Dynamics of the Tippe Top via Routhian Reduction

We consider a tippe top modeled as an eccentric sphere, spinning on a horizontal table and subject to a sliding friction. Ignoring translational effects, we show that the system is reducible using a Routhian reduction technique. The reduced system is a two dimensional system of second order differential equations, that allows an elegant and compact way to retrieve the classification of tippe tops in six groups as proposed in [1] according to the existence and stability type of the steady states.Comment: 16 pages, 7 figures, added reference. Typos corrected and a forgotten term in de linearized system is adde

Focal Plane Detector System of SHARAQ Spectrometer

International audienceThis report describes the basic performance of the detector system installed in the final momentum-dispersive focal plane of the SHARAQ spectrometer

Point vortices on the sphere: a case with opposite vorticities

We study systems formed of 2N point vortices on a sphere with N vortices of strength +1 and N vortices of strength -1. In this case, the Hamiltonian is conserved by the symmetry which exchanges the positive vortices with the negative vortices. We prove the existence of some fixed and relative equilibria, and then study their stability with the ``Energy Momentum Method''. Most of the results obtained are nonlinear stability results. To end, some bifurcations are described.Comment: 35 pages, 9 figure

Experimental investigation of the 30S(α, p) thermonuclear reaction in x-ray bursts

We performed the first measurement of 30 S+α resonant elastic scattering to experimentally examine the 30 S(α, p) stellar reaction rate in type I x-ray bursts. These bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of accreting neutron star binaries. The 30 S(α, p) reaction plays a critical role in burst models, yet very little is known about the compound nucleus 34 Ar at these energies nor the reaction rate itself. We performed a measurement of alpha elastic scattering with a radioactive beam of 30 S to experimentally probe the entrance channel. Utilizing a gaseous active target system and silicon detector array, we extracted the excitation function from 1.8 to 5.5 MeV near 160° in the center-of-mass frame. The experimental data were analyzed with an R -Matrix calculation, and we discovered several new resonances and extracted their quantum properties (resonance energy, width, spin, and parity). Finally, we calculated the narrow resonant thermonuclear reaction rate of 30 S(α, p) for these new resonances

SHARAQ Project: Progress in 2009

On March 23, 2009, the first beam was successfullytransported to the final focal plane of the SHARAQspectrometer. We investigated detector responses toheavy-ion beams and the ion optical properties ofthe SHARAQ spectrometer1) and the high-resolutionbeam line2) in the subsequent commissioning runs andfound that the system as a whole worked almost as perits design. The first physics run with the spectrometerwas performed in November 2009. In this article, wereview the progress in the SHARAQ project in 2009

Asteroids. From Observations to Models

We will discuss some specific applications to the rotation state and the shapes of moderately large asteroids, and techniques of observations putting some emphasis on the HST/FGS instrument.Comment: to appear in LNP; 28pages; written in 2003; Winter School "Dynamique des Corps Celestes Non Ponctuels et des Anneaux", Lanslevillard (FRANCE