Effects of Magnetic Braking and Tidal Friction on Hot Jupiters

Tidal friction is thought to be important in determining the long-term spin-orbit evolution of short-period extrasolar planetary systems. Using a simple model of the orbit-averaged effects of tidal friction Eggleton, Kiseleva & Hut (1998), we analyse the effects of the inclusion of stellar magnetic braking on the evolution of such systems. A phase-plane analysis of a simplified system of equations, including only the stellar tide together with a model of the braking torque proposed by Verbunt & Zwaan (1981), is presented. The inclusion of stellar magnetic braking is found to be extremely important in determining the secular evolution of such systems, and its neglect results in a very different orbital history. We then show the results of numerical integrations of the full tidal evolution equations, using the misaligned spin and orbit of the XO-3 system as an example, to study the accuracy of simple timescale estimates of tidal evolution. We find that it is essential to consider coupled evolution of the orbit and the stellar spin in order to model the behaviour accurately. In addition, we find that for typical Hot Jupiters the stellar spin-orbit alignment timescale is of the same order as the inspiral time, which tells us that if a planet is observed to be aligned, then it probably formed coplanar. This reinforces the importance of Rossiter-McLaughlin effect observations in determining the degree of spin-orbit alignment in transiting systems.Comment: 6 pages, 2 figures, to appear in IAU 259 Conference Proceeding

Real representation spheres and the real monomial Burnside ring

Cataloged from PDF version of article.We introduce a restriction morphism, called the Boltje morphism, from a given ordinary representation functor to a given monomial Burnside functor. In the case of a sufficiently large fibre group, this is Robert Boltje's splitting of the linearization morphism. By considering a monomial Lefschetz invariant associated with real representation spheres, we show that, in the case of the real representation ring and the fibre group {±1}, the image of a modulo 2 reduction of the Boltje morphism is contained in a group of units associated with the idempotents of the 2-local Burnside ring. We deduce a relation on the dimensions of the subgroup-fixed subspaces of a real representation. © 2011 Elsevier Inc

Internal wave breaking and the fate of planets around solar-type stars

Internal gravity waves are excited at the interface of convection and radiation zones of a solar-type star by the tidal forcing of a short-period planet. The fate of these waves as they approach the centre of the star depends on their amplitude. We discuss the results of numerical simulations of these waves approaching the centre of a star, and the resulting evolution of the spin of the central regions of the star, and the orbit of the planet. If the waves break, we find efficient tidal dissipation, which is not present if the waves perfectly reflect from the centre. This highlights an important amplitude dependence of the (stellar) tidal quality factor Q', which has implications for the survival of planets on short-period orbits around solar-type stars, with radiative cores.Comment: 2 pages, 1 figure, to be published in the proceeedings for IAU27

Resonance Contributions to η\eta Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model

The contributions of the resonances $D_{13}(1520)$, $S_{11}(1535)$, $S_{11}(1650)$, $D_{15}(1675)$, $F_{15}(1680)$, $D_{13}(1700)$, $P_{11}(1710)$, $P_{13}(1720)$ to $\gamma p\to \eta p$ are found from the data on cross sections, beam and target asymmetries using two approaches: fixed-t dispersion relations and an isobar model. Utilization of the two approaches and comparison of the results obtained with different parametrizations of the resonance contributions allowed us to make conclusions about the model-dependence of these contributions. We conclude that the results for the contributions of the resonances $D_{13}(1520)$, $S_{11}(1535)$, $F_{15}(1680)$ to corresponding multipole amplitudes are stable. With this the results for $D_{13}(1520)$ and $F_{15}(1680)$, combined with their PDG photoexcitation helicity amplitudes, allowed us to find the branching ratios $Br (D_{13}(1520)\to \eta N)=0.05\pm 0.02$, $Br (F_{15}(1680)\to \eta N)=0.16\pm0.04$ which have significantly better accuracy than the PDG data. The total Breit-Wigner width of the $S_{11}(1535)$ is model-dependent, we have obtained $\Gamma (S_{11}(1520))=142 MeV$ and $195 MeV$ using dispersion relations and the isobar model, respectively. The results for the $S_{11}(1650)$, $D_{15}(1675)$, $P_{11}(1710)$, $P_{13}(1720)$ are model dependent, only the signs and orders of magnitude of their contributions to multipole amplitudes are determined. The results for the $D_{13}(1700)$ are strongly model-dependent.Comment: 26 pages, 6 figure

Producing more rice with less water from irrigated systems

Irrigation management / Water use efficiency / Crop production / Water requirements / Water balance / Rice / Water distribution / Irrigated farming / Productivity / On-farm research / Irrigation scheduling / Groundwater / Conjunctive use / Rehabilitation / Modernization / Farmer participation / Farming systems / Irrigation systems / Crop-based irrigation / Asia / Philippines / Sri Lanka / Bangladesh / China / Malaysia / USA

Astrophysical SS factor for the 15N(p,γ)16O{}^{15}{\rm N}(p,\gamma){}^{16}{\rm O} reaction from RR-matrix analysis and asymptotic normalization coefficient for 16O→15N+p{}^{16}{\rm O} \to {}^{15}{\rm N} + p. Is any fit acceptable?

The $^{15}{\rm N}(p,\gamma)^{16}{\rm O}$ reaction provides a path from the CN cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor for this reaction is dominated by resonant capture through two strong $J^{\pi}=1^{-}$ resonances at $E_{R}= 312$ and 962 keV and direct capture to the ground state. Recently, a new measurement of the astrophysical factor for the $^{15}{\rm N}(p,\gamma)^{16}{\rm O}$ reaction has been published [P. J. LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. The analysis has been done using the $R$-matrix approach with unconstrained variation of all parameters including the asymptotic normalization coefficient (ANC). The best fit has been obtained for the square of the ANC $C^{2}= 539.2$ fm${}^{-1}$, which exceeds the previously measured value by a factor of $\approx 3$. Here we present a new $R$-matrix analysis of the Notre Dame-LUNA data with the fixed within the experimental uncertainties square of the ANC $C^{2}=200.34$ fm${}^{-1}$. Rather than varying the ANC we add the contribution from a background resonance that effectively takes into account contributions from higher levels. Altogether we present 8 fits, five unconstrained and three constrained. In all the fits the ANC is fixed at the previously determined experimental value $C^{2}=200.34$ fm${}^{-1}$. For the unconstrained fit with the boundary condition $B_{c}=S_{c}(E_{2})$, where $E_{2}$ is the energy of the second level, we get $S(0)=39.0 \pm 1.1$ keVb and normalized ${\tilde \chi}^{2}=1.84$, i.e. the result which is similar to [P. J. LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. From all our fits we get the range $33.1 \leq S(0) \leq 40.1$ keVb which overlaps with the result of [P. J. LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. We address also physical interpretation of the fitting parameters.Comment: Submitted to PR

Robust superfluid phases of 3He in aerogel

Within a phenomenological approach possible forms of the order parameter of the superfluid phases of 3He in a vicinity of the transition temperature are discussed. Effect of aerogel is described by a random tensor field interacting with the orbital part of the order parameter. With respect to their interaction with the random tensor field a group of "robust" order parameters which can maintain long-range order in a presence of the random field is specified. Robust order parameters, corresponding to Equal Spin Pairing (ESP) states are found and proposed as candidates for the observed A-like superfluid phase of liquid 3He in aerogel.Comment: 5 pages, prepared for QFS 200