scholarly journals RR Lyrae Variables in the Globular Cluster M55. The First Evidence for Nonradial Pulsations in RR Lyr Stars

2000 ◽  
Vol 176 ◽  
pp. 317-317 ◽  
Author(s):  
A. Olech ◽  
J. Kaluzny ◽  
I. B. Thompson ◽  
W. Pych ◽  
W. Krzemiński ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Dwarf Galaxy ◽  
Apparent Distance ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Present Sample ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
Color Excess

AbstractWe present the results of a photometric study of RR Lyrae variables in the field of the globular cluster M55. We have discovered nine new RR Lyrae stars, increasing the number of known variables in this cluster to 15 objects. Five of the newly discovered variables belong to Bailey type RRc and two to type RRab. Two background RRab stars are probable members of the Sagittarius dwarf galaxy. Fourier decomposition of the light curves was used to derive basic properties of the present sample of RR Lyrae variables. From an analysis of the RRc variables we obtain a mean mass of M = 0.53 ± 0.03 M⊙, luminosity log L = 1.75 ± 0.01 L⊙, Teff = 7193 ± 27 K, and helium abundance Y = 0.27 ± 0.01. We also derive the value of the color excess for M55 to be equal to E(B − V) = 0.11 ± 0.03. We estimate the values of the visual apparent distance moduli to be 13.65 ± 0.11 from RRab stars and 13.91 ± 0.08 from RRc stars. The light curves of three of the RRc variables exhibit changes in amplitude of over 0.1 mag on time scales of less than a week, rather short for the Blazhko effect, but with no evidence for another radial pulsational frequency. However, we do detect other periodicities which are clearly visible in the light curve after removing variations with the first overtone radial frequency. This is strong evidence for the presence of nonradial pulsations, a behavior common for 8 Scuti stars, but not yet observed among RR Lyr variables.

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 Theoretical UBVI Light Curves of Pulsating Stars

2000 ◽  
Vol 176 ◽  
pp. 334-337
Author(s):  
Michael U. Feuchtinger ◽  
Ernst A. Dorfi
Keyword(s):  
Radiative Transfer ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Fourier Decomposition ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Stellar Pulsation ◽  
Sample Application ◽  
Lyrae Stars ◽  
Good Agreement

AbstractBy performing detailed frequency-dependent radiative transfer computations we are able to calculate light curves in particular bandpasses from stellar pulsation models calculated by the Vienna nonlinear convective pulsation code. As a sample application we discuss UBVI light curves of RR Lyrae stars. The properties of these light curves are analyzed by means of standard Fourier decomposition, and a comparison to recent observations is performed. As main results we find a good agreement with important observed RR Lyrae properties like pulsation amplitudes and Fourier parameters in B, V, and I bands. Additionally, from the synthetic color curves we derive linear transformation laws between amplitudes as well as Fourier parameters in the different bandpasses.

scholarly journals CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

2020 ◽  
Vol 494 (3) ◽  
pp. 3212-3226 ◽  
Author(s):  
M A Yepez ◽  
A Arellano Ferro ◽  
D Deras
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Star ◽  
Variable Stars ◽  
Frequency Spectra ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
New Variables ◽  
Gaia Dr2

ABSTRACT We present an analysis of VI CCD time-series photometry of the Oo II type globular cluster M92. The variable star population of the cluster is studied with the aim of revising their classifications, identifications, frequency spectra, and to select indicators of the parental cluster metallicity and distance. The Fourier decomposition of RR Lyrae light curves lead to the estimation of mean [Fe/H]spec = −2.20 ± 0.18 and distance of 8.3 ± 0.2 kpc. Four new variables are reported: one RRd (V40), a multimode SX Phe (V41), an SR (V42), and one RRc (F1) that is most likely not a cluster member. The AC nature of V7 is confirmed. The double mode nature of the RRc star V11 is not confirmed and its amplitude modulations are most likely due to the Blazhko effect. Two modes are found in the known RRc variable V13. It is argued that the variable V30, previously classified as RRab is, in fact, a BL Her-type star not belonging to the cluster. Using the Gaia-DR2 proper motions, we identified 5012 stars in the field of the cluster, which are very likely cluster members, and for which we possess photometry, enabling the production of a refined colour–magnitude diagram. This also allowed us to identify a few variable stars that do not belong to the cluster. The RR Lyrae pulsation modes on the HB are cleanly separated by the first overtone red edge, a common feature in all Oo II-type clusters.

scholarly journals Possible Evolutionary Interpretation of the Dependences on the Diagrams for RR Lyrae Variables

1973 ◽  
Vol 21 ◽  
pp. 207-213
Author(s):  
V. P. Goranskij
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxy ◽  
Light Curves ◽  
Maximum Magnitude ◽  
Long Period ◽  
Rr Lyrae ◽  
Short Period ◽  
Magnitude Diagram ◽  
Blazhko Effect ◽  
Evolutionary Interpretation

