The Unusual Period Distribution of the RR Lyrae Variables in NGC 5897

AbstractAttention is called to the rather unusual distribution of the periods of the RR Lyrae variables in NGC 5897, a metal-poor halo globular cluster with a very low central concentration. Of the seven RR Lyrae stars known in the cluster, three have periods between 0.797 and 0.856 day and two have periods of 0.45 and 0.42 day. The other two have periods of 0.34 and 0.35 day with much lower amplitudes of variation. Due to the lack of crowding in this cluster photoelectric observations and Fourier decompositions of the resulting light curves should be possible for at least six of the RR Lyrae variables. In addition, the cluster appears to contain a non-variable horizontal branch star, SK 120, lying within the instability strip. As this is the only well documented case of such a star, photoelectric observations of this star would also be desirable.

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Humps and bumps: the effects of shocks on the optical light curves of fundamental-mode RR Lyrae stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936704 ◽

2020 ◽

Vol 635 ◽

pp. A66 ◽

Cited By ~ 1

Author(s):

Z. Prudil ◽

I. Dékány ◽

R. Smolec ◽

M. Catelan ◽

E. K. Grebel ◽

...

Keyword(s):

Main Shock ◽

Period Change ◽

Light Curves ◽

Horizontal Branch ◽

Instability Strip ◽

Rr Lyrae Stars ◽

Change Rate ◽

Rr Lyrae ◽

Red Edge ◽

Lyrae Stars

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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Light Curves and Metal Abundances of RR Lyrae Variables in the Bar of the Large Magellanic Cloud

International Astronomical Union Colloquium ◽

10.1017/s0252921100057481 ◽

2000 ◽

Vol 176 ◽

pp. 172-175 ◽

Cited By ~ 1

Author(s):

G. Clementini ◽

A. Bragaglia ◽

L. Di Fabrizio ◽

E. Carretta ◽

R. G. Gratton

Keyword(s):

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Light Curves ◽

Photometric System ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Visual Magnitude ◽

Metal Abundance ◽

Definition Of ◽

Lyrae Stars

AbstractThe Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance scale. However, a difference of 0.2−0.3 mag exists in its distance as predicted by the short and long distance scales. Distances to the LMC from Population II objects are founded on the RR Lyrae variables. We have undertaken an observational campaign devoted to the definition of the average apparent luminosity, and to the study of the mass–metallicity relation for RR Lyrae stars in the bar of the LMC. These are compared with analogous quantities for cluster RR Lyrae stars. The purpose is to see whether an intrinsic difference in luminosity, possibly due to a difference in mass, might exist between field and cluster RR Lyrae stars, which could be responsible for the well-known dichotomy between short and long distance scales. Preliminary results are presented on the V and B − V light curves, the average apparent visual magnitude, and the pulsational properties of 102 RR Lyrae stars in the bar of the LMC, observed at ESO in January 1999. The photometric data are accurately tied to the Johnson photometric system. Comparison is presented with the photometry of RR Lyrae stars in the bar of the LMC obtained by the MACHO collaboration (Alcock et al. 1996). Our sample includes 9 double-mode RR Lyrae stars selected from Alcock et al. (1997) for which an estimate of the metal abundance from the ΔS method is presented.

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The effect of stellar evolution on the light curves’ shapes of RR Lyrae stars in M3

International Astronomical Union Colloquium ◽

10.1017/s0252921100010563 ◽

2004 ◽

Vol 193 ◽

pp. 171-175

Author(s):

Johanna Jurcsik

Keyword(s):

Light Curve ◽

Stellar Evolution ◽

Light Curves ◽

Horizontal Branch ◽

Homogeneous Sample ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Lyrae Stars

AbstractThe light curve characteristics of a homogeneous sample of variables in M3 are studied in detail. Accurate light curves and mean magnitudes of about 100 RRab and 50 RRc stars which do not show any type of modulation are analyzed. According to their mean magnitudes and Fourier parameters the variables can be sorted into four groups, representing different stages of the horizontal branch stellar evolution.

