Humps and bumps: The effects of shocks on the optical light curves of fundamental-mode RR Lyrae stars. (arXiv:2001.08272v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Prudil_Z/0/1/0/all/0/1">Z. Prudil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dekany_I/0/1/0/all/0/1">I. Dékány</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smolec_R/0/1/0/all/0/1">R. Smolec</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Catelan_M/0/1/0/all/0/1">M. Catelan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grebel_E/0/1/0/all/0/1">E. K. Grebel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kunder_A/0/1/0/all/0/1">A. 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 (OGLE). We selected non-modulated
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 position 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 (CMD), 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
seem 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, thus having already left the
zero-age horizontal branch.
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 (OGLE). We selected non-modulated
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 position 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 (CMD), 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
seem 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, thus having already left the
zero-age horizontal branch.
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