scholarly journals The Lick Observatory Program on Proper Motions of RR Lyrae Stars

1971 ◽  
Vol 2 ◽  
pp. 790-791
Author(s):  
A. R. Klemola
Keyword(s):  
Proper Motions ◽  
Rr Lyrae Stars ◽  
Mean Error ◽  
Rr Lyrae ◽  
Star Catalogue ◽  
Homogeneous Set ◽  
The Mean ◽  
Year 2000 ◽  
Lyrae Stars

It is the purpose of this note to reveal the nature and progress of a long term astrometric program at the Lick Observatory (see references by S. Vasilevskis in Trans. Int. Astron. Union, XI B, 404, 1962). One of its many goals is the measurement of absolute proper motions of RR Lyrae stars with respect to faint galaxies. The first-epoch photographs, obtained in 1947-54 by Shane and Wirtanen for the sky north of declination – 23°, were supplemented later by plates of poorer quality down to –33° with the 20-in. astrograph. This means that first-epoch plates are now on hand which cover three-fourths of the sky and on which stars of 9-17 mag. may be measured for proper motions. Since these photographs represent the largest and most homogeneous set that will be available in the foreseeable future, we shall try to estimate the number of RR Lyrae stars which may be measured on them.As a guide we take the 1968 edition of the Russian Variable Star Catalogue, which contains a little over 4400 RR Lyrae stars. For the sky north of —33° nearly 2000 of these stars are brighter than average magnitude 17.0, 1000 brighter than 15.0, and about 350 brighter than 12.0. Experience with the Lick program shows that 80% of these stars should be measurable, after account is made for losses due to plate defects, blended images, and other factors.An important limitation to the usefulness of the measured motions is imposed by the size of the mean errors, which amount to 0.”7/century for an epoch difference of 20 yr. This mean error is the same size as the proper motion of a typical RR Lyrae star of 13.0 mag. But for an epoch difference of 50 yr the mean error drops to 0.”3/century, which is comparable to the motion of an RR Lyrae star of 15.0 mag. Useful results for the fainter RR Lyrae stars will not be possible until after a third epoch about the year 2000.

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.

scholarly journals Long-term photometric monitoring of Messier 5 variables - I. Period changes of RR Lyrae stars

2011 ◽  
Vol 411 (3) ◽  
pp. 1744-1762 ◽  
Author(s):  
B. Szeidl ◽  
Zs. Hurta ◽  
J. Jurcsik ◽  
C. Clement ◽  
M. Lovas
Keyword(s):  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Photometric Monitoring ◽  
Lyrae Stars

scholarly journals NGC 1261: A TIME-SERIES VI STUDY OF ITS VARIABLE STARS

2019 ◽  
Vol 55 (2) ◽  
pp. 337-350 ◽  
Author(s):  
A. Arellano Ferro ◽  
I. H. Bustos Fierro ◽  
J. H. Calderón ◽  
J. A. Ahumada
Keyword(s):  
Time Series ◽  
Variable Stars ◽  
Individual Values ◽  
Ccd Photometry ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Cluster Distance ◽  
The Mean ◽  
Lyrae Stars ◽  
Gaia Dr2

Time-series VI CCD photometry of the globular cluster NGC 1261 is employed to study its variable star population. A membership analysis of most variables based on Gaia DR2 proper motions and colours was performed prior to the estimation of the mean cluster distance and metallicity. The light curves of the member RR Lyrae were Fourier decomposed to calculate their individual values of distance, [Fe/H], radius and mass. The I band P-L for RR Lyrae stars was also employed. Our best estimates of the metallicity and distance of this Oo I cluster are [Fe/H]ZW =−1.42 ± 0.05 dex and d = 17.2 ± 0.4 kpc. No mixture of fundamental and first overtone RR Lyrae stars in the either-or or bimodal region is seen in this cluster, as it seems to be the rule for Oo I clusters with a red horizontal branch. A multi-approach search in a region of about 10' × 10' around the cluster revealed no new variable stars within the limitations of our CCD photometry.

scholarly journals Review of Observational Data on RR Lyrae Stars

1971 ◽  
Vol 2 ◽  
pp. 781-787
Author(s):  
G. van Herk
Keyword(s):  
Radial Velocity ◽  
Observational Data ◽  
Proper Motion ◽  
Point Of View ◽  
Proper Motions ◽  
Physical Point ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Complete Set ◽  
Lyrae Stars

