2008MNRAS.388..921P

We present the Chandra ACIS-S3 data of the old classical nova RR Pic (1925). The source has a count rate of 0.067±0.002 count/s in the 0.3-5.0 keV energy range. We detect the orbital period of the underlying binary system in the X-ray wavelengths. We also find that the neutral hydrogen column density differs for orbital minimum and orbital maximum spectra with values 0.25^+0.23_–0.18x10²² and 0.64^+0.13_–0.14x 10²²/cm2 at 3σ confidence level. The X-ray spectrum of RR Pic can be represented by a composite model of bremsstrahlung with a photoelectric absorption, two absorption lines centered around 1.1-1.4 keV and five Gaussian lines centered at emission lines around 0.3-1.1 keV corresponding to various transitions of S, N, O, C, Ne and Fe. The bremsstrahlung temperature derived from the fits ranges from 0.99 to 1.60 keV and the unabsorbed X-ray flux is found to be 2.5^+0.4_–1.2x10^–13erg/cm2/s in the 0.3-5.0 keV range with a luminosity of 1.1±0.2 10³¹erg/s at 600 pc. We also detect excess emission in the spectrum possibly originating from the reverse shock in the ejecta. A fit with a cooling flow plasma emission model shows enhanced abundances of He, C, N, O and Ne in the X-ray emitting region indicating existence of diffusive mixing.