Browsing by Author "Smolec, R."

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    Humps and bumps: the effects of shocks on the optical light curves of fundamental-mode RR Lyrae stars
    (EDP SCIENCES S A, 2020) Prudil, Z.; Dekany, I.; Smolec, R.; Catelan, M.; Grebel, E. K.; Kunder, A.
    We present the most extended and homogeneous study carried out so far of the main and early shocks in 1485 RR Lyrae stars in the Galactic bulge observed by the Optical Gravitational Lensing Experiment. We selected nonmodulated fundamental-mode RR Lyrae stars with good-quality photometry. Using a self-developed method, we determined the centers and strengths of main and early shock features in the phased light curves. We found that the positions of both humps and bumps are highly correlated with the pulsation properties of the studied variables. Pulsators with a pronounced main shock are concentrated in the low-amplitude regime of the period-amplitude diagram, while stars with a strong early shock have average and above-average pulsation amplitudes. A connection between the main and early shocks and the Fourier coefficients is also observed. In the color-magnitude diagram, we see a separation between stars with strong and weak shocks. Variables with a pronounced main shock cluster close to the fundamental red edge of the instability strip (IS), while stars with a strong early shock tend to clump in the center and near the fundamental blue edge of the IS. The appearance of shocks and their properties appear to be independent of the direction of evolution estimated from the period change rate of the studied stars. In addition, the differences in the period change rate between the two main Oosterhoff groups found in the Galactic bulge suggest that stars of Oosterhoff type I are located close to the zero-age horizontal branch while Oosterhoff type II variables are on their way toward the fundamental red edge of the instability strip, and have therefore already left the zero-age horizontal branch.
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    Main and Early Shocks in RR Lyrae Photometric Light Curves
    (2021) Prudil, Z.; Smolec, R.; Catelan, Márcio; Dékány, I.; Grebel, E. K.; Kunder, A.
    We explore the effect of the main and early shocks (giving rise to the so-called hump and bump features in the light curves, respectively) on the pulsation properties of non-modulated fundamental mode RR Lyrae stars. We utilized I-band photometry from the fourth release of the Optical Gravitational Lensing Experiment (OGLE). We determined the centers and strengths of humps and bumps in the phased light curves of the studied stars. The positions of both shock events in the phased light curves are highly correlated with the amplitudes, pulsation periods, and Fourier coefficients. RR Lyrae stars with prominent humps are located at the low-amplitude regime of the Bailey diagram, while variables with pronounced bumps have average and above average amplitudes. RR Lyrae stars close to the red edge of the instability strip have pronounced humps, while variables with a strong bump are located at the center and close to the blue edge of the instability strip. In general, the effect of the main and early shocks provides a new view on the period-amplitude distribution of fundamental mode RR Lyrae stars....
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    On the Oosterhoff dichotomy in the Galactic bulge - II. Kinematical distribution
    (2019) Prudil, Z.; Dekany, Istvan; Grebel, E.K.; Catelan, Márcio; Skarka, M.; Smolec, R.
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    On the Oosterhoff dichotomy in the Galactic bulge : I. Spatial distribution
    (2019) Prudil, Z.; Dekany, Istvan; Catelan, Márcio; Smolec, R.; Grebel, E.K.; Skarka, M.
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    Spatial and Kinematical Study of the Oosterhoff Dichotomy in the Galactic Bulge
    (2020) Prudil, Z.; Dékány, I.; Catelan, Marcio; Grebel, E. K.; Smolec, R.; Skarka, M.
    We present results of spatial and kinematical studies on the Oosterhoff dichotomy in the Galactic bulge based on data from the fourth data release of the Optical Gravitational Lensing Experiment (OGLE). The Oosterhoff groups I and II were separated by conventional augmenting techniques as well as by using a dimensionality reduction machine learning algorithm accompanied by a clustering algorithm. We find, as also seen in globular clusters, that the Oosterhoff II RR Lyrae stars are on the average cooler, more metal-poor, and more massive than RR Lyrae variables associated with the Oosterhoff I group. In addition, neither group seems to be spatially associated with the Galactic bar. For a fraction of our sample, we were able to obtain a 6D kinematical solution, and for these stars, the two Oosterhoff groups do not show a systematic difference in their space velocity distribution. Based on their orbits we estimate that 8 % of the bulge RR Lyrae stars are halo interlopers, and the majority of the studied stars are well confined within the Galactic bulge....