A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

Eisenstein, Daniel J.; Liebert, James; Harris, Hugh C.; Kleinman, S. J.; Nitta, A.; Silvestri, Nicole M.; Anderson, Scott; Barentine, John C.; Brewington, H.; Brinkmann, J.; Harvanek, Michael; Krzesiński, Jurek; Neilsen, Eric H.; Long, D.; Schneider, Donald P.; Snedden, Stephanie A.

doi:10.1086/507110

Cited by 396 publications

(489 citation statements)

References 75 publications

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“…This increase in the number of detected white dwarfs has extraordinarily improved our knowledge of the white dwarf luminosity and mass functions. In addition, spectroscopy of this much enlarged sample led to the discovery of new and interesting species of degenerate stars (Eisenstein et al 2006; Koester et al 2009). …”

Section: Mass Distributionmentioning

confidence: 99%

“…These are the so-called DA white dwarfs and they comprise about 85% of all white dwarfs -see Eisenstein et al (2006) and references therein. To the other family belong the H-deficient white dwarfs with He-rich atmospheres, usually known as non-DA white dwarfs, which make up to almost 15% of the total population.…”

Section: Spectroscopic Classificationmentioning

confidence: 99%

“…As a DO white dwarf evolves, the HeII recombines to form HeI, ultimately transforming into a DB white dwarf. The transition from DO to the cooler DB stage is interrupted by the non-DA gap (that occurs at 30 000 K < T eff < 45 000 K) where few objects with H-deficient atmospheres have been observed (Eisenstein et al 2006). To this list, we have to add those white dwarfs with hybrid atmospheres or peculiar abundances, and the recent discovery of a new white dwarf spectral type with carbon-dominated atmospheres, the "hot DQ" white dwarfs, with T eff ∼ 20 000 K (Dufour et al 2007, 2008a).…”

Section: Spectroscopic Classificationmentioning

confidence: 99%

See 2 more Smart Citations

Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

368

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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Section: Mass Distributionmentioning

confidence: 99%

Section: Spectroscopic Classificationmentioning

confidence: 99%

Section: Spectroscopic Classificationmentioning

confidence: 99%

See 1 more Smart Citation

Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

368

372

View full text Add to dashboard Cite

show abstract

“…Most of these stars are considered candidate sdBs with low temperatures, which cannot be distinguished clearly from blue horizontal branch (BHB) stars or low-mass DA or DB white dwarfs. Eisenstein et al (2006) used a semi-automatic method for the spectral classification of white dwarfs and hot subdwarfs from the SDSS DR4, and it is instructive to compare their sample to ours. Our colour cut-off is more restrictive and the confusion limit (S /N > 5) is brighter than that of Eisenstein et al (2006).…”

Section: Colour Selection and Visual Classificationmentioning

confidence: 99%

“…Eisenstein et al (2006) used a semi-automatic method for the spectral classification of white dwarfs and hot subdwarfs from the SDSS DR4, and it is instructive to compare their sample to ours. Our colour cut-off is more restrictive and the confusion limit (S /N > 5) is brighter than that of Eisenstein et al (2006). Due to the redder colour cuts, blue horizontal branch stars enter the Eisenstein et al sample, which we do not consider as hot subdwarf stars (see Heber 2009).…”

Section: Colour Selection and Visual Classificationmentioning

confidence: 99%

The MUCHFUSS project – searching for hot subdwarf binaries with massive unseen companions

Geier

Hirsch

Tillich

et al. 2011

A&A

102

109

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The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding sdBs with compact companions like supermassive white dwarfs (M > 1.0 M ), neutron stars or black holes. The existence of such systems is predicted by binary evolution theory and recent discoveries indicate that they are likely to exist in our Galaxy. A determination of the orbital parameters is sufficient to put a lower limit on the companion mass by calculating the binary mass function. If this lower limit exceeds the Chandrasekhar mass and no sign of a companion is visible in the spectra, the existence of a massive compact companion is proven without the need for any additional assumptions. We identified about 1100 hot subdwarf stars from the SDSS by colour selection and visual inspection of their spectra. Stars with high velocities have been reobserved and individual SDSS spectra have been analysed. In total 127 radial velocity variable subdwarfs have been discovered. Binaries with high RV shifts and binaries with moderate shifts within short timespans have the highest probability of hosting massive compact companions. Atmospheric parameters of 69 hot subdwarfs in these binary systems have been determined by means of a quantitative spectral analysis. The atmospheric parameter distribution of the selected sample does not differ from previously studied samples of hot subdwarfs. The systems are considered the best candidates to search for massive compact companions by follow-up time resolved spectroscopy.

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Hot White Dwarfs

Sion

2011

White Dwarf Atmospheres and Circumstellar Environments

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The article covers the physical properties and evolution of single white dwarfs ranging in temperature from 20,000K to 200,000 and higher, the hottest know electron-degenerate stars. After discussing the classification of their spectra, the author reviews the known properties, parameters, evolutionary state, as well as persisting and new puzzles regarding all spectroscopic subclasses of Hot White Dwarfs: the hot DA white dwarfs, the DAO white dwarfs, the PG1159 degenerates, the DO white dwarfs, the DB white dwarfs, the DBA white dwarfs, and the Hot DQ white dwarfs (an entirely new class). The most recent observational and theoretical advances are brought to bear on the topic.The spectroscopic properties of white dwarfs are determined by a host of physical processes which control and/or modify the flow of elements and, hence, surface abundances in high gravity atmospheres: convective dredge-up, mixing and dilution, accretion of gas and dust from the interstellar medium and debris disks, gravitational and thermal diffusion, radiative forces, mass loss due to wind outflow and episodic mass ejection, late nuclear shell burning and late thermal pulses, rotation, magnetic fields, and possible composition relics of prior pre-white dwarf evolutionary states. Virtually all of these processes and factors may operate in hot white dwarfs, leading to the wide variety of observed spectroscopic phenomena and spectral evolution.The basic thrust of research on hot white dwarfs is three-fold: (1) to elucidate the evolutionary links between the white dwarfs and their pre-white dwarf progenitors, whether from the asymptotic giant branch (AGB), the extended horizontal branch, stellar mergers, or binary evolution; (2) to understand the physics of the different envelope processes operating in hot white dwarfs as they cool; and (3) to disentangle and elucidate the relationships between the different spectroscopic subclasses and hybrid subclasses of hot white dwarfs as spectral evolution proceeds. This includes the source of photospheric metals, the chemical species observed, and the measured surface abundances in hot degenerates. The evolutionary significance of certain observed ion species is complicated by the role of radiative forces and weak winds in levitating and ejecting elements at temperatures >20,000 K.

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A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4

Cited by 396 publications

References 75 publications

Evolutionary and pulsational properties of white dwarf stars

Evolutionary and pulsational properties of white dwarf stars

The MUCHFUSS project – searching for hot subdwarf binaries with massive unseen companions

Hot White Dwarfs

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