[ITAL]Hubble Space Telescope[/ITAL] Ultraviolet Observations of the Cores of M3 and M13

Ferraro, F. R.; Paltrinieri, B.; Pecci, F. Fusi; Cacciari, C.; Dorman, Ben; Rood, Robert T.

doi:10.1086/310780

Cited by 95 publications

(119 citation statements)

References 24 publications

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“…1.ÈColor-magnitude diagrams for the Oosterho † II cluster M2 (LC99) and the Oosterho † I cluster M3 (Ferraro et al 1997 ;Carretta et al 1998 the CMD Ðtting into three sections : from the RGB tip to the base of the RGB, the base of the RGB to the upper main sequence, and the upper main sequence to the lower main sequence. We included 0.5 mag in overlap for the three Ðtting regions to ensure continuity.…”

Section: M2 (Ngc 7089)mentioning

confidence: 99%

“…We excluded Blazhko variables (V2, V16, V17, V21, LC184, LC456, and LC798) Ferraro et al (1997) obtained BV I CCD photometry of M3 using the 3.6 m Canada-France-Hawaii telescope and they presented the CMD in their Figure 5, combined with the recalibrated older photographic study of Buonanno et al (1994). We reproduce their CMD in Figure 1b of this paper.…”

Section: M2 (Ngc 7089)mentioning

confidence: 99%

“…Carretta et al (1998) presented new BV I CCD photometry of 60 RR Lyrae variables in M3. As they noted, their photometric calibration is tied directly to that of Ferraro et al (1997). In order to construct our database for M3 RRab variables, we examined the light curves given by .…”

Section: M2 (Ngc 7089)mentioning

confidence: 99%

“…By interpolating the Ðducial sequences of M2 and M3, we obtain mag for (B[V ) 0,g \ 0.78^0.03 M2 and 0.78^0.02 mag for M3. Using the relation given by Ferraro et al (1997) [ 0,g scale obtained by Carretta & Gratton (1997). Using their new relation Zinn & West (1984).…”

Section: The Index Is the Dereddened (B[v ) Color Of (B[v )mentioning

confidence: 99%

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RR Lyrae Luminosity Differences between Oosterhoff Group I and II Cluster Systems and the Origin of the Oosterhoff Dichotomy

Lee

Carney

1999

The Astronomical Journal

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We present a comparative study of the Oosterho † II cluster M2 and the Oosterho † I cluster M3. Both have similar metallicities, [Fe/H] \ [1.62 for M2 and [1.66 for M3, but very di †erent horizontal-branch (HB) morphologies (B[R)/(B ] V ] R) \ 0.92 for M2 and 0.08 for M3. A period shift analysis and main-sequence Ðtting show that RRab variables in M2 are about 0.2 mag brighter than those in M3. Comparisons of the M2 period shift with Oosterho † I clusters NGC 3201 and NGC 7006 also yield similar results, while a comparison between M2 and the Oosterho † II cluster NGC 5986 reveals that the RR Lyrae luminosities are very similar. The luminosity di †erence is thought to be due to the evolutionary e †ect described in 1990 by Lee, Demarque, & Zinn : the M2 RRab variables have evolved away from the zero-age horizontal branch (ZAHB), while most M3 RRab variables lie near the ZAHB. A comparison of the mean period change rates of two clusters supports this hypothesis. Our relative age estimation using the di †erence in color between the base of giant branch and turn-o † point shows that M2 is about 2 Gyr older than M3. Our result strongly suggests that the Oosterho † dichotomy is due to age di †erences between Oosterho † group I and II. This is consistent with the idea that the global second parameter is age.We discuss the kinematic di †erences between Oosterho † group I and II clusters. Our result shows that the Oosterho † group I clusters have zero or retrograde rotation with km s~1 and Sv rot T \ [68^56 km s~1, while the Oosterho † group II clusters have prograde rotation with p los \ 131^28 Sv rot T \ ]94^47 km s~1 and km s~1, conÐrming a similar conclusion of van den Bergh. The p los \ 115^29 di †erence in kinematics and ages between Oosterho † group I and II clusters suggests that they may have di †erent origins : The Oosterho † II clusters were formed very early in the proto-Galaxy while the Oosterho † I clusters were formed at di †erent locations and at a later time, and were probably merger events. The period distributions of an unbiased sample of Ðeld RRab variables with kpc and Â Z Â ¹ 3 ÂZ Â º 5 kpc indicate that they may belong to di †erent populations, with peak periods of 0.65 and 0.55 days, respectively. If the hypothesis that the Oosterho † dichotomy is due to evolution is correct, then this period shift among the Ðeld RR Lyrae variables suggests that the RRab population with kpc is Â Z Â ¹ 3 somewhat older than the RRab population with kpc. This also suggests di †erent formation his-Â Z Â º 5 tories.In an appendix, we discuss that the frequently used Gaussian HB mass-dispersion rate (i.e., the massloss rate at the red giant branch [RGB] tip) in synthetic HB model calculations cannot fully explain the extended blue HB population and the pulsational properties of RR Lyrae variables in M2. Comparisons with synthetic HB models strongly suggests that an enhanced mass loss is required that extends the HB toward lower HB masses. We also discuss statistical e †ects on the metallicity estimate using for ...

