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A study of chemistry, dynamics and dust in nova outflows

Pontefract, Matthew; (1999) A study of chemistry, dynamics and dust in nova outflows. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Since the celebrated outburst of nova DQ Herculis (1936), observations of which suggested that dust grains were being formed with high efficiency, research into the chemical processes leading to dust nucleation has flourished. Observations show that dust formation is not only highly efficient but a common occurrence in nova outbursts, yet the chemical pathways leading to dust are poorly understood. A study of chemical processes within outflowing ejectum material through closely linked, quasi self-consistent chemical models from just a few days post-outburst until the formation of dust nucleation sites is presented. Chemical modelling, incorporating new and updated chemistry within a realistic radiation field, is followed by a study of dynamics with a now fluid dynamic model incorporating chemistry explicitly within the conservation equations. In contrast to previous studies, we find that a rich chemistry of small molecules develops within a few days after outburst. This leads to the formation of a large abundance of nucleation sites from many model configurations. We find also that CO does not saturate within these chemical scenarios; this negates previous assumptions and helps to explain observations not only in novae, but also in objects such as planetary nebulae. Constraints are placed on physical conditions within the ejecta. Two outflow configurations are modelled with a simplified chemistry embedded in a fluid dynamic code. We suggest an explanation for the time-dependent behaviour of CO molecular lines observed in nova V705 Cas, and further constrain the physical parameters for this nova. It is found that, as a result of the dynamics, a rich chemistry may occur only within localised regions of the principal ejectum and that the results are consistent with observation. It is suggested that further development of this model, particularly with respect to the radiation field, will lead to a deeper understanding of both physical and chemical processes within nova outflows.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: A study of chemistry, dynamics and dust in nova outflows
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Nova outbursts
URI: https://discovery.ucl.ac.uk/id/eprint/10098082
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