RR Lyrae variables in Galactic globular clusters

Cassisi, S.; Castellani, M.; Caputo, F.; Castellani, V.

doi:10.1051/0004-6361:20041048

Cited by 74 publications

(146 citation statements)

References 34 publications

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“…However, our distance modulus of NGC 6723 from the theoretical Wesenheit function by Cassisi et al (2004) appears to be slightly smaller than those from other methods (see Table 7). In Figure 16, we show a plot of M V (RR) from the absolute trigonometric parallaxes by Benedict et al (2011) as a function of metallicity along with our revised metallicity-luminosity relation as presented in Equation (17).…”

Section: Wesenheit Function From Theoretical Models: W (Bv ) Thcontrasting

confidence: 61%

“…Improvement of Equation (21) in the future would be very desirable. Cassisi et al (2004) studied the slope and the zero point of the theoretical Wesenheit function incorporating evolutionary and pulsational properties for various metallicities and HB types. They provided the theoretical Wesenheit function W (BV ) th ,…”

Section: Notesmentioning

confidence: 99%

“…Note that V14 and V15 have somewhat brighter V int than other regular RRab-type variable stars. If we exclude V14, V15, V16, and NV2 (see Appendix A), our true distance modulus of NGC 6723 based on the theoretical Wesenheit function by Cassisi et al (2004) becomes (m − M) 0 = 14.530 ± 0.017 from 10 RRab variable stars, and the distance from the Sun is 8.05 ± 0.06 kpc.…”

Section: Wesenheit Function From Theoretical Models: W (Bv ) Thmentioning

confidence: 99%

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Toward a Better Understanding of the Distance Scale From Rr Lyrae Variable Stars: A Case Study for the Inner Halo Globular Cluster NGC 6723

Lee¹,

López‐Morales²,

Hong³

et al. 2013

ApJS

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We present BV photometry for 54 variables in the metal-rich inner halo globular cluster NGC 6723. With the discovery of new RR Lyrae variables (RRLs), we obtain P ab = 0.541 ± 0.066 and P c = 0.292 ± 0. We obtain (m − M) 0 = 14.65 ± 0.05, equivalent to a distance from the Sun of 8.47 ± 0.17 kpc, for NGC 6723 from various distance measurement methods using RRLs. We find that RRLs in NGC 6723 do not have magnitude dependency on the radial distance because there is not a severe degree of apparent crowdedness. Finally, we show that a relation exists between the degree of photometric contamination and the apparent crowdedness of the central region of globular cluster systems, |μ − μ r | ∝ log ρ c d 2 . The use of this relation can play a significant role in mitigating the discrepancy in establishing a cosmic distance scale using RRLs in resolved stellar populations in near-field cosmology.

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Section: Wesenheit Function From Theoretical Models: W (Bv ) Thcontrasting

confidence: 61%

Section: Notesmentioning

confidence: 99%

Section: Wesenheit Function From Theoretical Models: W (Bv ) Thmentioning

confidence: 99%

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Toward a Better Understanding of the Distance Scale From Rr Lyrae Variable Stars: A Case Study for the Inner Halo Globular Cluster NGC 6723

Lee¹,

López‐Morales²,

Hong³

et al. 2013

ApJS

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“…Horizontal branch stars, of a temperature similar to that of SDSS J1742+2531, should have a gravity that is this low or even lower (see Fig. 3 of Hansen et al 2011 using the evolutionary tracks of Cassisi et al 2004), depending on the star's mass. Moreover as discussed below in Sect.…”

