HR 5907: Discovery of the most rapidly rotating magnetic early B-type star by the MiMeS Collaboration★†

Grunhut, J.; Rivinius, Thomas; Wade, G. A.; Townsend, R. H. D.; Marcolino, W. L. F.; Bohlender, D.; Szeifert, T.; Petit, Véronique; Matthews, J. M.; Rowe, Jason F.; Moffat, A. F. J.; Kallinger, T.; Kuschnig, R.; Guenther, D. B.; Ruciński, S. M.; Sasselov, Dimitar; Weiss, W. W.

doi:10.1111/j.1365-2966.2011.19824.x

Cited by 74 publications

(93 citation statements)

References 41 publications

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“…Groote & Hunger 1997), only two other stars, HR 5907 and HR 7355, are known to belong to this group, which is called the σ Ori E analogues (Grunhut et al 2012;Rivinius et al 2013). Their very strong magnetic fields and extraordinary fast rotation pose a mystery for theories of star formation and magnetic field evolution.…”

Section: Discussionmentioning

confidence: 99%

B fields in OB stars (BOB): FORS 2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439

Hubrig

Schöller

Fossati

et al. 2015

A&A

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Aims. Massive B-type stars with strong magnetic fields and fast rotation are very rare and pose a mystery for theories of star formation and magnetic field evolution. Only two such stars, called σ Ori E analogues, were known until recently. A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, announced the discovery of two additional rigidly rotating magnetosphere stars, HD 23478 and HD 345439. The magnetic fields in these newly discovered σ Ori E analogues have not been investigated so far. Methods. In the framework of our ESO Large Programme and one normal ESO programme, we carried out low-resolution FORS 2 spectropolarimetric observations of HD 23478 and HD 345439. Results. In the measurements of hydrogen lines, we discover a rather strong longitudinal magnetic field of up to 1.5 kG in HD 23478 and up to 1.3 kG using the entire spectrum. The analysis of HD 345439 using four subsequent spectropolarimetric subexposures does not reveal a magnetic field at a significance level of 3σ. On the other hand, individual subexposures indicate that HD 345439 may host a strong magnetic field that rapidly varies over 88 min. The fast rotation of HD 345439 is also indicated by the behaviour of several metallic and He i lines in the low-resolution FORS 2 spectra that show profile variations already on this short time-scale.

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Section: Discussionmentioning

confidence: 99%

B fields in OB stars (BOB): FORS 2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439

Hubrig

Schöller

Fossati

et al. 2015

A&A

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“…Some Hestrong stars are known to rotate near critical velocity (Grunhut et al 2012;Rivinius et al 2013), and the nightly variation in the magnetic field (Sect. 3) implies that CPD −57 • 3509 is rotating at a much higher velocity than the observed rather low v sin i = 35 km s −1 would suggest.…”

Section: Codes and Analysis Methodologymentioning

confidence: 99%

B fields in OB stars (BOB): Detection of a magnetic field in the He-strong star CPD −57° 3509

Przybilla

Fossati

Hubrig

et al. 2016

A&A

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Aims. We report the detection of a magnetic field in the helium-strong star CPD −57 • 3509 (B2 IV), a member of the Galactic open cluster NGC 3293, and characterise the star's atmospheric and fundamental parameters. Methods. Spectropolarimetric observations with FORS2 and HARPSpol are analysed using two independent approaches to quantify the magnetic field strength. A high-S/N FLAMES/GIRAFFE spectrum is analysed using a hybrid non-LTE model atmosphere technique. Comparison with stellar evolution models constrains the fundamental parameters of the star. Results. We obtain a firm detection of a surface averaged longitudinal magnetic field with a maximum amplitude of about 1 kG. Assuming a dipolar configuration of the magnetic field, this implies a dipolar field strength larger than 3.3 kG. Moreover, the large amplitude and fast variation (within about 1 day) of the longitudinal magnetic field implies that CPD −57 • 3509 is spinning very fast despite its apparently slow projected rotational velocity. The star should be able to support a centrifugal magnetosphere, yet the spectrum shows no sign of magnetically confined material; in particular, emission in Hα is not observed. Apparently, the wind is either not strong enough for enough material to accumulate in the magnetosphere to become observable or, alternatively, some leakage process leads to loss of material from the magnetosphere. The quantitative spectroscopic analysis of the star yields an effective temperature and a logarithmic surface gravity of 23 750 ± 250 K and 4.05 ± 0.10, respectively, and a surface helium fraction of 0.28 ± 0.02 by number. The surface abundances of C, N, O, Ne, S, and Ar are compatible with the cosmic abundance standard, whereas Mg, Al, Si, and Fe are depleted by about a factor of 2. This abundance pattern can be understood as the consequence of a fractionated stellar wind. CPD −57 • 3509 is one of the most evolved He-strong stars known with an independent age constraint due to its cluster membership.

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“…The chemically peculiar Ap/Bp stars have their distinct chemical surface abundance to this particular effect (e.g., Alecian & Stift 2017). Moreover, these magnetic fields can lead to surface abundance inhomogeneities (i.e., spots) by suppressing thermal convection at the stellar surface, as seen from tomographic images (e.g., HD 75049; Kochukhov et al 2015), the rotational modulation of absorption lines (e.g., HR 5907; Grunhut et al 2012) or from the photometric brightness (e.g., σ Ori E; Oksala et al 2015). A&A 605, A104 (2017) In addition, the stellar wind is affected by the large-scale magnetic field, as ionized ejected mass follows the magnetic field lines, leading to typical observational signatures.…”

Section: The Effect Of Magnetism In Early-type Starsmentioning

confidence: 99%

Magnetic characterization of the SPB/β Cep hybrid pulsator HD 43317

Buysschaert

Neiner

Briquet

et al. 2017

A&A

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Large-scale magnetic fields at the surface of massive stars do not only influence the outer-most layers of the star, but also have consequences for the deep interior, only observationally accessible through asteroseismology. We performed a detailed characterization of the dipolar magnetic field at the surface of the B3.5V star HD 43317, a SPB/β Cep hybrid pulsator, by studying the rotationally modulated magnetic field of archival and new Narval spectropolarimetry. Additionally, we employed a grid-based approach to compare the Zeeman signatures with model profiles. By studying the rotational modulation of the He lines in both the Narval and HARPS spectroscopy caused by co-rotating surface abundance inhomogeneities, we updated the rotation period to 0.897673 ± 0.000004 d. The inclination angle between the rotation axis and the observer's line of sight remains ill-defined, because of the low level of variability in Stokes V and deformations in the intensity profiles by stellar pulsation modes. The obliquity angle between the rotation and magnetic axes is constrained to β ∈ [67, 90] • , and the strength of the dipolar magnetic field is of the order of 1 kG to 1.5 kG. This magnetic field at the stellar surface is sufficiently strong to warrant a uniformly rotating radiative envelope, causing less convective core overshooting, which should be visible in future forward seismic modeling.

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HR 5907: Discovery of the most rapidly rotating magnetic early B-type star by the MiMeS Collaboration★†

Cited by 74 publications

References 41 publications

B fields in OB stars (BOB): FORS 2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439

B fields in OB stars (BOB): FORS 2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439

B fields in OB stars (BOB): Detection of a magnetic field in the He-strong star CPD −57° 3509

Magnetic characterization of the SPB/β Cep hybrid pulsator HD 43317

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