CCD Photometry of RR Lyrae Stars in NGC 6388 and M15

The dependences of the numbers of variable stars in globular clusters on the chemical composition are studied. For given metallicity the numbers of RR Lyrae stars reduced to some definite total number of stars in the cluster are different for the two groups of globular clusters introduced by Mironov.

Search for Variables in the Galactic Globular Clusters NGC 6544 and NGC 6642

10.1017/s0252921100117774 ◽

1993 ◽

Vol 139 ◽

pp. 337-337

Author(s):

Martha L. Hazen

Keyword(s):

Globular Clusters ◽

Slow Variable ◽

Variable Stars ◽

Horizontal Branch ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

A Value ◽

Short Period ◽

Period Variable ◽

A search for variable stars in the globular cluster NGC 6544 has revealed only one possible short period variable within the tidal radius of the cluster. A search in NGC 6642 yielded 16 new RR Lyrae stars within the tidal radius and 5 new field RRs. The previously discovered (Hoffleit 1972) V1 is a slow variable, and V2 is an RR Lyrae star. Photometry of the variables within the tidal radius gives a mean B for the horizontal branch of < B > = 17.0 mag. With E(B – V) = 0.37 mag and (B – V) = 0.35 mag for RR Lyraes, a value for V(HB) = 16.3 mag is derived. This is about one mag fainter than previous estimates (Webbink 1985), and places NGC 6642 at a distance of approximately 7.9 kpc.

NGC 1261: A TIME-SERIES VI STUDY OF ITS VARIABLE STARS

Revista Mexicana de Astronomía y Astrofísica ◽

10.22201/ia.01851101p.2019.55.02.18 ◽

2019 ◽

Vol 55 (2) ◽

pp. 337-350 ◽

Cited By ~ 3

Author(s):

A. Arellano Ferro ◽

I. H. Bustos Fierro ◽

J. H. Calderón ◽

J. A. Ahumada

Keyword(s):

Time Series ◽

Variable Stars ◽

Individual Values ◽

Ccd Photometry ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Cluster Distance ◽

The Mean ◽

Lyrae Stars ◽

Gaia Dr2

Time-series VI CCD photometry of the globular cluster NGC 1261 is employed to study its variable star population. A membership analysis of most variables based on Gaia DR2 proper motions and colours was performed prior to the estimation of the mean cluster distance and metallicity. The light curves of the member RR Lyrae were Fourier decomposed to calculate their individual values of distance, [Fe/H], radius and mass. The I band P-L for RR Lyrae stars was also employed. Our best estimates of the metallicity and distance of this Oo I cluster are [Fe/H]ZW =−1.42 ± 0.05 dex and d = 17.2 ± 0.4 kpc. No mixture of fundamental and first overtone RR Lyrae stars in the either-or or bimodal region is seen in this cluster, as it seems to be the rule for Oo I clusters with a red horizontal branch. A multi-approach search in a region of about 10' × 10' around the cluster revealed no new variable stars within the limitations of our CCD photometry.

RR Lyrae Stars in Globular Clusters

10.1017/s025292110005747x ◽

2000 ◽

Vol 176 ◽

pp. 165-171

Author(s):

Alistair R. Walker

Keyword(s):

Globular Clusters ◽

Stellar Populations ◽

Variable Stars ◽

Rr Lyrae Stars ◽

Technical Aspects ◽

Rr Lyrae ◽

AbstractOf the several types of variable stars that occur in globular clusters, RR Lyrae stars have deservedly received the most attention. These stars are ideally suited for comparisons between evolution and pulsation theory, they play a prominent role in distance determinations, and are valuable tracers of the oldest stellar populations. After a brief discussion of technical aspects, we review some of the recent observational work.

UBV Magnitudes and Colours of 62 RR Lyrae Stars in ω Centauri (NGC 5139)

10.1017/s0252921100033376 ◽

1973 ◽

Vol 21 ◽

pp. 88-94

Author(s):

E. H. Geyer

Keyword(s):

Globular Clusters ◽

Variable Stars ◽

Horizontal Branch ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Horizontal Branch Stars ◽

Photoelectric Measurements ◽

It has been shown by the author (Geyer, 1967), and independently by Dickens and Woolley (1967), that there occur horizontal branch stars well within the RR Lyrae variable gap of the c–m-diagram of ω Centauri. Variability of these objects is not known, and presumably is unlikely, because the cluster is so well studied for variable stars. For the observationally best studied globular clusters M3, M13, M15 and M92 (Sandage, 1969), this phenomenon is not found. The author’s original published c–w-diagram of NGC 5139 showed about 10 stars with (B–V)≥0.2 and V-magnitudes comparable with those of RR Lyrae stars of the cluster. Unpublished photoelectric measurements of some of these stars, carried out in 1968 with the 40-in photometric reflector of ESO by the author, support this finding. Also the study of blue horizontal branch stars by Newell, Rodgers and Searle (1969) of the Herst-monceux catalog of ω Centauri (Woolley et al., 1966) confirms these results, the importance of which for the understanding of the horizontal branch stars and RR Lyrae variables is obvious.

