CCD Observations and Period Change of the Type ab RR Lyrae Star DV Mon

The BVR CCD observations of W UMa-type eclipsing binary SS Arietis were made for ten nights from November 1996 to December 1996 at the Sobaeksan Astronomy Observatory. From the observed light curves, nine new times of minimum lights were derived from the Kwee and van Woerden’s method. Improved light elements for this system were determined from these minimum lights with all the published minima. The analysis of the times of minima of SS Ari confirms that the orbital period of SS Ari has been suffering from a sinusoidal variation as the suggestions of other previous investigators (Kaluzny & Pojmanski 1984, Demircan & Selam 1993). The calculation shows that the cyclic period change has a period of about 56.3yrs with an amplitude of about 0.d052. The period variation has been discussed in terms of two potential mechanisms: 1) the light-time effect due to a hypothetical third body and 2) deformations in the convective envelope of a magnetically active component. The BVR light curves of SS Ari observed for about one month showed the existence of cycle to cycle light variations. Long-term light changes of SS Ari are discussed in terms of the period variation of the binary system.

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A Century in Period Changes of the Variables in M15

International Astronomical Union Colloquium ◽

10.1017/s0252921100037635 ◽

1995 ◽

Vol 155 ◽

pp. 387-388

Author(s):

Katalin Barlai ◽

B. Szeidl

Keyword(s):

Globular Cluster ◽

Period Change ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Lyrae Stars ◽

Linear Period

AbstractPeriod behaviour of 62 RR Lyrae stars in the M15 globular cluster has been investigated. About one half of the sample (30 stars) exhibited linear period change. The remaining 32 variables can be characterized by abrupt or erratic changes in their periods.

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CCD Observations of Variable Stars in Globular Clusters

International Astronomical Union Colloquium ◽

10.1017/s0252921100011933 ◽

1989 ◽

Vol 111 ◽

pp. 285-285

Author(s):

H.A. Smith ◽

J.R. Kuhn ◽

J. Curtis

Keyword(s):

Globular Cluster ◽

Globular Clusters ◽

Variable Stars ◽

Michigan State University ◽

State University ◽

Ccd Photometry ◽

Rr Lyrae ◽

Short Period ◽

Ccd Observations ◽

Period Variable

AbstractBVR observations of the relatively metal-rich globular cluster NGC 6388 have been obtained with a CCD on the CTIO 0.9 m telescope. Eighteen possible short period variable stars have been discovered in or near the cluster. At least 10 of these are probable RR Lyrae members of NGC 6388. We confirm the finding of Hazen and Hesser that this cluster is one of the most metal-rich to contain a significant number of RR Lyraes. A program of CCD photometry of field and cluster variable stars has been initiated on the 0.6m telescope of the Michigan State University Observatory.

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3.17. MACHO RR Lyrae stars in the Galactic bulge: the spatial distribution

Symposium - International Astronomical Union ◽

10.1017/s0074180900084308 ◽

1998 ◽

Vol 184 ◽

pp. 123-124

Author(s):

D. Minniti ◽

C. Alcock ◽

D. Alves ◽

K. Cook ◽

S. Marshall ◽

...

Keyword(s):

Spatial Distribution ◽

Density Distribution ◽

Surface Density ◽

Galactic Bulge ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Type C ◽

Type Ab ◽

Lyrae Stars

We have analyzed a sample of 1150 type ab, and 550 type c RR Lyrae stars found in 24 of 94 bulge fields of the MACHO database. These fields cover a range in Galactocentric distances from 0.3 to 1.6 kpc. In combination with the data on the outer bulge fields of Alard (1997) and Wesselink (1987), here we present the surface density distribution of bulge RR Lyrae between 0.3 and 3 kpc.

