An Intensity Variability Diagram (IVD) for GX339-4

Black hole (BH) transients are known to undergo spectral transitions and exhibit a number of distinct spectral states which trace out, in an anticlockwise direction, a characteristic q-shape on a hardness Intensity diagram (HID). In this work, we introduce the intensity variability diagram (IVD) as a complementary diagnostic to the traditional HID. The variability is represented by a characteristic minimum timescale (MTS), which is extracted directly from the lightcurves of the source as it undergoes transitions among its various spectral states. We use GX339-4 as a test case, a source that has been studied extensively. Specifically, we performed a temporal analysis of RXTE data for the 2002-2003 outburst of GX339-4. We find a potential connection, in the form of a positive non-linear correlation (albeit with significant dispersion), between the traditional measure of variability, RMS, and the new variable, MTS. The correlation is examined using simulated data.