Confidence contours for Sgr A* spectral parameters at several epochs: mean unabsorbed 2–10 keV flux vs. X-ray absorbing column, N _H, (left) and photon index vs. N _H (right). Black/blue/purple lines are for the quiescent (dotted lines) and major flare (solid lines) emission observed by Chandra in ObsID 14392. Brown/red/orange lines are for flare emission observed by XMM-Newton on 2007 April 4 (dashed lines) and on 2002 October 3 (solid lines; Porquet et al. 2003, 2008), re-analyzed with the same spectral model as applied to the Chandra observation. Contours are 68%, 90%, and 99% significance for two interesting parameters. Flare flux is in units of 10 ⁻¹² erg cm ⁻² s ⁻¹ and quiescent flux is in units of 10 ⁻¹⁴ erg cm ⁻² s ⁻¹.