HD 35502: a hierarchical triple system with a magnetic B5IVpe primary

Abstract

We present our analysis of HD 35502 based on high-and medium-resolution spectropolarimetric observations. Our results indicate that the magnetic B5IVsnp star is the primary component of a spectroscopic triple system and that it has an effective temperature of 18.4 0.6 kK, a mass of 5.7 0.6 M , and a polar radius of 3.0 +1.1 -0.5 R . The two secondary components are found to be essentially identical A-type stars for which we derive effective temperatures (8.9 0.3 kK), masses (2.1 0.2 M ), and radii (2.1 0.4 R ). We infer a hierarchical orbital configuration for the system in which the secondary components form a tight binary with an orbital period of 5.668 66(6) d that orbits the primary component with a period of over 40 yr. Least-Squares Deconvolution profiles reveal Zeeman signatures in Stokes V indicative of a longitudinal magnetic field produced by the B star ranging from approximately -4 to 0 kG with a median uncertainty of 0.4 kG. These measurements, along with the line variability produced by strong emission in H, are used to derive a rotational period of 0.853 807(3) d. We find that the measured v sin i = 75 5 km s -1 of the B star then implies an inclination angle of the star's rotation axis to the line of sight of 24 +6 -10