... Archives . ... Astronomers usually present errors as +-stddev on the quantities of interest, but that presupposes that the errors are uncorrelated. ... where the error bars here come from the stddev of the fluxes predicted by each DEM realization that comes out of the MCMC analysis. ... MCMC is used to draw the parameters that determine the DEM as a function of temperature, which in turn is used to calculate the intensity in each temperature bin. i.e., these are the model uncertainties. ...