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Title: Accreting neutron stars and black holes
Author: Wang, Zhuqing
ISNI:       0000 0004 7972 4414
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2018
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X-ray binary systems o↵er the best way to measure the masses of the accreting compact objects. Following the discovery of the narrow Bowen emission lines in the prototypical low-mass X-ray binary, Sco X-1, arising from the X-ray illuminated atmosphere of the donor star, the Bowen diagnostic has been used as a general tool to obtain dynamical information for persistent sources and/or transients during outburst. Here I exploit the Doppler tomography technique and develop Monte Carlo style bootstrap tests in order to obtain the most robust binary parameter constraints even in the low signal-to-noise ratio regime. Using a new set of analysis tools, I show that we can push the limit of observations to moderately faint (B ⇠ 19) persistent sources with 8-m class telescopes. The method has also been applied to the case of the accreting millisecond X-ray pulsar XTE J1814−338, where the Bowen technique played a crucial role in the derivation of the radial velocity of the secondary, K2. The resulting constraints on the binary component masses suggest the presence of a 'redback' millisecond pulsar in XTE J1814−338 during an X-ray quiescent state. Sco X-1 remains the most important Bowen blend system for benchmarking our method as well as a critical target for continuous gravitational wave searches. I provide revised constraints on key orbital parameters in direct support of continuous-wave observations of Sco X-1 in the Advanced- LIGO era. In light of the new constraints on orbital parameters, the ranges of search parameters T0 and Porb should be updated with the refined period and ephemeris. More importantly, the range for the projected semi-major axis (axsini) needs to be expanded in order to cover the full parameter space. In the last chapter, I present a summary of the method and the key results of its application to all 7 systems (including two transients). The list of Bowen targets can be expanded as new transient outbursts are detected, which may provide us with the opportunities to find stellar-mass black holes. Finally, I remark that the method developed in this thesis can be used to characterize other features in Doppler maps, e.g., the accretion disc and spiral arms.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics