Document Type
Article
Publication Title
Monthy Notices of the Royal Astronomical Society
Abstract
We employ high-resolution spectroscopy and spectropolarimetry to derive the physical proper- ties and magnetic characteristics of the multiple system HD 164492C, located in the young open cluster M20. The spectrum reveals evidence of three components: a broad-lined early B star (HD 164492C1), a narrow-lined early B star (HD 164492C2) and a late B star (HD 164492C3). Components C2 and C3 exhibit significant (>100 km s−1) bulk radial velocity variations with a period of 12.5351(7) d that we attribute to eccentric binary motion around a common centre- of-mass. Component C1 exhibits no detectable radial velocity variations. Using constraints derived from modelling the orbit of the C2 C3 binary and from synthesis of the combined spectrum, we determine the approximate physical characteristics of the components. We con- clude that a coherent evolutionary solution consistent with the published age of M20 implies a distance to M20 of 0.9 0.2 kpc, corresponding to the smallest published values. We con- firm the detection of a strong magnetic field in the combined spectrum. The field is clearly associated with the broad-lined C1 component of the system. Repeated measurement of the longitudinal magnetic field allows the derivation of the rotation period of the magnetic star, Prot = 1.369 86(6) d. We derive the star’s magnetic geometry, finding i = 63 ± 6◦, β = 33 ± 6◦ and a dipole polar strength Bd = 7.9+1.2 kG. Strong emission – varying according to the magnetic period – is detected in the H −1.0 α profile. This is consistent with the presence of a centrifugal magnetosphere surrounding the rapidly rotating magnetic C1 component.
First Page
2517
Last Page
2530
DOI
10.1093/mnras/stw2799
Publication Date
11-2-2016
Recommended Citation
Wade, G. A.; Shultz, M.; Sikora, J.; Bernier, M.-E.; Rivinius, Th.; Alecian, E.; Petit, V.; Grunhut, J. H.; and BinaMIcS collaboration, "HD 164492C: a rapidly rotating, Hα-bright, magnetic early B star associated with a 12.5 d spectroscopic binary" (2016). Aerospace, Physics, and Space Science Faculty Publications. 673.
https://repository.fit.edu/apss_faculty/673
