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Supergiant fast X-ray transients and their place within the high mass X-ray binary population

Supergiant fast X-ray transients and their place within the high mass X-ray binary population
Supergiant fast X-ray transients and their place within the high mass X-ray binary population
Supergiant Fast X-ray Transients (SFXT) are a class of HMXB that have only recently been unveiled by the wide field, high sensitivity monitoring of the Galactic Plane performed by the INTEGRAL observatory. Characterised by rapid X-ray flaring behaviour, on the order of hours, these extreme transients display X-ray dynamic ranges of 104 - 105 with peak outburst luminosities of ~1036 erg s-1. In this work, detailed studies of four of the twelve confirmed SFXTs are presented. Soft and hard X-ray observations are used to probe the nature of these individual sources and the accretion processes occurring within them. In each case the orbital period and hard X-ray outburst history is determined from INTEGRAL data. An RXTE study also discovered the likely neutron star spin period of IGR J17544-42619 and showed that a centrifugal barrier to the accretion flow may generate the deep X-ray quiescent states observed in this source. Orbital phase targeted INTEGRAL and XMM-Newton observations of IGR J16418-4532 allowed the detailed characterisation of this system. The detection of an X-ray intensity dip suggests that IGR J16418-4532 may undergo accretion regime transitions and implies the presence of a highly magnetised neutron star (B~1014 G). Through considerations of the orbital configurations of these systems it is concluded that the accretion processes occurring in SFXTs are heavily influenced by both the variable stellar wind environment and the action of higher order accretion processes, such as impeded accretion regimes and/or magnetic and centrifugal barriers. An assessment is made as to how the SFXTs may be reconciled with the classical, persistent supergiant X-ray binary population. Beyond the persistent versus transient segregation of the whole SgXRB population, a more physically meaningful divide may be drawn between systems that spend the majority of the time in an impeded or un-impeded accretion regime. Additionally, some members of the SFXT class may show a direct evolutionary link between HMXB systems with a main sequence and post main sequence companion for the first time.
Drave, Sebastian
8a673ab2-7fda-425c-824e-57c64d5a45c9
Drave, Sebastian
8a673ab2-7fda-425c-824e-57c64d5a45c9
Bird, Antony
045ee141-4720-46fd-a412-5aa848a91b32

Drave, Sebastian (2013) Supergiant fast X-ray transients and their place within the high mass X-ray binary population. University of Southampton, Faculty of Physical Sciences and Engineering, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Supergiant Fast X-ray Transients (SFXT) are a class of HMXB that have only recently been unveiled by the wide field, high sensitivity monitoring of the Galactic Plane performed by the INTEGRAL observatory. Characterised by rapid X-ray flaring behaviour, on the order of hours, these extreme transients display X-ray dynamic ranges of 104 - 105 with peak outburst luminosities of ~1036 erg s-1. In this work, detailed studies of four of the twelve confirmed SFXTs are presented. Soft and hard X-ray observations are used to probe the nature of these individual sources and the accretion processes occurring within them. In each case the orbital period and hard X-ray outburst history is determined from INTEGRAL data. An RXTE study also discovered the likely neutron star spin period of IGR J17544-42619 and showed that a centrifugal barrier to the accretion flow may generate the deep X-ray quiescent states observed in this source. Orbital phase targeted INTEGRAL and XMM-Newton observations of IGR J16418-4532 allowed the detailed characterisation of this system. The detection of an X-ray intensity dip suggests that IGR J16418-4532 may undergo accretion regime transitions and implies the presence of a highly magnetised neutron star (B~1014 G). Through considerations of the orbital configurations of these systems it is concluded that the accretion processes occurring in SFXTs are heavily influenced by both the variable stellar wind environment and the action of higher order accretion processes, such as impeded accretion regimes and/or magnetic and centrifugal barriers. An assessment is made as to how the SFXTs may be reconciled with the classical, persistent supergiant X-ray binary population. Beyond the persistent versus transient segregation of the whole SgXRB population, a more physically meaningful divide may be drawn between systems that spend the majority of the time in an impeded or un-impeded accretion regime. Additionally, some members of the SFXT class may show a direct evolutionary link between HMXB systems with a main sequence and post main sequence companion for the first time.

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Published date: June 2013
Organisations: University of Southampton, Astronomy Group

Identifiers

Local EPrints ID: 353977
URI: http://eprints.soton.ac.uk/id/eprint/353977
PURE UUID: c8be49f2-e689-4bc8-bc83-d738c318fde4
ORCID for Antony Bird: ORCID iD orcid.org/0000-0002-6888-8937

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Date deposited: 01 Jul 2013 10:32
Last modified: 02 Aug 2018 00:34

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