1. Quantile-based Color-Color Diagram (QCCD) for spectral analysis with low statistics Various spectral shapes in QCCD of median (m=Q 50 ) vs. quartile ratio (Q 25 /Q 75 ) e.g.: Power law model (  = 0.. 4 & N H =10 20.. 5x10 21 ) in 03-8.0 keV J. Hong, E. Schlegel & J.E. Grindlay, ApJ, 2004 in press http://hea-www.harvard.edu/ChaMPlane/quantile

2. QCCD is uniformly more sensitive than conventional CCD. e.g. simulations with 50 count source (25 bkg count) QCCD (0.3-8.0 keV) Conventional CCD of hard color vs. soft color (S:0.3-0.9, M:0.9-2.5, H:2.5-8.0 keV)

3. Median is a better substitute for hardness ratio (e.g. median or hardness ratio dist. for three example power law spectra  =2, N H =10 20, 5x10 21, 5x10 22 cm -2 ) Hardness Ratio vs. count (rate) 0.3-2.0-8.0 keV Median vs. count (rate) 0.3-8.0 keV