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Multi-wavelength observations of Galactic black hole X-ray transients

Multi-wavelength observations of Galactic black hole X-ray transients
Multi-wavelength observations of Galactic black hole X-ray transients
Galactic black hole X-ray transients (BHXRTs) represent the ideal opportunity to study accretion physics in extreme environments. Questions relating to accretion geometry, the mass of the compact object, how transient outbursts start and how jets form and evolve can only be answered by observing BHXRTs across multiple wavelengths. In this thesis I take a multi-wavelength approach to studying BHXRTs, and attempt to reconcile many aspects of accretion physics using a number of techniques.I have used timing analysis techniques to discover a super-orbital periodicity of 420 days in the X-ray and optical light curves of the BHXRT Swift J1753.5-0127, whilst also uncovering the likely orbital period of the candidate BHXRT MAXI J1305-704. X-ray spectral observations of Swift J1753.5-0127 revealed its first ever transition to a soft accretion state. This was found to be one of the lowest luminosity soft states ever recorded in such a system, at < 1% the Eddington luminosity, which proved crucial in the subsequent radio observations. Collaborators and I found that the compact jet had been quenched by a factor > 25, indicating that jet quenching was not dependent on accretion rate.In the optical regime, spectroscopy can reveal details about the mass of the compact object, which is important for population studies of black holes (BHs). I place a lower limit on the mass of Swift J1753.5-0127at M1 > 7:41:2M, confirming it as a BH and removing it from the so-called 'mass gap.' However, optical observations can also reveal details about the accretion geometry of a source, as in the case of the BHXRT V404 Cyg, in which collaborators and I combined optical spectroscopy and photometry and found evidence for the 2015 outburst initiating 1 week before the X-ray outburst was detected. Our results were found to be consistent with the current disc instability model for transient outbursts. I summarise these findings and suggest avenues for future work in the closing pages of this thesis. Overall, this work shows that we can only truly understand BHXRTs once we have studied them across multiple wavelengths, and only in doing so can we discuss the underlying physics behind some of the most extreme regions of the Universe.
University of Southampton
Shaw, Aarran
ec30710a-0499-4f4f-9685-4510f75efe79
Shaw, Aarran
ec30710a-0499-4f4f-9685-4510f75efe79
Charles, Philip
0429b380-0754-4dc1-8def-885c7fa6a086

Shaw, Aarran (2016) Multi-wavelength observations of Galactic black hole X-ray transients. University of Southampton, Doctoral Thesis, 142pp.

Record type: Thesis (Doctoral)

Abstract

Galactic black hole X-ray transients (BHXRTs) represent the ideal opportunity to study accretion physics in extreme environments. Questions relating to accretion geometry, the mass of the compact object, how transient outbursts start and how jets form and evolve can only be answered by observing BHXRTs across multiple wavelengths. In this thesis I take a multi-wavelength approach to studying BHXRTs, and attempt to reconcile many aspects of accretion physics using a number of techniques.I have used timing analysis techniques to discover a super-orbital periodicity of 420 days in the X-ray and optical light curves of the BHXRT Swift J1753.5-0127, whilst also uncovering the likely orbital period of the candidate BHXRT MAXI J1305-704. X-ray spectral observations of Swift J1753.5-0127 revealed its first ever transition to a soft accretion state. This was found to be one of the lowest luminosity soft states ever recorded in such a system, at < 1% the Eddington luminosity, which proved crucial in the subsequent radio observations. Collaborators and I found that the compact jet had been quenched by a factor > 25, indicating that jet quenching was not dependent on accretion rate.In the optical regime, spectroscopy can reveal details about the mass of the compact object, which is important for population studies of black holes (BHs). I place a lower limit on the mass of Swift J1753.5-0127at M1 > 7:41:2M, confirming it as a BH and removing it from the so-called 'mass gap.' However, optical observations can also reveal details about the accretion geometry of a source, as in the case of the BHXRT V404 Cyg, in which collaborators and I combined optical spectroscopy and photometry and found evidence for the 2015 outburst initiating 1 week before the X-ray outburst was detected. Our results were found to be consistent with the current disc instability model for transient outbursts. I summarise these findings and suggest avenues for future work in the closing pages of this thesis. Overall, this work shows that we can only truly understand BHXRTs once we have studied them across multiple wavelengths, and only in doing so can we discuss the underlying physics behind some of the most extreme regions of the Universe.

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Published date: October 2016
Organisations: University of Southampton, Physics & Astronomy

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Local EPrints ID: 410313
URI: http://eprints.soton.ac.uk/id/eprint/410313
PURE UUID: 4f0c3221-79da-4850-924e-48b1a700ae1d

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Date deposited: 07 Jun 2017 04:01
Last modified: 13 Mar 2019 19:52

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