Ewa Niemczura

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We have gathered and analyzed 1493 high-quality multicolor Geneva photometric data taken over 21 years of the B3Vstar HD 129929. We detect six frequencies, among which appear the effects of rotational splitting with a spacing of approximately 0.0121 cycles per day, which implies that the star rotates very slowly. A nonadiabatic analysis of the oscillations(More)
Context. The ground–based campaigns on δ Sct stars revealed richer and richer frequency spectra of these opacity–driven pulsators, thanks to continuous improvements in their exploitation. It has also been suggested that the detection of a wealth of very low amplitude modes was only a matter of signal–to–noise ratio. Access to this treasure, impossible from(More)
Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by ground-based spectroscopy and interferometry, which show it to be(More)
We derive basic stellar parameters (angular diameters, effective temperatures, metallicities) and interstellar reddening for all β Cephei stars observed during the IUE satellite mission, including those belonging to three open clusters. The parameters are derived by means of an algorithmic procedure of fitting theoretical flux distributions to the(More)
The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution. The unknown nature of the mixing processes as well as the extent of the central mixed region is particularly(More)
Context. We present the results of an extensive ground-based photometric and spectroscopic campaign on the γ Dor CoRoT target HD 49434. This campaign was preparatory to the CoRoT satellite observations, which took place from October 2007 to March 2008. Aims. Whereas satellite data will be limited to the detection of low-degree pulsation modes with poor(More)
HD 66051 is an eclipsing system with an orbital period of about 4.75 d that exhibits out-of-eclipse variability with the same period. New multicolour photometric observations confirm the longevity of the secondary variations, which we interpret as a signature of surface inhomogeneities on one of the components. Using archival and newly acquired(More)
We present a spectroscopic survey of γDoradus stars. The high-resolution, high signalto-noise spectra of fifty-two objects were collected by five different spectrographs. The spectral classification, atmospheric parameters (Teff , log g, ξ), v sin i and chemical composition of the stars were derived. The spectral and luminosity classes of the γDor stars(More)
MOST time series photometry of μ Eri, an SB1 eclipsing binary with a rapidly rotating SPB primary, is reported and analysed. The analysis yields a number of sinusoidal terms, mainly due to the intrinsic variation of the primary, and the eclipse light curve. New radial-velocity observations are presented and used to compute parameters of a spectroscopic(More)