Magnetic field geometry and chemical abundance distribution of the He-strong star CPD -57 3509

Abstract

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 FORS2 and high-resolution UVES 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 6.36d 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 3.9-4.5kG. 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. Further, 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 beta Cep-like pulsations. A small periodic variability in line with the changes of the magnetic field strength is clearly seen in the photometric data.

11 pages, 5 tables, 7 figures, accepted for publication in MNRAS

References in corpus (8)

• The Gaia mission
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• UCAC5: New Proper Motions using Gaia DR1
• Evolution of surface CNO abundances in massive stars
• Hot Stuff for One Year (HSOY) - A 583 million star proper motion catalogue derived from Gaia DR1 and PPMXL
• The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD184927

Cited by in corpus (4)

• The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia
• The Gaia-ESO survey: A spectroscopic study of the young open cluster NGC 3293
• Detection of anomalous element distribution in the extremely slowly rotating magnetic O9.7 V star HD 54879
• The magnetic field of the stripped primary in the upsilon Sgr system, a member of the rare class of hydrogen-deficient binaries