scholarly journals Pulsation Variables in the AF stars of the Case Low-Dispersion Survey

1993 ◽  
Vol 139 ◽  
pp. 340-348
Author(s):  
T.D. Kinman
Keyword(s):  
Main Sequence ◽  
Galactic Plane ◽  
Balmer Line ◽  
Rr Lyrae Stars ◽  
Photoelectric Photometry ◽  
Blue Stragglers ◽  
Rr Lyrae ◽  
Wide Range ◽  
Lyrae Stars ◽  
Low Dispersion

AbstractThe AF stars are those of spectral types A and F that have been discovered on objective-prism plates taken with the Burrell Schmidt in the Case Low-Dispersion Northern Sky Survey (Pesch and Sanduleak, 1983). In SA 57, this survey is complete to V = 16.5. In this field and also in the Lick Astrograph RR Lyrae survey field RR 7 (in the anticenter) the AF stars comprise (a) blue horizontal branch stars and RR Lyrae stars of the halo and (b) stars which have the higher surface gravities of main sequence stars. The two groups can be separated primarily by their differing Balmer jumps and Balmer line-widths. The latter group (which may well include blue stragglers of both Pop I and Pop II) extends some 10 kpc above the galactic plane and shows a wide range of metallicity. Photoelectric photometry of this AF star sample has allowed the detection field RR Lyrae stars of lower-amplitudes than could have been found by conventional blinking techniques; this has led to a significant increase in the number of RR Lyrae stars that are known in SA 57 and RR 7. The cooler main sequence and/or blue straggler AF stars lie in the zone of pulsational instability and one higher-amplitude δ-Scuti star was detected in field RR 7. It is suggested that these AF stars provide a good sample for studying the incidence of pulsation in the population of older stars that extends beyond the thin disk.

scholarly journals Convection during the formation of gaseous giants and stars

2006 ◽  
Vol 2 (S239) ◽  
pp. 211-216
Author(s):  
Günther Wuchterl
Keyword(s):  
System Of Equations ◽  
The Sun ◽  
Rr Lyrae Stars ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Rr Lyrae ◽  
Wide Range ◽  
Consistent Solution ◽  
Convection Model ◽  
Lyrae Stars

AbstractConvection theories for star and planet formation studies have to be (1) simple, to allow a self-consistent solution with other relevant processes, (2) time-dependent, because convection often starts in collapse-flows, and (3) robust, i.e. physically well-behaved under a wide range of conditions ranging from the quiet protoplanetary nebula to supercritical protostellar accretion-shocks with Mach-numbers of a few hundred. I describe how the equations of radiation fluid-dynamics can be augmented by a one-equation convection model in order to construct a system of equations that contains the Sun, brown dwarfs and planets as well as their nearly isothermal parent-clouds. The system of equations is calibrated to the Sun and tested by the solar convection zone and the pulsations of RR-Lyrae stars. I discuss the following applications: (1) star formation as the collapse of Bonnor-Ebert spheres of masses ranging from the stellar domain to the brown dwarf region, (2) the approach to the main sequence, (3) companion mass determinations for direct imaging searches for exoplanets, with GQ Lupi as an example, and (4) the formation of Pegasi-planets, and the “large core” exoplanet, HD 149 026, in particular.

Theoretical Problems of Beta Cephei Stars

1979 ◽  
Vol 46 ◽  
pp. 467-473
Author(s):  
Yoji Osaki
Keyword(s):  
Small Group ◽  
Spectral Type ◽  
Main Sequence ◽  
Massive Stars ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
M 10 ◽  
Classical Cepheids ◽  
Lyrae Stars

The Beta Cephei (or Beta Canis Majoris) stars are a small group of pulsating variables of early spectral type. There are some 20 “classical” β Cephei stars, and several new or suspected variables in this group. The classical β Cephei stars are confined in a narrow “instability strip” which lies about 1 mag above and nearly parallel to the zero-age main-sequence of massive stars (M~10-20 M⊙). They are thus located far away from other well-known pulsating variables such as classical Cepheids and RR Lyrae stars in the HR diagram.

