Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001. / Includes bibliographical references (p. 145-157). / I have carried out several investigations of the long-term behavior of galactic X-ray sources using the 4.5-year database of the All Sky Monitor (ASM), and pointed observations made with the Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer (RXTE). I have conducted a systematic search through the ASM data of all the 300 X-ray sources monitored for evidence of periodic behavior. Follow-up investigations are pursued on the discoveries I made in (1) the state transition and orbital modulation of the black hole candidate Cyg X-1; (2) a 4.4-d period in a previously poorly-known X-ray source X 1908+075; and (3) a 98-d period in another previously poorly known X-ray source XTE J1716-389. In Cyg X-1, I have detected its orbital period in the low-hard state but not in the high-soft state. I show that absorption of X-rays by a stellar wind from the companion star can reproduce the observed modulations in the hard state. To explain the low orbital modulation in the soft-state data, a reduction of the wind density during the soft state would be required. In addition, I have discovered an evolution of the correlation between the 1.5-12 keV X-ray count rate of Cyg X-1 and its spectral hardness during the 1996 spectral state transition. I present a quantitative study of this evolution using both the ASM and the PCA data. Implications of our findings are discussed. I have discovered a 4.4-d period in the ASM light curves of the X-ray source XTE J1716-389. I present the results of the investigations on this 98-d periodic modulation using both the ASM and the PCA data. The possible cause of this period and the nature of this system are discussed. / by Linqing Wen. / Ph.D.
| Identifer | oai:union.ndltd.org:MIT/oai:dspace.mit.edu:1721.1/8278 |
| Date | January 2001 |
| Creators | Wen, Linqing, 1969- |
| Contributors | Hale V.D. Bradt., Massachusetts Institute of Technology. Dept. of Physics., Massachusetts Institute of Technology. Dept. of Physics. |
| Publisher | Massachusetts Institute of Technology |
| Source Sets | M.I.T. Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 157 p., 11021930 bytes, 11021685 bytes, application/pdf, application/pdf, application/pdf |
| Rights | M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission., http://dspace.mit.edu/handle/1721.1/7582 |
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