Extended Data Fig. 3: The X-ray long-term evolution of GSN 069.
From: Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus
a, The X-ray spectra from the XMM1, XMM2, XMM4 and Chandra observations, excluding time-intervals containing QPEs. All spectra have been divided by the corresponding detector effective area to ease comparison. The XMM3 spectrum is not shown, as it is basically superimposed on the XMM4 one. Spectra have been slightly re-binned for visual clarity. b, The best-fitting SEDs according to the best-fitting models presented in Extended Data Table 2. c, The 0.3–2 keV flux evolution of GSN 069 since first X-ray detection, including the XMM-Newton slew data point. The dashed grey line is a power-law decay model with index fixed at −5/3, while the dotted magenta line is an exponential decay law with best-fitting e-folding timescale of about 5 yr. d, The 0.2–2 keV luminosity of the best-fitting diskbb model as a function of disk temperature (see Extended Data Table 2). The dashed line is the best-fitting relation Ldiskbb ∝ T4.5 ± 0.5 to the XMM-Newton data only, consistent with constant-area blackbody emission (L ∝ T4). The Chandra data point (green) is far off the L ∝ T4 relation, its temperature being too hot to be ascribed to disk emission for the given luminosity. Errors in a represent the 1σ confidence intervals, while error bars in c and d represent the 90% confidence intervals as obtained from X-ray spectral fitting (Extended Data Table 2). Some of the error bars are smaller than the symbol size.
