Compton Degradation of Gamma-ray Line Emission from Radioactive Isotopes in the Classical Nova V2491 Cygni
Abstract
To account for the non-thermal emission from the classical nova V2491 Cygni, we perform a series of numerical calculations of radiative transfer of γ-ray photons from the radioactive isotope 22Na in the matter ejected from a white dwarf. Using a simple wind model for the dynamical evolution of the ejecta and a Monte Carlo code, we calculate radiative transfer of the γ-ray photons in the ejecta. Repeated scattering of the γ-ray photons by electrons in the ejecta, i.e., Compton degradation, results in an extremely flat spectrum in the hard X-ray range, which successfully reproduces the observed spectrum of the X-ray emission from V2491 Cygni. The amount of the isotope 22Na synthesized in the ejecta is required to be 3 × 10-5 M sun to account for the flux of the hard X-ray emission. Our model indicates that the ejecta become transparent to the γ-ray photons within several tens days. Using the results, we briefly discuss the detectability of the γ-ray line emission by the INTEGRAL gamma-ray observatory and the Fermi Gamma-ray Space Telescope.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2010
- DOI:
- 10.1088/2041-8205/723/1/L84
- arXiv:
- arXiv:1007.4386
- Bibcode:
- 2010ApJ...723L..84S
- Keywords:
-
- gamma rays: general;
- novae;
- cataclysmic variables;
- nuclear reactions;
- nucleosynthesis;
- abundances;
- stars: individual: V2491 Cygni;
- white dwarfs;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 5 pages, 4 figures, to appear in ApJL