Variable Stars and Evolution in Globular Clusters

10.1017/s0252921100033510 ◽

1973 ◽

Vol 21 ◽

pp. 187-195

Author(s):

Pierre Demarque

Keyword(s):

Globular Clusters ◽

Main Sequence ◽

Absolute Magnitude ◽

Variable Stars ◽

Rr Lyrae Stars ◽

The Past ◽

Rr Lyrae ◽

Lyrae Stars ◽

Distance Indicators

Traditionally, cluster variables have been used as distance indicators and have in this sense played an important role in our understanding of stellar evolution. In particular, the determination of the distance moduli of globular clusters and of the absolute magnitude of the main sequence turnoff, thus yielding the ages of the cluster, have relied heavily in the past on observations of RR Lyrae stars.

Wide-field variability survey of the globular cluster NGC 4833

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313014956 ◽

2013 ◽

Vol 9 (S301) ◽

pp. 441-442

Author(s):

Grzegorz Kopacki

Keyword(s):

Globular Cluster ◽

Variable Stars ◽

Wide Field ◽

Red Giants ◽

Type Ii ◽

Rr Lyrae Stars ◽

Preliminary Results ◽

Rr Lyrae ◽

Lyrae Stars ◽

Field Variability

AbstractWe present preliminary results of the variability survey in the field of the globular cluster NGC 4833. We observed all 34 variable stars known in the cluster. In addition, we have found two new SX Phoenicis stars, one new RR Lyrae star, twelve new eclipsing systems mostly of the W Ursae Majoris type, nine new variable red giants, and ten new field-stars showing irregular variations. Properties of RR Lyrae stars indicate that NGC 4833 is an Oosterhoff's type II globular cluster.

CCD Photometry of RR Lyrae Stars in M3

10.1017/s0252921100117749 ◽

1993 ◽

Vol 139 ◽

pp. 325-331

Author(s):

C. Cacciari ◽

E. Carretta ◽

F. Ferraro ◽

F. Fusi Pecci ◽

G. Tessicini ◽

...

Keyword(s):

Temperature Distribution ◽

Ccd Photometry ◽

Rr Lyrae Stars ◽

Preliminary Results ◽

Rr Lyrae ◽

Period Shift ◽

Shift Effect ◽

AbstractNew CCD BVI observations of RR Lyrae variables in M3 are presented. Mean magnitudes and colours are derived, as well as their relations with periods and amplitudes, and comparisons are made with previous data (Sandage 1981, 1990). Preliminary results are presented on the temperature distribution of the variables and the period-shift effect with respect to M15 and M68.

The Helium Abundance in the Envelopes of the Bluest RR Lyrae Stars in Globular Clusters and Dependence of Globular Cluster Variable Star Properties on Chemical Composition

10.1017/s0252921100033571 ◽

1973 ◽

Vol 21 ◽

pp. 229-234

Author(s):

A. V. Mironov

Keyword(s):

Chemical Composition ◽

Globular Clusters ◽

Variable Star ◽

Variable Stars ◽

Type I ◽

Helium Abundance ◽

Type Ii ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

AbstractThe helium abundance Y in the envelopes of RR Lyrae stars in globular clusters has been estimated. The values of Y range from 0.07 to 0.59. The properties of variable stars in globular clusters of two types distinguished by a type of dependence of the horizontal branch form on the chemical composition are compared. The clusters of type I are shown to be on the average poorer in RR Lyrae stars than those of type II. The RR Lyrae stars in type I clusters are on the average brighter by 0.1 mag. It is found that as Y increases, the cluster richness in W Virginis variables decreases.

A Survey of Magellanic Cloud Clusters for RR Lyrae Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900039838 ◽

1984 ◽

Vol 108 ◽

pp. 37-38

Author(s):

J. A. Graham ◽

J. M. Nemec

Keyword(s):

Variable Stars ◽

Magellanic Cloud ◽

Magellanic Clouds ◽

The Other ◽

Rr Lyrae Stars ◽

Preliminary Results ◽

Rr Lyrae ◽

Other Hand ◽

Cloud Clusters ◽

Preliminary results are presented of a search for RR Lyrae variable stars in old clusters in the Magellanic Clouds. RR Lyraes have been found in NGC 1786 and NGC 2210. With the exceptions of NGC 339 (SMC) and NGC 2019 and Hodge 11 (LMC), all clusters classified as type VII by Searle, Wilkinson and Bagnuolo (1980) contain RR Lyrae variables. On the other hand, none have yet been found in clusters of type VI.