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dc.contributor.authorJurua, Edward
dc.date.accessioned2022-02-23T10:22:30Z
dc.date.available2022-02-23T10:22:30Z
dc.date.issued2008-08
dc.identifier.citationJurua, E. (2008). The anomalous low state of the X-ray binary system Hercules X-1 (Doctoral dissertation, University of the Free State).en_US
dc.identifier.urihttp://ir.must.ac.ug/xmlui/handle/123456789/1550
dc.description.abstractThe light curve of Hercules X-1 (Her X-1) shows a peculiar 35-day modulation of the X-ray flux cycling between low and high states. The 35-day modulation is believed to result from the occultation of the neutron star by a warped processing disc around the central neutron star. Since the discovery of the 35-day cycle of Her X-1, it has entered the anomalous low state a number of times, with the most recent being during the 2003 - 2004 period. Using RXTE ASM observations of Her X-1 after the 2003 - 2004 anomalous low state, it is shown that Her X-1 turned on with a new precession period and main-on flux. It is further shown that there is a positive correlation between the precession period and the main-on flux. Using optical observations of Her X-1 during both the anomalous low state and the normal high state it is shown that the orbital (1.7 day) light curve of Her X-1 varies systematically over the 35-day precession cycle. It is also shown that there is insignificant change in the 35-day morphology of the light curves between the anomalous low state and normal high state of Her X-1, suggesting a very slight change in the disc warp between the two states. Comparison of optical and X-ray light curves suggest that the significant amount of X-ray flux during the anomalous low state originates from the companion star. Analysis of both RXTE PCA and XMM-Newton observations of Her X-1 during the 2003 - 2004 anomalous low state, show that Her X-1 was brighter during this period compared to the normal high state brightness, and that there are two components of X-ray flux during the anomalous low state: reflection component from the companion star and coronal component from the accretion disc corona.en_US
dc.description.sponsorshipSouth African Astronomical Observatory (SAAO, Mbarara University of Science and Technology and the Department of Physics, University of the Free State and Prof. P.J. Meintjes.en_US
dc.language.isoen_USen_US
dc.publisherDoctoral dissertation, University of the Free Stateen_US
dc.subjectAccretion:accretion discsen_US
dc.subjectBinaries:eclipsingen_US
dc.subjectStars:individual (Hercules X-1)en_US
dc.subjectStars:neutronen_US
dc.subjectX-rays:starsen_US
dc.subjectInstabilitiesen_US
dc.titleThe Anomalous Low State of the X-ray Binary System Hercules X-1en_US
dc.typeThesisen_US


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