scholarly journals Double-Mode RR Lyrae Stars in IC 4499

1988 ◽  
Vol 126 ◽  
pp. 591-592
Author(s):  
Christine M. Clement ◽  
James M. Nemec ◽  
Robert J. Dickens ◽  
Elizabeth A. Bingham
Keyword(s):  
Zero Point ◽  
Distance Modulus ◽  
Type I ◽  
Rr Lyrae Stars ◽  
Average Mass ◽  
Rr Lyrae ◽  
Cluster Distance ◽  
Metal Abundances ◽  
The Mean ◽  
Lyrae Stars

Thirteen double-mode RR Lyrae (RRd) stars, with mean magnitudes c = 18.30 ± 0.10 and <V>c = 17.80 ± 0.15, have been identified in the variable-rich Oosterhoff type I globular cluster IC 4499. The stars have surprisingly uniform properties, and are considerably different from RRd stars found in Oo II systems. The mean first-overtone period (Fig.1) is <P1>=0.357d ± 0.005d (cf. <P1>=0.40d for Oo II RRd stars), and the mean ratio of the first-overtone period to the fundamental period is <P1/P0>= 0.7443 ± 0.0002. The mean double-mode pulsation mass for the 13 stars, using the King Ia (Y=0.279, Z=0.001) mass calibration, is 0.535 ± 0.003 M⊙. Such an average mass is 0.11 M⊙ smaller (i.e. ~17% smaller) than that for RRd stars found in Oo II systems, and possibly ~0.01 M⊙smaller than the mean mass for the two RRd stars in M3 (it is important to note that the zero point of these mass determinations is uncertain by at least 15%). The metal abundances for the RRd stars, and for the system of RR Lyrae stars as a whole, are found to be consistent with <[Fe/H]>=-1.38 ± 0.20, determined from δS spectroscopy. In the Peterson diagram (Fig.2), all known RRd stars now divide (apparently by mass) into two groups (split according to Oosterhoff type). With a reddening of EB-V=0.26 ± 0.03, the cluster distance modulus is (m-M)o=16.23m ± 0.23m.

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 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.

scholarly journals Revised Baade–Wesselink Analysis of RR Lyrae Stars

2000 ◽  
Vol 176 ◽  
pp. 176-181 ◽  
Author(s):  
Carla Cacciari ◽  
Gisella Clementini1 ◽  
Fiorella Castelli ◽  
Fabrizio Melandri
Keyword(s):  
Radial Velocity ◽  
Zero Point ◽  
Absolute Magnitude ◽  
Mean Value ◽  
Physical Parameters ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Proper Comparison ◽  
The Mean ◽  
Lyrae Stars

AbstractWe have applied the Baade–Wesselink method to two field RR Lyrae stars, i.e. SW And and RR Cet, and derived their distances and physical parameters. With respect to previous B–W analyses we have applied the following improvements: i) use of all sets of available data, after proper comparison for homogeneity and compatibility; ii) use of the most recent and accurate model atmospheres, with turbulent velocity Vturb = 4 km s−1 and the no-overshooting approximation, and comparison with other treatments of convection; iii) use of the instantaneous gravity along the pulsation cycle rather than the mean value; iv) comparison with modified radial velocity curves according to various assumptions on radial velocity gradients in the atmosphere; and v) careful reanalysis of the temperature scale. The main aim of this study is to evaluate the effect of the above items on the B–W results and verify whether any (or a combination) of them can possibly account for the discrepancy of the absolute magnitude zero-point with respect to other independent determinations.

scholarly journals The kinematics and zero point of the log P –〈MK〉 relation for galactic field RR Lyrae variables via statistical parallax

2004 ◽  
Vol 193 ◽  
pp. 128-132 ◽  
Author(s):  
A.K. Dambis ◽  
O.V. Vozyakova
Keyword(s):  
Zero Point ◽  
Log P ◽  
Distance Modulus ◽  
Proper Motions ◽  
Galactocentric Distance ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Solar Galactocentric Distance ◽  
Lyrae Stars ◽  
Maximum Likelihood Technique

AbstractThe kinematical parameters of the local field RR Lyrae population and the zero point of the log P –〈MK〉 relation for these variables are inferred by applying the statistical parallax (maximum-likelihood) technique to a sample of 379 RR Lyrae stars with known periods, radial-velocities, metallicities, K-band photometry, and absolute proper motions on the ICRS system. Hipparcos, Tycho-2, SPM, UCAC1 and NPM1 were used as the sources of proper motions. The K-band magnitudes were adopted from the 2MASS All-Sky Data Release. The parameters of the velocity distribution are found to be (U0 = −13 ± 9, V0 = −41 ± 7, W0 = −19±4) kms−1, (σU = 66±9, σV = 47±7, σW = 23±5) km s−1 and (U0 = −11±10, V0 = −224±8, W0 = −8±6) km s−1 (σU = 158±9, σV = 95±5, σW = 88±5) km s−1 for the thick-disk (the purest disk sample, 56 stars) and halo (the purest halo sample, 264 stars) objects, respectively. The zero point of the infrared PL relation of Jones et al. (1992 – based on the results obtained using the Baade-Wesselink method) is confirmed: we find 〈MK〉 = −2.33⋅log PF−0.89±0.09, which is only brighter than found using the Baade-Wesselink method (Jones et al. 1992). A conversion of the resulting log P –〈MK〉 relation to V-band luminosities yields the metallicity-luminosity relation 〈MV〉 = +1.12 + 0.18 ⋅ [Fe/H] ± 0.10. Our results imply a solar Galactocentric distance of R0 = 7.8±0.4 kpc and an LMC distance modulus of DMLMC = 18.17 ±0.10 (cluster RR Lyraes) or DMLMC = 18.10±0.10 (field RR Lyraes), thereby favoring the so-called short distance scale.

scholarly journals IR characteristics of Type II Cepheids in the LMC and in the Galaxy

1991 ◽  
Vol 148 ◽  
pp. 109-111
Author(s):  
C. David Laney
Keyword(s):  
Globular Clusters ◽  
Distance Modulus ◽  
Type I ◽  
Type Ii ◽  
Normal Type ◽  
Rr Lyrae Stars ◽  
Galactic Field ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Lyrae Stars

JHK observations have been obtained of Type II Cepheids in the LMC, in globular clusters, and in the galactic field. The P-L relations at J and H imply an LMC distance modulus consistent with Mv˜0.6 for RR Lyrae stars. Modest excesses at K are seen in some LMC objects. One previously reported LMC Type II Cepheid appears to be a Type I Cepheid, and two others are much redder in J-H than normal Type II Cepheids. HV11211 is a Type I Cepheid in the SMC.

scholarly journals Standard Galactic field RR Lyrae II: a Gaia DR2 calibration of the period–Wesenheit–metallicity relation

2019 ◽  
Vol 490 (3) ◽  
pp. 4254-4270 ◽  
Author(s):  
Jillian R Neeley ◽  
Massimo Marengo ◽  
Wendy L Freedman ◽  
Barry F Madore ◽  
Rachael L Beaton ◽  
...  
Keyword(s):  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Distance Modulus ◽  
Rr Lyrae Stars ◽  
Galactic Field ◽  
Rr Lyrae ◽  
Lyrae Stars ◽  
Distance Indicators ◽  
Made In

ABSTRACT RR Lyrae stars have long been popular standard candles, but significant advances in methodology and technology have been made in recent years to increase their precision as distance indicators. We present multiwavelength (optical UBVRcIc and Gaia G, BP, RP; near-infrared JHKs; mid-infrared [3.6], [4.5]) period–luminosity–metallicity (PLZ), period–Wesenheit–metallicity (PWZ) relations, calibrated using photometry obtained from the Carnegie RR Lyrae Program and parallaxes from the Gaia second data release for 55 Galactic field RR Lyrae stars. The metallicity slope, which has long been predicted by theoretical relations, can now be measured in all passbands. The scatter in the PLZ relations is on the order of 0.2 mag, and is still dominated by uncertainties in the parallaxes. As a consistency check of our PLZ relations, we also measure the distance modulus to the globular cluster M4, the Large Magellanic Cloud and the Small Magellanic Cloud, and our results are in excellent agreement with estimates from previous studies.

Metal abundances of RR Lyrae stars in globular clusters

1982 ◽  
Vol 261 ◽  
pp. 576 ◽  
Author(s):  
H. A. Smith ◽  
G. J. Perkins
Keyword(s):  
Globular Clusters ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Metal Abundances ◽  
Lyrae Stars

scholarly journals The Zero Point of Extinction toward Baade's Window from RR Lyrae Stars

1998 ◽  
Vol 494 (1) ◽  
pp. 396-399 ◽  
Author(s):  
C. Alcock ◽  
R. A. Allsman ◽  
D. R. Alves ◽  
T. S. Axelrod ◽  
A. C. Becker ◽  
...  
Keyword(s):  
Zero Point ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

scholarly journals GAIA PARALLAX ZERO POINT FROM RR LYRAE STARS

2017 ◽  
Vol 50 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Andrew Gould ◽  
Juna A. Kollmeier
Keyword(s):  
Zero Point ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Lyrae Stars

scholarly journals RR Lyrae Stars in the Newly Discovered Ultra-faint Dwarf Galaxy Centaurus I*

2021 ◽  
Vol 162 (6) ◽  
pp. 253
Author(s):  
C. E. Martínez-Vázquez ◽  
W. Cerny ◽  
A. K. Vivas ◽  
A. Drlica-Wagner ◽  
A. B. Pace ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Relative Rate ◽  
Distance Modulus ◽  
Rr Lyrae Stars ◽  
Full Sample ◽  
Rr Lyrae ◽  
The One ◽  
Lyrae Stars

Abstract We report the detection of three RR Lyrae (RRL) stars (two RRc and one RRab) in the ultra-faint dwarf (UFD) galaxy Centaurus I (Cen I) and two Milky Way (MW) δ Scuti/SX Phoenicis stars based on multi-epoch giz DECam observations. The two RRc stars are located within two times the half-light radius (r h ) of Cen I, while the RRab star (CenI-V3) is at ∼6 r h . The presence of three distant RRL stars clustered this tightly in space represents a 4.7σ excess relative to the smooth distribution of RRL in the Galactic halo. Using the newly detected RRL stars, we obtain a distance modulus to Cen I of μ 0 = 20.354 ± 0.002 mag (σ = 0.03 mag), a heliocentric distance of D ⊙ = 117.7 ± 0.1 kpc (σ = 1.6 kpc), with systematic errors of 0.07 mag and 4 kpc. The location of the Cen I RRL stars in the Bailey diagram is in agreement with other UFD galaxies (mainly Oosterhoff II). Finally, we study the relative rate of RRc+RRd (RRcd) stars (f cd) in UFD and classical dwarf galaxies. The full sample of MW dwarf galaxies gives a mean of f cd = 0.28. While several UFD galaxies, such as Cen I, present higher RRcd ratios, if we combine the RRL populations of all UFD galaxies, the RRcd ratio is similar to the one obtained for the classical dwarfs (f cd ∼ 0.3). Therefore, there is no evidence for a different fraction of RRcd stars in UFD and classical dwarf galaxies.

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