\begin{table}%t2 \par \caption {\label{BBfits}WD atmosphere model plus {\sc mekal} fits to V598~Pup spectra at three epochs. } %\centerline {\begin{tabular}{ccccccccc} \hline\hline Satellite & Day since & No. of counts & Atmos. {\it kT} & Atmos. flux$^{a}$ & {\sc mekal} {\it kT} & {\sc mekal} {\it kT} & {\sc mekal} flux$^{a}$ & C-stat/d.o.f.\\ & Optical peak & in spectrum & (eV) & (erg cm$^{-2}$ s$^{-1}$)& (eV)& (eV) & (erg cm$^{-2}$ s$^{-1}$) \\ \hline XMM & 147 & MOS1: 653 & 35~$\pm$~1$^{b}$ & (8.1~$\pm$~0.3)~$\times$~10$^{-12}$ & $\rm 187^{+14}_{-12}$ & $\rm 788^{+92}_{-86}$ & (3.0~$\pm$~0.4)~$\times$~10$^{-13}$& 383/342 \\ & & MOS2: 641\\ & & pn: 3458\\ Swift & 172 & 117 & $\rm 63^{+5}_{-4}$ & $\rm 8.9^{+3.2}_{-2.2}$~$\times$~10$^{-13}$& $\rm 636^{+218}_{-335}$ & --& $\rm 1.7^{+0.7}_{-0.5}$~$\times$~10$^{-13}$& 76/56 \\ Swift & 247 & 88 & $\rm 68^{+>18}_{-5}$& $\rm 2.0^{+0.7}_{-0.5}$~$\times$~10$^{-13}$ & $\rm 608^{+153}_{-144}$ & -- & $\rm 8.3^{+2.6}_{-3.1}$~$\times$~10$^{-14}$& 39/54 \\ \hline \end{tabular} } \par \smallskip The day since peak corresponds to the mid-time of the spectrum. The absorbing column was fixed at 4.8~$\times$~10$^{20}$~cm$^{-2}$ (Read et~al. \cite{Read08}). The XMM-Newton EPIC MOS1, MOS2 and pn spectra were fitted simultaneously, with a free constant of normalisation between them: with the pn constant fixed to unity, MOS 1 and MOS 2 have constants of 0.91~$\pm$~0.08 and 0.96~$\pm$~0.08 respectively. The temperature of the WD atmosphere component for the day 247 observation is constrained by the upper limit allowed by the model.\\ $^{a}$ Unabsorbed, over 0.3--10~keV.\\ $^{b}$ A systematic error of up to 25\% may be required in addition; see text for details. \vspace*{-3mm} \end{table}