The separation of RRab variables into two sequences on the amplitude-period diagram was found by Belserene (1954) for globular cluster variables, and by Detre (1965) for field variables. It is significant that the sequence of short period variables is steeper on this diagram than that for stars of longer period. Szeidl (1965) pointed out that other characteristics of the light curves and photometric quantities such as the asymmetry of light curve ε, mean color index B—V, median magnitude mmed, maximum magnitude mmax are also separated into distinct sequences. Figures 1, 2 and 3 show these sequences on the colour-magnitude, colour-period, period-amplitude (or period-maximum magnitude, minimum magnitude) diagrams for RRab variables in the globular clusters M3, ω Cen and in the dwarf galaxy in Draco. On these figures RRab variables of the long period sequence are marked by crosses. The colour-magnitude and colour-period diagrams for M3 were obtained by Roberts and Sandage (1955); the period-maximum magnitude, minimum magnitude diagram obtained by Szeidl (1965) is constructed for stars measured by Roberts and Sandage. To get the most accurate F-magnitudes and colour indices for variables in ω Cen the data of Dickens and Saunders (1965) and Geyer and Szeidl (1970) have been averaged. The diagrams for RR Lyr variables in the Draco system were obtained by Baade and Swope (1961). The variables which show the Blazhko effect were excluded.

scholarly journals Double-mode RR lyrae stars in the Draco dwarf galaxy and in other stellar systems

1984 ◽  
Vol 105 ◽  
pp. 465-466 ◽  
Author(s):  
James M. Nemec
Keyword(s):  
Dwarf Galaxy ◽  
Mass Loss Rate ◽  
The Other ◽  
Mode Switching ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Period Shift ◽  
Blazhko Effect ◽  
Metal Abundance ◽  
Lyrae Stars

Eleven double-mode (dm) RR Lyrae stars, with periods midway between the periods for the c-type and ab-type RR Lyrae stars, have been identified in the Draco dwarf galaxy by reanalyzing the photometry of Baade and Swope (1961) for 35 stars. The stars are V11, 72, 75, 83, 112, 138, 143, 156, 165, 169 and 190, three of which previously were noted as dm RR Lyraes by Goranskij (1982). The methods of Stellingwerf (1978) and Stobie (1970) were used to find the periods. The period ratios, periods and amplitudes suggest that the stars radially pulsate simultaneously in the fundamental and first overtone modes. The beat masses, estimated from the P1/P0 vs. P0 diagram (Petersen 1973), using as calibration the King Ia (Y=0.299, Z=0.001) models of Cox, Hodson and Clancy (1983, hereafter CHC), are Mbeat/Mo=0.65 for nine stars, = 0.60 for V75 and = 0.55 for V165. If the mass loss rate prior to arriving on the horizontal branch is proportional to the metal abundance (Stobie 1971, CHC), V75 and V165 should be more metal rich than the other nine dm RR Lyraes. In the period-amplitude (P-A) diagram, at a given amplitude, V165 has a smaller period shift relative to the standard M3 line than do the higher mass stars. Subsequently, the correlations of Preston (1959) and Sandage (1982) suggest that it is more metal-rich than the other nine dm RR Lyrae stars in Draco. Furthermore, reanalysis of the P-A and period-mean magnitude relations of all the RR Lyrae stars in Draco shows evidence for a widespread range in the metal abundances. Stars with large period shifts relative to the M3 relation are found to be more luminous than stars with smaller period shifts. The frequency of variable amplitude (ie. Blazhko effect) RR Lyrae stars is greatest for the ab-type stars with short periods. The brightnesses of the highest maxima appear to fit the P-A relation, and the amplitudes of the lowest maxima are variable, with V123 being an extreme example. Figure 3 of Szeidl (1975) shows the analogous situation for M3 RR Lyrae stars with the Blazhko effect. These findings suggest that the amplitude variability is related to the mode-switching activity of the dm RR Lyrae stars.

scholarly journals The Impact of Observing Strategy on the Reliable Classification of Standard Candle Stars: Detection of Amplitude, Period, and Phase Modulation (Blazhko Effect) of RR Lyrae Stars with LSST

2021 ◽  
Vol 258 (1) ◽  
pp. 4
Author(s):  
Nina Hernitschek ◽  
Keivan G. Stassun
Keyword(s):  
Phase Modulation ◽  
Variable Stars ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Standard Candle ◽  
Blazhko Effect ◽  
The Impact ◽  
Lyrae Stars

