Synthetic properties of bright metal-poor variables

Criscienzo, M. Di; Caputo, F.; Marconi, M.; Cassisi, S.

doi:10.1051/0004-6361:20066541

Cited by 55 publications

(64 citation statements)

References 50 publications

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“…They also show that there is no significant trend with metallicity over the range −2.2 < ∼ [Fe/H] < ∼ −0.5, in agreement with theoretical predictions (Bono et al 1997(Bono et al , 2003Di Criscienzo et al 2007) and indicating that this K-band PL-relation should be applicable for GC P2C as well. The metallicity of the P2C in the GB is unknown, but that of RR Lyrae is estimated to be on average on the derived slope of the NIR PL-relations.…”

Section: Discussionsupporting

confidence: 81%

The distance to the Galactic centre based on Population II Cepheids and RR Lyrae stars

Groenewegen¹,

Udalski

Bono

2008

A&A

112

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Context. The distance to the Galactic centre (GC) is important for determining the distance scale in the Universe. The value derived by Eisenhauer et al. (2005) of 7.62 ± 0.32 kpc based on the orbit of one star around the central black hole is shorter than most other distance estimates based on a variety of different methods. Aims. To establish an independent distance to the GC with high accuracy, Population-ii Cepheids were used that have been discovered in the ogle-ii and ogle-iii surveys.Methods. Thirty-nine Population-ii Cepheids were monitored with the SOFI infrared camera on 4 nights spanning 14 days, typically obtaining between 5 and 11 epochs of data. Light curves were fitted using the known periods from the OGLE data to determine the mean K-band magnitude with an accuracy of 0.01−0.02 mag. It so happens that 37 RR Lyrae stars are in the field-of-view of the observations, and mean K-band magnitudes are derived for this sample as well. Results. After correction for reddening, the period-luminosity relation of Population-ii Cepheids in the K-band is determined, and the derived slope of −2.24 ± 0.14 is consistent with the value derived by Matsunaga et al. (2006, MNRAS, 370, 1979. Fixing the slope to their more accurate value results in a zero point and implies a distance modulus to the GC of 14.51 ± 0.12, with an additional systematic uncertainty of 0.07 mag. Similarly, from the RR Lyrae K-band period-luminosity relation, we derive a value of 14.48 ± 0.17(random) ± 0.07 (syst.). The two independent determinations are averaged to find 14.50 ± 0.10(random) ± 0.07(syst.), or 7.94 ± 0.37 ± 0.26 kpc. The absolute magnitude scale of the adopted period-luminosity relations is tied to an LMC distance modulus of 18.50 ± 0.07.

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Section: Discussionsupporting

confidence: 81%

The distance to the Galactic centre based on Population II Cepheids and RR Lyrae stars

Groenewegen¹,

Udalski

Bono

2008

A&A

112

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“…This code has been extensively used to investigate the properties of different classes of evolved pulsating stars, from the low-mass RR Lyrae and BL Herculis (e.g., Bono et al 2003;Marconi et al 2003Marconi et al , 2011Di Criscienzo et al 2007; to anomalous, classical, or ultra-long-period Cepheids (Bono et al 2000;Fiorentino et al 2002;Marconi et al 2004Marconi et al , 2005Fiorentino et al 2007;Marconi et al 2010). Very little has been done to interpret intermediate-mass stars in the MS phasesuch as the metal-rich δ Scuti stars (Bono et al 1997b;McNamara et al 2007) and the metal-poor SXPs (Gilliland et al 1998;Bono et al 2002).…”

Section: Evolutionary and Pulsation Modelsmentioning

confidence: 99%

Blue Straggler Masses From Pulsation Properties. Ii. Topology of the Instability Strip