The data on which my work on the secular parallaxes of RR Lyrae stars is based (Bull. Astron. Inst. Neth.18) were in many respects so incomplete that I have tried to interest astronomers to get a more complete set of data. The number of stars for which I had a proper motion was only 168, and for which a radial velocity was known, was 180, with an overlap of only 138 stars. The accuracy of the proper motions was certainly unsatisfactory for 43% of the total. The greatest trouble in dealing with such insufficient numbers arises when one wants to subdivide the material into groups which are homogeneous from a physical point of view. Many subdivisions, in making up my paper, were not tried at all, simply because the material was inadequate.In recent years plenty of work has been done by various investigators, of which I will at this point only mention the work on proper motions done at the Leander McCormick Observatory, and the great number of radial velocities determined by Dr. Clube and his associates. I do not, however, believe we are yet in a position to consider the whole subject as finished. Discussions about space motions, as given by Professor Oort in the book Stellar Structures, Volume V, will, at this time, be hardly improved upon. I still feel we should increase the number of stars substantially in order to get a better statistical discussion possible. This means we have to go to fainter stars. Plenty of these stars will be found on the plates which have served to make the Charts of the Carte du Ciel, which means we have at least one old position available for proper motions. At Leiden we are now engaged in the determination or redetermination of the proper motions of 430 RR Lyrae stars.

scholarly journals RR Lyrae in M15: Fourier Decomposition and Physical Parameters

2006 ◽  
Vol 2 (S240) ◽  
pp. 605-612
Author(s):  
G. García Lugo ◽  
A. Arellano Ferro ◽  
Patricia Rosenzweig
Keyword(s):  
Globular Clusters ◽  
Light Curves ◽  
Physical Parameters ◽  
Rr Lyrae Stars ◽  
Mean Values ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
The Mean ◽  
Lyrae Stars

AbstractThe V and R light curves for 30 RR Lyrae stars in M15 were used to calculate their physical parameters. The Blazhko effect, previously reported in V12, was not detected. The determined values of the iron content and distance of the cluster are: [Fe/H] = −1.98 ± 0.24 and d = 8.67 ± 0.41 kpc, respectively. The mean values of the physical parameters determined for the RR Lyrae stars place the cluster precisely into the sequences Oosterhoff type – metallicity and metallicity – effective temperature, valid for globular clusters.

scholarly journals Theory Of Multiperiodic RR Lyrae Stars

1976 ◽  
Vol 29 ◽  
pp. 153-165
Author(s):  
R. F. Stellingwerf
Keyword(s):  
Rr Lyrae Stars ◽  
Simultaneous Excitation ◽  
Rr Lyrae ◽  
Different Types ◽  
Blazhko Effect ◽  
The Subject ◽  
Lyrae Stars ◽  
Current Pulsation ◽  
Made In

The subject “Multiperiodic RR Lyrae Stars” encompasses two entirely different types of phenomena: 1) long-term modulation of amplitude known as the Blazhko-effect and 2) simultaneous excitation of several radial modes. In the first category the observational material is now quite extensive, but very little theoretical analysis has been undertaken. In the second case the results of pulsation theory are applicable, but only one such object has been found. Much progress in our understanding of RR Lyrae stars has been made in recent years, however, and many results do have a bearing on the present problem. Several excellent reviews of current pulsation theory are available (see Iben 1971c, or Cox 1974a,b). I will therefore restrict my comments to those results bearing directly on choice of mode for RR Lyrae stars.

scholarly journals The Absolute Magnitude Of RR Lyrae Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 580-580
Author(s):  
T. Tsujimoto ◽  
M. Miyamoto ◽  
Y. Yoshii
Keyword(s):  
Hubble Constant ◽  
Likelihood Estimation ◽  
Absolute Magnitude ◽  
Proper Motions ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Trigonometric Parallaxes ◽  
The Absolute ◽  
Age Of The Universe ◽  
Lyrae Stars

