A remarkable change of the spectrum of the magnetic Of?p star HD 148937 reveals evidence of an eccentric, high-mass binary

Wade, G. A.; Smoker, J. V.; Evans, Christopher J.; Howarth, Ian D.; Barbá, R. H.; Cox, Nicholas; Morrell, N.; Nazé, Yaël; Cami, J.; Farhang, Amin; Walborn, N. R.; Arias, J. I.; Gamen, R.

doi:10.1093/mnras/sty3304

Cited by 12 publications

(16 citation statements)

References 41 publications

(91 reference statements)

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“…In respect to the possible binary nature of HD 54879, it was suggested in recent years that three out of five Of?p stars are members of binary systems. Long-term radial velocity changes indicating binarity were reported for the Of?p star HD 191612 (Howarth et al 2007) who suggested P orb = 1542 d. According to Wade et al (2019), the Of?p star HD 148937 is likely a high-mass, double-lined spectroscopic binary (Wade et al 2019). Also for the Of?p star HD 108 Naze et al (2008) reported that a very long-term binary cannot be excluded.…”

Section: Discussionmentioning

confidence: 98%

The very slow rotation of the magnetic O9.7 V star HD 54879

Hubrig

Järvinen

Schöller

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The first FORS 2 spectropolarimetric observation of the longitudinal magnetic field of HD 54879 of the order of −600 G with a lower limit of the dipole strength of ∼ 2 kG dates back to 2014. Since then observations showed a gradual decrease of the absolute value of the mean longitudinal magnetic field. In the course of the most recent monitoring of HD 54879 using FORS 2 spectropolarimetric observations from 2017 October to 2018 February, a longitudinal magnetic field strength change from about −300 G down to about −90 G was reported. A sudden increase of the absolute value of the mean longitudinal magnetic field and an accompanying spectral variability was detected on 2018 February 17. New FORS 2 spectropolarimetric data obtained from 2018 December to 2019 February confirm the very slow magnetic field variability, with the field decreasing from about 150 G to −100 G over two months. Such a slow magnetic field variability, related to the extremely slow rotation of HD 54879, is also confirmed using high-resolution HARPSpol and ESPaDOnS spectropolarimetry. The re-analysis of the FORS 2 polarimetric spectra from 2018 February indicates that the previously reported field increase and the change of the spectral appearance was caused by improper spectra extraction and wavelength calibration using observations obtained at an insufficient signal-to-noise ratio. The presented properties of HD 54879 are discussed in the context of the Of?p spectral classification.

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Section: Discussionmentioning

confidence: 98%

The very slow rotation of the magnetic O9.7 V star HD 54879

Hubrig

Järvinen

Schöller

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…This may reflect an incomplete characterization of the sample of magnetic O-type stars. Many such systems have been found to be spectroscopic binaries, leading to an increase in the inferred surface magnetic field strength (e.g., ζ Ori Aa and HD 148937; Blazère et al 2015;Wade et al 2019); B d is still a lower limit for the extremely slow rotator HD 108 (Shultz & Wade 2017); and while magnetic fields have still not been detected in the magellanic cloud Of?p stars (Walborn et al 2015;Bagnulo et al 2017), preliminary models of their magnetospheric variability suggest the mean B d of this population to be about 7 kG (Munoz et al 2018), consistent with that of the Galactic magnetic AB stars.…”

