Detection of a centrifugal magnetosphere in one of the most massive stars in the Oph star-forming cloud
arXiv:1712.05939 · doi:10.1002/asna.201713457
Abstract
Recent XMM-Newton observations of the B2 type star rho Oph A indicated a periodicity of 1.205d, which was ascribed to rotational modulation. Since variability of X-ray emission in massive stars is frequently the signature of a magnetic field, we investigated whether the presence of a magnetic field can indeed be invoked to explain the observed X-ray peculiarity. Two FORS2 spectropolarimetric observations in different rotation phases revealed the presence of a negative (<B_z>_all=-419+-101G) and positive (<B_z>_all=538+-69G) longitudinal magnetic field, respectively. We estimate a lower limit for the dipole strength as B_d = 1.9+-0.2kG. Our calculations of the Kepler and Alfven radii imply the presence of a centrifugally supported, magnetically confined plasma around rho Oph A. The study of the spectral variability indicates a behaviour similar to that observed in typical magnetic early-type Bp stars.
arXiv comment7 pages, 1 table, 5 figures, accepted for publication in AN
References in corpus (19)
- 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)
- Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
- 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
- Measurements of magnetic fields over the pulsation cycle in six roAp stars with FORS1 at the VLT
- New measurements of magnetic fields of roAp stars with FORS1 at the VLT
- Magnetic field measurements of O stars with FORS1 at the VLT
- B fields in OB stars (BOB): Concluding the FORS2 observing campaign
- Magnetic Field Generation in Stars
- Basic parameters and properties of the rapidly rotating magnetic helium strong B star HR7355
- High-Resolution Chandra X-ray Imaging and Spectroscopy of the Sigma Orionis Cluster
- Chandra Observation of the Trifid Nebula: X-ray emission from the O star complex and actively forming pre-main sequence stars
- Exploring the origin of magnetic fields in massive stars: II. New magnetic field measurements in cluster and field stars
- Short time scale spectral variability in the A0 supergiant HD92207 and the importance of line profile variations for the interpretation of FORS2 spectropolarimetric observations
- 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 Two Rare Rigidly-Rotating Magnetosphere Stars in the APOGEE Survey
- The first stars of the Rho Ophiuchi Dark Cloud. XMM-Newton view of Rho Oph and its neighbors
- The early B-type star Rho Oph A is an X-ray lighthouse