with the 8 m ESO Very Large Telescope, allowed us to detect weak spectral features down to a line equivalent width as small as ~1 Å

We analyse N-body galaxy merger experiments involving disc galaxies. Mergers of disc-bulge-halo models are compared to those of bulgeless, disc-halo models to quantify the effects of the central bulge on merger dynamics and the structure of the remnant. Our models explore galaxy mass ratios 1:1 through 3:1, and use higher bulge mass fractions than

We report the discovery of a new, non-eclipsing SU UMa-type dwarf nova, HS 2219+1824. Photometry obtained in quiescence (V≈17.5) reveals a double-humped light curve from which we derive an orbital period of ≃86.2 min. Additional photometry obtained during a superoutburst reaching V≃12.0 clearly shows superhumps with a period of ≃89.05 min. The

The observed coronal loop oscillations and their damping are often theoretically described by the use of a very simple coronal loop model, viz. a straight, longitudinally invariant, axi-symmetric, and pressureless flux tube with a different density inside and outside of the loop. In this paper we generalize the model by including longitudinal

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An analysis of different structures of the spiders supporting the flat mirror of a Newton type telescope was made, in order to reduce the diffraction effects of the spider on the images produced by the telescope. After applying different numerical solutions used by different authors, and without satisfactory results, a novel solution based on the