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The outbursts and environments of novae

Hounsell, R (2012) The outbursts and environments of novae. Doctoral thesis, Liverpool John Moores University.

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Abstract

Classical and Recurrent novae (CNe/RNe) are interacting close binary systems in which mass is transferred from a donor star to the surface of an accreting compact companion resulting in an outburst. Their study is important for our understanding of several branches of modern day astrophysics. The work presented in this thesis has focused on three particular topics: (i) Nova V458 Vulpeculae and its surrounding planetary nebula; (ii) Detailed nova light curves from the Solar Mass Ejection Imager (SMEI); and (iii) Vl721 Aquilae, an usually fast, luminous, and highly extinguished nova. A brief account is also given of more generalised work on novae in M31, and areas for future investigation are discussed. Nova V458 Vulpeculae is one of only two novae observed to lie within a planetary neb- ula (PN). Due to the outburst a light echo effect within the PN is experienced. Using Ha data taken over four years the illumination of the PN with time has been examined and a 3D visualisation obtained. Comparison of light echo data from PN models gen- erated with the morphokinematical modelling tool XS5 to observed PN light echo data indicate the presence of a PN with a bipolar external shell and an elliptical internal shell. Results have also confirmed that the PN is at a distance of 13 kpc. SMEI is a space-borne instrument based on-board the Coriolis satellite. It provides precision visible-light photometry of point sources down to 8th magnitude and near complete sky-map coverage at 102-minute cadence. Using SMEI data detailed light curves of novae have been obtained which offer unprecedented temporal resolution around, and especially before, maximum light, a phase of the nova eruption normally not covered by ground-based observations. They have allowed the exploration of fun- damental parameters for individual objects including the epoch of the initial explosion, the reality and duration of any pre-maximum halt, the presence of secondary maxima, speed of decline of the initial light curve, plus precise timing of the onset of dust for- mation. The SME1 data archive undoubtedly holds a plethora of transient events and variable stars. A code designed to search for such events has been created and imple- mented on four years of SME1 data from one of its three cameras generating over 1500 variable objects, some of which were un-catalogued and are potentially very interest- mg. Finally data on the unusually fast and luminous Nova Vl721 Aquilae has been exam- ined. Pre-outburst N1R images from the 2MASS catalogue revealed the presence of a progenitor system, the absolute magnitudes and colours of which suggested the object to have a sub-giant secondary, and so belong to the U Sco class of RNe. Post-outburst spectra of the object revealed the presence of triple-peaked Ha and 01 profiles. Spec- tral fitting of these profiles indicated a high ejection velocity of 3350 km S-l. The triple-peaked nature of the Ha profile suggested that the accretion disc of the system is viewed face-on. This is supported by models created in XS5, which also indicated an axis ratio of rv 1.4 for the ejecta.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Date Deposited: 31 Mar 2017 10:21
Last Modified: 31 Mar 2017 10:21
URI: http://researchonline.ljmu.ac.uk/id/eprint/6158

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