The White Dwarf Cooling Sequence of the Globular Cluster Messier 4

Hansen, Brad M. S.; Brewer, J.; Fahlman, G. G.; Gibson, Brad K.; Ibata, Rodrigo; Limongi, Marco; Rich, R. Michael; Richer, Harvey B.; Shara, Michael M.; Stetson, P. B.

doi:10.1086/342528

Cited by 223 publications

(222 citation statements)

References 42 publications

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“…al. [86] also proposed an age of 12.7 ± 0.7 Gyr, using the white dwarf cooling sequence method (for full review of the cosmic age see [5]). The age of universe integrated from the big bang up to now is given by: Figure 11 shows the dependence of H 0 t 0 (Hubble parameter times the age of universe) on Ωr c for a flat universe.…”

Section: Age Of Universementioning

confidence: 99%

Observational Constraints with Recent Data on the DGP Modified Gravity

2008

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We study one of the simplest covariant modified-gravity models based on the Dvali-Gabadadze-Porrati (DGP) brane cosmology, a self-accelerating universe. In this model gravitational leakage into extra dimensions is responsible of late-time acceleration. We mainly focus on the effects of the model parameters on the geometry and the age of universe. Also we investigate the evolution of matter density perturbations in the modified gravity model, and obtain an analytical expression for the growth index, f . We show that increasing Ωr c leads to less growth of the density contrast δ, and also decreases the growth index. We give a fitting formula for the growth index at the present time and indicate that dominant term in this expression verifies the well-known approximation relation f ≃ Ω γ m . As the observational test, the new Supernova Type Ia (SNIa) Gold sample and Supernova Legacy Survey (SNLS) data, size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), the position of the acoustic peak from the CMB observations and the Cluster Baryon Gas Mass Fraction (gas) are used to constrain the parameters of the DGP model. We also combine previous results with large scale structure formation (LSS) from the 2dFGRS survey. Finally to check the consistency of the DGP model, we compare the age of old cosmological objects with age of universe in this model.

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Section: Age Of Universementioning

confidence: 99%

Observational Constraints with Recent Data on the DGP Modified Gravity

2008

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“…These stable clocks drift at their cooling rate; measuring the drift rate in the absence of orbital companions allows us to calibrate our evolutionary models. These models are useful in determining ages of the Galactic disk and halo using white dwarfs as chronometers (e.g., Winget et al 1987;Hansen et al 2002). Therefore, we preferentially choose to observe hDAV candidates in the range 11,700-12,300 K to increase the sample of known stable pulsators with both the above objectives in mind.…”

Section: Biases In Candidate Selectionmentioning

confidence: 99%

Redefining the Empirical ZZ Ceti Instability Strip

Mukadam

Winget

Hippel

et al. 2004

ApJ

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We use the new ZZ Ceti stars ( hydrogen-atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey ( Mukadam et al. 2004) to redefine the empirical ZZ Ceti instability strip. This is the first time since the discovery of white dwarf variables in 1968 that we have a homogeneous set of spectra acquired using the same instrument on the same telescope, and with consistent data reductions, for a statistically significant sample of ZZ Ceti stars. The homogeneity of the spectra reduces the scatter in the spectroscopic temperatures, and we find a narrow instability strip of width $950 K , from 10,850 to 11,800 K. We question the purity of the DAV instability strip, as we find several nonvariables within. We present our best fit for the red edge and our constraint for the blue edge of the instability strip, determined using a statistical approach.

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“…Accordingly, significant efforts have recently been invested in successfully modeling the observed properties of several white dwarf populations with a high degree of realism. These include the Galactic disk and halo -see the very recent works of Cojocaru et al (2014Cojocaru et al ( , 2015 and references therein -and the system of Galactic open Article published by EDP Sciences A35, page 1 of 8 Bellini et al 2010;Bedin et al 2010) and globular clusters (Hansen et al 2002;García-Berro et al 2014;Torres et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The white dwarf population within 40 pc of the Sun

Torres

Garcı́a–Berro

2016

A&A

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Context. The white dwarf luminosity function is an important tool to understand the properties of the solar neighborhood, like its star formation history, and its age. Aims. Here we present a population synthesis study of the white dwarf population within 40 pc from the Sun, and compare the results of this study with the properties of the observed sample. Methods. We use a state-of-the-art population synthesis code based on Monte Carlo techniques, which incorporates the most recent and reliable white dwarf cooling sequences, an accurate description of the Galactic neighborhood, and a realistic treatment of all the known observational biases and selection procedures. Results. We find a good agreement between our theoretical models and the observed data. In particular, our simulations reproduce a previously unexplained feature of the bright branch of the white dwarf luminosity function, which we argue is due to a recent episode of star formation. We also derive the age of the solar neighborhood employing the position of the observed cut-off of the white dwarf luminosity function, to obtain ∼8.9 ± 0.2 Gyr. Conclusions. We conclude that a detailed description of the ensemble properties of the population of white dwarfs within 40 pc of the Sun allows us to obtain interesting constraints on the history of the Solar neighborhood.

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The White Dwarf Cooling Sequence of the Globular Cluster Messier 4

Cited by 223 publications

References 42 publications

Observational Constraints with Recent Data on the DGP Modified Gravity

Observational Constraints with Recent Data on the DGP Modified Gravity

Redefining the Empirical ZZ Ceti Instability Strip

The white dwarf population within 40 pc of the Sun

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