Search results for: E. Niemczura

Items from 1 to 8 out of 8 results

article

New β Cephei variable in the Southern open cluster NGC 6200: ALS 3728

C. Ulusoy, E. Niemczura, B. Ulaş, T. Gülmez

New Astronomy > 2013 > 23-24 > Complete > 55-58

We report the evidence of a new β Cephei type variable located in the Southern open cluster NGC 6200: ALS 3728. Spectroscopic and photometric observations of NGC 6200 stars were carried out at the South African Astronomical Observatory (SAAO) in 2011. It was found that ALS 3728 has a frequency of about 4.95 d ⁻¹ with highest amplitude. The star also shows a remarkable stillstand phase just...

article

An asteroseismic study of the Southern β Cephei star ALS 3721

C. Ulusoy, E. Niemczura, B. Ulaş, T. Gülmez

New Astronomy > 2013 > 22 > Complete > 51-56

We present the results of a new investigation aimed to identify the pulsational characteristics of the Southern β Cephei star ALS 3721. Spectroscopic and multicolour photometric data were acquired at the South African Astronomical Observatory (SAAO), South Africa in 2011. Frequency analysis showed that the oscillations of ALS 3721 could be attributed to the two main frequencies with higher significance...

article

Pulsational amplitude growth of the star KIC 3429637 (HD 178875) in the context of Am and ρ Pup stars

Simon J. Murphy, A. Grigahcène, E. Niemczura, D. W. Kurtz, more

Monthly Notices of the Royal Astronomical Society > 427 > 2 > 1418 - 1428

KIC 3429637 (HD 178875) is a δ Sct star whose light curve shows continuous pulsational amplitude growth in Kepler mission photometry. Analysis of the three largest amplitude peaks in the Fourier transform indicates different growth rates for all three. We have ruled out instrumental causes, and determine the amplitude growth to be intrinsic to the star. We calculate time‐dependent convection models...

article

A cyclic bipolar wind in the interacting binary V 393 Scorpii

R. E. Mennickent, Z. Kołaczkowski, G. Djurasevic, E. Niemczura, more

Monthly Notices of the Royal Astronomical Society > 427 > 1 > 607 - 624

V 393 Scorpii is a double periodic variable characterized by a relatively stable non‐orbital photometric cycle of 253 d. Mennickent et al. argue for the presence of a massive optically thick disc around the more massive B‐type component and describe the evolutionary stage of the system. In this paper, we analyse the behaviour of the main spectroscopic optical lines during the long non‐orbital photometric...

article

Unusual high‐frequency oscillations in the Kepler Scuti star KIC 4840675

L. A. Balona, M. Breger, G. Catanzaro, M. S. Cunha, more

Monthly Notices of the Royal Astronomical Society > 424 > 2 > 1187 - 1196

We show that the star KIC 4840675 observed by Kepler is composed of three stars with a rapidly rotating A‐type star and two solar‐type fainter companions. The A‐type star is a δ Scuti variable with a dominant mode and many other modes of lower amplitude, including several low‐frequency variations. The low‐frequency variation with highest amplitude can be interpreted as rotational modulation with the...

article

Pulsational content and abundance analysis of some δ Scuti stars observed by CoRoT

E. Poretti, L. Mantegazza, E. Niemczura, M. Rainer, more

Astronomische Nachrichten > 331 > 9‐10 > 1049 - 1052

Several δ Sct stars were photometrically monitored with the satellite CoRoT and observed in high‐resolution spectroscopy from ground. We present here the preliminary results of the abundance analysis of several potential CoRoT targets. Moreover, new insights are given about the problem of the huge number of detected frequencies by comparing δ Sct stars with normal A‐type stars (© 2010 WILEY‐VCH Verlag...

article

The metallicity of β Cephei stars on the basis of the satellite ultraviolet spectra

J. Daszyńska, E. Niemczura, H. Cugier

Advances in Space Research > 2003 > 31 > 2 > 387-392

We derive the mean stellar parameters like angular diameter, effective temperature, and metallicity from ultraviolet spectra for all β Cephei stars observed during the IUE satellite mission, including those belonging to the three open clusters. For this purpose we fit the theoretical flux distributions of Kurucz's models to observed low-resolution spectra of the stars. We focus on the metallicity...

article

The mean stellar parameters from IUE and hipparcos data

E. Niemczura, J. Daszyńska, H. Cugier

Advances in Space Research > 2003 > 31 > 2 > 399-404

We elaborate an automatic procedure fitting theoretical flux distributions (Kurucz 1996) to observed low resolution stellar spectra. The procedure is based on the least squares optimalization algorithm and enable us to determine the basic stellar parameters, which minimize RMS (Root Mean Square). This efficient method allows us to retrieve simultaneously T _e _f _f , log g, [m/H], θ and...

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