scholarly journals Fourier Coefficients of OGLE Variables

2000 ◽  
Vol 176 ◽  
pp. 275-275
Author(s):  
Siobahn Morgan ◽  
Melanie Simet ◽  
Stephanie Bargenquast ◽  
Chris Dickerson
Keyword(s):  
Globular Clusters ◽  
Fourier Coefficients ◽  
Galactic Center ◽  
Variable Stars ◽  
Physical Characteristics ◽  
Rr Lyrae ◽  
Made In

AbstractFourier coefficients for the variable stars in the OGLE survey of the Galactic Center and several globular clusters are presented. The characteristics of the RR Lyrae, δ Scuti and SX Phe stars are presented and a comparison to those observed in other studies is made. In some cases the coefficients of the stars can be used to determine distances and the physical characteristics of the variables.

scholarly journals Search for variable stars in globular clusters

1986 ◽  
Vol 118 ◽  
pp. 287-288
Author(s):  
M. L. Hazen-Liller
Keyword(s):  
Globular Clusters ◽  
Galactic Center ◽  
Variable Stars ◽  
Galactic Bulge ◽  
Rr Lyrae ◽  
High Metallicity

A program to search poorly studied southern globular clusters for variable stars is being carried out on the 1-m Yale telescope at CTIO. Recently two galactic bulge clusters of moderately high metallicity have been found to contain RR Lyrae variables; a cluster of similar metallicity a little farther from the galactic center apparently has none.

scholarly journals General Properties of the Two Groups of Globular Clusters and Their Variable Stars

1975 ◽  
Vol 67 ◽  
pp. 541-543
Author(s):  
A. V. Mironov ◽  
N. N. Samus'
Keyword(s):  
Chemical Composition ◽  
Globular Clusters ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
General Properties ◽  
Rr Lyrae ◽  
Lyrae Stars

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.

scholarly journals CCD Observations of Variable Stars in Globular Clusters

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.

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

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 ◽  
Lyrae Stars

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.

scholarly journals RR Lyrae variables in Baade's window

1979 ◽  
Vol 84 ◽  
pp. 201-202
Author(s):  
B. Blanco ◽  
V. M. Blanco
Keyword(s):  
Southern Hemisphere ◽  
Galactic Center ◽  
Variable Stars ◽  
Zenith Distance ◽  
Rr Lyrae ◽  
Pioneer Study ◽  
New Variables

In his pioneer study of the RR Lyrae variable stars near NGC 6522, in the relatively unobscured window close to the galactic center (1 = 0.9, b = −3.9), Baade (1963) was limited by the high zenith distance of the galactic center as seen from Palomar, and suggested that southern hemisphere observations would be of value. Subsequent studies of the region have been based on the variables found in Baade's original search. Southern hemisphere plates were taken by Hartwick et al. (1972), and their re-analysis of a sample of Baade's variables showed many periods to be in error. They did not, however, search the plates for new variables. Plaut (1973) re-analyzed all the variables but no search for new variables was done.

scholarly journals RR Lyrae stars as probes of the Milky Way structure and formation

2015 ◽  
Vol 11 (S317) ◽  
pp. 116-119
Author(s):  
Pawel Pietrukowicz ◽  
Keyword(s):  
Galactic Center ◽  
Variable Stars ◽  
Wide Field ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
The Galaxy ◽  
First Results ◽  
Formation And Evolution ◽  
Lyrae Stars ◽  
Distance Indicators

AbstractRR Lyrae stars being distance indicators and tracers of old population serve as excellent probes of the structure, formation, and evolution of our Galaxy. Thousands of them are being discovered in ongoing wide-field surveys. The OGLE project conducts the Galaxy Variability Survey with the aim to detect and analyze variable stars, in particular of RRab type, toward the Galactic bulge and disk, covering a total area of 3000 deg2. Observations in these directions also allow detecting background halo variables and unique studies of their properties and distribution at distances from the Galactic Center to even 40 kpc. In this contribution, we present the first results on the spatial distribution of the observed RRab stars, their metallicity distribution, the presence of multiple populations, and relations with the old bulge. We also show the most recent results from the analysis of RR Lyrae stars of the Sgr dwarf spheroidal galaxy, including its center, the globular cluster M54.

scholarly journals RR Lyrae Variable Stars and the Distance Scale

1978 ◽  
Vol 80 ◽  
pp. 53-57
Author(s):  
S. V. M. Clube ◽  
J. A. Dawe
Keyword(s):  
Galactic Halo ◽  
Galactic Center ◽  
Variable Stars ◽  
Magellanic Clouds ◽  
Solar Neighborhood ◽  
Royal Greenwich Observatory ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars ◽  
Kinematical Parameters

