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 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 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 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 Detailed study of the Milky Way globular cluster Laevens 3

2019 ◽  
Vol 490 (2) ◽  
pp. 1498-1508
Author(s):  
Nicolas Longeard ◽  
Nicolas Martin ◽  
Rodrigo A Ibata ◽  
Michelle L M Collins ◽  
Benjamin P M Laevens ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
Mass Segregation ◽  
Stellar Properties ◽  
Lyrae Stars ◽  
Gaia Dr2

ABSTRACT We present a photometric and spectroscopic study of the Milky Way satellite Laevens 3. Using MegaCam/Canada–France–Hawaii Telescope $g$ and $i$ photometry and Keck II/DEIMOS multi-object spectroscopy, we refine the structural and stellar properties of the system. The Laevens 3 colour–magnitude diagram shows that it is quite metal-poor, old ($13.0 \pm 1.0$ Gyr), and at a distance of $61.4 \pm 1.0$ kpc, partly based on two RR Lyrae stars. The system is faint ($M_V = -2.8^{+0.2}_{-0.3}$ mag) and compact ($r_h = 11.4 \pm 1.0$ pc). From the spectroscopy, we constrain the systemic metallicity (${\rm [Fe/H]}_\mathrm{spectro} = -1.8 \pm 0.1$ dex) but the metallicity and velocity dispersions are both unresolved. Using Gaia DR2, we infer a mean proper motion of $(\mu _\alpha ^*,\mu _\delta)=(0.51 \pm 0.28,-0.83 \pm 0.27)$ mas yr−1, which, combined with the system’s radial velocity ($\langle v_r\rangle = -70.2 \pm 0.5 {\rm \, km \,\, s^{-1}}$), translates into a halo orbit with a pericenter and apocenter of $40.7 ^{+5.6}_{-14.7}$ and $85.6^{+17.2}_{-5.9}$ kpc, respectively. Overall, Laevens 3 shares the typical properties of the Milky Way’s outer halo globular clusters. Furthermore, we find that this system shows signs of mass segregation that strengthens our conclusion that Laevens 3 is a globular cluster.

scholarly journals Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

2019 ◽  
Vol 623 ◽  
pp. A116 ◽  
Author(s):  
Pierre Kervella ◽  
Alexandre Gallenne ◽  
Nancy Remage Evans ◽  
Laszlo Szabados ◽  
Frédéric Arenou ◽  
...  
Keyword(s):  
Proper Motion ◽  
Binary Systems ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
Orbital Parameters ◽  
Rr Lyrae ◽  
Multiple Stars ◽  
Classical Cepheids ◽  
The Mean ◽  
Lyrae Stars

Context. Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, to date only one RRL has convincingly been demonstrated to be a binary, TU UMa, out of tens of thousands of known RRLs. Aims. Our aim is to detect the binary and multiple stars present in a sample of Milky Way CCs and RRLs. Methods. In the present article, we combine the HIPPARCOS and Gaia DR2 positions to determine the mean proper motion of the targets, and we search for proper motion anomalies (PMa) caused by close-in orbiting companions. Results. We identify 57 CC binaries from PMa out of 254 tested stars and 75 additional candidates, confirming the high binary fraction of these massive stars. For 28 binary CCs, we determine the companion mass by combining their spectroscopic orbital parameters and astrometric PMa. We detect 13 RRLs showing a significant PMa out of 198 tested stars, and 61 additional candidates. Conclusions. We determine that the binary fraction of CCs is likely above 80%, while that of RRLs is at least 7%. The newly detected systems will be useful to improve our understanding of their evolutionary states. The discovery of a significant number of RRLs in binary systems also resolves the long-standing mystery of their extremely low apparent binary fraction.

STRucture and Evolution of the GAlaxy (STREGA): The case of Pal 3

2019 ◽  
Vol 14 (S351) ◽  
pp. 478-481
Author(s):  
M. I. Moretti ◽  
I. Musella ◽  
M. Marconi ◽  
V. Ripepi ◽  
R. Molinaro
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
North East ◽  
The North ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Lyrae Stars ◽  
Candidate Variable

AbstractIn the context of the STRucture and Evolution of the GAlaxy survey, we describe the preliminary results obtained for the fields around the globular cluster Pal 3 (about 2.75 square degrees), by exploiting the obtained g, r, i time series photometry. The final aim is to use variable stars as tools to verify and study the presence of streams around Pal 3. We found 20 candidate variable stars of which 7 RR Lyrae stars possibly belonging to Pal 3, also at large distance from the center. The distribution of the candidate RR Lyrae seems to confirm a preferential distribution in the north-east direction, confirming previous results in literature.

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 Optical and Near-infrared Pulsation Properties of RR Lyrae and Population II Cepheid Variables in the Messier 15 Globular Cluster

2021 ◽  
Vol 922 (1) ◽  
pp. 20
Author(s):  
Anupam Bhardwaj ◽  
Marina Rejkuba ◽  
G. C. Sloan ◽  
Marcella Marconi ◽  
Soung-Chul Yang
Keyword(s):  
Globular Cluster ◽  
Near Infrared ◽  
Variable Stars ◽  
Log P ◽  
Distance Modulus ◽  
Distance Measurements ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Cepheid Variables ◽  
Lyrae Stars

Abstract Messier 15 (NGC 7078) is an old and metal-poor post core-collapse globular cluster that hosts a rich population of variable stars. We report new optical (gi) and near-infrared (NIR, JK s ) multi-epoch observations for 129 RR Lyrae, 4 Population II Cepheids (3 BL Herculis, 1 W Virginis), and 1 anomalous Cepheid variable candidate in M15 obtained using the MegaCam and the WIRCam instruments on the 3.6 m Canada–France–Hawaii Telescope. Multi-band data are used to improve the periods and classification of variable stars, and determine accurate mean magnitudes and pulsational amplitudes from the light curves fitted with optical and NIR templates. We derive optical and NIR period–luminosity relations for RR Lyrae stars which are best constrained in the K s band, m K s = − 2.333 ( 0.054 ) log P + 13.948 ( 0.015 ) with a scatter of only 0.037 mag. Theoretical and empirical calibrations of RR Lyrae period–luminosity–metallicity relations are used to derive a true distance modulus to M15: 15.196 ± 0.026 (statistical) ± 0.039 (systematic) mag. Our precise distance moduli based on RR Lyrae stars and Population II Cepheid variables are mutually consistent and agree with recent distance measurements in the literature based on Gaia parallaxes and other independent methods.

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