Asteroseismic analysis of the pulsating subdwarf B star KIC 11558725: an sdB+WD system with divergent frequency multiplets and mode trapping observed by Kepler

We analyse the full Kepler short cadence data set of the pulsating subdwarf B star KIC 11558725. KIC 11558725 is in an sdB+WD binary system with a period of 10.05 d and is known to be subsynchronously rotating. From the full data set, we detected 245 pulsation frequencies, mostly in the gravity (g-) mode region, but some in the pressure (p-) mode region as well. We are able to identify 142 of these pulsations as ≤ 2 modes and 27 as = 6 modes. Frequency splittings in the gand p-mode regions indicate that KIC 11558725 is a solid-body rotator with a rotation period of ∼44 d. The = 6 multiplets do not show a constant splitting, with the splitting increasing over the course of the observations. Multiplet structure constrains the inclination of the pulsation axis to be greater than ∼80◦. KIC 11558725 also displays mode trapping in two regions of its asymptotic sequence.