Limits to Transits of the Neptune-mass planet orbiting Gl 581

We have monitored the Neptune-mass exoplanet-hosting M-dwarf Gl 581 with the 1m Swope Telescope at Las Campanas Observatory over two predicted transit epochs. A neutral density filter centered at 550nm was used during the first epoch, yielding 6.33 hours of continuous light curve coverage with an average photometric precision of 1.6 mmags and a cadence of 2.85 min. The second epoch was monitored in B-band over 5.85 hours, with an average photometric precision of 1.2 mmags and 4.28 min cadence. No transits are apparent on either night, indicating that the orbital inclination is less than 88.1 deg for all planets with radius larger than 0.38 R_Nep = 1.48 R_Earth. Because planets of most reasonable interior composition have radii larger than 1.55 R_Earth we place an inclination limit for the system of 88.1 deg. The corresponding minimum mass of Gl 581b remains 0.97 M_Nep = 16.6 M_Earth.Comment: 7 pages, 2 figures, 1 table, to appear in PAS

Heavy Baryons and electromagnetic decays

In this talk I review the theory of electromagnetic decays of the ground state baryon multiplets with oneheavy quark, calculated using Heavy Hadron Chiral Perturbation Theory. The M1 and E2 amplitudes for (S^{*}-> S gamma), (S^{*} -> T gamma) and (S -> T gamma)are separately analyzed. All M1 transitions are calculated up to O(1/\Lambda_\chi^2). The E2 amplitudes contribute at the same order for (S^{*}-> S gamma), while for (S^{*} -> T gamma) they first appear at O(1/(m_Q \Lambda_\chi^2))and for (S -> T gamma) are completely negligible. Once the loop contributions is considered, relations among different decay amplitudes are derived. Furthermore, one can obtain an absolute prediction for the widths of Xi^{0'(*)}_c-> Xi^{0}_c gamma and Xi^{-'(*)}_b-> Xi^{-}_b gamma.Comment: Talk presented at 4^{th} International Conference Hyperons, Charm and Beauty Hadrons Conference, Valencia June 200

Basic studies of baroclinic flows

A fully nonlinear 3-dimensional numerical model (GEOSIM), previously developed and validated for several cases of geophysical fluid flow, has been used to investigate the dynamical behavior of laboratory experiments of fluid flows similar to those of the Earth's atmosphere. The phenomena investigated are amplitude vacillation, and the response of the fluid system to uneven heating and cooling. The previous year's work included hysteresis in the transition between axisymmetric and wave flow. Investigation is also continuing of the flows in the Geophysical Fluid Flow Cell (GFFC), a low-gravity Spacelab experiment. Much of the effort in the past year has been spent in validation of the model under a wide range of external parameters including nonlinear flow regimes. With the implementation of a 3-dimensional upwind differencing scheme, higher spectral resolution, and a shorter time step, the model has been found capable of predicting the majority of flow regimes observed in one complete series of baroclinic annulus experiments of Pfeffer and co-workers. Detailed analysis of amplitude vacillation has revealed that the phase splitting described in the laboratory experiments occurs in some but not all cases. Through the use of animation of the models output, a vivid 3-dimensional view of the phase splitting was shown to the audience of the Southeastern Geophysical Fluid Dynamics Conference in March of this year. A study on interannual variability was made using GEOSIM with periodic variations in the thermal forcing. Thus far, the model has not predicted a chaotic behavior as observed in the experiments, although there is a sensitivity in the wavenumber selection to the initial conditions. Work on this subject, and on annulus experiments with non-axisymmetric thermal heating, will continue. The comparison of GEOSIM's predictions will result from the Spacelab 3 GFFC experiments continued over the past year, on a 'back-burner' basis. At this point, the study (in the form of a draft of a journal article) is nearly completed. The results from GEOSIM compared very well with the experiments, and the use of the model allows the demonstration of flow mechanics that were not possible with the experimental data. For example, animation of the model output shows that the forking of the spiral bands is a transient phenomenon, due to the differential east-west propagation of convection bands from different latitudes