Two-color CCD Photometry of Variable Stars in NGC 7006

Wehlau, Amelia; Slawson, Robert W.; Nemec, J. M.

doi:10.1086/300694

Cited by 26 publications

(15 citation statements)

References 12 publications

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“…4 that the majority of our RRab variables lie below the mean line for Oosterhoff type I clusters, as defined by the RRab stars in the globular cluster M3. A similar result is also found by Kaluzny et al (2000) for the cluster M5 and by Wehlau, Slawson & Nemec (1999) for the cluster NGC 7006. These results suggest that, while there is a clear correlation of Oosterhoff type with metallicity (see Table 4), within at least the Oosterhoff type I clusters there is an additional dependence of V amplitude at a given period upon metallicity, with the more metal‐rich stars having lower V amplitudes, i.e.…”

Section: Resultssupporting

confidence: 87%

The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362

Olech¹,

Kałużny²,

Thompson³

et al. 2001

Monthly Notices of the Royal Astronomical Society

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We present V‐ and B‐band charge‐coupled device (CCD) photometry of 35 RR Lyr stars in the Southern hemisphere globular cluster NGC 6362. Fourier decomposition of the light curves was used to estimate the basic properties of these variables. From the analysis of the RRc stars we obtain a mean mass M=0.531±0.014 M⊙, luminosity log L/L⊙=1.656±0.006, effective temperature Teff=7429±20 and helium abundance Y=0.292±0.002. The mean values of the absolute magnitude, metallicity (on Jurcsik's scale) and effective temperature for 14 RRab stars with ‘regular’ light curves are: MV=0.86±0.01,[Fe/H]=−0.93±0.04 and Teff=6555±25, respectively. From the B−V colours, periods and metallicities of the RRab stars we estimate the colour excess for NGC 6362 to be equal to E(B−V)=0.08±0.01. Using this value we derive the colours of the blue and red edges of the instability strip in NGC 6362 to be (B−V)BE0=0.17 and (B−V)RE0=0.43. From the relations between the Fourier coefficients of RRab and RRc stars and their absolute magnitudes we estimate the apparent distance modulus to NGC 6362 to be (m−M)V=14.46±0.10. From the mean value of log L/L⊙ of the RRc stars we obtain 14.59±0.03. The V‐band light curves of three of the RRc stars exhibit changes in amplitude of over 0.1 mag on the time‐scale of around one week. Near the radial first overtone frequency we find one or two peaks, which strongly suggests that these variables belong to the newly identified group of non‐radial pulsating RR Lyr stars.

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Section: Resultssupporting

confidence: 87%

The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362

Olech¹,

Kałużny²,

Thompson³

et al. 2001

Monthly Notices of the Royal Astronomical Society

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“…What is said for NGC 3201 can be repeated for NGC 7006, whose RR Lyrs show again a peaked period distribution (Wehlau, Slawson & Nemec 1999). Given the morphology of the HB, composed mainly by red and variable stars, the required per cent of helium‐enhanced objects is of about 27 per cent, Y up to about 0.27.…”

Section: The Peaked Period Distribution Of Rr Lyr Starsmentioning

confidence: 89%

The fraction of second generation stars in globular clusters from the analysis of the horizontal branch^★

D’Antona

Caloi

2008

Monthly Notices of the Royal Astronomical Society

158

128

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The majority of globular clusters show chemical inhomogeneities in the composition of their stars, apparently due to a second stellar generation in which the forming gas is enriched by hot‐CNO cycled material processed in stars belonging to a first stellar generation. Clearly this evidence prompts questions on the modalities of formation of globular clusters. An important preliminary input to any model for the formation of multiple generations is to determine which is today the relative number fraction of ‘normal’ and anomalous stars in each cluster. As it is very difficult to gather very large spectroscopic samples of globular cluster stars to achieve this result with good statistical significance, we propose to use the horizontal branch (HB). We assume that, whichever the progenitors of the second generation, the anomalies also include enhanced helium abundance. In fact, helium variations have been recently recognized to be able to explain several puzzling peculiarities (gaps, RR Lyr periods and period distribution, ratio of blue to red stars, blue tails) in HBs. We summarize previous results and extend the analysis in order to infer the percentage in number of the first and second generation in as many clusters as possible. We show that, with few exceptions, approximately 50 per cent or more of the stars belong to the second generation. In other cases, in which at first sight one would think of a simple stellar population, we give arguments and suggest that the stars might all belong to the second generation. We provide in the appendix a detailed discussion and new fits of the optical and ultraviolet data of NGC 2808, the classic example of a multiple helium populations cluster, consistently including a reproduction of the main‐sequence splittings and an examination of the problem of ‘blue hook’ stars. We also show a detailed fit of the totally blue HB of M13, one among the clusters that are possibly fully made up by second generation stars. We conclude that the formation of the second generation is a crucial event in the life of globular clusters. The problem of the initial mass function required to achieve the observed high fraction of second generation stars can be solved only if the initial cluster was much more massive than the present one and most of the first generation low‐mass stars have been preferentially lost. As shown by D'Ercole et al., by modelling the formation and dynamical evolution of the second generation, the mass loss due to the explosions of the Type II supernovae of the first generation may be the process responsible for triggering the expansion of the cluster, the stripping of its outer layers and the loss of most of the first generation low‐mass stars.

