which highlights these lines in the residuals. []{data-label="fig:spectra"}](burst-spectral-comparison.pdf){width="\linewidth"}

We investigated the spectral shape of the burst emission by extracting a spectrum from a $4{{\rm\,s}\xspace}$ interval at the peak of the burst (Figure \[fig:spectra\]). We first attempted to model this spectrum by adding a blackbody component to the preburst spectrum model, holding all parameters except for those of the blackbody constant. At a ${\ensuremath{\chi^2_r}\xspace}$ of $28$ for 631 dof, this model failed to account for a large excess below 1.5 keV and above 5 keV.

In an attempt to account for the residuals we applied a free scaling factor to the components describing the preburst spectrum [@Worpel2013], so that our model was

> `tbabs(bbodyrad + f(diskbb + nthcomp))`,

where `bbodyrad` is a blackbody component with its normalization proportional to surface area. At a [$\chi^2_r$]{}of 5.4 for 630 dof, this model failed to remove the large residuals. Additionally, at $f=159$, the magnitude of the obtained scaling factor is not realistic, as it is much larger than the ${f\sim2-10}$ that is typically observed [@Worpel2013].

In an alternative approach to account for the large soft excess, we adopted a model consisting of the fixed preburst model plus two blackbody components. This model provided a 