scholarly journals The Distribution of Field Horizontal–Branch Stars in the Galactic Halo

1977 ◽  
Vol 4 (2) ◽  
pp. 73-74
Author(s):  
A. G. Davis Philip
Keyword(s):  
Density Distribution ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Horizontal Branch ◽  
Schmidt Telescope ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
General Program ◽  
Objective Prism

Since the time allowed per paper at this joint discussion is short only one aspect of the stellar distribution at high galactic latitudes will be presented here, namely the distribution of field horizontal-branch stars (FHB) in the galactic halo. First, the method by which FHB stars are found will be described. Second, the density distribution of FHB stars will be compared with that of the RR Lyrae stars.As part of a general program to study the stellar density distribution perpendicular to the galactic plane a number of possible FHB stars has been discovered. In each survey area objective prism plates (at a dispersion of 280 Å/mm. to a limiting magnitude of V = 14) are taken with the Michigan Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory or the Schmidt telescope at the Warner and Swasey Observatory. A set of direct plates are taken also to obtain photographic magnitudes for the stars with spectral classifications.

scholarly journals Period Changes of RR Lyrae Stars in the LMC Globular Cluster NGC 2257

1984 ◽  
Vol 108 ◽  
pp. 39-40 ◽  
Author(s):  
James M. Nemec ◽  
Martha H. Liller ◽  
James E. Hesser
Keyword(s):  
Physical Properties ◽  
Globular Cluster ◽  
Period Change ◽  
Stellar Systems ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Lyrae Stars

The period changes of RR Lyrae stars can be compared with models of horizontal branch stars as a means of investigating the physical properties of the stars themselves, and of the stellar systems in which they are found (Smith and Sandage 1981). The present study is the first in which period change rates of extragalactic RR Lyraes have been estimated.

scholarly journals Search for RR Lyrae stars in DES ultrafaint systems: Grus I, Kim 2, Phoenix II, and Grus II

2019 ◽  
Vol 490 (2) ◽  
pp. 2183-2199 ◽  
Author(s):  
C E Martínez-Vázquez ◽  
A K Vivas ◽  
M Gurevich ◽  
A R Walker ◽  
M McCarthy ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Dark Energy Survey ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
Lyrae Stars ◽  
Energy Survey ◽  
D 43

ABSTRACT This work presents the first search for RR Lyrae stars (RRLs) in four of the ultrafaint systems imaged by the Dark Energy Survey using SOAR/Goodman and Blanco/DECam imagers. We have detected two RRLs in the field of Grus I, none in Kim 2, one in Phoenix II, and four in Grus II. With the detection of these stars, we accurately determine the distance moduli for these ultrafaint dwarf satellite galaxies; μ0 = 20.51 ± 0.10 mag (D⊙ = 127 ± 6 kpc) for Grus I and μ0 = 20.01 ± 0.10 mag (D⊙ = 100 ± 5 kpc) for Phoenix II. These measurements are larger than previous estimations by Koposov et al. and Bechtol et al., implying larger physical sizes; 5 per cent for Grus I and 33 per cent for Phoenix II. For Grus II, of the four RRLs detected, one is consistent with being a member of the galactic halo (D⊙ = 24 ± 1 kpc, μ0 = 16.86 ± 0.10 mag), another is at D⊙ = 55 ± 2 kpc (μ0 = 18.71 ± 0.10 mag), which we associate with Grus II, and the two remaining at D⊙ = 43 ± 2 kpc (μ0 = 18.17 ± 0.10 mag). Moreover, the appearance of a subtle red horizontal branch in the colour–magnitude diagram of Grus II at the same brightness level of the latter two RRLs, which are at the same distance and in the same region, suggests that a more metal-rich system may be located in front of Grus II. The most plausible scenario is the association of these stars with the Chenab/Orphan Stream. Finally, we performed a comprehensive and updated analysis of the number of RRLs in dwarf galaxies. This allows us to predict that the method of finding new ultrafaint dwarf galaxies using two or more clumped RRLs will work only for systems brighter than MV ∼ −6 mag.

scholarly journals Carbon Stars in the SMC

1994 ◽  
Vol 161 ◽  
pp. 513-515 ◽  
Author(s):  
D.H. Morgan ◽  
D. Hatzidimitriou
Keyword(s):  
Spatial Distribution ◽  
Horizontal Branch ◽  
Carbon Stars ◽  
Schmidt Telescope ◽  
Horizontal Branch Stars ◽  
Objective Prism

More than 1000 new carbon stars have been identified in a ∼200 deg2 area of the SMC during a survey of UK Schmidt Telescope objective-prism plates. Their spatial distribution is like that of the red horizontal branch stars.

scholarly journals Two-Color Observations of RR Lyrae Stars in M14

1973 ◽  
Vol 21 ◽  
pp. 95-100
Author(s):  
Amelia Wehlau ◽  
Nicholas Potts
Keyword(s):  
Variable Star ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Magnitude Diagram ◽  
Lyrae Stars ◽  
Photographic Photometry

AbstractTwo-color photographic photometry has been carried out on RR Lyrae variables in M14. The position of these variables in the color-magnitude diagram is shown, and it is noted that there is a lack of horizontal branch stars to the red of the variable star gap. Color-amplitude, period-amplitude and color-period relations for the RR Lyrae variables measured are shown.

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

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 ◽  
Lyrae Stars

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.

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 results on field and cluster RR Lyraes

1993 ◽  
Vol 139 ◽  
pp. 335-336
Author(s):  
G. Clementini ◽  
R. Merighi ◽  
M. Tosi ◽  
R. Gratton ◽  
E. Carretta
Keyword(s):  
High Resolution ◽  
Horizontal Branch ◽  
Chemical Abundance ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
The Galaxy ◽  
Metal Abundance ◽  
Lyrae Stars ◽  
Good Agreement

AbstractRR Lyrae stars both in the field and in clusters can be used to derive the metal abundance of the regions and systems where they are found.(1) New data have been collected on a sample of field ab-type RR Lyraes with the aim of studying the composition of the halo and the disk of the galaxy, (Clementini et al. 1992a, in preparation), using the relation found by Clementini et al. (1991), (hereafter CTM91), between [Fe/H] and the equivalent width of the Ca II K-line W‘(K). (2) A quantitative chemical abundance analysis of the ab type RR Lyrae (V29) in the globular cluster M4 has been performed using high resolution, high S/N spectroscopy. We obtain [Fe/H]=–1.3 ± 0.2 and the α– elements (Mg and Ti) are overabundant by 0.6 dex. These results are in good agreement with determinations from high resolution spectra of giants and blue horizontal branch stars (Clementini et al. 1992b, in preparation).

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