Berahitdin Albayrak

The Blazhko effect of RR Lyrae in 2003-2004

Aims. Extensive photometry of RR Lyr was obtained over a 421-day interval in 2003-2004, covering more than 10 Blazhko cycles in a multisite campaign. The length and density of this data set allow for a detailed analysis. Methods. We used Fourier techniques to study RR Lyrs behavior over the pulsation and the Blazhko cycle. We propose a two-frequency model for decomposing the frequency spectrum. Results. The light variations were fitted with the main radial frequency, its harmonics up to 11th order, and the detected triplet frequencies. No significant quintuplet components were found in the frequency spectrum. Given the total time span of the measurements, we can now unambiguously conclude that the Blazhko period has become notably shorter than the previously known value of 40.8 days, whereas the main pulsation period remained roughly the same. Changes in the modulation period have been reported for other well-studied Blazhko variables. They challenge the explanations for the Blazhko effect which link the modulation period directly to the rotation period. The new photometry reveals an interval in the pulsation cycle of RR Lyr during which the stars intensity barely changes over the Blazhko cycle. This interval occurs during the infalling motion and between the supposed phases of the early and the main shock. The data also permit a more detailed study of the light curve shape at different phases in the Blazhko period through Fourier parameters.

A light and period study of SV Camelopardalis

New BVR light curves and times of minimum light for the short period RS CVn system SV Cam were analysed to derive the physical parameters of the system and the parameters of the third body orbit. The light curves obtained at the TUBITAK National Observatory during two nights in 2000 show considerable asymmetry and night-to-night variations. The analysis of the light curves is made using Djurasevics inverse problem method. The Roche model with spotted areas on the hotter primary component yields a good fit to observations. The extensive series of published photoelectric minima times indicate that the eclipsing pair orbits around the common mass center of the triple system with a period of 41.32 yr.

A spectroscopic atlas of Deneb (A2 Iae)

We present a spectroscopic atlas of Deneb (A2 Iae) obtained with the long camera of the 1.22-m telescope of the Dominion Astrophysical Observatory using Reticon and CCD detectors. For3826-5212 the inverse dispersion is 2.4 A mm 1 with a resolution of 0.072 A. At the continuum the mean signal-to-noise ratio is 1030. The wavelengths in the laboratory frame, the equivalent widths, and the identifications of the various spectral features are given. This atlas should provide useful guidance for studies of other stars with similar spectral types. The stellar and synthetic spectra with their corresponding line identifications can be examined at http://www.brandonu.ca/physics/gulliver/atlases.html

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New photoelectric BV light curves of three close eclipsing binaries XY Leo, EE Cet and AQ Psc were observed and studied with the aim to derive the physical parameters of these systems. The following results were obtained: (a) the W-type contact binary system XY Leo is in a marginal overcontact configuration (fover ∼ 2.4%) with a relatively large temperature difference between the components (∼330 K); (b) due to the proximity of the companion of EE Cet in the visual binary ADS 2163, the light curves of EE Cet were contaminated by the third light, having a relatively large impact on the system-parameter estimates, and the solutions made with the third light parameter, L3 ∼ 0.54, describe EE Cet as a high-overcontact (fover ∼ 33%) W-type system; (c) the A-type W UMa contact eclipsing binary AQ Psc is in an overcontact configuration (fover ∼ 20%). The relatively small temperature difference (∼150 K) and large difference in component masses suggest a significant energy transfer through the connecting neck of the common envelope. The absolute system parameters are obtained by combining our photometric solution with the spectroscopic elements given by other authors.

3826–5212

In the present study, the activity of the eclipsing binary of the W UMa-type system SW Lac is examined by analysing the new BV photoelectric observations obtained in 2001, 2002 and 2003 at the Ankara University Observatory. During this period, the seasonal light curves show significant differences and asymmetries. A simultaneous analysis of the light curves is made using Djuray sevics inverse-problem method. To explain the light-curve asymmetries and the different maximum light levels in the seasonal light curves we used a Roche model that involved regions containing spots on the components. The analysis shows that SW Lac is in an overcontact configuration with a relatively high degree of overcontact fover ∼ 31%. The Roche model with spotted areas on the more massive and cooler component yields a good fit of the observations for the whole set of the seasonal light curves, without any changes of the basic system parameters. This indicates that the complex nature of the light-curve variations during the examined period can be explained by the changes of spotted areas on the cooler component, which cover a significant part of the stellar surface.

A Photometric Study of the Contact Binaries: XY Leo, EE Cet and AQ Psc

Photoelectric BV light curves of the recently discovered eclipsing binary NN Vir were studied for the first time to derive the physical parameters of the system. The light curves were obtained at the Ankara University Observatory during three nights in May, 2002. The solutions made by using Djurasevics inverse problem method describe the NN Vir system as a high overcontact configuration (

Modeling the changing spot features of SW Lacertae: A three year study

f_{\rm over} \sim 58\%

A photometric study of NN Virginis

) with a relatively small temperature differences between the components (

Physical parameters of some close binaries: ET Boo, V1123 Tau, V1191 Cyg, V1073 Cyg and V357 Peg

\Delta T=T_{\rm h}-T_{\rm c}\sim 160

A Period Study of the Close Binary V508 Ophiuchi

K). These solutions suggest a significant mass and energy transfer from the more massive primary onto the less massive secondary. The hot area on the less massive star, near the neck region, can be taken as a consequence of this mass and energy exchange between the components through the connecting neck of the common envelope.