PhD Thesis (PDF) - Department of Astronomy - University of Virginia

Fig. 5.17.— Percentage of Analysis Sample sources that appear variable (at the
> 2σ level) between two observations against the time period between the observations.
Note that the error bars are not independent as the pairs contain the same
five observations. The dotted horizontal line represents the percentage of sources
that would appear variable just due to statistical fluctuations. Although there is a
rough tendency for more variable sources on longer timescales, a constant variability
percentage of 11.3% is statistically consistent with the data. Although very soft
sources may be misidentified as variable sources at the four longest timescales due to
improper correction of QE degradation, this effect is well within the displayed errors.
variability over the entire period of five observations. We refer to these sources as
Long-Term Luminosity Variables (LTLVs), and the probability PL,All that the vari-
ability arises from statistical fluctuations is given in column 12 of Table 5.11. The χ 2 ,
when compared to a single merged luminosity and combined with the appropriate de-
grees of freedom (one less than the number of observations a source is in the FOV), is
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