Section: Dipolar Magnetic Field Strengthsmentioning

confidence: 99%

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

Shultz

Wade

Rivinius

et al. 2019

Monthly Notices of the Royal Astronomical Society

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138

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Magnetic confinement of stellar winds leads to the formation of magnetospheres, which can be sculpted into Centrifugal Magnetospheres (CMs) by rotational support of the corotating plasma. The conditions required for the CMs of magnetic early B-type stars to yield detectable emission in Hα -the principal diagnostic of these structures -are poorly constrained. A key reason is that no detailed study of the magnetic and rotational evolution of this population has yet been performed. Using newly determined rotational periods, modern magnetic measurements, and atmospheric parameters determined via spectroscopic modelling, we have derived fundamental parameters, dipolar oblique rotator models, and magnetospheric parameters for 56 early B-type stars. Comparison to magnetic A-and O-type stars shows that the range of surface magnetic field strength is essentially constant with stellar mass, but that the unsigned surface magnetic flux increases with mass. Both the surface magnetic dipole strength and the total magnetic flux decrease with stellar age, with the rate of flux decay apparently increasing with stellar mass. We find tentative evidence that multipolar magnetic fields may decay more rapidly than dipoles. Rotational periods increase with stellar age, as expected for a magnetic braking scenario. Without exception, all stars with Hα emission originating in a CM are 1) rapid rotators, 2) strongly magnetic, and 3) young, with the latter property consistent with the observation that magnetic fields and rotation both decrease over time.

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“…In the best cases, these systems offer dynamical mass and radius estimates to better than one per cent (Torres et al 2010). Such precise measurements combined with the powerful constrains of co-evolution and identical initial chemical composition have allowed the thorough investigation of the importance of rotation in stellar evolutionary theory (Brott et al 2011a,b;Ekström et al 2012Ekström et al , 2018de Mink et al 2013;Schneider et al 2014), the calibration of pre-through post-main-sequence evolution (Torres et al 2013;Higl & Weiss 2017;Beck et al 2018a;Kirkby-Kent et al 2018), the critical investigation of magnetic fields in stars (Takata et al 2012;Grunhut et al 2013;Torres et al 2014b;Pablo et al 2015;Kochukhov et al 2018;Wade et al 2019), the calibration of distances (Guinan et al 1998;Ribas et al 2000aRibas et al , 2005Hensberge et al 2000;Bonanos et al 2006;Pietrzyński et al 2013;Gallenne et al 2016;Suchomska et al 2019), the investigation of abundances and rotational velocities (Pavlovski & Hensberge 2005;Pavlovski & Southworth 2009;Pavlovski et al , 2018Simón-Díaz et al 2017), and the calibration of asteroseismic modelling (De Cat et al 2000, 2004; Aerts & Harmanec 2004;Schmid et al 2015;Schmid & Aerts 2016;Beck et al 2018a,b;Johnston et al 2019). Additionally, the development of such precise measurements has led to the reported systematic discrepancy between masses obtained via dynamics or empirical spectral relations and fitting theoretically calculated evolutionary tracks…”

Section: Introductionmentioning

confidence: 99%

Modelling of the B-type binaries CW Cephei and U Ophiuchi

Johnston

Pavlovski

Tkachenko

2019

A&A

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Context. Intermediate-mass stars are often overlooked. They are not supernova progenitors, but still host convective cores and complex atmospheres that require computationally expensive treatment. This means that there is a general lack of this class of stars modelled by state-of-the-art stellar structure and evolution codes. Aims. We used high-quality spectroscopy to update the dynamically obtained stellar parameters and to produce a new evolutionary assessment of the bright B0.5+B0.5 and B5V+B5V binary systems CW Cep and U Oph. Methods. We used new spectroscopy obtained with the Hermes spectrograph to revisit the photometric binary solution of the two systems. The updated mass ratio and effective temperatures are incorporated to obtain new dynamical masses for the primary and secondary. With these data we performed evolutionary modelling using isochrone-clouds to investigate the core properties of these stars. Results. We report the first abundances for CW Cep and U Oph, and we report an updated dynamical solution for the two systems. We find that we cannot uniquely constrain the amount of core boundary mixing in any of the stars we consider. Instead, we report their core masses and compare our results to previous studies. Conclusions. We find that the per-cent level precision on fundamental stellar quantities are accompanied with core mass estimates to a precision between ∼5% and 15%. We find that differences in analysis techniques can lead to substantially different evolutionary modelling results, which calls for the compilation of a homogeneously analysed sample to draw inferences on internal physical processes.

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A remarkable change of the spectrum of the magnetic Of?p star HD 148937 reveals evidence of an eccentric, high-mass binary

Cited by 12 publications

References 41 publications

The very slow rotation of the magnetic O9.7 V star HD 54879

The very slow rotation of the magnetic O9.7 V star HD 54879

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

Modelling of the B-type binaries CW Cephei and U Ophiuchi

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