Fiorentino

Marconi

Bono

et al. 2015

ApJ

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We present a new set of nonlinear, convective radial pulsation models for main-sequence stars computed assuming three metallicities: Z = 0.0001, 0.001, and 0.008. These chemical compositions bracket the metallicity of stellar systems hosting SX Phoenicis stars (SXPs, or pulsating Blue Stragglers), namely, Galactic globular clusters and nearby dwarf spheroidals. Stellar masses and luminosities of the pulsation models are based on alpha-enhanced evolutionary tracks from the BASTI website. We are able to define the topology of the instability strip (IS)and in turn the pulsation relations for the first four pulsation modes. We found that third overtones approach a stable nonlinear limit cycle. Predicted and empirical ISs agree quite well in the case of 49 SXPs belonging to ω Cen. We used theoretical period-luminosity (PL) relations in Band V bands to identify their pulsation mode. We assumed Z = 0.001 and Z = 0.008 as mean metallicities of SXPs in ω Cen. We found respectively 13-15 fundamental, 22-6 first-overtone, and 9-4 second-overtone modes. Five are unstable in the third-overtone mode only for Z = 0.001. Using the above mode identification and applying the proper mass-dependent PL relations, we found masses ranging from ∼1.0 to 1.for Z = 0.001 and 0.008, respectively. Our investigation supports the use of evolutionary tracks to estimate SXP masses. We will extend our analysis to higher helium content, which may have an impact on our understanding of the blue stragglerstars formation scenario.

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“…The star represents one P2C candidate from OGLE-III that we have included in our sample. The solid line represents the theoretical prediction for BL Her type stars from Di Criscienzo et al (2007), while the dashed line is the observed Wesenheit relation for fundamental-mode classical Cepheids (Soszyński et al 2008a). classical Cepheids is hampered by the fact that the first-overtone (FO) AC fall on the extension of the period-luminosity relation to shorter periods of the fundamental (F) classical Cepheids (period < ∼ 2.5 d Caputo et al 2004;Soszyński et al 2008c). For these stars, the shape of the light curve is the most efficient diagnostic to separate the two groups.…”

Section: The Ogle-iii Samplementioning

confidence: 99%

Anomalous Cepheids in the Large Magellanic Cloud

Fiorentino

Monelli

2012

A&A

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Context. The properties of variable stars can give independent constraints on the star formation history of the host galaxy, by determining the age and metallicity of the parent population. Aims. We investigate the pulsation properties of 84 Anomalous Cepheids (ACs) detected by the OGLE-III survey in the Large Magellanic Cloud (LMC), in order to understand the formation mechanism and the characteristics of the parent population they came from. Methods. We used an updated theoretical pulsation scenario to derive the mass and the pulsation mode of each AC in the sample. We also used a Kolmogorov-Smirnov test to analyze the spatial distribution of the ACs, in comparison with that of other groups of variable stars, and connect their properties with the star formation history of the LMC. Results. We find that the mean mass of ACs is 1.2 ± 0.2 M . We show that ACs do not follow the same spatial distribution of classical Cepheids. This and the difference in their period-luminosity relations further support the hypothesis that ACs are not the extension to low luminosity of classical Cepheids. The spatial distribution of ACs is also different from that of bona-fide tracers of the old population, such as RR Lyrae stars and population II Cepheids. We therefore suggest that the majority of ACs in the LMC are made of intermediate-age (1-6 Gyr), metal-poor single stars. Finally, we investigate the relation between the frequency of ACs and the luminosity of the host galaxy, disclosing that purely old systems follow a very tight relation and that galaxies with strong intermediate-age and young star formation tend to have an excess of ACs, in agreement with their hosting ACs formed via both single and binary star channels.

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Synthetic properties of bright metal-poor variables

Cited by 55 publications

References 50 publications

The distance to the Galactic centre based on Population II Cepheids and RR Lyrae stars

The distance to the Galactic centre based on Population II Cepheids and RR Lyrae stars

Blue Straggler Masses From Pulsation Properties. Ii. Topology of the Instability Strip

Anomalous Cepheids in the Large Magellanic Cloud

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