Speaker
Description
Shock interaction in classical novae occurs when a fast outflow from the white dwarf collides with slower matter ejected earlier in the outburst. These shocks radiate across the electromagnetic spectrum: from radio synchrotron, to thermal optical/UV/X-ray emission, to gamma-rays. We present a parameterized one-dimensional toy model for shock interaction in classical novae that uses multi-wavelength observations to predict gamma-ray emission and test acceleration physics. In this picture, particle acceleration occurs primarily at the reverse shock generated by the collision of the white dwarf outflow with the cool, dense shell of material released at earlier times. The maximum energy of the accelerated protons, as set by a Hillas-like argument, is proportional to the thickness of the hot post-shock region, which is in turn constrained by X-ray and optical observations. For this empirically-motivated thickness, and assuming efficient magnetic amplification near the shock, we predict maximum particle energies of order 10 GeV, consistent with observed cut-offs in the spectra of Fermi-detected classical novae around the time of the nova optical peak. However, as the shock expands to larger radii the maximum proton energy can grow to more than 10 TeV, enabling the potential detection of classical novae by atmospheric Cherenkov telescopes.
