The frequency of heating events in the corona is an important constraint on the coronal heating mechanisms .
Observations indicate that the intensities and velocities measured in active region cores are effectively steady , suggesting that heating events occur rapidly enough to keep high temperature active region loops close to equilibrium .
In this paper , we couple observations of Active Region 10955 made with XRT and EIS on Hinode to test a simple steady heating model .
First we calculate the differential emission measure of the apex region of the loops in the active region core .
We find the DEM to be broad and peaked around 3 MK .
We then determine the densities in the corresponding footpoint regions .
Using potential field extrapolations to approximate the loop lengths and the density-sensitive line ratios to infer the magnitude of the heating , we build a steady heating model for the active region core and find that we can match the general properties of the observed DEM for the temperature range of 6.3 < Log T < 6.7 .
This model , for the first time , accounts for the base pressure , loop length , and distribution of apex temperatures of the core loops .
We find that the density-sensitive spectral line intensities and the bulk of the hot emission in the active region core are consistent with steady heating .
We also find , however , that the steady heating model can not address the emission observed at lower temperatures .
This emission may be due to foreground or background structures , or may indicate that the heating in the core is more complicated .
Different heating scenarios must be tested to determine if they have the same level of agreement .