4 research outputs found
The X-ray and radio emission from SN 2002ap: The importance of Compton scattering
The radio and X-ray observations of the Type Ic supernova SN 2002ap are
modeled. We find that inverse Compton cooling by photospheric photons explains
the observed steep radio spectrum, and also the X-ray flux observed by XMM.
Thermal emission from the shock is insufficient to explain the X-ray flux. The
radio emitting region expands with a velocity of, roughly, 70,000 km/s. From
the ratio of X-ray to radio emission we find that the energy densities of
magnetic fields and relativistic electrons are close to equipartion.Comment: 15 pages, 2 figures, ApJ accepte
Radio Emission and Particle Acceleration in SN 1993J
The radio light curves of SN 1993J are found to be well fit by a synchrotron
spectrum, suppressed by external free-free absorption and synchrotron
self-absorption. A standard r^-2 circumstellar medium is assumed, and found to
be adequate. The magnetic field and number density of relativistic electrons
behind the shock are determined. The strength of the magnetic field argues
strongly for turbulent amplification behind the shock. The ratio of the
magnetic and thermal energy density behind the shock is ~0.14. Synchrotron and
Coulomb cooling dominate the losses of the electrons. The injected electron
spectrum has a power law index -2.1, consistent with diffusive shock
acceleration, and the number density scales with the thermal electron energy
density. The total energy density of the relativistic electrons is, if
extrapolated to gamma ~ 1, ~ 5x10^-4 of the thermal energy density. The
free-free absorption required is consistent with previous calculations of the
circumstellar temperature of SN 1993J, T_e ~ (2-10)x10^5 K. The relative
importance of free-free absorption, Razin suppression, and the synchrotron
self-absorption effect for other supernovae are briefly discussed. Guidelines
for the modeling and interpretation of VLBI observations are given.Comment: accepted for Ap.
Gamma-Ray Burst Spectral Correlations: Photospheric and Injection Effects
We present a physical framework that can account for most of the observed
spectral properties of the prompt gamma-ray burst emission. This includes the
variety of spectral shapes, shape evolutions, and spectral correlations between
flux and spectral peak, within bursts described by Borgonovo & Ryde, and among
bursts described by Amati/Ghirlanda. In our proposed model the spectral peak is
given by the photospheric emission from a relativistic outflow for which the
horizon length is much smaller than the radial width. The observed duration of
the thermal flash will be given by the radial light-crossing time. This then
gives that the typical emission site is at ~10e11 cm from the center, with a
Lorentz factor of ~300. This emission is accompanied by non-thermal emission
from dissipation locations outside the photosphere. The relative strength of
these two components depend on injection effects at the central engine leading
to varying relative location of the saturation and photospheric radii. The
total emission can then reproduce the observed variety. The spectral
correlations are found by assuming that the amount of energy dissipated depends
non-linearly on the averaged particle density. Beside the spectral correlations
this also gives a description of how the relative strength of the thermal
component varies with temperature within a burst.Comment: ApJ accepted, acknowledgement adde