Thanks to large dedicated surveys , large-scale magnetic fields have been detected for about 10 % of early-type stars .
We aim to precisely characterize the large-scale magnetic field of the magnetic component of the wide binary o Lup , by using high-resolution ESPaDOnS and HARPSpol spectropolarimetry to analyse the variability of the measured longitudinal magnetic field .
In addition , we investigate the periodic variability using space-based photometry collected with the BRITE-Constellation by means of iterative prewhitening .
The rotational variability of the longitudinal magnetic field indicates a rotation period P _ { \mathrm { rot } } = 2.95333 ( 2 ) d and that the large-scale magnetic field is dipolar , but with a significant quadrupolar contribution .
Strong differences in the strength of the measured magnetic field occur for various chemical elements as well as rotational modulation for Fe and Si absorption lines , suggesting a inhomogeneous surface distribution of chemical elements .
Estimates of the geometry of the large-scale magnetic field indicate i = 27 \pm 10 ^ { \circ } , \beta = 74 ^ { +7 } _ { -9 } { } ^ { \circ } , and a polar field strength of at least 5.25 kG .
The BRITE photometry reveals the rotation frequency and several of its harmonics , as well as two gravity mode pulsation frequencies .
The high-amplitude g-mode pulsation at f = 1.1057 d ^ { -1 } dominates the line-profile variability of the majority of the spectroscopic absorption lines .
We do not find direct observational evidence of the secondary in the spectroscopy .
Therefore , we attribute the pulsations and the large-scale magnetic field to the B5IV primary of the o Lup system , but we discuss the implications should the secondary contribute to or cause the observed variability .