The present determination of the absolute magnitude .Mv(RR) of RR Lyrae stars is twofold, relying upon Hipparcos proper motions and trigonometric parallaxes separately. First, applying the statistical parallax method to the proper motions, we find < Mv(RR)>= 0.69 ± 0.10 for 99 halo RR Lyraes with <[Fe/H]> = -1.58. Second, applying the Lutz-Kelker correction to the RR Lyrae HIP95497 with the most accurately measured parallax, we obtain Mv(RR) = 0.57-0.74 at [Fe/H]=-1.6. Furthermore, allowing full use of low accuracy and negative parallaxes as well for 125 RR Lyraes with - 2.49≤[Fe/H]≤0.07, the maximum likelihood estimation yields the relation, Mv(RR)= (0.59±0.37)+(0.20±0.63)([Fe/H]+1.60), which formally agrees with the recent preferred relation. The same estimation yields again My (RR) = 0.65 ± 0.33 for the 99 halo RR Lyraes. Although the formal errors in the latter two estimates are rather large, all of the four results suggest the fainter absolute magnitude, My(RR)=0.6-0.7 at [Fe/H]=-1.6. The present results still provide the lower limit on the age of the universe which is inconsistent with a fiat, matter-dominated universe and current estimates of the Hubble constant.

scholarly journals Kinematics of RR Lyrae stars in the Galactic bulge with OGLE-IV and Gaia DR2

2020 ◽  
Vol 498 (4) ◽  
pp. 5629-5642
Author(s):  
Hangci Du ◽  
Shude Mao ◽  
E Athanassoula ◽  
Juntai Shen ◽  
Pawel Pietrukowicz
Keyword(s):  
Velocity Dispersion ◽  
Line Of Sight ◽  
Proper Motions ◽  
Galactic Bulge ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Halo Stars ◽  
Central Regions ◽  
Lyrae Stars ◽  
Gaia Dr2

ABSTRACT We analyse the kinematics and spatial distribution of 15 599 fundamental-mode RR Lyrae (RRL) stars in the Milky Way bulge by combining OGLE-IV photometric data and Gaia DR2 proper motions. We show that the longitudinal proper motions and the line-of-sight velocities can give similar results for the rotation in the Galactic central regions. The angular velocity of bulge RRLs is found to be around 35 km s−1 kpc−1, significantly smaller than that for the majority of bulge stars (50–60 km s−1 kpc−1); bulge RRLs have larger velocity dispersion (120–140 km s−1) than younger stars. The dependence of the kinematics of the bulge RRLs on their metallicities is shown by their rotation curves and spatial distributions. Metal-poor RRLs ([Fe/H]&lt;−1) show a smaller bar angle than metal-rich ones. We also find clues suggesting that RRLs in the bulge are not dominated by halo stars. These results might explain some previous conflicting results over bulge RRLs and help understand the chemodynamical evolution of the Galactic bulge.

scholarly journals Blazhko-type fundamental-mode RR Lyrae stars in the globular cluster M3

2019 ◽  
Vol 490 (1) ◽  
pp. 80-95 ◽  
Author(s):  
J Jurcsik
Keyword(s):  
Globular Cluster ◽  
Fundamental Mode ◽  
Stellar System ◽  
Relative Strength ◽  
Similar Distribution ◽  
Type I ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
The Mean ◽  
Lyrae Stars

ABSTRACT Blazhko stars from the extended BVIC time series of RRab stars in the globular cluster M3 are analysed. This is the largest sample of Blazhko stars with full details of their Blazhko properties in a homogeneous stellar system. Blazhko periods and light-curve solutions are determined/estimated for 83 fundamental-mode variables. The lack of phase modulation in Oosterhoff type II stars and the diminishing relative strength of the modulation in long-period Oosterhoff type I stars are regular tendencies found between the pulsation and modulation properties of Blazko stars. Similarly to previous results, no modulation of the longest-period stars is detected. The onset of modulation in a previously regular RRab star and the similar distribution of modulated and non-modulated stars imply that the modulation is a temporal property of RR Lyrae (RRL) stars, which may occur at any time in any RRab star except the coolest ones. Comparing the modulation periods in M3 and in other samples of Blazhko stars, the mean log(Pmod) value is found to depend on the metallicity of the system. The separation of temperature- and radius-change induced variations supports our previous finding that the photometric radius variation does not show any modulation. The pulsation-averaged mean brightness and temperature of Blazhko stars are found to be larger in the large-amplitude phase of the modulation than in the small-amplitude phase. The larger the amplitude of the modulation, the larger the changes of the mean parameters detected.

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