Section: Sdss J1742+2531mentioning

confidence: 99%

TOPoS

Bonifacio

Caffau

Spite

et al. 2015

A&A

170

232

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Context. In the course of the Turn Off Primordial Stars (TOPoS) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. These stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. We here present our analysis of six CEMP stars. Aims. We want to provide the most complete chemical inventory for these six stars in order to constrain the nucleosynthesis processes responsible for the abundance patterns. Methods. We analyse both X-Shooter and UVES spectra acquired at the VLT. We used a traditional abundance analysis based on OSMARCS 1D local thermodynamic equilibrium (LTE) model atmospheres and the turbospectrum line formation code. were not able to detect any iron lines, yet we could place a robust (3σ) upper limit of [Fe/H] < −5.0 and measure the Ca abundance, with [Ca/H] = −5.0, and carbon, A(C) = 6.90, suggesting that this star could be even more metal-poor than SDSS J1742+2531. This makes these two stars the seventh and eighth stars known so far with [Fe/H] < −4.5, usually termed ultra-iron-poor (UIP) stars. No lithium is detected in the spectrum of SDSS J1742+2531 or SDSS J1035+0641, which implies a robust upper limit of A(Li) < 1.8 for both stars. Conclusions. Our measured carbon abundances confirm the bimodal distribution of carbon in CEMP stars, identifying a high-carbon band and a low-carbon band. We propose an interpretation of this bimodality according to which the stars on the high-carbon band are the result of mass transfer from an AGB companion, while the stars on the low-carbon band are genuine fossil records of a gas Article published by EDP Sciences A28, page 1 of 20 A&A 579, A28 (2015) cloud that has also been enriched by a faint supernova (SN) providing carbon and the lighter elements. The abundance pattern of the UIP stars shows a large star-to-star scatter in the [X/Ca] ratios for all elements up to aluminium (up to 1 dex), but this scatter drops for heavier elements and is at most of the order of a factor of two. We propose that this can be explained if these stars are formed from gas that has been chemically enriched by several SNe, that produce the roughly constant [X/Ca] ratios for the heavier elements, and in some cases the gas has also been polluted by the ejecta of a faint SN that contributes the lighter elements in variable amounts. The absence of lithium in four of the five known unevolved UIP stars can be explained by a dominant role of fragmentation in the formation of these stars. This would result either in a destruction of lithium in the pre-main-sequence phase, through rotational mixing or to a lack of late accretion from a reservoir of fresh gas. The phenomenon should have varying degrees of efficiency.

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“…Accordingly, considerable attention has been devoted to this subject over the past several years, with several papers recently published on its accurate determination, by both empirical and theoretical approaches (e.g., Del Principe et al 2006;Solima et al 2006Solima et al , 2008Feast et al 2008;Pietrzyński et al 2008;Szewczyk et al 2008). From the theoretical point of view, its properties have been investigated by Bono et al (2001Bono et al ( , 2003, Cassisi et al (2004), and Catelan et al (2004).…”

Section: Introductionmentioning

confidence: 99%

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud

Borissova¹,

Rejkuba²,

Minniti

et al. 2009

A&A

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Context. RR Lyrae variable stars are the primary Population II distance indicator. Likewise, the Large Magellanic Cloud (LMC) constitutes a key step in the extragalactic distance scale. Aims. By combining near-IR photometry and spectroscopically measured metallicities for a homogeneous sample of 50 RR Lyr stars in the LMC, we investigate the metallicity dependence of the period-luminosity relation in the near-infrared (IR), use the newly derived relations to re-derive the distance to the LMC, and compare the distance moduli obtained from RR Lyr and red clump stars. Methods. This paper presents new (single-epoch) J-band and (multi-epoch) K s -band photometry of RR Lyr stars in 7 different LMC fields, observed with the near-IR camera SOFI at ESO's New Technology Telescope. Additional K s -band data for another two LMC fields were taken with the ISPI infrared array at CTIO's Blanco 4m telescope. The near-IR photometry was cross-correlated with the MACHO and OGLE databases, resulting in a catalog of 62 RR Lyr stars with BVRI JK s photometry. A subsample of 50 stars also has spectroscopically measured metallicities. Results. In the deep JK color-magnitude diagrams of 7 fields, red giant branch, red clump and RR Lyr stars are detected. The majority of RR Lyr stars are located within the instability strip with near-IR colors between 0.14 ≤ (J − K s ) 0 < 0.32. The period-luminosity relation only has a very mild dependence on metallicity in the K band, consistent with no dependence: M Ks = 2.11(±0.17) log P + 0.05(±0.07) [Fe/H] − 1.05. In the J band the currently available data do not allow firm conclusions regarding the metallicity dependence of the period-luminosity relation. Conclusions. The distance modulus of the LMC, derived using our near-IR period-luminosity-metallicity relation for RR Lyr stars, is (m − M) 0 = 18.53 ± 0.13, in very good agreement with the distance modulus from the red clump stars, 18.46 ± 0.07. However, LMC modulus derived from the RR Lyrae stars depends on the parallax of the star RR Lyrae.

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RR Lyrae variables in Galactic globular clusters

Cited by 74 publications

References 34 publications

Toward a Better Understanding of the Distance Scale From Rr Lyrae Variable Stars: A Case Study for the Inner Halo Globular Cluster NGC 6723

Toward a Better Understanding of the Distance Scale From Rr Lyrae Variable Stars: A Case Study for the Inner Halo Globular Cluster NGC 6723

TOPoS

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud

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