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.

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One -dimensional infrared speckle scans of Ross 614 AB were recorded at a wavelength of 2.2μm. For each scan an estimate of the instantaneous quality of the seeing was calculated and the scan was binned accordingly. The three bins corresponding to the three best seeing conditions were further processed by applying the shift -and -add algorithm to the set of images contained within each bin, thereby generating three shift- and -add images with differing shift -and -add point -spread- functions. After windowing the shift -and -add images (using edge -extension) to reduce the effect of contamination, we have obtained parameters corresponding to the separation and brightness ratio of a two component model of the double star Ross 614 AB by deconvolving the three shift -and -add images with the aid of the zero-and -add technique. Least squares analysis on the positions of the clusters of zeros found from zero- and -add yields a separation of 1.04 arcseconds and a brightness ratio of 4.3 for the binary system at this wavelength. An extension of the processing, which takes explicit account of the nonlinear motion of the scanning mechanism gives improved estimates of 1.04 arcseconds and 3.9 for the separation and brightness ratio, respectively.

Most star formation in galaxies takes place in embedded clusters, within Giant Molecular Clouds (GMCs). Stars also generally form as part of binary star systems, with almost all massive stars having at least one close companion. Binaries shape the physical properties of older star clusters by setting their central density and ejecting low-mass stars, but also play a role during cluster formation by modifying the mechanical and radiative feedback from massive stars and shedding enriched material in the cluster’s gas reservoir. Conversely, dynamical interactions between stars in dense stellar environments are known to form, modify, and destroy binary systems. In consequence, the populations of binaries observed in the Galactic field and in old stellar clusters are understood to be shaped by a combination of the physics of star formation and subsequent dynamical interactions in embedded clusters, although the relative importance of these processes remains unknown. In this thesis, we implement a prescription for an initial population of binaries in the coupled N-body and radiation hydrodynamics star cluster formation code Torch, and investigate how this initial population is modified in the earliest stages of cluster formation, while gas and stars coexist. As an ansatz for the initial population of binaries, we use the properties of main-sequence binaries in the Galactic field. We first perform a suite of simulations initialized from a 10^4 M⦿ cloud, in which the simulations only differ by their stellar content (i.e. presence or absence of an initial population of binaries, and stochasticity of star formation). We compare the populations of binaries identified 1.2–2 Myr after the onset of star formation and find that an initial population of binaries is needed at all masses to reproduce the multiplicity fraction observed in main-sequence stars. We also show that this initial population is modified in a systematic manner before the effects of feedback from massive stars shape the gas. We further find evidence of both preferential formation and preferential destruction of binaries via dynamical interactions. The net effect of these interactions shifts the distributions of primary masses and semi-major axes to lower values, and the distributions of mass ratios and eccentricities to larger values. In a second time, we perform simulations with different virial parameters and initial turbulent velocity patterns, and find that the trends previously identified are robust to those changes in our initial conditions. We however find that both the virial parameter and the initial turbulent velocity pattern have a strong influence on the star formation rate, and therefore on the rapidity with which the distributions are modified. We conclude that dynamical interactions in embedded clusters are important for shaping the populations of binaries observed in the MilkyWay, thus opening the floor to future investigations of the impact of binaries on star cluster formation. / Thesis / Master of Science (MSc)

<p> Despite numerous efforts to better understand binary star evolution, some aspects of it remain poorly constrained. In particular, the evolution of eccentric binaries has remained elusive mainly because the Roche lobe formalism derived for circular binaries does not apply, and other approximations must be used. Here, we report the results of our Smoothed Particle Hydrodynamics simulations of eccentric binaries using a novel way of modeling only the outermost layers of the stars with appropriate boundary conditions. We find that our boundary treatment conserves energy well and that it is well suited for the modeling of interacting binary stars. Using this new technique, along with properly relaxed model stars, we find clear trends in the mass transfer episodes. In particular, we show that these episodes can be described by Gaussians with a FWMH of ~ 0.12 P orb and that the peak rates occur after periastron, around an orbital phase of ~ 0.55, independent of the eccentricity and masses of the stars. The accreted material, on the other hand, is observed to form a rather sparse envelope around either or both stars. Although the fate of this envelope is not modeled in our simulations, we show that a constant fraction (~5%) of the material transferred is ejected from the systems. We discuss this result in terms of the poorly constrained non-conservative mass transfer scenario and argue that it can help calibrate it. Finally, we discuss the limitations of our technique and conditions under which it performs best. The results presented in this thesis represent an improvement upon previous hydrodynamical work and could be used in analytical and binary population synthesis studies to better constrain the evolution of eccentric binaries and the formation of exotic stellar populations. </p> / Thesis / Doctor of Philosophy (PhD)

The extreme environments around compact object binaries make them rich laboratories to study some of the most energetic and enigmatic astrophysical phenomena known or unbeknownst to us. Many such high-energy astrophysical events are powered by relativistic, magnetized outflows that arise from the interaction of the compact object with its companion star during its evolution. Such macroscopic outflows are expected to be sources of magnetic dissipation, and consequently, particle energization, through microscopic processes such as magnetic reconnection, turbulence, or large-scale shocks. In this dissertation, I present novel scenarios that predict, and offer explanations to the observed, high-energy electromagnetic and multimessenger signals, potentially generated by the magnetized outflows from compact object binaries during different stages of their evolution. These scenarios are modeled using analytical calculations and numerical simulations.

Analyses of the light variation of the 6 Scuti star CC Andromedae and of the radial velocity variation of the ß Canis Majoris star 6 Scorpii, a single -line spectroscopic binary, indicate that the long period modulations exhibited are caused by tidal deformations induced in the hydrogen and /or helium ionization zones of each primary by a faint companion, resulting in surface zonal variations of the amplitude and phase of each primary's normal radial pulsations. The variations in the tide raising potential calculated at the center of the apparent disk of o Scorpii correlate very strongly with the observed variations in the phase zero -point of the fundamental pulsation. It is suggested that all the ß Canis Majoris and 6 Scuti stars exhibiting long period modulation, and probably also the RR Lyrae stars showing a Blazhko effect, do so because of tidal perturbations induced by faint companions.