The white dwarf population within 40 pc of the Sun

Torres, Santiago; Garcı́a–Berro, E.

doi:10.1051/0004-6361/201528059

Cited by 24 publications

(28 citation statements)

References 51 publications

(88 reference statements)

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“…stars only. The best-fit thin disk age is 8.7±0.1 Gyr, which is consistent with 8.9±0.2 Gyr as measured by Torres & García-Berro (2016). However, this age measurement is clearly wrong since it ignores the contribution of thick disk stars and it assumes solar metallicity for all objects in the sample.…”

Section: Thick Disk Number Densitysupporting

confidence: 78%

“…However, their best-fit model significantly overpredicts the number of white dwarfs near the maximum of the luminosity function. Torres & García-Berro (2016) can explain this discrepancy with an initial-final mass relation that has a slope 30% larger than the observed relation for stars more massive than M 4  from Catalán et al (2008). However, there is no evidence for such a steep initial-final mass relation (Kalirai et al 2008;Williams et al 2009), and we find this explanation unlikely.…”

Section: = -mentioning

confidence: 57%

“…Both Limoges et al (2015) and Torres & García-Berro (2016) found evidence of an enhanced star formation rate in the past 300-600 Myr in the local 40 pc white dwarf sample. On the other hand, we do not find any evidence of a deviation from a constant star formation rate in the past 2.5 Gyr in the Munn (Bonatto et al 2006).…”

Section: -+mentioning

confidence: 94%

“…Torres & García-Berro (2016) revisited the analysis of the 40 pc sample with a population synthesis code. They drew their sample of stars from a Salpeter mass function, used the initialfinal mass relation of Catalán et al (2008), and cooling tracks of Renedo et al (2010) and Althaus et al (2007).…”

Section: = -mentioning

confidence: 99%

“…Based on the analysis of Kowalski & Saumon (2006), we assumed a 100% fraction of H atmosphere white dwarfs in our analysis. Torres & García-Berro (2016) use fractions of 80% DA and 20% DB in their analysis of the 40 pc sample. To explore the effects of DB white dwarfs on our age measurements, we repeat our analysis of the disk luminosity function assuming a DB white dwarf fraction of 20%.…”

Section: Thin Disk and Thick Disk Ages: Caveatsmentioning

confidence: 99%

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The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs

Kilic

Munn

Harris

et al. 2017

ApJ

145

133

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We present a detailed analysis of the white dwarf luminosity functions derived from the local 40 pc sample and the deep proper motion catalog of Munn et al. Many previous studies have ignored the contribution of thick disk white dwarfs to the Galactic disk luminosity function, which results in an erroneous age measurement. We demonstrate that the ratio of thick/thin disk white dwarfs is roughly 20% in the local sample. Simultaneously fitting for both disk components, we derive ages of 6.8-7.0 Gyr for the thin disk and 8.7±0.1 Gyr for the thick disk from the local 40 pc sample. Similarly, we derive ages of 7.4-8.2 Gyr for the thin disk and 9.5-9.9 Gyr for the thick disk from the deep proper motion catalog, which shows no evidence of a deviation from a constant star formation rate in the past 2.5 Gyr. We constrain the time difference between the onset of star formation in the thin disk and the thick disk to be 1.6 0.4Gyr. The faint end of the luminosity function for the halo white dwarfs is less constrained, resulting in an age estimate of 12.5 3.4 -+Gyr for the Galactic inner halo. This is the first time that ages for all three major components of the Galaxy have been obtained from a sample of field white dwarfs that is large enough to contain significant numbers of disk and halo objects. The resultant ages agree reasonably well with the age estimates for the oldest open and globular clusters.

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Section: Thick Disk Number Densitysupporting

confidence: 78%

Section: = -mentioning

confidence: 57%

Section: -+mentioning

confidence: 94%

Section: = -mentioning

confidence: 99%

Section: Thin Disk and Thick Disk Ages: Caveatsmentioning

confidence: 99%

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The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs

Kilic

Munn

Harris

et al. 2017

ApJ

145

133

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The white dwarf luminosity function

Garcı́a–Berro

Oswalt

2016

New Astronomy Reviews

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White dwarfs are the final remnants of low-and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for ∼ 10 Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other relevant ingredients are needed to compare theory and observations. In this review we summarize the recent attempts to empirically determine the white dwarf luminosity function for the different Galactic populations. We also discuss the biases that may affect its interpretation. Finally, we elaborate on the theoretical ingredients needed to model the white dwarf luminosity function, paying special attention to the remaining uncertainties, and we comment on some applications of the white dwarf cooling theory. Astrophysical problems for which white dwarf stars Email addresses: enrique.garcia-berro@upc.edu (Enrique García-Berro), terry.oswalt@erau.edu (Terry D. Oswalt) Preprint submitted to New Astronomy ReviewsAugust 10, 2016 may provide useful leverage in the near future are also discussed.

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The binarity of the local white dwarf population

Toonen

Hollands

Gänsicke

et al. 2017

A&A

174

194

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Context. As endpoints of stellar evolution, white dwarfs (WDs) are powerful tools to study the evolutionary history of the Galaxy. In particular, the multiplicity of WDs contains information regarding the formation and evolution of binary systems. Aims. Can we understand the multiplicity of the local WD sample from a theoretical point of view? Population synthesis methods are often applied to estimate stellar space densities and event rates, but how well are these estimates calibrated? This can be tested by a comparison with the 20 pc sample, which contains ≃ 100 stars and is minimally affected by selection biases. Methods. We model the formation and evolution of single stars and binaries within 20 pc with a population synthesis approach. We construct a model of the current sample of WDs and differentiate between WDs in different configurations, that is single WDs, and resolved and unresolved binaries containing a WD with either a main-sequence (MS) component or with a second WD. We also study the effect of different assumptions concerning the star formation history, binary evolution, and the initial distributions of binary parameters. We compile from the literature the available information on the sample of WDs within 20 pc, with a particular emphasis on their multiplicity, and compare this to the synthetic models. Results. The observed space densities of single and binary WDs are well reproduced by the models. The space densities of the most common WD systems (single WDs and unresolved WD-MS binaries) are consistent within a factor two with the observed value. We find a discrepancy only for the space density of resolved double WDs. We exclude that observational selection effects, fast stellar winds, or dynamical interactions with other objects in the Milky Way explain this discrepancy. We find that either the initial mass ratio distribution in the Solar neighbourhood is biased towards low mass-ratios, or more than ten resolved DWDs have been missed observationally in the 20 pc sample. Furthermore, we show that the low binary fraction of WD systems (∼25%) compared to Solartype MS-MS binaries (∼50%) is consistent with theory, and is mainly caused by mergers in binary systems, and to a lesser degree by WDs hiding in the glare of their companion stars. Lastly, Gaia will dramatically increase the size of the volume-limited WD sample, detecting the coolest and oldest WDs out to ≃ 50 pc. We provide a detailed estimate of the number of single and binary WDs in the Gaia sample.

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The white dwarf population within 40 pc of the Sun

Cited by 24 publications

References 51 publications

The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs

The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs

The white dwarf luminosity function

The binarity of the local white dwarf population

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