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From Observation to Simulation: Understanding Surprising Evolutions in Nova Ejecta

Authors: F. Healy, T. J. O’Brien, R. Beswick, M. K. Argo

Journal: Transactions of IAA RAS vol. 41

Pages: 9–17

Year: 2017

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About the paper

Keywords: VLBI, Astrometry

A classical nova occurs when a white dwarf (WD) in an interacting binary system undergoes a thermonuclear runaway (TNR) on its surface, leading to a large expulsion of material into the interstellar medium, as well as a dramatic optical brightening. Simple isothermal, spherically symmetric, homogeneous models for thermal radio emission from novae predict a light curve which brightens as t² (while the ejected shell is optically thick) and then declines as t¯³ (once it becomes optically thin). However, observations of novae indicate that these models are flawed. For example, e-MERLIN, VLBI and VLA observations of Nova Mon 2012 have shown a complex, aspherical ejecta which evolves over time, whilst other studies have shown light curves which are not in agreement with the predictions of the models. In this talk we present new modelling of the radio emission from a variety of hypothesized ejecta structures. These models allow improved estimation of mass loss rate, which in turn tell us more about the mechanisms whereby the mass is lost, and allow us to investigate classical novae as possible Type 1a supernova progenitors. Developing an understanding of the geometry and possible collimation of the ejecta may also have implications for the study of particle acceleration in radio novae and similar systems.