Discovery of an X-ray Emitting Nebula around the Recurrent Nova T Pyxidis

Abstract

I resolved and detected an X-ray nebulosity around the recurrent nova T Pyx using a 98.8 ksec observation with the ACIS-S detector on-board the Chandra Observatory during the quiescent phase of the nova before its outburst in 2011. The nebula shows an elliptical shape with an inner semi-major axis $\sim$ 0.45 arc sec and an outer semi-major axis $\sim$ 0.9 arc sec which indicates a torus-like or a ring-like shell structure around the nova. There is also a (conical) elongation towards the southern direction of about 1.85 arc sec. This structure may be part of a bipolar outflow from the source/nova. The count rate of the nebulosity is 0.0025$\pm$0.0010 c s$^{-1}$ and that of the the central binary is $\sim$ 0.003 c s$^{-1}$ over the 0.2-9.0 keV energy range. The best fitted spectrum of the X-ray nebula is a two-component plasma model (e.g., a double MEKAL) with $\sim$ 0.6 keV and $\sim$ 2.2 keV along with two different neutral hydrogen column densities of (0.2-0.9)$\times 10^{22}$ cm$^{-2}$ and (3.0-26.0)$\times 10^{22}$ cm$^{-2}$ for the two temperatures, respectively. I calculate an absorbed X-ray flux of (0.6-10.0)$\times10^{-14}$ erg cm$^{-2}$ s$^{-1}$ with a luminosity of (0.08-2.0)$\times10^{32}$ erg s$^{-1}$ (at 3.5 kpc) for the X-ray nebula. The estimated shocked mass is $\le1.8\times10^{-5}$ M$_{\odot}$. The central source spectrum can be fitted by a single MEKAL model with a temperature 9.2$^{<}_{-5.4}$ keV yielding a luminosity of about 5.2$\times10^{31}$ erg s$^{-1}$. The orbital period of the system is detected in the Chandra light curve.