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Section: M2 (Ngc 7089)mentioning

confidence: 99%

Section: M2 (Ngc 7089)mentioning

confidence: 99%

Section: M2 (Ngc 7089)mentioning

confidence: 99%

Section: The Index Is the Dereddened (B[v ) Color Of (B[v )mentioning

confidence: 99%

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RR Lyrae Luminosity Differences between Oosterhoff Group I and II Cluster Systems and the Origin of the Oosterhoff Dichotomy

Lee

Carney

1999

The Astronomical Journal

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“…This problem has been widely debated until the present date, but without reaching a consensus (e.g. Catelan & de Freitas Pacheco 1993;Lee et al 1994;Stetson et al 1996;Sarajedini et al 1997;Ferraro et al 1997;Catelan 2009a;Dotter et al 2010;Gratton et al 2010, and references therein). A&A 547, A5 (2012) between ∼11 500 and ∼8000 K for detecting the initial helium abundance in HB stars.…”

Section: Introductionmentioning

confidence: 99%

Effects of helium enrichment in globular clusters

Valcarce

Catelan

Sweigart

2012

A&A

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Aims. Recently, the study of globular cluster (GC) color−magnitude diagrams (CMDs) has shown that some of them harbor multiple populations with different chemical compositions and/or ages. In the first case, the most common candidate is a spread in the initial helium abundance, but this quantity is difficult to determine spectroscopically due to the fact that helium absorption lines are not present in cooler stars, whereas for hotter GC stars gravitational settling of helium becomes important. As a consequence, indirect methods to determine the initial helium abundance among populations are necessary. For that reason, in this series of papers, we investigate the effects of a helium enrichment in populations covering the range of GC metallicities. Methods. In this first paper, we present the theoretical evolutionary tracks, isochrones, and zero-age horizontal branch (ZAHB) loci calculated with the Princeton-Goddard-PUC (PGPUC) stellar evolutionary code, which has been updated with the most recent input physics and compared with other theoretical databases. The chemical composition grid covers 9 metallicities ranging from Z = 1.60 × 10 −4 to 1.57 × 10 −2 (−2.25 < ∼ [Fe/H] < ∼ −0.25), 7 helium abundances from Y = 0.230 to 0.370, and an alpha-element enhancement of [α/Fe] = 0.3. Results. The effects of different helium abundances that can be observed in isochrones are: splits in the main sequence (MS), differences in the luminosity (L) and effective temperature (T eff ) of the turn off point, splits in the sub giant branch being more prominent for lower ages or higher metallicities, splits in the lower red giant branch (RGB) being more prominent for higher ages or higher metallicities, differences in L of the RGB bump (with small changes in T eff ), and differences in L at the RGB tip. At the ZAHB, when Y is increased there is an increase of L for low T eff , which is affected in different degrees depending on the age of the GC being studied. Finally, the ZAHB morphology distribution depending on the age explains how for higher GC metallicities a population with higher helium abundance could be hidden at the red ZAHB locus.

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Tracing the History of the Galaxy with Globular Clusters

Fenaro

Astrophysics and Space Science Library

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[ITAL]Hubble Space Telescope[/ITAL] Ultraviolet Observations of the Cores of M3 and M13

Cited by 95 publications

References 24 publications

RR Lyrae Luminosity Differences between Oosterhoff Group I and II Cluster Systems and the Origin of the Oosterhoff Dichotomy

RR Lyrae Luminosity Differences between Oosterhoff Group I and II Cluster Systems and the Origin of the Oosterhoff Dichotomy

Effects of helium enrichment in globular clusters

Tracing the History of the Galaxy with Globular Clusters

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