We present a new oscillation code, GYRE, which solves the stellar pulsation equations (both adiabatic and non-adiabatic) using a novel Magnus Multiple Shooting numerical scheme devised to overcome certain weaknesses of the usual relaxation and shooting schemes appearing in the literature. The code is accurate (up to 6th order in the number of grid points), robust, efficiently makes use of multiple processor cores and/or nodes, and is freely available in source form for use and distribution. We verify the code against analytic solutions and results from other oscillation codes, in all cases finding good agreement. Then, we use the code to explore how the asteroseismic observables of a 1.5 M ⊙ star change as it evolves through the red-giant bump.

No abstract

In this paper we view a relaxing complex system such as entangled polymer melt to consist of three parts: (1) an individual primary species PS of interest; (2) a heat bath (HB) whose interaction with the PS provides the primary mechanism of relaxation; (3) other relaxing species whose interactions with the PS, the PS-C coupling, are for us the principal characteristic of complexity. The PS-C coupling is represented by time dependent constraints whose effect begins only after the primary relaxation process due to the PS-HB interaction is already underway. The overall process is described both physically and theoretically. The latter is described classically by means of time dependent Dirac constraint theory applied to a Liouville operator formalism. The physical and theoretical discussion leads to a time dependent relaxation rate W(t). The specific form of W(t) is adduced based on the requirement of time-temperature equivalence or thermorheological simplicity. The result is a time independent relaxation rate W0 for times short compared to the onset of the effect of the time dependent constraints at tc=ω−1c, and a time dependent rate W0(ωct)−n for times long compared to tc. The case W0tc<1 is of most interest because the relaxation process then reveals the effect of complexity empirically. The empirically observed result is then just the Kohlrausch form. Furthermore, a second relation between τ0≡W−10 and the effective relaxation time in the Kohlrausch form follows immediately. It is also noted that the present framework can be applied more generally in relaxation phenomena if thermorheological simplicity is viewed as a special case of correlation or constraint scaling in which dW/W=−ndt/t for t>tc.

No abstract

We propose that the reported dearth of Kepler Objects of Interest (KOIs) with orbital periods P orb 2 − 3 days around stars with rotation periods P rot 5 − 10 days can be attributed to tidal ingestion of close-in planets by their host stars. We show that the planet distribution in this region of the log P orb −log P rot plane is qualitatively reproduced with a model that incorporates tidal interaction and magnetic braking as well as the dependence on the stellar core-envelope coupling timescale. We demonstrate the consistency of this scenario with the inferred break in the P orb distribution of close-in KOIs and point out a potentially testable prediction of this interpretation.