Mon. Not. R. Astron. Soc., 471, 1543-1552 (2017/October-3)
Magnetic field geometry and chemical abundance distribution of the He-strong star CPD -57°3509.
HUBRIG S., PRZYBILLA N., KORHONEN H., ILYIN I., SCHOLLER M., JARVINEN S.P., NIEVA M.-F., SCHOLZ R.-D., KIMESWENGER S., RAMOLLA M., KHOLTYGIN A.F. and BRIQUET M.
Abstract (from CDS):
The magnetic field of CPD -57°3509 was recently detected in the framework of the BOB (B fields in OB stars) collaboration. We acquired low-resolution spectropolarimetric observations of CPD -57°3509 with the FOcal Reducer low-dispersion Spectrograph 2 and high-resolution UV-Visual Echelle Spectrograph observations randomly distributed over a few months to search for periodicity, to study the magnetic field geometry and to determine the surface distribution of silicon and helium. We also obtained supplementary photometric observations at a timeline similar to the spectroscopic and spectropolarimetric observations. A period of 6.36 d was detected in the measurements of the mean longitudinal magnetic field. A sinusoidal fit to our measurements allowed us to constrain the magnetic field geometry and estimate the dipole strength in the range of 3.9-4.5 kG. Our application of the Doppler imaging technique revealed the presence of He I spots located around the magnetic poles, with a strong concentration at the positive pole and a weaker one around the negative pole. In contrast, high-concentration Si III spots are located close to the magnetic equator. Furthermore, our analysis of the spectral variability of CPD -57°3509 on short time-scales indicates distinct changes in shape and position of line profiles possibly caused by the presence of β Cep like pulsations. A small periodic variability in line with the changes of the magnetic field strength is clearly seen in the photometric data.
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: abundances - stars: evolution - stars: individual: CPD -57 3509 - stars: magnetic field - stars: massive - stars: oscillations - stars: oscillations
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