Outburst risetimes and durations

There are two rise-times of interest in SGR outbursts the growth time t grow which is the e-folding time for the energy-flux growth during the initial, rapid brightening and the peak time Tpeak which is the time from the initial onset of the event until the (highest) peak of the light curve. A third time-scale of interest in the brightest SGR events is tspike, the duration of the initial, hard-spectrum, extremely bright phase of the event which we refer to as the hard spike. In some flares,...

Effects of 3D hydro on the spectra of Type Ia supernovae

To represent a typical 1-D explosion model for SNe Ia we look at the structure of W7 (Nomoto et al. 1984 Thielemann et al. 1986). In the inner region, v < 8000 km s-1, we find Fe-peak material. The next region, 8000 < v < 15000 km s-1, consists of the intermediate mass elements, Ti, Ca, S, Si, and Mg. Each of those two regions typically contain about half of the 1.4 M0 ejecta. A small quantity of unburned carbon and oxygen is often found at higher velocities, v > 15000 km s-1. In...

Core collapse MHD and jet formation A Magnetic helicity currents

It is not at all proven that the large magnetic fields expected in core collapse generate jets, but there are a number of clues pointing in that direction. For the more traditional situation in which collapse leads to the formation of a neutron star, the premise is that there is a rapid formation of a strong magnetic field with B 100 Bqed < < (4 P)1 2, that is much above the QED limit, but less than equipartition with the ambient pressure. This field is expected to be primarily toroidal...

Dynamical and secular shear instabilities

The condition for the dynamical shear instability DSI is given by N2 o2 lt Ri c 1 4 e.g. Meader amp Meynet 2000 , where N2 is the Brunt-Vaisala frequency and o is the shear factor o 3m 3 ln r. Fig. 11.1 shows the critical value of o for the dynamical shear instability i.e, odyn crit as function of density, with the physical conditions as indicated in the figure caption. The stability criterion can be relaxed if thermal diffusion reduces the buoyancy force such that PrRe,cN2 o2 lt Ri c, where Pr...