The End of the MACHO Era: Limits on Halo Dark Matter from Stellar Halo Wide Binaries

Yoo, Jaiyul; Chanamé, Julio; Gould, Andrew

doi:10.1086/380562

Cited by 188 publications

(223 citation statements)

References 19 publications

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“…It should also be possible to improve limits in the range 10 M < M < 100 M by combining the results presented here with the MACHO high mass results (Alcock et al 2001b). This may narrow the small remaining allowed macho mass range between the range excluded by microlensing and that excluded by the abundance of halo wide binary stars (Yoo et al 2004).…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

Limits on the Macho content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds

Tisserand

Guillou

Afonso

et al. 2007

A&A

941

908

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Aims. The EROS-2 project was designed to test the hypothesis that massive compact halo objects (the so-called "machos") could be a major component of the dark matter halo of the Milky Way galaxy. To this end, EROS-2 monitored over 6.7 years 33 × 10 6 stars in the Magellanic clouds for microlensing events caused by such objects. Methods. In this work, we use only a subsample of 7 × 10 6 bright stars spread over 84 deg 2 of the LMC and 9 deg 2 of the SMC. The strategy of using only bright stars helps to discriminate against background events due to variable stars and allows a simple determination of the effects of source confusion (blending). The use of a large solid angle makes the survey relatively insensitive to effects that could make the optical depth strongly direction dependent. Results. Using this sample of bright stars, only one candidate event was found, whereas ∼39 events would have been expected if the Halo were entirely populated by objects of mass M ∼ 0.4 M . Combined with the results of EROS-1, this implies that the optical depth toward the Large Magellanic Cloud (LMC) due to such lenses is τ < 0.36 × 10 −7 (95% CL), corresponding to a fraction of the halo mass of less than 8%. This optical depth is considerably less than that measured by the MACHO collaboration in the central region of the LMC. More generally, machos in the mass range 0.6 × 10 −7 M < M < 15 M are ruled out as the primary occupants of the Milky Way Halo.

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Section: Discussion Of the Resultsmentioning

confidence: 99%

Limits on the Macho content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds

Tisserand

Guillou

Afonso

et al. 2007

A&A

941

908

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“…Since then, the EROS (Lasserre et al 2000; Goldman et al 2002;Tisserand et al 2006), OGLE (Udalski et al 1994), MOA (Muraki et al 1999) and SuperMACHO (Becker et al 2005) teams have monitored millions of stars during several years in both the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) to search for microlensing events. Most of them have challenged the results of the MACHO experiment -see, for instance, Yoo et al (2004) and references therein. In addition, there have been claims that white dwarfs could be the stellar objects reported in the Hubble Deep Field (Ibata et al 1999;Méndez & Minniti 2000).…”

Section: Introductionmentioning

confidence: 99%

Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

379

372

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White dwarf stars are the final evolutionary stage of the vast majority of stars, including our Sun. Since the coolest white dwarfs are very old objects, the present population of white dwarfs contains a wealth of information on the evolution of stars from birth to death, and on the star formation rate throughout the history of our Galaxy. Thus, the study of white dwarfs has potential applications to different fields of astrophysics. In particular, white dwarfs can be used as independent reliable cosmic clocks, and can also provide valuable information about the fundamental parameters of a wide variety of stellar populations, like our Galaxy and open and globular clusters. In addition, the high densities and temperatures characterizing white dwarfs allow to use these stars as cosmic laboratories for studying physical processes under extreme conditions that cannot be achieved in terrestrial laboratories. Last but not least, since many white dwarf stars undergo pulsational instabilities, the study of their properties constitutes a powerful tool for applications beyond stellar astrophysics. In particular, white dwarfs can be used to constrain fundamental properties of elementary particles such as axions and neutrinos, and to study problems related to the variation of fundamental constants.These potential applications of white dwarfs have led to a renewed interest in the calculation of very detailed evolutionary and pulsational models for these stars. In this work, we review the essentials of the physics of white dwarf stars. We enumerate the reasons that make these stars excellent chronometers and we describe why white dwarfs provide tools for a wide variety of applications. Special emphasis is placed on the physical processes that lead to the formation of white dwarfs as well as on the different energy sources and processes responsible for chemical abundance changes that occur along their evolution. Moreover, in the course of their lives, white dwarfs cross different pulsational instability strips. The existence of these instability strips provides astronomers with an unique opportunity to peer into their internal structure that would otherwise remain hidden from observers. We will show that this allows to measure with unprecedented precision the stellar masses and to infer their envelope thicknesses, to probe the core chemical stratification, and to detect rotation rates and magnetic fields. Consequently, in this work, we also review the pulsational properties of white dwarfs and the most recent applications of white dwarf asteroseismology.

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“…The shape of their separation distribution, in particular towards the most extreme, widest separations, should therefore allow constraints on the mass and frequency of the disruptive perturbers (Retterer & King 1982), as well as to estimate the age of a population (Poveda & Allen 2004). Wide binary-based MACHO constraints have been placed (but subsequently criticised) by several authors (Bahcall et al 1985a;Weinberg et al 1987;Weinberg 1990;Wasserman & Weinberg 1991;Yoo et al 2004;Quinn et al 2009). …”

Section: Introductionmentioning

confidence: 99%

The stellar correlation function from SDSS

Longhitano¹,

Binggeli²

2010

A&A

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We study the statistical properties of the wide binary population in the Galaxy field with projected separations larger than 200 AU by constructing the stellar angular two-point correlation function (2PCF) from a homogeneous sample of nearly 670 000 main sequence stars. The selected stars lie within a rectangular region around the Northern Galactic Pole and have apparent r-band magnitudes between 15 and 20.5 mag and spectral classes later than G5 (g − r > 0.5 mag). The data were taken from the Sixth Data Release of the Sloan Digital Sky Survey. We model the 2PCF by means of the Wasserman-Weinberg technique including several assumptions on the distribution of the binaries' orbital parameters, luminosity function, and density distribution in the Galaxy. In particular, we assume that the semi-major axis distribution is described by a single powerlaw. The free model parameters -the local wide binary number density n WB and the power-law index λ of the semi-major axis distribution -are inferred simultaneously by least-square fitting. We find the separation distribution to follow Öpik's law (λ = 1) up to the Galactic tidal limit, without any break and a local density of 5 wide binaries per 1000 pc 3 with both components having spectral type later than G5. This implies that about 10% of all stars in the solar neighbourhood are members of such a late-type wide binary system. With a relative statistical (2σ) error of about 10%, our findings are in general agreement with previous studies of wide binaries. The data suggest that about 800 very wide pairs with projected separations larger than 0.1 pc exist in our sample, whereas none are found beyond 0.8 pc. Modern large-scale surveys make the 2PCF method a viable tool for studying wide binary stars and a true complement to common proper motion studies. The method is, however, seriously limited by the noise from optical pairs and the (over)simplifying assumptions made to model the selection effects and to interpret the measured clustering signal.

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The End of the MACHO Era: Limits on Halo Dark Matter from Stellar Halo Wide Binaries

Cited by 188 publications

References 19 publications

Limits on the Macho content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds

Limits on the Macho content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds

Evolutionary and pulsational properties of white dwarf stars

The stellar correlation function from SDSS

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