A study is presented on the spectroscopic properties of a sample of star- forming dwarf galaxies in extreme density environments, as part of an ongoing project intended to evaluate the influence of the environment on the evolution of dwarf galaxies. Subsets of dwarf galaxies in nearby voids, and in the field of the local supercluster have been

Context. The Fourier transform method is a popular tool for deriving the rotational velocities of stars from their spectral line profiles. However, its domain of validity does not include line-profile variables with time-dependent profiles. Aims: We investigate the performance of the method for such cases, by interpreting the line-profile

Aims.The purpose of this work is to analyze the reliability of the magnetic field strengths inferred from the 630 nm pair of Fe i lines in internetwork quiet Sun regions. Methods: .Some numerical experiments have been performed that demonstrate the inability of these lines to recover the magnetic field strength in such low flux solar regions

We report new observations of the central star of the planetary nebula VV 47 carried out to verify earlier assertions that the short-period pulsation modes detected in the star are driven by the ɛ-mechanism. In our data, VV 47 was not variable up to a limit of 0.52 mmag in the Fourier amplitude spectrum up to the Nyquist frequency of 21.7 mHz

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