Radio Frequency Models of Novae in eruption. I. The Free-Free Process in Bipolar Morphologies

Abstract

Observations of novae at radio frequencies provide us with a measure of the total ejected mass, density profile and kinetic energy of a nova eruption. The radio emission is typically well characterized by the free-free emission process. Most models to date have assumed spherical symmetry for the eruption, although it has been known for as long as there have been radio observations of these systems, that spherical eruptions are to simplistic a geometry. In this paper, we build bipolar models of the nova eruption, assuming the free-free process, and show the effects of varying different parameters on the radio light curves. The parameters considered include the ratio of the minor- to major-axis, the inclination angle and shell thickness (further parameters are provided in the appendix). We also show the uncertainty introduced when fitting spherical model synthetic light curves to bipolar model synthetic light curves. We find that the optically thick phase rises with the same power law ($S_{\nu }\propto t^2$) for both the spherical and bipolar models. In the bipolar case there is a "plateau" phase -- depending on the thickness of the shell as well as the ratio of the minor- to major-axis -- before the final decline, that follows the same power law ($S_{\nu }\propto t^{-3}$) as in the spherical case. Finally, fitting spherical models to the bipolar model synthetic light curves requires, in the worst case scenario, doubling the ejected mass, more than halving the electron temperature and reducing the shell thickness by nearly a factor of 10. This implies that in some systems we have been over predicting the ejected masses and under predicting the electron temperature of the ejecta.

9 pages, 6 figures, accepted for publication in ApJ, accompanying movie to figure 3 available at http://www.ast.uct.ac.za/~valerio/papers/radioI/

References in corpus (8)

• An asymmetric shock wave in the 2006 outburst of the recurrent nova RS Ophiuchi
• Shocks in nova outflows. I. Thermal emission
• The Radio Light Curve of the Gamma-Ray Nova in V407 Cyg: Thermal Emission from the Ionized Symbiotic Envelope, Devoured from Within by the Nova Blast
• The nature and evolution of Nova Cygni 2006
• A three-dimensional view of the remnant of Nova Persei 1901 (GK Per)
• The Distance and Morphology of V723 Cassiopeiae (NOVA CASSIOPEIA 1995)
• V723 Cas (Nova Cassiopeiae 1995): MERLIN observations from 1996 to 2001
• Simulations and interpretation of the 6-cm MERLIN images of the classical nova V723 Cas

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• A Radio Emission Analysis of Classical Nova V351 Pup (1991)
• Classical Novae in the ASKAP Pilot Surveys