Physics in the extreme: X-ray and optical studies of magnetic white dwarfs and related objects

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dc.contributor.advisor Callanan, Paul en
dc.contributor.advisor Garnavich, Peter en
dc.contributor.author Kennedy, Mark R.
dc.date.accessioned 2017-06-01T13:47:37Z
dc.date.available 2017-06-01T13:47:37Z
dc.date.issued 2017
dc.date.submitted 2017
dc.identifier.citation Kennedy, M. 2017. Physics in the extreme: X-ray and optical studies of magnetic white dwarfs and related objects. PhD Thesis, University College Cork. en
dc.identifier.endpage 207 en
dc.identifier.uri http://hdl.handle.net/10468/4038
dc.description.abstract In this thesis, we present results from optical and X-ray studies of compact binary systems. These observations are used to constrain orbital parameters - mainly periods and inclinations for several cataclysmic variables - and examine the accretion structures within the systems. In Chapters 3 and 4, optical and X-ray studies of two interesting cataclysmic variables systems, Lanning 386 and MASTER OTJ192328.22+612413.5, are presented. The X-ray and optical data of these objects suggest that both systems have a high inclination and harbour weakly magnetic white dwarfs with spin periods 17-22 min. There is also a strong focus on studying the long term behaviour in intermediate polars in this thesis. Chapter 5 presents results from Kepler observations of FO Aquarii taken over 69 consecutive days. The shape of the light curve is consistent with the outer edge of the accretion disc being eclipsed and the detected period is longer than the last reported period of 1254.284(16) s, suggesting that FO Aqr was now spinning down, and had a positive P˙ at the time of the observations. Chapter 6 continues the work on FO Aquarii, and presents X-ray data taken during a low accretion state. The X-ray spectrum shows an increase in the ratio of the soft X-ray flux to the hard X-ray flux due to a change in the partial covering fraction of the white dwarf and a change in the hydrogen column density within the disc. XMM-Newton observations of FO Aqr during the subsequent recovery suggest that the system had not yet returned to its typical high state by November 2016. The spin period of the white dwarf in 2014 and 2015 is refined to 1254.3342(8) s. Chapter 7 focuses on CSS120422:J111127+571239, an “evolved main-sequence” channel cataclysmic variable. We present spectroscopy of CSS120422:J111127+571239 using the COS FUV instrument on the Hubble Space Telescope and using the MODS spectrograph on the Large Binocular Telescope. The UV spectrum shows Si IV, N V and He II, but no detectable C IV. The anomalous nitrogen/carbon ratio is seen in a small number of other CVs and confirms a unique binary evolution. We also present and compare the optical spectrum of V418 Ser and advocate that it is also an evolved main-sequence system. Finally, Chapter 8 presents results on UW Coronae Borealis, a low mass X-ray x Abstract binary that shows both Type 1 X-ray and optical bursts. The orbital period is refined to 110.97680(1) min. 17 optical bursts are presented, with 10 of these bursts being resolved temporally. The average e-folding time of 19 ± 3s for the bursts is consistent with the previously found value. Optical bursts are observed during a previously identified gap in orbital phase centred on φ = 0.967, meaning the reprocessing site is not eclipsed as previously thought. Finally, the apparent P-Cygni profiles present in some of the atomic lines in the optical spectra are due to transient absorption, which suggests the origin of the absorption is not a wind from the primary. en
dc.description.sponsorship Naughton Foundation (Martin and Carmel Naughton Graduate Fellowship); University College Cork (Strategic Research Fund) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2017, Mark Kennedy. en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject Astronomy en
dc.subject Interacting binary stars en
dc.subject Accretion en
dc.subject Physics en
dc.subject Cataclysmic variables en
dc.title Physics in the extreme: X-ray and optical studies of magnetic white dwarfs and related objects en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral Degree (Structured) en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.check.info No embargo required en
dc.description.version Accepted Version
dc.contributor.funder Naughton Foundation en
dc.contributor.funder University College Cork en
dc.description.status Not peer reviewed en
dc.internal.school Physics en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out No en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en
ucc.workflow.supervisor paulc@miranda.ucc.ie
dc.internal.conferring Summer 2017 en


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