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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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RR Lyrae Variables in the Second-Parameter Globular Cluster NGC 7006

International Astronomical Union Colloquium ◽

10.1017/s0252921100118111 ◽

1993 ◽

Vol 139 ◽

pp. 420-420

Author(s):

Amelia Wehlau ◽

James M. Nemec

Keyword(s):

Globular Cluster ◽

Outer Region ◽

Period Change ◽

Published Data ◽

Rr Lyrae Stars ◽

Radial Gradient ◽

Rr Lyrae ◽

Inner Region ◽

Lyrae Stars ◽

Median Rate

AbstractThe distant globular cluster NGC7006 was one of the first clusters studied for which the distribution of stars along the horizontal branch of its C-M diagram showed evidence for a “second parameter” in addition to metallicity. Studies of the more than 60 known RR Lyrae stars in this cluster should yield some statistically significant trends or correlations which might help to identify the second parameter. In the first stage of this study (Wehlau, Nemec, Han-Ian $ Rich 1992, AJ, 103, 1583) photographic data from 1984 were combined with previously published data from the 1930's and 1950's and used to obtain period change rates for 46 variables. The median rate was found to fall one standard error below that predicted by the Yale evolutionary HB models. In addition, statistically significant evidence was found for a radial gradient in period change rates in the sense that rates for variables in the outer region of the cluster were more negative.In the second stage of the investigation B and V magnitudes derived from CCD frames of the cluster are being used to obtain colors and to increase the number of variables for which good periods are known, in particular variables in the inner region of this centrally concentrated cluster.

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Period Changes of RR Lyrae Stars in the LMC Globular Cluster NGC 2257

Symposium - International Astronomical Union ◽

10.1017/s007418090003984x ◽

1984 ◽

Vol 108 ◽

pp. 39-40 ◽

Cited By ~ 1

Author(s):

James M. Nemec ◽

Martha H. Liller ◽

James E. Hesser

Keyword(s):

Physical Properties ◽

Globular Cluster ◽

Period Change ◽

Stellar Systems ◽

Horizontal Branch ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Horizontal Branch Stars ◽

Lyrae Stars

The period changes of RR Lyrae stars can be compared with models of horizontal branch stars as a means of investigating the physical properties of the stars themselves, and of the stellar systems in which they are found (Smith and Sandage 1981). The present study is the first in which period change rates of extragalactic RR Lyraes have been estimated.

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A New Look at the Blazhko Effect in RR Lyrae Stars with High-Quality Data from the MACHO Project

International Astronomical Union Colloquium ◽

10.1017/s0252921100057912 ◽

2000 ◽

Vol 176 ◽

pp. 291-298 ◽

Cited By ~ 10

Author(s):

D. W. Kurtz ◽

C. Alcock ◽

R. A. Allsman ◽

D. Alves ◽

T. S. Axelrod ◽

...

Keyword(s):

Phase Modulation ◽

Period Change ◽

Quality Data ◽

High Quality Data ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Blazhko Effect ◽

First Results ◽

Lyrae Stars ◽

Better Than

AbstractWe present the first results of the analysis of 22 Blazhko stars. We find: 1) Blazhko RRab stars that are nearly pure amplitude modulators; 2) Blazhko RRab stars that have both amplitude and phase modulation; 3) A Blazhko RRab star that has an abrupt period change; 4) Proof of the Blazhko effect in RRc stars. Our data show the character of the amplitude and phase modulations of the light curves over the Blazhko cycles far better than has been previously possible.

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A unified construction of stellar evolution and chemical evolution models for the multiple populations in globular clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007518 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 302-304

Author(s):

Sohee Jang ◽

Jenny J. Kim ◽

Young-Wook Lee

Keyword(s):

Star Formation ◽

Chemical Evolution ◽

Globular Clusters ◽

Evolution Model ◽

Star Formation History ◽

Multiple Populations ◽

Rr Lyrae ◽

Formation History ◽

Type Ab ◽

Chemical Evolution Model

AbstractRecent investigations of multiple stellar populations in globular clusters (GCs) suggest that the horizontal-branch (HB) morphology and mean period of type ab RR Lyrae variables are mostly sensitive to helium abundance, while the star formation timescale has the greatest effect on our chemical evolution model constructed to reproduce the Na-O anti-correlation of GCs. Therefore, by combining the results from synthetic HB model with those from chemical evolution model, we could put better constraints on star formation history and chemical evolution in GCs with multiple populations. From such efforts made for four GCs, M4, M5, M15, and M80, we find that consistent results can be obtained from these two independent models.

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