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The XMM-Newton Detection of Extended Emission from the Nova Remnant of T Pyxidis

We report the detection of an extended X-ray nebulosity with an elongation from northeast to southwest in excess of 15$^{\prime\prime}$ in a radial profile and imaging of the recurrent nova T Pyx using the archival data obtained with the X-ray Multi-Mirror Mission (XMM), European Photon Imaging Camera (pn instrument). The signal to noise ratio (S/N) in the extended emission (above the point source and the background) is 5.2 over the 0.3-9.0 keV energy range and 4.9 over the 0.3-1.5 keV energy range. We calculate an absorbed X-ray flux of 2.3$\times10^{-14}$ erg cm$^{-2}$ s$^{-1}$ with a luminosity of 6.0$\times10^{32}$ erg s$^{-1}$ from the remnant nova in the 0.3-10.0 keV band. The source spectrum is not physically consistent with a blackbody emission model as a single model or a part of a two-component model fitted to the XMM-Newton data ({$kT{\rm_{BB}}$} $>$ 1 keV). The spectrum is best described by two MEKAL plasma emission models with temperatures at 0.2$^{+0.7}_{-0.1}$ keV and 1.3$^{+1.0}_{-0.4}$ keV. The neutral hydrogen column density derived from the fits is significantly more in the hotter X-ray component than the cooler one which we may be attributed to the elemental enhancement of nitrogen and oxygen in the cold material within the remnant. The shock speed calculated from the softer X-ray component of the spectrum is 300-800 km s$^{-1}$ and is consistent with the expansion speeds of the nova remnant derived from the Hubble Space Telescope (HST) and ground-based optical wavelength data. Our results suggest that the detected X-ray emission may be dominated by shock-heated gas from the nova remnant.