A Search for Variable Stars at the Galactic Center

1989 ◽  
pp. 487-492 ◽  
Author(s):  
Joseph W. Haller ◽  
Marcia J. Rieke
Keyword(s):  
Galactic Center ◽  
Variable Stars

scholarly journals A Search for Variable Stars at the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 487-492 ◽  
Author(s):  
Joseph W. Haller ◽  
Marcia J. Rieke
Keyword(s):  
Stellar Population ◽  
Galactic Center ◽  
Ccd Camera ◽  
Variable Stars ◽  
Detector Array ◽  
High Luminosity ◽  
Bolometric Luminosity ◽  
Long Period ◽  
Long Period Variables ◽  
K 13

A study of the Galactic Center stellar population is continuing with a sensitive 2μm CCD camera. Using a 64 × 64 detector array, background limited images are recorded with modest amounts of observing time (tobs ≈ 20 sec to reach K=13). Magnitudes have been extracted using DAOPHOT from repeated imaging of the central 5′ × 5′ to search among approximately 1500 stars for long period variables (LPV's, P > 200d), particularily Miras. Miras have a well defined period-luminosity relationship as well as one in period-mass. This program investigates the nature of highly luminous stars at the Galactic Center. Presently 12 variables have been found and have several characteristics consistent with Miras. They have a maximum bolometric luminosity of −4.4 mag, which supports the case that high luminosity stars in the central 6 pc are young supergiants.

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<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.

Variable stars in a galactic center field

1986 ◽  
Vol 92 ◽  
pp. 809 ◽  
Author(s):  
A. Terzan ◽  
A. F. Wehlau ◽  
W. H. Wehlau
Keyword(s):  
Galactic Center ◽  
Variable Stars

scholarly journals Absolute Proper Motions of Bulge Giants in the Hipparcos System

1998 ◽  
Vol 11 (1) ◽  
pp. 572-572
Author(s):  
D. Minniti ◽  
M.G. Lattanzi ◽  
J.J. Claria ◽  
G. Massone ◽  
R. Casalegno
Keyword(s):  
Galactic Center ◽  
Galactic Disk ◽  
Variable Stars ◽  
Minor Axis ◽  
Eclipsing Binaries ◽  
Proper Motions ◽  
Galactocentric Distance ◽  
Ccd Photometry ◽  
The Absolute ◽  
Red Clump

Three windows towards the Galactic bulge, located at (l, b) = (1.6,-2.8), (5.2,-3.5), and (4.2,-4.8), were identified from deep astrometric plates. Deep BVRI CCD photometry of these fields reaching V = 18.5 was obtained at the ESO Dutch telescope. The color-color and color magnitude diagrams of these fields allow us to select different bulge tracers, including blue horizontal branch stars, red clump giants, and RGB tip stars, as well as disk main-sequence stars. A first catalogue of some 2000 red clump giants was constructed, and measurement of their proper motions in under way. We are deriving absolute proper motions in the Hipparcos system using a two step procedure. First, plates from the Cordoba archive of the Astrographic Catalogue (epochs 1903-1913) are used in combination with recent plates from theESO GPO telescope to tie a set of intermediate magnitude field stars in the Hipparcos system of positions and proper motions. Second, deeper intermediate epoch (1958) and final epoch CCD images (epoch 1996.5) are used to determine the absolute proper motions of the fainter bulge stars. The average uncertainty in the absolute proper motion of a single giant, based on a preliminary sample of few tens of stars, is 0”.006 yr-1. This relatively small error, in combination with the sample size, would allow usto study the shape of the velocity ellipsoid for the different Galactic components present in the inner regions as function of Galactocentric distance, and also to measure an accurate distance to the Galactic center and the mass of the bulge. In addition, we identified about 20 faint objects which are potential members of the Sgr dwarf, based on their location in the color-magnitude diagrams, and are also measuring their proper motions. Other windows with measured proper motions are located along the Galactic minor axis, including Baade’s window at l, b = (1, −4) (Spaenhauer, A., Jones, B. F., &: Whitford, A. E., 1992, A3, 103, 297), and the Plaut field at l, b = (0, - 8 ) (Mendez, R. et al., 1997, in 4th ESO/CTIO Workshop on “The Galactic Center”, in press). Our proper motions are complementary, probing the kinematics off the Galactic minor axis, where the signature of rotation should be evident. The fields chosen for this study overlap fields that the MACHO project is following since 1993. Their variable star database would provide with excellent tracers of different populations. The 3-D motions of these different Galactic components would be measured for the first time. These include RR Lyrae tracers of the inner metal-poor halo, Miras, LPVs and delta Scuti stars tracers of the metal-rich bulge, and eclipsing binaries tracers of the Galactic disk (Minniti, D., et al., 1996, in IAP Coll. on “Variable Stars and the Astrophysical Returns of Microlensing Surveys”, ed. R. Ferlet, p. 257; Alcock, C, et al., 1997, astro-ph/9707311).

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 Variable stars in the Galactic center, as revealed by the VVV Survey

2017 ◽  
Vol 152 ◽  
pp. 01026
Author(s):  
Claudio Navarro Molina ◽  
Jura Borissova ◽  
Márcio Catelan ◽  
Radostin Kurtev ◽  
Nicolás Medina
Keyword(s):  
Galactic Center ◽  
Variable Stars

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.

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