2018 Abstracts

2018 Abstracts

Dr Chris Tout

Title: Highly Magnetic White Dwarfs and other Stars
Abstract: White dwarfs with surface magnetic fields in excess of 1MG are found as isolated single stars and relatively more often in magnetic cataclysmic variables.  Some 1,253 white dwarfs with a detached low-mass main-sequence companion are identified in the Sloan Digital Sky Survey but none of these is observed to show evidence for Zeeman splitting of hydrogen lines associated with a magnetic field in excess of 1MG.  If such high magnetic fields on white dwarfs result from the isolated evolution of a single star then there should be the same fraction of high field white dwarfs among this SDSS binary sample as among single stars.  Thus we deduce that the origin of such high magnetic fields must be intimately tied to the formation of cataclysmic variables.  The formation of a CV must involve orbital shrinkage from giant star to main-sequence star dimensions.  It is believed that this shrinkage occurs as the low-mass companion and the white dwarf spiral together inside a common envelope.  CVs emerge as very close but detached binary stars that are then brought together by magnetic braking or gravitational radiation.  We propose that the smaller the orbital separation at the end of the common envelope phase, the stronger the magnetic field and investigate simple dynamo models for which this is a natural outcome.

Jielai Zhang

Title: Exploring the low surface brightness Universe with the Dragonfly Telephoto Array
Abstract: The low surface brightness Universe is largely unexplored. The limiting factors for low surface brightness observations are not photon statistics or image resolution, instead they are systematic factors such as a telescope s internal reflections, sky subtraction, flat fielding and the wide-angle point-spread-function. The Dragonfly Telephoto Array addresses these factors by a combination of hardware and software. The telescope consists of 48 commercial Canon telephoto lenses, and is able to see low surface brightness structures about 10 times fainter than previously possible with its 2.4 x 3.2 degree wide field of view. I will describe the technology behind Dragonfly, and how I and my team have used it to discover enormous stellar disks, properties of interstellar dust and ultra-diffuse-galaxies .

Dr Stuart Ryder

Title: Binary companions to stripped-envelope supernovae
Abstract: The classes of Type, Ib, and Ic core-collapse supernovae appear to represent progressively greater stripping of the progenitor star's outer envelope prior to explosion, but it is unclear how much of this stripping is due to stellar winds and mass-loss, or to interaction with a massive binary companion. We have used the Hubble Space Telescope to search for surviving binary companions to nearby stripped-envelope supernovae in the ultraviolet. I will describe our results for the broad-lined Type Ic SN 2002ap, and for the Type IIb SN 2001ig.

Dr Rubina Kotak

Title: Faint and fast, bright and long-lived transient: what are they telling us?
Abstract: One of the main challenges of current supernova research is to identify the nature of stars that explode, and to link this knowledge to observed supernova properties. Nowhere is this problem more urgent than the most massive stars in the local and the distant Universe. Recent exciting results have challenged currently accepted paradigms of stellar evolution, and for these supernovae, ever more exotic scenarios are being proposed. I will discuss a few special cases with the currently-accepted framework that highlight gaps in our knowledge.

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