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“…Indeed, the RRab in UFDs tend to contribute significantly to the long-period tail of dSphs (see Figure 9 in Stetson et al 2014a). (Wehlau et al 1999), NGC 2257 (Walker 1993), and NGC 1466 (Walker 1992). The mean and the σ of the period distribution observed in dSphs (in bold in Table 1) does not increase when the RRab sample is almost doubled due to the inclusion of newly detected RRab stars (Peter B.…”

Section: The Missing Hasp Rrab In Dsphsmentioning

confidence: 96%

Weak Galactic Halo-Dwarf Spheroidal Connection From Rr Lyrae Stars

Fiorentino

Bono

Monelli

et al. 2014

ApJ

110

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Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=0ec17ef7-1d59-43a3-a011-961097dcc88f http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=0ec17ef7-1d59-43a3-a011-961097dcc88fThe Astrophysical Journal Letters, 798:L12 (6pp), 2015 January 1 doi:10.1088/2041-8205/798/1/L12 C 2015. The American Astronomical Society. All rights reserved. WEAK GALACTIC HALO-DWARF SPHEROIDAL CONNECTION FROM RR LYRAE STARS ABSTRACTWe discuss the role that dwarf galaxies may have played in the formation of the Galactic halo (Halo) using RR Lyrae stars (RRL) as tracers of their ancient stellar component. The comparison is performed using two observables (periods, luminosity amplitudes) that are reddening and distance independent. Fundamental mode RRL in 6 dwarf spheroidals (dSphs) and 11 ultra faint dwarf galaxies (∼1300) show a Gaussian period distribution well peaked around a mean period of Pab =0.610 ± 0.001 days (σ = 0.03). The Halo RRL (∼15,000) are characterized by a broader period distribution. The fundamental mode RRL in all the dSphs apart from Sagittarius are completely lacking in High Amplitude Short Period (HASP) variables, defined as those having P 0.48 days and A V 0.75 mag. Such variables are not uncommon in the Halo and among the globular clusters and massive dwarf irregulars. To further interpret this evidence, we considered 18 globulars covering a broad range in metallicity (−2.3 [Fe/H] −1.1) and hosting more than 35 RRL each. The metallicity turns out to be the main parameter, since only globulars more metal-rich than [Fe/H] ∼−1.5 host RRL in the HASP region. This finding suggests that dSphs similar to the surviving ones do not appear to be the major building-blocks of the Halo. Leading physical arguments suggest an extreme upper limit of ∼50% to their contribution. On the other hand, massive dwarfs hosting an old population with a broad metallicity distribution (Large Magellanic Cloud, Sagittarius) may have played a primary role in the formation of the Halo.

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Two-color CCD Photometry of Variable Stars in NGC 7006

Cited by 26 publications

References 12 publications

The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362

The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362

The fraction of second generation stars in globular clusters from the analysis of the horizontal branch^★

Weak Galactic Halo-Dwarf Spheroidal Connection From Rr Lyrae Stars

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Two-color CCD Photometry of Variable Stars in NGC 7006

Cited by 26 publications

References 12 publications

The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362

The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362

The fraction of second generation stars in globular clusters from the analysis of the horizontal branch★

Weak Galactic Halo-Dwarf Spheroidal Connection From Rr Lyrae Stars

Contact Info

Product

Resources

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The fraction of second generation stars in globular clusters from the analysis of the horizontal branch^★