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Convective effects and the RR lyrae instability strip

Symposium - International Astronomical Union ◽

10.1017/s0074180900031314 ◽

1984 ◽

Vol 105 ◽

pp. 461-463

Author(s):

R. F. Stellingwerf

Keyword(s):

Nonlinear Behavior ◽

Instability Strip ◽

Unstable Region ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Red Edge ◽

Diffusive Convection ◽

Structure Equations ◽

Lyrae Stars

The effects of nonlinear, nonlocal, diffusive convection have been included in the structure equations of pulsational hydrodynamic analyses of a series of RR Lyrae models. We find a well-defined red edge of the unstable region that depends on mode of pulsation. It is shown that this result has strong implications for the nonlinear behavior of RR Lyrae stars.

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Theoretical UBVI Light Curves of Pulsating Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100058012 ◽

2000 ◽

Vol 176 ◽

pp. 334-337

Author(s):

Michael U. Feuchtinger ◽

Ernst A. Dorfi

Keyword(s):

Radiative Transfer ◽

Light Curves ◽

Rr Lyrae Stars ◽

Fourier Decomposition ◽

Pulsating Stars ◽

Rr Lyrae ◽

Stellar Pulsation ◽

Sample Application ◽

Lyrae Stars ◽

Good Agreement

AbstractBy performing detailed frequency-dependent radiative transfer computations we are able to calculate light curves in particular bandpasses from stellar pulsation models calculated by the Vienna nonlinear convective pulsation code. As a sample application we discuss UBVI light curves of RR Lyrae stars. The properties of these light curves are analyzed by means of standard Fourier decomposition, and a comparison to recent observations is performed. As main results we find a good agreement with important observed RR Lyrae properties like pulsation amplitudes and Fourier parameters in B, V, and I bands. Additionally, from the synthetic color curves we derive linear transformation laws between amplitudes as well as Fourier parameters in the different bandpasses.

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K-band light curves for RR Lyrae stars in the globular clusters M5 and M92

Publications of the Astronomical Society of the Pacific ◽

10.1086/132973 ◽

1992 ◽

Vol 104 ◽

pp. 159 ◽

Cited By ~ 7

Author(s):

Jesper Storm ◽

Bruce W. Carney ◽

David W. Latham

Keyword(s):

Globular Clusters ◽

Light Curves ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Lyrae Stars ◽

K Band

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The red edge of the instability strip of RR Lyrae stars

Chinese Astronomy and Astrophysics ◽

10.1016/0275-1062(82)90063-7 ◽

1982 ◽

Vol 6 (1) ◽

pp. 43-48 ◽

Cited By ~ 2

Author(s):

Xiong Da-run

Keyword(s):

Instability Strip ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Red Edge ◽

Lyrae Stars

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Some RR Lyrae Variables with Blažko Effect

Symposium - International Astronomical Union ◽

10.1017/s0074180900010767 ◽

1975 ◽

Vol 67 ◽

pp. 553-553

Author(s):

G. H. Chis ◽

V. Ureche

Keyword(s):

Light Curves ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Lyrae Stars

Observations of some RR Lyrae stars with varying periods and shapes of the light curves were discussed. These are:TU Com (Ureche, V., 1965)WY Dra (Chis, D., Chis, G. H., and Mihoc, I. (1974))SW Psc (Ureche, V. (1971a, b))

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Theoretical Problems of Beta Cephei Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100073759 ◽

1979 ◽

Vol 46 ◽

pp. 467-473

Author(s):

Yoji Osaki

Keyword(s):

Small Group ◽

Spectral Type ◽

Main Sequence ◽

Massive Stars ◽

Instability Strip ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

M 10 ◽

Classical Cepheids ◽

Lyrae Stars

The Beta Cephei (or Beta Canis Majoris) stars are a small group of pulsating variables of early spectral type. There are some 20 “classical” β Cephei stars, and several new or suspected variables in this group. The classical β Cephei stars are confined in a narrow “instability strip” which lies about 1 mag above and nearly parallel to the zero-age main-sequence of massive stars (M~10-20 M⊙). They are thus located far away from other well-known pulsating variables such as classical Cepheids and RR Lyrae stars in the HR diagram.

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