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 CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

2020 ◽  
Vol 494 (3) ◽  
pp. 3212-3226 ◽  
Author(s):  
M A Yepez ◽  
A Arellano Ferro ◽  
D Deras
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Star ◽  
Variable Stars ◽  
Frequency Spectra ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
New Variables ◽  
Gaia Dr2

ABSTRACT We present an analysis of VI CCD time-series photometry of the Oo II type globular cluster M92. The variable star population of the cluster is studied with the aim of revising their classifications, identifications, frequency spectra, and to select indicators of the parental cluster metallicity and distance. The Fourier decomposition of RR Lyrae light curves lead to the estimation of mean [Fe/H]spec = −2.20 ± 0.18 and distance of 8.3 ± 0.2 kpc. Four new variables are reported: one RRd (V40), a multimode SX Phe (V41), an SR (V42), and one RRc (F1) that is most likely not a cluster member. The AC nature of V7 is confirmed. The double mode nature of the RRc star V11 is not confirmed and its amplitude modulations are most likely due to the Blazhko effect. Two modes are found in the known RRc variable V13. It is argued that the variable V30, previously classified as RRab is, in fact, a BL Her-type star not belonging to the cluster. Using the Gaia-DR2 proper motions, we identified 5012 stars in the field of the cluster, which are very likely cluster members, and for which we possess photometry, enabling the production of a refined colour–magnitude diagram. This also allowed us to identify a few variable stars that do not belong to the cluster. The RR Lyrae pulsation modes on the HB are cleanly separated by the first overtone red edge, a common feature in all Oo II-type clusters.

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<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 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 Near-Field Cosmology with RR Lyrae Variable Stars: A First View of Substructure in the Southern Sky

2015 ◽  
Vol 11 (S317) ◽  
pp. 338-339 ◽  
Author(s):  
C. Navarrete ◽  
S. Duffau ◽  
A. K. Vivas ◽  
M. Catelan ◽  
G. Hajdu ◽  
...  
Keyword(s):  
Real Time ◽  
Southern Hemisphere ◽  
Near Field ◽  
Variable Stars ◽  
Radial Velocities ◽  
Current Status ◽  
Low Resolution ◽  
Rr Lyrae ◽  
The Individual

AbstractWe present the current status of the spectroscopic follow-up of a large number of RR Lyrae (RRL) halo overdensity candidates recently found by Torrealba et al. (2015) using southern-hemisphere data from the Catalina Real-time Transient Survey (CRTS). Characterizing the individual RRL stars in these overdensities is crucial to confirm them as real halo substructures. Low-resolution spectra have been obtained for RRL stars in 11 different overdensities, using the SOAR and Magellan telescopes. Radial velocities and metallicities have been derived so far for 123 and 99 RRL stars, respectively.

scholarly journals The galactic distance scale

1979 ◽  
Vol 84 ◽  
pp. 195-200 ◽  
Author(s):  
J. A. Graham
Keyword(s):  
Recent Work ◽  
Galactic Center ◽  
Variable Stars ◽  
Distance Scale ◽  
Rr Lyrae ◽  
A Value ◽  
The Galaxy ◽  
Distance Indicators

Recent work on the distance scale of the Galaxy has largely been in the direction of refining previously established methods. The RR Lyrae variable stars appear to be better distance indicators than was once thought and they have been used in determining Ro, the distance to the Galactic center. Ro is probably somewhat less than 10 kpc but greater than 7 kpc. Most methods point to a value near 8.5 kpc.

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 The Variable Stars in NGC 6723

1973 ◽  
Vol 21 ◽  
pp. 178-179
Author(s):  
John Menzies
Keyword(s):  
Southern Hemisphere ◽  
Globular Cluster ◽  
Variable Stars ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Magnitude Diagram ◽  
The Mean ◽  
Lyrae Stars

Abstract*.A study has been made of the variables in the Southern Hemisphere globular cluster NGC 6723, which is suspected of being relatively metal-rich on the basis of its colour-magnitude diagram and of its integrated spectral type of G3. Seven new RR Lyrae stars and two bright red, probably semiregular, variables have been found and the suspected variable of Fourcade and Laborde has been confirmed. The complement of RR Lyrae stars is now 27, consisting of 4 c-type and 23 ab-type variables, the mean periods being Pc = 0.d292 and Pab = 0.d537. On the basis of the two-colour diagram of the horizontal branch stars the cluster is considered to be virtually un-reddened. Applying Christy’s models to the data from this study we find the following parameters for the variables: Mv= 1.m10, mass = 0.42 M⊙, and Y=0.4.

scholarly journals New type II Cepheids from VVV data towards the Galactic center

2019 ◽  
Vol 625 ◽  
pp. A151 ◽  
Author(s):  
V. F. Braga ◽  
R. Contreras Ramos ◽  
D. Minniti ◽  
C. E. Ferreira Lopes ◽  
M. Catelan ◽  
...  
Keyword(s):  
Near Infrared ◽  
Galactic Center ◽  
Variable Stars ◽  
Type Ii ◽  
Statistical Parameters ◽  
Rr Lyrae ◽  
Classical Cepheids ◽  
Starting Point ◽  
The Galaxy ◽  
New Type

Context. The Galactic center (GC) is the densest region of the Milky Way. Variability surveys towards the GC potentially provide the largest number of variable stars per square degree within the Galaxy. However, high stellar density is also a drawback due to blending. Moreover, the GC is affected by extreme reddening, therefore near infrared observations are needed. Aims. We plan to detect new variable stars towards the GC, focusing on type II Cepheids (T2Cs) which have the advantage of being brighter than RR Lyrae stars. Methods. We perform parallel Lomb-Scargle and Generalized Lomb-Scargle periodogram analysis of the Ks-band time series of the VISTA variables in the Vía Láctea survey, to detect periodicities. We employ statistical parameters to clean our sample. We take account of periods, light amplitudes, distances, and proper motions to provide a classification of the candidate variables. Results. We detected 1019 periodic variable stars, of which 164 are T2Cs, 210 are Miras and 3 are classical Cepheids. We also found the first anomalous Cepheid in this region. We compare their photometric properties with overlapping catalogs and discuss their properties on the color-magnitude and Bailey diagrams. Conclusions. We present the most extensive catalog of T2Cs in the GC region to date. Offsets in E(J − Ks) and in the reddening law cause very large (∼1–2 kpc) uncertainties on distances in this region. We provide a catalog which will be the starting point for future spectroscopic surveys in the innermost regions of the Galaxy.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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