A statistical parallax algorithm (Clube and Dave, 1978a,b), using the technique of maximum likelihood, has been applied to a set of 103 ‘ab’ - RR Lyrae stars in the solar neighborhood (r 2&lt;kpc), using observational data from the Royal Greenwich Observatory Bulletins. A second set of 130 ‘ab’ - RR Lyrae stars has been kindly supplied to us by Dr. A. Heck (Université de Liège) to permit a comparison between our analyses. The purpose of this investigation was:(a) to investigate the variations of kinematical parameters and absolute luminosities of these stars as functions of Preston's index ΔS and of log (Period).(b) to identify those RR Lyrae stars in the solar neighborhood which most closely resemble those in the galactic halo, those near the galactic center, and those in the Magellanic Clouds.

scholarly journals A Study of Double- and Multi-mode RR Lyrae Variables

2015 ◽  
Vol 24 (4) ◽  
Author(s):  
A. V. Khruslov
Keyword(s):  
Globular Clusters ◽  
Variable Stars ◽  
B Stars ◽  
Galactic Field ◽  
Rr Lyrae ◽  
Period Distribution ◽  
Evolution Stage ◽  
Multi Mode ◽  
Radial Pulsations

AbstractWe present the results of our new study of known RR Lyrae variable stars. All observations available for these stars in the Catalina Surveys were analyzed, and double-mode variations were identified. We studied the Petersen diagram and the period distribution for the double-mode RR Lyrae variables in the Galactic field, pulsating in the first-overtone and fundamental modes. The double-peaked character of the period distribution was detected for Galactic RR(B) stars, corresponding to Oosterhoff’s classes of globular clusters, which indicates that the age and evolution stage of RR(B) stars in the field and RR Lyrae variables in globular clusters are probably the same. Besides, we discovered five RRC stars with two simultaneously excited non-radial pulsations (equidistant triplets).

scholarly journals RR Lyrae Stars and Novae in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 207-215 ◽  
Author(s):  
J. A. Graham
Keyword(s):  
Variable Stars ◽  
Magellanic Clouds ◽  
Rr Lyrae Stars ◽  
Entire Area ◽  
Classical Novae ◽  
Rr Lyrae ◽  
Cloud Clusters ◽  
Large Numbers ◽  
Lyrae Stars ◽  
Made In

RR Lyrae variable stars and classical novae can be used very effectively for locating and studying the old stellar populations in the Magellanic Clouds. RR Lyrae stars are found in large numbers in both Clouds at about 19m. Apart from the concentrated searches within Cloud clusters, intensive surveys for field variables have so far been made in four areas, each about 1° square. Novae have the advantage of being as bright as 10m at maximum light. They can be detected with small telescopes and surveys have covered almost the entire area of each Cloud. Needs and prospects for future surveys are discussed. Both types of object are suitable for investigating the early chemical composition of the Clouds and its subsequent enrichment with heavy elements. Studies of the old populations in the Clouds are reinforcing the view that, while some stars in the Magellanic Clouds are as old as any in our Galaxy, the major bursts of star formation came along comparatively recently.

scholarly journals Oscillations of HB Red Variable Stars

1998 ◽  
Vol 185 ◽  
pp. 401-402
Author(s):  
D.R. Xiong ◽  
Q. L. Cheng ◽  
L. Deng
Keyword(s):  
Globular Clusters ◽  
Turbulent Viscosity ◽  
Variable Stars ◽  
Instability Strip ◽  
Rr Lyrae ◽  
Short Period ◽  
Spatial Oscillations ◽  
The Right ◽  
Thermodynamic Coupling ◽  
Low Amplitude

Using a nonlocal time-dependent theory of convection, we have calculated the linear non-adiabatic oscillations of the Horizontal Branch (HB) stars, with both the dynamic and thermodynamic coupling between convection and oscillations been carefully treated. Turbulent pressure and turbulent viscosity have been included consistently in our equations of non-adiabatic pulsation. When the coupling between convection and oscillations is ignored, for all models with Te ≤ 7350K, the fundamental through the second overtone are pulsationally unstable; while for Te ≤ 6200K all the models are unstable up to (at least) the 9th overtone. When the coupling between convection and oscillations is included, the RR Lyrae instability strip is very well predicted. Within the strip most models are pulsationally unstable only for the fundamental and the first few overtones. Turbulent viscosity is an important damping mechanism. Being exclusively distinct from the luminous red variables (long period variables), the HB stars to the right of the RR Lyrae strip are pulsationally stable for the fundamental and low-order overtones, but become unstable for some of the high-order overtones. This may provide a valuable clue for the short period, low amplitude red variables found outside the red edge of the RR Lyrae strip on the H-R diagram of globular clusters. Moreover, we present a new radiation modulated excitation mechanism functioning in radiation flux gradient regions. The effects of nonlocal convection and the dynamic coupling between convection and oscillations are discussed. The spatial oscillations of the thermal variables in the pulsational calculations have been effectively suppressed.

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