KIC 10001893: a pulsating sdB star with multiple trapped modes

KIC 10001893 is a V1093 Her type pulsating subdwarf-B (sdB) star, which was observed extensively by the Kepler spacecraft. It was a part of the survey searching for compact pulsators in the Kepler field of view. An amplitude spectrum of the star demonstrates a rich content of g modes between 102 and 496 mu Hz as well as a few p modes above 2000 mu Hz. In total, we found 110 frequencies. The g-mode region contains 104 frequencies, while the p-mode region contains just 6, altogether indicating the hybrid nature of KIC 10001893. The main goal of our analysis was to identify the detected modes and to find some features, which will significantly help modelling the star. We found no multiplets that point at a pole-on orientation; however, we defined modal degrees and relative radial orders using asymptotic period spacing. Eventually, we assigned 32 dipole l = 1 and 18 quadrupole l = 2 modes. The most remarkable feature we found is trapped modes, which are clearly seen in a reduced-period diagram. It is the second time that three trapped modes are detected in one pulsating sdB star. Since the more trapped modes we find, the better sounding of the stellar interior we can do, this feature provides important constraints on the physical structure of the star.