Milky Way’s structure based on thousands of Cepheids and RR Lyrae stars from OGLE

2019 ◽  
Vol 14 (S353) ◽  
pp. 1-5
Author(s):  
Pawel Pietrukowicz
Keyword(s):  
Galactic Plane ◽  
Variable Stars ◽  
Thin Disk ◽  
Rr Lyrae Stars ◽  
Robust Detection ◽  
Rr Lyrae ◽  
Classical Cepheids ◽  
Type Variable ◽  
Lyrae Stars ◽  
Distance Indicators

AbstractClassical Cepheids and RR Lyrae-type variable stars are widely-used tracers of young (< 300 Myr) and old (> 10 Gyr) stellar populations, respectively. These stars also serve as distance indicators allowing for Galactic structure studies. Robust detection of pulsating variables requires precise and relatively frequent observations over several years. Recently, the OGLE survey has discovered nearly 1,300 new genuine classical Cepheids and 15,000 RR Lyrae stars along the southern Galactic plane. Here, we present the picture of the Milky Way’s thin disk drawn with the Cepheids and the view of the Galactic old population that emerges from the set of known RR Lyrae stars.

scholarly journals Physical parameters for RR Lyrae stars in the sdss filter system

2012 ◽  
Vol 8 (S289) ◽  
pp. 126-129 ◽  
Author(s):  
Márcio Catelan ◽  
Gabriel I. Torrealba ◽  
Claudio Cáceres ◽  
Horace A. Smith ◽  
Nathan De Lee ◽  
...  
Keyword(s):  
Physical Parameters ◽  
Photometric System ◽  
Rr Lyrae Stars ◽  
Filter System ◽  
Rr Lyrae ◽  
Wide Range ◽  
Lyrae Stars ◽  
Very High

AbstractWe present a calibration of the metallicity and physical parameters (temperature, luminosity, gravity, mass, radius) for RR Lyrae stars using the ugrizsdss photometric system. Our work is based on calculations of synthetic horizontal branches (HBs), fully taking into account evolutionary effects for a wide range in metallicities and HB morphologies. We provide analytical fits that are able to provide all quantities mentioned with very high (internal) precision, based solely on mean sdss magnitudes and colors.

scholarly journals The LMC Globular Cluster Hodge 11 (=SL 868)

1984 ◽  
Vol 108 ◽  
pp. 43-44
Author(s):  
L. L. Stryker ◽  
J. M. Nemec ◽  
J. E. Hesser ◽  
R.D. McClure
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Cluster ◽  
Open Clusters ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Lyrae Stars ◽  
Termination Point

The age of the star cluster H11 has been controversial for a number of years. The color-magnitude diagram (CMD) of Walker (1979) to V=21.5 was interpreted as an “…evolved main-sequence, whose termination point corresponds to an age of about 0.6 Gyr, but with a giant branch which is displaced blueward by about Δ (B-V)o=0.4 from the positions of the giant branches of open clusters of similar age in our Galaxy.” On the other hand, the integrated colors are similar to those of metal-poor globular clusters in the Galaxy (Freeman and Gascoigne 1977, and references therein), and “…incompatible with an age of say 0.3 Gyr.” Searle, Wilkinson and Bagnuolo (1980) classify it as Group VII, the oldest group. The system has no RR Lyrae stars (Graham and Nemec 1984).

scholarly journals Variable Stars and Evolution in Globular Clusters

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.

scholarly journals The Luminosities of Horizontal Branches and RR Lyrae Stars in Globular Clusters

2004 ◽  
Vol 193 ◽  
pp. 525-529 ◽  
Author(s):  
D.H. McNamara ◽  
M.B. Rose ◽  
P.J. Brown ◽  
D.I. Ketcheson ◽  
J.E. Maxwell ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Absolute Magnitude ◽  
Apparent Magnitude ◽  
Rr Lyrae Stars ◽  
Blue Stragglers ◽  
Rr Lyrae ◽  
The Absolute ◽  
The Difference ◽  
Absolute Magnitudes ◽  
Lyrae Stars

AbstractWe have utilized the latest stellar models of the Y2 (Yonsei-Yale) collaborators and color-magnitude diagrams of globular clusters to infer ages and absolute magnitudes of their horizontal branches (HB). The intrinsic (B – V) color indices of the turn-offs, of the globular clusters were used to find ages. For 47 clusters that appear to be coeval (within ±0.7 Gyr), we find an average age of 12.5 Gyr. We adopt this age and infer the absolute magnitudes of the turn-offs, from the clusters [Fe/H] values. The absolute magnitude of the horizontal branches or RR Lyrae stars are then determined from the difference between the apparent magnitudes of the horizontal branches (or RR Lyrae stars) and the apparent magnitude of the turn-offs, VTO. We conclude: 1) The slope of the MV(HB), [Fe/H] relation is ~0.3 for clusters with [Fe/H] values between —0.5 to —1.5. The relation has zero slope for [Fe/H] values smaller than −1.5. 2) For [Fe/H] < -1.3, the MV(HB) or MV values of RRLyrae stars are not only a function of [Fe/H], but the horizontal-branch type in the sense that the clusters with the blue horizontal branches have more luminous horizontal branches than clusters with red horizontal branches. The same results are found by inferring the luminosities of the HBs from pulsating blue stragglers.

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