A volume-limited survey of mCP stars within 100 pc II: rotational and magnetic properties

Sikora, J.; Wade, G. A.; Power, J.; Neiner, C.

doi:10.1093/mnras/sty2895

Cited by 97 publications

(92 citation statements)

References 79 publications

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“…Another piece in this puzzle is the lack of descendants with strong fields (which are easier to detect) but lower surface gravity. The absence of such stars is consistent with previous suggestions that the magnetic fields of OB stars are subject to a flux decay mechanism, in contrast to the evolution of the magnetic fields of A and Ap stars which are consistent with flux conservation (Landstreet et al 2007;Neiner et al 2017;Sikora et al 2019). The flux decay rate could, in principle, be inferred empirically by matching the observed relationship of log g and B p .…”

Section: Magnetic Evolution Of Known Magnetic B-type Starssupporting

confidence: 89%

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

Keszthelyi

Meynet

Shultz

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The time evolution of angular momentum and surface rotation of massive stars is strongly influenced by fossil magnetic fields via magnetic braking. We present a new module containing a simple, comprehensive implementation of such a field at the surface of a massive star within the Modules for Experiments in Stellar Astrophysics (mesa) software instrument. We test two limiting scenarios for magnetic braking: distributing the angular momentum loss throughout the star in the first case, and restricting the angular momentum loss to a surface reservoir in the second case. We perform a systematic investigation of the rotational evolution using a grid of OB star models with surface magnetic fields (M = 5 − 60 M , Ω/Ω crit = 0.2 − 1.0, B p = 1 − 20 kG). We then employ a representative grid of B-type star models (M = 5, 10, 15 M , Ω/Ω crit = 0.2, 0.5, 0.8, B p = 1, 3, 10, 30 kG) to compare to the results of a recent selfconsistent analysis of the sample of known magnetic B-type stars. We infer that magnetic massive stars arrive at the zero age main sequence with a range of rotation rates, rather than with one common value. In particular, some stars are required to have close-to-critical rotation at the ZAMS. However, magnetic braking yields surface rotation rates converging to a common low value, making it difficult to infer the initial rotation rates of evolved, slowly-rotating stars.

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Section: Magnetic Evolution Of Known Magnetic B-type Starssupporting

confidence: 89%

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

Keszthelyi

Meynet

Shultz

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The total unsigned magnetic flux of the primary is log Φ = log [(B d R 2 * )/(G R 2 ⊙ )] = 3.6±0.1. This is at the lower limit of the range of magnetic fluxes reported by Sikora et al (2019b) for their volume-limited sample of Ap/Bp stars, which extended up to the mass range occupied by HD 62658. Since Sikora et al (2019b) found no evidence for flux decay in this mass range, HD 62658's magnetic flux is not obviously anomalous for its age.…”

Section: Discussionmentioning

confidence: 62%

“…For the secondary, this analysis finds 1, 2, and 3σ upper limits on B d of 110 G, 340 G, and 1260 G. This field is thus almost certainly below the 300 G critical field limit identified by the survey of weak-field Ap/Bp stars conducted by Aurière et al (2007), and verified by the volume limited survey of Ap stars presented by Sikora et al (2019b). As such, if the star has a magnetic field it is likely to be of the ultraweak variety exhibited by Vega, Sirius, or Alhena, i.e.…”

Section: Bayesian Modelling Of Line Profilesmentioning

confidence: 53%

MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’

Shultz

Johnston

Labadie-Bartz

et al. 2019

Monthly Notices of the Royal Astronomical Society

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HD 62658 (B9p V) is a little-studied chemically peculiar star. Light curves obtained by the Kilodegree Extremely Little Telescope (KELT) and Transiting Exoplanet Survey Satellite (TESS) show clear eclipses with a period of about 4.75 d, as well as out-of-eclipse brightness modulation with the same 4.75 d period, consistent with synchronized rotational modulation of surface chemical spots. High-resolution ESPaDOnS circular spectropolarimetry shows a clear Zeeman signature in the line profile of the primary; there is no indication of a magnetic field in the secondary. PHOEBE modelling of the light curve and radial velocities indicates that the two components have almost identical masses of about 3 M ⊙ . The primary's longitudinal magnetic field B z varies between about +100 and −250 G, suggesting a surface magnetic dipole strength B d = 850 G. Bayesian analysis of the Stokes V profiles indicates B d = 650 G for the primary and B d < 110 G for the secondary. The primary's line profiles are highly variable, consistent with the hypothesis that the out-of-eclipse brightness modulation is a consequence of rotational modulation of that star's chemical spots. We also detect a residual signal in the light curve after removal of the orbital and rotational modulations, which might be pulsational in origin; this could be consistent with the weak line profile variability of the secondary. This system represents an excellent opportunity to examine the consequences of magnetic fields for stellar structure via comparison of two stars that are essentially identical with the exception that one is magnetic. The existence of such a system furthermore suggests that purely environmental explanations for the origin of fossil magnetic fields are incomplete.

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“…Fitting B z curves has a major advantage in its ability to incorporate any type of longitudinal field measurement, thus benefiting from large volumes of historic data (Bychkov et al, 2005) as well as observational material supplied by modern low- (Bagnulo et al, 2015) and high-resolution (Morel et al, 2015;Wade et al, 2016) spectropolarimetric surveys. Dipolar fits of B z data enable analysis of statistically unbiased stellar samples (Aurière et al, 2007;Sikora et al, 2019) and currently represent the only practical approach to the problem of studying evolutionary changes of magnetic field characteristics of early-type stars (Shultz et al, 2019b).…”

Section: Multipolar Fits To Integral Magnetic Observablesmentioning

confidence: 99%

“…Studies based on dipolar modelling of B z curves have established that polar field strengths of B and A stars follow a log-normal distribution with the most probable Oleg Kochukhov B d of about 2.5 kG and revealed a lower cutoff at B d ≈ 300 G (Aurière et al, 2007;Sikora et al, 2019). There is an evidence of a long-term decay of the dipolar field component.…”

Section: Multipolar Fits To Integral Magnetic Observablesmentioning

confidence: 99%

Stellar Magnetic Fields

Kochukhov¹

Cosmic Magnetic Fields

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This review discusses the problem of reconstruction of surface magnetic field topologies of early-type stars with a focus on mapping methods utilising information content of high-resolution spectropolarimetric observations. Basic principles of the Zeeman Doppler imaging tomographic mapping technique are outlined and its recent applications to magnetic early-type stars are summarised. The current observational and modelling challenges faced by the studies of surface magnetic fields in these stars are also discussed. pta.edu.pl/proc/2019dec17/123

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A volume-limited survey of mCP stars within 100 pc II: rotational and magnetic properties

Cited by 97 publications

References 79 publications

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’

Stellar Magnetic Fields

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