2026-09-23T08:33:49Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/21822 2023-07-10 col_2142_5131 col_2142_8859 com_2142_5130 com_2142_8858 com_2142_234

Watson, W.D. Scappaticci, Gerardo Angelo 2011-05-07T13:20:12Z 2011-05-07T13:20:12Z 10000-01-01 1992 In Part I the time variability of the radiation emitted by astrophysical masers is studied by numerically solving the system of time dependent non-linear partial differential equations of radiative transfer through a masing gas. The calculations demonstrate for the first time how oscillations, with periods which are comparable to the light travel time through the maser, might develop as a result of radiative instabilities. In addition, we perform a linear stability analysis of the radiative transfer equations and the rate equations for the molecular populations of the masing transition. We use this stability analysis to determine the conditions and parameters for which an astrophysical maser would become unstable. Our results are in agreement with recent observations of astrophysical masers in which fluctuations are found on time scales as short as one thousand seconds. In Part II statistical methods are applied to analytically calculate the properties of the fluctuations, in intensity and luminosity, of gravitationally lensed images of quasars, due to compact masses lying within the deflecting galaxy. We compute the fluctuations in intensity, and apparent luminosity, of the gravitationally lensed source as measured by quantities such as the standard deviation, autocorrelation function, and power spectrum. We also compare our results with numerical data we received from P. Schneider and A. Weiss, which for the first time directly compares a Monte Carlo type method with a totally analytical calculation. Made available in DSpace on 2011-05-07T13:20:12Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9305679.pdf: 4680563 bytes, checksum: 0aca201fe6612956b10a3a9ffcec7c75 (MD5) Previous issue date: 1992 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:53:26Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:24:42-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9305679 (UMI)AAI9305679 http://hdl.handle.net/2142/21822 eng Copyright 1992 Scappaticci, Gerardo Angelo Physics, Astronomy and Astrophysics Propagation of radiation in astrophysical media: Gravitational lenses and astrophysical masers text University of Illinois at Urbana-Champaign Dissertation Ph.D. Physics Physics