Multiwavelength studies of accretion disks around compact objects
Name
58965153-MIT.pdf
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Author(s)
Wang, Zhongxiang, 1968-
Advisor(s)
Deepto Chakrabarty.
Alternative Title
Multi wavelength studies of accretion disks around compact objects
Date Issued
2004
Publisher
Massachusetts Institute of Technology
Abstract
(cont.) to the XPS in SNR RCW 103. The multiple IR band measurements of 1E 1048.1-5937 provide marginal evidence for spectral flattening, and cannot rule out an accretion disk scenario for AXPs.
In this thesis, I present multiwavelength studies of phenomena related to accretion disks around compact objects. The observations were made mainly with ground-based telescopes and the Hubble Space Telescope. I observed several known and candidate ultracompact low-mass X-ray binaries (LMXBs) and found that their optical spectra all show a lack of hydrogen emission lines, supporting the theoretical prediction that mass donors in ultracompact LMXBs must be H-depleted. Time-resolved photometry of the candidate source 4U 1543-624 revealed an 18 minute orbital periodicity, verifying the ultracompact nature of this binary. These studies strongly support the identification of several candidate systems with similar X-ray spectral features as ultracompact binaries. In the ultracompact binary 4U 1820-30, which has the shortest orbital period (685 s) among the known LMXBs, I discovered a 692-s periodicity from its far-ultraviolet (FUV) time series data. I interpret this longer-period FUV signal as a superhump oscillation, arising from a tidal resonance in the accretion disk of an extreme-mass-ratio binary. I also present multiband imaging of the fields surrounding five newly discovered X-ray millisecond pulsars (MSPs) in an effort to identify and study their optical/IR counterparts. For the MSP SAX J1808.4-3658, the optical light curve taken during its 1998 X-ray outburst shows an exponential decay in intensity, roughly following the X-ray light curve early in the outburst. An optical counterpart of XTE J1814-338 was also detected. Finally, optical/IR observations of anomalous X-ray pulsars (AXPs) and X-ray point sources (XPSs) in young supernova remnants (SNRs) identified the IR counterpart to the AXP 1E 1048.1-5937 and a likely IR counterpart
Description
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.
Includes bibliographical references (p. 133-149).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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