Abstract The Vera C. Rubin Observatory will carry out its Legacy Survey of Space and Time (LSST) with a single-exposure depth of r ∼ 24.7 and an anticipated baseline of 10 yr, allowing access to the Milky Way’s old halo not only deeper than, but also with a longer baseline and better cadence than, e.g., PS1 3π. This will make the LSST ideal to study populations of variable stars such as RR Lyrae stars (RRL). Here, we address the question of observing strategy optimization of LSST, as survey footprint definition, single-visit exposure time, as well as the cadence of repeat visits in different filters are yet to be finalized. We present metrics used to assess the impact of different observing strategies on the reliable detectability and classification of standard candle variable stars, including detection of amplitude, period, and phase modulation effects of RRL (the so-called Blazhko effect), by evaluating metrics for simulated potential survey designs. So far, due to the depths and cadences of typical all-sky surveys, it has been nearly impossible to study this effect on a larger sample. All-sky surveys with relatively few observations over a moderately long baseline allow only for fitting phase-folded RRL light curves, thus integrating over the complete survey length and hiding any information regarding possible period or phase modulation during the survey. On the other hand, surveys with cadences fit to detect slightly changing light curves usually have a relatively small footprint. LSST’s survey strategy, however, will allow for studying variable stars in a way that makes population studies possible.

scholarly journals Fourier Decomposition Parameters for the Halo RR Lyrae Variables U and V Caeli

1985 ◽  
Vol 82 ◽  
pp. 272-275
Author(s):  
L. Hansen ◽  
J. O. Petersen
Keyword(s):  
Light Curve ◽  
Light Curves ◽  
Published Data ◽  
Amplitude Ratios ◽  
Rr Lyrae Stars ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Lyrae Stars ◽  
Phase Differences

AbstractUBVRI light curves are obtained for the two halo RR Lyrae variables U Caeli with period 0.420 days (73 observations) and V Caeli with period 0.571 days (42 observations). It is shown that their light curve characteristics are very similar to those of field RR Lyrae stars.Fourier decompositions are studied for all five magnitudes and the resulting amplitude ratios and phase differences are discussed. The differences in the Fourier decomposition parameters between the five magnitudes are shown to be relatively small. Comparisons of the Fourier decomposition parameters for the two halo RR Lyrae stars with recently published data for field RR Lyrae stars show no systematic differences.

scholarly journals RR Lyrae variables in globular clusters and nearby galaxies

2004 ◽  
Vol 193 ◽  
pp. 113-123
Author(s):  
M. Catelan
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Galactic Halo ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Nearby Galaxies ◽  
Lyrae Stars

AbstractI point out that the Oosterhoff dichotomy for globular cluster and field RR Lyrae stars may place the strongest constraints so far on the number of dwarf spheroidal-like protogalactic fragments that may have contributed to the formation of the Galactic halo. The first calibration of the RR Lyrae period-luminosity relation in I, J, H, K taking evolutionary effects into account is provided. Problems in the interpretation of RR Lyrae light curves and evolutionary properties are briefly reviewed.

scholarly journals The Blazhko Effect in RR Lyrae

1993 ◽  
Vol 139 ◽  
pp. 410-418
Author(s):  
Terry J. Teays
Keyword(s):  
Light Curves ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
International Ultraviolet Explorer ◽  
Blazhko Effect ◽  
Low Dispersion ◽  
Range Of Values ◽  
Pulsation Cycle ◽  
Visual Light

AbstractThe cause of the Blazhko effect, the long-term modulation of the light and radial velocity curves of some RR Lyr stars, is still not understood. The observational characteristics of the Blazhko effect are discussed in §1. Some preliminary results are presented from aomw recent of campaigns to observe RR Lyr, using the International Ultraviolet Explorer along with ground-based spectroscopy and photometry, throughout a pulsation cycle, at a variety of Blazhko phases. A set of ultraviolet light curves have been generated from low dispersion IUE spectra. In addition, the (visual) light curves from IUE's Fine Error Sensor are analyzed using the Fourier decomposition technique. The values of the parameters ϕ21 and R21 at different Blazhko phasas of RR Lyr span the range of values found for non-Blazhko variables of similar period.

scholarly journals Comparison of the Pulsation Properties of the Rr Lyrae Stars in ω Centauri with those of Classical Cepheids

1985 ◽  
Vol 82 ◽  
pp. 276-279
Author(s):  
J. O. Petersen
Keyword(s):  
Quantitative Description ◽  
Light Curves ◽  
Powerful Method ◽  
Amplitude Ratios ◽  
Rr Lyrae Stars ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Classical Cepheids ◽  
Lyrae Stars ◽  
Phase Differences

In the last few years several studies have shown that Fourier decomposition technique is a powerful method for quantitative description of light curves of pulsation variables. This technique was introduced by Simon & Lee (1981), who showed that amplitude ratios and phase differences provide a very useful description of the Hertzsprung progression for classical Cepheids. Recently, Simon & Teays (1982) discussed 70 RR Lyrae field stars.In the present study I analyse 130 photographic mean light curves of RR Lyrae variables in ω Centauri taken from Martin (1938). I wish (i) to compare the Fourier decomposition parameters of the ω Cen RR Lyrae stars with those of the field variables as studied by Simon & Teays, (ii) to discuss the evidence for progression sequences among the ω Cen variables and (iii) to compare the basic pulsation properties of the RRab variables in ω Cen with those of classical Cepheids.

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