Period change rates for 46 RR Lyrae stars in NGC 7006

Wehlau, Amelia; Nemec, J. M.; Hanlan, Patricia C.; Rich, R. Michael

doi:10.1086/116171

Cited by 17 publications

(8 citation statements)

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“…Lee (1991) has argued that published period changes for the RR Lyrae stars in the five clusters, M3, NGC 6934, M5, M15, and w Cerilauri support this hypothesis. A recent study of 46 RR Lyrae variables in NGC 7006 (Wehlau et al 1992) indicates that the period changes in this cluster deviate somewhat from Lee's predicted relationship, but not enough to be considered in conflict with his models. Unfortunately, the existing data for M68 are not suitable for testing Lee's theory.…”

Section: Fourier Decomposition Of the Light Curvesmentioning

confidence: 64%

The RR Lyrae variables in the globular cluster M68

Clement¹,

Ferance

Simon³

1993

ApJ

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New observations, made with the Helen Sawyer Hogg telescope at Las Campanas, have been analyzed in a search for double-mode pulsators (RRd stars) in the metal-poor globular cluster, Messier 68. Of the 30 stars studied, nine have been identified as RRd stars; V33, which exhibited the characteristics of an RRd star in 1950, now appears to be an RRc star. Reliable periods and period ratios have been determined for six of the RRd stars. Masses for these RRd stars, calculated from fitting formulas given by Kovacs, Buchler, & Marom, range from 0.75 to 0.90 M 0' depending on the assumed luminosity and metal abundance. These masses are in the same range as those for the RRd stars in M15, whose RRd sample resembles that of M68 very closely. Fourier parameters determined for the light curves of the M68 variables show that the RRc stars in the two clusters are also very similar. In particular, on the plot of phase parameter

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Section: Fourier Decomposition Of the Light Curvesmentioning

confidence: 64%

The RR Lyrae variables in the globular cluster M68

Clement¹,

Ferance

Simon³

1993

ApJ

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“…Jurcsik et al 2001). Thought to be driven by horizontal branch evolution, these pulsation period changes are typically monotonic and of order 1 d per 0.1 GYr (Wehlau et al 1992). However, there are cases in which the variation is more chaotic and on a faster time‐scale (Jurcsik et al 2001), so we must address this mechanism.…”

Section: Discussionmentioning

confidence: 99%

Long-term properties of accretion discs in X-ray binaries -- I. The variable third period in SMC X-1

Clarkson

Charles

Coe

et al. 2003

Monthly Notices of the Royal Astronomical Society

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Long‐term X‐ray monitoring data from the Rossi X‐Ray Timing Explorer (RXTE) All‐Sky Monitor (ASM) and the Compton Gamma Ray Observatory (CGRO) Burst And Transient Source Experiment (BATSE) reveal that the third (superorbital) period in SMC X‐1 is not constant, but varies between 40 and 60 d. A dynamic power spectrum analysis indicates that the third period has been present continuously throughout the five years of ASM observations. This period changed smoothly from 60 to 45 d and then returned to its former value, on a time‐scale of approximately 1600 d. During the nearly 4 yr of overlap between the CGRO and RXTE missions, the simultaneous BATSE hard X‐ray data confirm and extend this variation in SMC X‐1. Our discovery of such an instability in the superorbital period of SMC X‐1 is interpreted in the context of recent theoretical studies of warped, precessing accretion discs. We find that the behaviour of SMC X‐1 is consistent with a radiation‐driven warping model.

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“…Period change studies have been conducted for RR Lyrae stars in a number of the Milky Way's globular clusters, with some clusters being studied several times as more data became available. Though a complete listing of such studies is beyond the scope of this review, we note recent studies for the Milky Way globular clusters M3 (Jurcsik et al 2012), M5 (Szeidl et al 2011), ω Cen (Jurcsik et al 2001), M15 (Silbermann & Smith 1995;Barlai & Szeidl 1995), NGC 4147 (Stetson et al 2005), NGC 5053 (Nemec 2004), NGC 7006 (Wehlau et al 1992), and IC4499 (Kunder et al 2011).…”

Section: Period Changes In Globular Cluster Rr Lyraementioning

confidence: 99%

Period Changes of Mira Variables, RR Lyrae Stars, and Type II Cepheids

Smith

2013

Preprint

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Mira variables, RR Lyrae variables, and type II Cepheids all represent evolved states of low-mass stars, and long term observations have revealed that changes in pulsation period occur for each of these classes of variable. Most Mira variables show small or no period changes, but a few show large period changes that can plausibly be associated with thermal pulses on the asymptotic red giant branch. Individual RR Lyrae stars show period changes that do not accord with the predictions of stellar evolution theory. This may be especially true for RR Lyrae stars that exhibit the Blazhko effect. However, the average period changes of all of the RR Lyrae variables within a globular cluster prove a better but still imperfect match for the predictions of evolutionary theory. The observed period changes of short period type II Cepheids (BL Her stars) as well as those of long period type II Cepheids (W Vir stars) are in broad agreement with the rates of period changes expected from their evolutionary motions through the instability strip.

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Period change rates for 46 RR Lyrae stars in NGC 7006

Cited by 17 publications

References 0 publications

The RR Lyrae variables in the globular cluster M68

The RR Lyrae variables in the globular cluster M68

Long-term properties of accretion discs in X-ray binaries -- I. The variable third period in SMC X-1

Period Changes of Mira Variables, RR Lyrae Stars, and Type II Cepheids

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