The magnetic early B-type stars – III. A main-sequence magnetic, rotational, and magnetospheric biography

Shultz, Matt; Wade, G. A.; Rivinius, Th.; Alécian, E.; Neiner, C.; Petit, Véronique; Owocki, S. P.; ud‐Doula, Asif; Kochukhov, O.; Bohlender, D.; Keszthelyi, Z.

doi:10.1093/mnras/stz2551

Cited by 102 publications

(151 citation statements)

References 169 publications

(246 reference statements)

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“…Comparing the values of these two radii, it follows that R K ≪ R A , classifying ρ Oph A as a star with a centrifugal magnetosphere. We also find that the dimensionless parameter log(R A /R K ) is ≈ 0.8, placing ρ Oph A just at the boundary of where magnetic early-type stars are Hα emitters, which are characterized by log(R A /R K ) 0.8 (Petit et al 2013;Shultz et al 2019b).…”

Section: The Magnetosphere Of ρ Oph Amentioning

confidence: 75%

“…The fast rotation of ρ Oph A might produce rotational oblateness. We calculate the ratio between the polar and equatorial radii following the procedure described in Shultz et al (2019b). We estimated R p /R eq = 0.86 ± 0.02, which puts ρ Oph A between the cases of the two fast rotators: HR 7355 (R p /R eq = 0.83) and HR 5907 (R p /R eq = 0.88) (Grunhut et al 2012;Rivinius et al 2013).…”

Section: The Orm Geometry Of ρ Oph Amentioning

confidence: 99%

“…Following the simplified hypothesis of completely rigid magnetic field lines, Townsend & Owocki (2005) developed the Rigidly Rotating Magnetospheric (RRM) model, where the presence of circumstellar plasma, forced to rigidly co-rotate with the star by the magnetic field, can explain the rotational behavior of the Hα emission observed in some fast rotating and strong magnetic early-type stars (Groote & Hunger 1997;Shultz et al 2019a). In particular, the study of the typical Hα signature of a RRM has been used to classify early type magnetic stars with centrifugal magnetospheres (Petit et al 2013;Shultz et al 2019b).…”

Section: Introductionmentioning

confidence: 99%

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Evidence for radio and X-ray auroral emissions from the magnetic B-type star ρ Oph A

Leto

Trigilio

Leone³

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present new ATCA multi-wavelength radio measurements (range 2.1-21.2 GHz) of the early-type magnetic star ρ Oph A, performed in March 2019 during 3 different observing sessions. These new ATCA observations evidence a clear rotational modulation of the stellar radio emission and the detection of coherent auroral radio emission from ρ Oph A at 2.1 GHz. We collected high-resolution optical spectra of ρ Oph A acquired by several instruments over a time span of about ten years. We also report new magnetic field measurements of ρ Oph A that, together with the radio light curves and the temporal variation of the equivalent width of the He I line (λ = 5015Å), were used to constrain the rotation period and the stellar magnetic field geometry. The above results have been used to model the stellar radio emission, modelling that allowed us to constrain the physical condition of ρ Oph A's magnetosphere. Past XMM-Newton measurements showed periodic X-ray pulses from ρ Oph A. We correlate the X-ray light curve with the magnetic field geometry of ρ Oph A. The already published XMM-Newton data have been re-analyzed showing that the X-ray spectra of ρ Oph A are compatible with the presence of a non-thermal X-ray component. We discuss a scenario where the emission phenomena occurring at the extremes of the electromagnetic spectrum, radio and X-ray, are directly induced by the same plasma process. We interpret the observed X-ray and radio features of ρ Oph A as having an auroral origin.

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Section: The Magnetosphere Of ρ Oph Amentioning

confidence: 75%

Section: The Orm Geometry Of ρ Oph Amentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evidence for radio and X-ray auroral emissions from the magnetic B-type star ρ Oph A

Leto

Trigilio

Leone³

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Atmospheric parameters for these stars based upon spec- troscopic modelling and Gaia data release 2 parallaxes were presented by Shultz et al (2019a). Shultz et al (2019c) combined these observables to calculate fundamental stellar parameters, magnetic parameters (assuming an inclined dipole topology), stellar wind parameters, and magnetospheric parameters. The estimated masses of the observed stars range from 4.3 to 17.5 M , and were determined from the nonmagnetic evolutionary models of Ekström et al (2012).…”

Section: Progenitors Of Slow Rotatorsmentioning

confidence: 99%

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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“…Bagnulo et al (2006) and Landstreet et al (2007Landstreet et al ( , 2008 have shown that the magnetic field at the surface of mCP stars decreases with time because of magnetic flux conversation with increased stellar radius and additional decay (cf. also Fossati et al 2016;Shultz et al 2019). The time scales involved vary strongly with mass (∼250 Myr for stars of 2-3 M ⊙ to ∼15 Myr for stars of 4-5 M ⊙ according to Landstreet et al 2008).…”

Section: Colour-magnitude Diagrammentioning

confidence: 99%

New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

Bernhard

Hümmerich

Paunzen

2020

Monthly Notices of the Royal Astronomical Society

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Magnetic chemically peculiar (mCP) stars allow the investigation of such diverse phenomena as atomic diffusion, magnetic fields and stellar rotation. The aim of the present investigation is to enhance our knowledge of the rotational properties of mCP stars by increasing the sample of objects with accurately determined rotational periods. To this end, archival photometric time-series data from the ASAS-3, KELT and MASCARA surveys were employed to improve existing rotational period information and derive rotational periods for mCP stars hitherto not known to be photometric variables. Our final sample consists of 294 mCP stars, a considerable amount of which (more than 40%) are presented here as photometric variables for the first time. In addition, we identified 24 mCP star candidates that show light variability in agreement with rotational modulation but lack spectroscopic confirmation. The rotational period distribution of our sample agrees well with the literature. Most stars are between 100 Myr and 1 Gyr old, with an apparent lack of very young stars. No objects were found on the zero age main sequence; several stars seem to have evolved to the subgiant stage, albeit well before the first dredge-up. We identified four eclipsing binaries (HD 244391, HD 247441, HD 248784 and HD 252519), which potentially host an mCP star. This is of great interest because mCP stars are very rarely found in close binary systems, particularly eclipsing ones. Using archival spectra, we find strong evidence that the HD 252519 system indeed harbours an mCP star component.

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The magnetic early B-type stars – III. A main-sequence magnetic, rotational, and magnetospheric biography

Cited by 102 publications

References 169 publications

Evidence for radio and X-ray auroral emissions from the magnetic B-type star ρ Oph A

Evidence for radio and X-ray auroral emissions from the magnetic B-type star ρ Oph A

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

New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

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