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A Study of Planetary Nebulae Possessing Binary Central Stars
[Thesis]. Manchester, UK: The University of Manchester; 2014.
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Abstract
In this thesis, detailed studies of three different types of binary central stars withinplanetary nebulae (bCSPNe) are presented, with the aim of investigating the effectssuch a range of binary systems has on the morphology and kinematics of the surroundingnebulae, as well as discussing what the implication is for the interaction betweenthe stars themselves. A close binary, an intermediate period binary, and a compactbinary system are examined.The close binary PN HaTr 4 is the first system to be studied via detailed spatiokinematicalanalysis and modelling, and it is one of few known to contain a postcommonenvelope (CE) central star system. CE evolution is believed to play an importantrole in the shaping of PNe, but the exact nature of this role is yet to be understood.High spatial and spectral resolution spectroscopy is presented alongside deep narrowbandimagery to derive the three-dimensional morphology of HaTr 4. The nebula isfound to display an extended ovoid morphology with an enhanced equatorial regionconsistent with a toroidal waist - a feature believed to be typical amongst PNe withpost-CE central stars. The nebular symmetry axis is found to lie perpendicular to theorbital plane of the central binary, concordant with the idea that the formation andevolution of HaTr 4 has been strongly influenced by its central binary.Next, PN LoTr 1 is studied using a combination of spectra and photometry, andis thought to contain an intermediate-period binary central star system (P = 100–1500d). Here, we confirm the binary nature of the central star of LoTr 1, consisting of aK1 III star and a hot white dwarf (WD). The nebula of LoTr 1 presents a very differentmorphology than that of other seemingly similar bCSPNe possessing barium stars,A70 and WeBo 1 (included in this study for direct comparison), which may be anindication of a difference in their mass-transfer episodes. There is no evidence ofbarium enhancement in the K1 III companion, but it is shown to have a rotation periodof 6.4 d which is most likely a sign of mass accretion. Such a system represents arare opportunity to further the investigation into the formation of barium stars andintermediate period, post-asymptotic giant branch (AGB) systems.Finally, the first analysis of an object from the new POPIPlaN catalogue of PNe ispresented. Photometry of the central star system of PN G033.8+01.5 showed it to bea compact binary of P = 0.1268 d, consisting of a cool M2 V main sequence star anda hot WD surrounded by a very asymmetric PN. The very short orbital period leadsto the possibility of PN G033.8+01.5 being a cataclysmic variable candidate, which inturn leads to the question of whether the visible nebulous material is that of a true PNor if it is the remnant of an outburst.