Three New Magnetic White Dwarf Stars

Putney, A.

doi:10.1086/309689

Cited by 63 publications

(42 citation statements)

References 26 publications

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“…WD1309 + 853 This is MWD with B p = 4.9 MG (Putney, 1995). WD1310 + 583 Limoges et al (2015) gives a distance of 23.2 ± 0.8 pc, however, using the same T eff and log g we find 26.3 ± 0.3 pc.…”

Section: Wd0009+ 501mentioning

confidence: 65%

The 25 parsec local white dwarf population

Holberg

Oswalt

Sion

et al. 2016

Mon. Not. R. Astron. Soc.

101

103

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We have extended our detailed survey of the local white dwarf population from 20 to 25 pc, effectively doubling the sample volume, which now includes 232 stars. In the process, new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25 pc sample is estimated to be about 68 per cent complete (the corresponding 20 pc sample is now 86 per cent complete). The space density of white dwarfs is unchanged at 4.8 ± 0.5 × 10 −3 pc −3 . This new study includes a white dwarf mass distribution and luminosity function based on the 232 stars in the 25 pc sample. We find a significant excess of single stars over systems containing one or more companions (74 per cent versus 26 per cent). This suggests mechanisms that result in the loss of companions during binary system evolution. In addition, this updated sample exhibits a pronounced deficiency of nearby 'Sirius-like' systems. 11 such systems were found within the 20 pc volume versus only one additional system found in the volume between 20 and 25 pc. An estimate of white dwarf birth rates during the last ∼8 Gyr is derived from individual remnant cooling ages. A discussion of likely ways new members of the local sample may be found is provided.Key words: binaries: close -white dwarfs. I N T RO D U C T I O NThere is considerable interest in establishing a complete census of the population of nearby stars, particularly for those of the lowest luminosity, such as white dwarfs (WDs), late M-stars and sub-stellar L and T dwarfs. For the WD stars, previous publications (Holberg et al. 2002, 2008a, hereafter LWD02 and LWD08, respectively) have discussed the sample extending to 20 pc from the Sun. Since 2008, the 20 pc sample has grown by 10 members and distance estimates have been improved for many other WDs in this range. In addition, Giammichele, Bergeron & Dufour (2012 -hereafter GBD) have conducted a thorough spectral analysis of most WDs within the existing 20 pc sample. These developments provide a firm basis for a more homogeneous and unbiased determination of spectral types and stellar parameters. Thus, an improved knowledge base now exists with which to characterize the 20 pc local sample, since its completeness now approaches 86 per cent. In this paper, our previous 20 pc (LS20) sample is updated and extended out to a distance of 25 pc (LS25). Our formal sample limit is actually 25.2 pc, since at this distance, the added volume is exactly twice that of the original LS20 sample, which facilitates direct comparisons between the two subsamples. For example, the higher completeness E-mail: holberg@argus.lpl.arizona.edu factor of LS20 permits extrapolation of population properties to the less complete LS25.The LS25 is a volume-limited sample in which distance is the fundamental criterion for inclusion. Such a sample has several properties that are not easily matched by magnitude-limited samples that include many more WDs. For example, LS25 is an all-sky survey th...

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Section: Wd0009+ 501mentioning

confidence: 65%

The 25 parsec local white dwarf population

Holberg

Oswalt

Sion

et al. 2016

Mon. Not. R. Astron. Soc.

101

103

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“…G183−35 was identified as a high proper motion object by Giclas, Burnham, & Thomas (1971) and classified to be a DC white dwarf by Hintzen & Strittmatter (1974) based on low-resolution spectroscopy. Putney (1995) performed a spectropolarimetric survey of several white dwarfs, including G183−35, and detected H lines split into three components due to a magnetic field strength of 6.8 ± 0.5 MG. In addition, she found evidence of a change in both line shapes and polarization spectra taken more than a year apart, and interpreted this as evidence of rotation in this object.…”

Section: Introductionmentioning

confidence: 99%

A magnetic white dwarf with five H α components

Kilic

Rolland

Bergeron

et al. 2019

Monthly Notices of the Royal Astronomical Society

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G183−35 is an unusual white dwarf that shows an Hα line split into five components, instead of the usual three components seen in strongly magnetic white dwarfs. Potential explanations for the unusual set of lines includes a double degenerate system containing two magnetic white dwarfs and/or rotational modulation of a complex magnetic field structure. Here we present time-resolved spectroscopy of G183−35 obtained at the Gemini Observatory. These data reveal two sets of absorption lines that appear and disappear over a period of about 4 hours. We also detect low-level (0.2%) variability in optical photometry at the same period. We demonstrate that the spectroscopic and photometric variability can be explained by the presence of spots on the surface of the white dwarf and a change in the average field strength from about 4.6 MG to 6.2 MG. The observed variability is clearly due to G183−35's relatively short spin period. However, rotational modulation of a complex magnetic field by itself cannot explain the changes seen in the central Hα component. An additional source of variability in the line profiles, most likely due to a chemically inhomogeneous surface composition, is also needed. We propose further observations of similar objects to test this scenario.

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“…The first one is the intense magnetic field observed in compact objects such as white dwarfs, neutron stars, or magnetized strange quark stars (see, for example, Refs. [26][27][28][29][30] and references therein). Indeed, it is a well-established fact that a magnetic field acting on a Fermi gas produces pressure anisotropy (see Refs.…”

Section: Introductionmentioning

confidence: 99%

General relativistic polytropes for anisotropic matter: The general formalism and applications

2013

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We set up in detail the general formalism to model polytropic general relativistic stars with anisotropic pressure. We shall consider two different possible polytropic equations, all of which yield the same Lane-Emden equation in the Newtonian limit. A heuristic model based on an ansatz to obtain anisotropic matter solutions from known solutions for isotropic matter is adopted to illustrate the effects of the pressure anisotropy on the structure of the star. In this context, the Tolman mass, which is a measure of the active gravitational mass, is invoked to explain some features of the models. Prospective extensions of the proposed approach are pointed out.

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Three New Magnetic White Dwarf Stars

Cited by 63 publications

References 26 publications

The 25 parsec local white dwarf population

The 25 parsec local white dwarf population

A magnetic white dwarf with five H α components

General relativistic polytropes for anisotropic matter: The general formalism and applications

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