Long-term X-ray Variability of NGC 4945 Page: 3 of 23
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Long-term X-ray Variability of NGC 4945. AMARA MILLER (University of Cali-
fornia Davis, Davis, CA 95616) GRZEGORZ MADEJSKI (Stanford Linear Accel-
erator Center, Stanford, CA, 94305).
Though short-term X-ray variability has been studied for the active galaxy
NGC 4945, long-term studies promise to contribute to our understanding of the
processes involved in accretion onto supermassive black holes. In order to under-
stand the relationship between black hole mass and breaks in the power spectral
density (PSD), the long-term X-ray variability of NGC 4945 was studied over the
energy range 8-30 keV. Observations occurred over the year 2006 using the Rossi
X-ray Timing Explorer. The data was reduced using the package FTOOLS, most
notably the scripts Rex and faxbary. Light curves were produced and a PSD
was obtained using a Fast Fourier Transform algorithm. Preliminary studies of
the light curve show greater X-ray variability at higher frequencies. This result
complements previous studies of NGC 4945 by Martin Mueller. However, the PSD
produced must go through further study before accurate results can be obtained.
A way to account for the window function of the PSD must be found before the
behavior at lower frequencies can be studied with accuracy and the relationship be-
tween black hole mass and the break in NGC 4945's PSD can be better understood.
Further work includes exploration into ways to subtract the window function from
the PSD, as well as a closer analysis of the PSD produced by averaging the data
into logarithmic bins. The possibility of a better way to bin the data should be
considered so that the window function would be minimized.
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Miller, Amara & /UC, Davis /SLAC. Long-term X-ray Variability of NGC 4945, report, August 29, 2007; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc883646/m1/3/: accessed September 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.