The Magnetic Early B-type Stars I: Magnetometry and Rotation

Abstract

The rotational and magnetic properties of many magnetic hot stars are poorly characterized, therefore the MiMeS and BinaMIcS collaborations have collected extensive high-dispersion spectropolarimetric datasets of these targets. We present longitudinal magnetic field measurements $⟨B_{\mathrm{z}}⟩$ for 52 early B-type stars (B5 to B0), with which we attempt to determine their rotational periods $P_{\mathrm{rot}}$. Supplemented with high-resolution spectroscopy, low-resolution DAO circular spectropolarimetry, and archival Hipparcos photometry, we determined $P_{\mathrm{rot}}$ for 10 stars, leaving only 5 stars for which $P_{\mathrm{rot}}$ could not be determined. Rotational ephemerides for 14 stars were refined via comparison of new to historical magnetic measurements. The distribution of $P_{\mathrm{rot}}$ is very similar to that observed for the cooler Ap/Bp stars. We also measured $v\sin i$ and $v_{\mathrm{mac}}$ for all stars. Comparison to non-magnetic stars shows that $v\sin i$ is much lower for magnetic stars, an expected consequence of magnetic braking. We also find evidence that $v_{\mathrm{mac}}$ is lower for magnetic stars. LSD profiles extracted using single-element masks revealed widespread, systematic discrepancies in $⟨B_{\mathrm{z}}⟩$ between different elements: this effect is apparent only for chemically peculiar stars, suggesting it is a consequence of chemical spots. Sinusoidal fits to H line $⟨B_{\mathrm{z}}⟩$ measurements (which should be minimally affected by chemical spots), yielded evidence of surface magnetic fields more complex than simple dipoles in 6 stars for which this has not previously been reported; however, in all 6 cases the second- and third-order amplitudes are small relative to the first-order (dipolar) amplitudes.

38 pages, 47 figures, accepted for publication in MNRAS

References in corpus (27)

• The surprising magnetic topology of tauSco: fossil remnant or dynamo output?
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
• On non-axisymmetric magnetic equilibria in stars
• B fields in OB stars (BOB): Concluding the FORS2 observing campaign
• New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars
• On the use of the Fourier Transform to determine the projected rotational velocity of line-profile variable B stars
• The detection of variable radio emission from the fast rotating magnetic hot B-star HR7355 and evidence for its X-ray aurorae
• Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey
• On the consistency of magnetic field measurements of Ap stars: lessons learned from the FORS1 archive
• Magnetic field topology and chemical abundance distributions of the young, rapidly rotating chemically peculiar star HR5624
• HD 156324: a tidally locked magnetic triple spectroscopic binary with a disrupted magnetosphere
• The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD184927
• B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid Nebula, one of the youngest star forming regions
• Discovery of magnetic A supergiants: the descendants of magnetic main sequence B stars
• The magnetic field and spectral variability of the He-weak star HR 2949
• The pulsating magnetosphere of the extremely slowly rotating magnetic $\beta$ Cep star ${\xi }^1$ CMa
• B fields in OB stars (BOB): FORS2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD23478 and HD345439
• HD 164492C: a rapidly-rotating, H$\alpha$-bright, magnetic early B star associated with a 12.5d spectroscopic binary
• An infrared diagnostic for magnetism in hot stars
• The IACOB project: IV. New predictions for high-degree non-radial mode instability domains in massive stars and connection with macroturbulent broadening
• The challenge of measuring magnetic fields in strongly pulsating stars: the case of HD 96446
• Discovery of magnetic fields in three He variable Bp stars with He and Si spots
• Identification of pulsational modes in rotating slowly pulsating B-type stars

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