HD 164492C: a rapidly-rotating, H$\alpha$-bright, magnetic early B star associated with a 12.5d spectroscopic binary

Abstract

We employ high resolution spectroscopy and spectropolarimetry to derive the physical properties and magnetic characteristics of the multiple system HD 164492C, located in the young open cluster M20. The spectrum reveals evidence of 3 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) 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 modeling the orbit of the C2+C3 binary and from synthesis of the combined spectrum, we determine the approximate physical characteristics of the components. We conclude that a coherent evolutionary solution consistent with the published age of M20 implies a distance to the system of $0.9\pm 0.2$ kpc, corresponding to the smallest published values. We confirm 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, $P_{\mathrm{rot}}=1.36986(6)$ d. We derive the star's magnetic geometry, finding $i=63\pm 6$ deg, $\beta =33\pm 6$ deg and a dipole polar strength $B_{\mathrm{d}}=7.9_{-1.0}^{+1.2}$ kG. Strong emission - varying according to the magnetic period - is detected in the H$\alpha$ profile. This is consistent with the presence of a centrifugal magnetosphere surrounding the rapidly rotating magnetic C1 component.

arXiv commentAccepted by MNRAS

References in corpus (21)

• Mass-loss predictions for O and B stars as a function of metallicity
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Automated data reduction workflows for astronomy
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• Least squares deconvolution of the stellar intensity and polarization spectra
• A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• Mass loss in main-sequence B stars
• Absolute Proper Motions of Open Clusters: I. Observational data
• Molecular clouds in the Trifid nebula M20; Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars
• HR 5907: Discovery of the most rapidly rotating magnetic B-type star by the MiMeS Collaboration
• Basic parameters and properties of the rapidly rotating magnetic helium strong B star HR7355
• Variation of the extinction law in the Trifid nebula
• First HARPSpol discoveries of magnetic fields in massive stars
• The Discovery of a Strong Magnetic Field and Co-rotating Magnetosphere in the Helium-weak Star HD 176582
• 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
• The magnetic field of the double-lined spectroscopic binary system HD 5550
• HD 35502: a hierarchical triple system with a magnetic B5IVpe primary
• HST and UKIRT Observations of the Center of the Trifid Nebula: Evidence for the Photoevaporation of a Proplyd and a Protostellar Condensation

Cited by in corpus (17)

• The Magnetic Early B-type Stars III: A main sequence magnetic, rotational, and magnetospheric biography
• The Magnetic Early B-type Stars I: Magnetometry and Rotation
• The Magnetic Early B-type Stars IV: Breakout or Leakage? H$\alpha$ emission as a diagnostic of plasma transport in centrifugal magnetospheres
• The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia
• HD 156324: a tidally locked magnetic triple spectroscopic binary with a disrupted magnetosphere
• A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907
• Lucky Spectroscopy, an equivalent technique to Lucky Imaging. Spatially resolved spectroscopy of massive close visual binaries using the William Herschel Telescope
• $\epsilon$ Lupi: measuring the heartbeat of a doubly-magnetic massive binary with BRITE-Constellation
• Lucky spectroscopy, an equivalent technique to Lucky Imaging: II. Spatially-resolved intermediate-resolution blue-violet spectroscopy of 19 close massive binaries using the William Herschel Telescope
• The binary system of the spinning-top Be star Achernar
• B fields in OB stars (BOB): The magnetic triple stellar system HD 164492C in the Trifid nebula
• Detection of an extremely strong magnetic field in the double-degenerate binary merger product HD 144941
• The magnetic field and magnetosphere of Plaskett's star: A fundamental shift in our understanding of the system
• The early B-type star Rho Oph A is an X-ray lighthouse
• Photometric properties and stellar parameters of the rapidly rotating magnetic early-B star HD 345439
• The Young Stellar Population, Distance, and Cloud-Cloud Collision Induced Star Formation Scenario of the Trifid Nebula
• MOBSTER -- VII. Using light curves to infer magnetic and rotational properties of stars with centrifugal magnetospheres