Magnetic White Dwarfs

Ferrario, Lilia; Martino, D. de; Gänsicke, B. T.

doi:10.1007/978-1-4939-3550-5_5

Cited by 4 publications

(9 citation statements)

References 441 publications

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“…Equipartition fields of ∼2 × 10 5 G generated by a core dynamo would evolve into fields of ∼2 × 10 7 G if their flux is conserved from the MS to the WD phase. Thus, the field strengths inferred for core-dynamo-generated fields are squarely within the observed distribution of WD surface fields (Ferrario et al 2015a(Ferrario et al , 2015b. Figure 3 shows that the core convective region is restricted to mass coordinates below ≈0.5 M e for stars of M  2.5 M e .…”

Section: Magnetic Fields In Wdssupporting

confidence: 71%

“…Therefore, strongly magnetized regions may extend all the way to the WD surface where they can be observed. Stars over M  3 M e produce WDs of M WD  0.7 M e , similar to the typical masses of magnetic WDs (Ferrario et al 2015a). Thus, some magnetic WDs may be magnetized due to MS convective core dynamos, which could partially explain why magnetic WDs are more massive on average.…”

Section: Magnetic Fields In Wdsmentioning

confidence: 52%

“…The exact fraction of WDs that have strong fields is debated but is of the order of 10% (Hollands et al 2015). Moreover, there is a dearth of magnetic WDs with field strengths below 10 MG, and the magnetic WDs are systematically more massive (Ferrario et al 2015a).…”

Section: Magnetic Fields In Wdsmentioning

confidence: 99%

“…Using the MS-WD mass relation of Renedo et al (2010) and Andrews et al (2015), these low-mass stars account for the majority of WDs, whose mass distribution peaks near 0.6 M e (Rebassa- Mansergas et al 2015). Since the ohmic diffusion time is very long in WDs (Ferrario et al 2015a), we expect that core-dynamo-generated fields are unlikely to be visible at the surface of most WDs.…”

Section: Magnetic Fields In Wdsmentioning

confidence: 99%

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Asteroseismic Signatures of Evolving Internal Stellar Magnetic Fields

Cantiello

Fuller

Bildsten

2016

ApJ

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Recent asteroseismic analyses indicate the presence of strong (B  10 5 G) magnetic fields in the cores of many red giant stars. Here, we examine the implications of these results for the evolution of stellar magnetic fields, and we make predictions for future observations. Those stars with suppressed dipole modes indicative of strong core fields should exhibit moderate but detectable quadrupole mode suppression. The long magnetic diffusion times within stellar cores ensure that dynamo-generated fields are confined to mass coordinates within the main-sequence (MS) convective core, and the observed sharp increase in dipole mode suppression rates above 1.5 M e is likely explained by the larger convective core masses and faster rotation of these more massive stars. In clump stars, core fields of ∼10 5 G can suppress dipole modes, whose visibility should be equal to or less than the visibility of suppressed modes in ascending red giants. High dipole mode suppression rates in low-mass (M  2 M e ) clump stars would indicate that magnetic fields generated during the MS can withstand subsequent convective phases and survive into the compact remnant phase. Finally, we discuss implications for observed magnetic fields in white dwarfs and neutron stars, as well as the effects of magnetic fields in various types of pulsating stars.

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Section: Magnetic Fields In Wdssupporting

confidence: 71%

Section: Magnetic Fields In Wdsmentioning

confidence: 52%

Section: Magnetic Fields In Wdsmentioning

confidence: 99%

Section: Magnetic Fields In Wdsmentioning

confidence: 99%

See 2 more Smart Citations

Asteroseismic Signatures of Evolving Internal Stellar Magnetic Fields

Cantiello

Fuller

Bildsten

2016

ApJ

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“…While the magnetic flux conservation of a progenitor remains an attractive possibility, a likely origin of the such strong magnetic fields is a dynamo process that operates during the envelope evolution, see Ferrario et al (2016). Recently, observations have shown that the formation of high magnetic white dwarfs can be related to strong binary interactions during post-mainsequence phases of stellar evolution (Nordhaus et al 2011).…”

Section: Introductionmentioning

confidence: 99%

AR Scorpii and possible gravitational wave radiation from pulsar white dwarfs

Franzon¹,

Schramm²

2017

Monthly Notices of the Royal Astronomical Society

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In view of the new recent observation and measurement of the rotating and highlymagnetized white dwarf AR Scorpii Marsh et al. (2016), we determine bounds of its moment of inertia, magnetic fields and radius. Moreover, we investigate the possibility of fast rotating and/or magnetized white dwarfs to be source of detectable gravitational wave (GW) emission. Numerical stellar models at different baryon masses are constructed. For each star configuration, we compute self-consistent relativistic solutions for white dwarfs endowed with poloidal magnetic fields by solving the Einstein-Maxwell field equations in a self-consistent way. The magnetic field supplies an anisotropic pressure, leading to the braking of the spherical symmetry of the star. In this case, we compute the quadrupole moment of the mass distribution. Next, we perform an estimate of the GW of such objects. Finally, we show that the new recent observation and measurement pulsar white dwarf AR Scorpii, as well as other stellar models, might generate gravitational wave radiation that lies in the bandwidth of the discussed next generation of space-based GW detectors DECI-hertz interferometer Gravitational wave Observatory (DECIGO) and Big Bang Observer (BBO).

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Optimizing Molecular Geometries in Strong Magnetic Fields

Irons

David

Teale

2021

J. Chem. Theory Comput.

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An efficient implementation of geometrical derivatives at the Hartree–Fock (HF) and current-density functional theory (CDFT) levels is presented for the study of molecular structure in strong magnetic fields. The required integral derivatives are constructed using a hybrid McMurchie–Davidson and Rys quadrature approach, which combines the amenability of the former to the evaluation of derivative integrals with the efficiency of the latter for basis sets with high angular momentum. In addition to its application to evaluating derivatives of four-center integrals, this approach is also applied to gradients using the resolution-of-the-identity approximation, enabling efficient optimization of molecular structure for many-electron systems under a strong magnetic field. The CDFT contributions have been implemented for a wide range of density functionals up to and including the meta-GGA level with current-density dependent contributions and (range-separated) hybrids for the first time. Illustrative applications are presented to the OH and benzene molecules, revealing the rich and complex chemistry induced by the presence of an external magnetic field. Challenges for geometry optimization in strong fields are highlighted, along with the requirement for careful analysis of the resulting electronic structure at each stationary point. The importance of correlation effects is examined by comparison of results at the HF and CDFT levels. The present implementation of molecular gradients at the CDFT level provides a cost-effective approach to the study of molecular structure under strong magnetic fields, opening up many new possibilities for the study of chemistry in this regime.

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Magnetic White Dwarfs

Cited by 4 publications

References 441 publications

Asteroseismic Signatures of Evolving Internal Stellar Magnetic Fields

Asteroseismic Signatures of Evolving Internal Stellar Magnetic Fields

AR Scorpii and possible gravitational wave radiation from pulsar white dwarfs

Optimizing Molecular Geometries in Strong Magnetic Fields

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