The Long-term Secular Mass Accretion Rate of the Recurrent Nova T Pyxidis

We present Hubble Space Telescope ultraviolet spectroscopy of the recurrent nova T Pyxidis obtained more than five years after its 2011 outburst, indicating that the system might not have yet reached its deep quiescent state. The ultraviolet data exhibit a 20% decline in the continuum flux from the pre-outburst deep quiescence state to the post-outburst near quiescent state. We suggest that a decline across each recurring nova eruption might help explain the proposed 2 mag steady decline of the system since 1866. Using an improved version of our accretion disk model as well as International Ultraviolet Explorer ultraviolet and optical data, and the 4.8 kpc distance derived by Sokoloski et al. (and confirmed by De Gennaro Aquino et al.), we corroborate our previous findings that the quiescent mass accretion rate in T Pyx is of the order of 10^-6 M _o yr^-1. Such a large mass accretion rate would imply that the mass of the white dwarf is increasing with time. However, with the just-released Gaia DR 2 distance of ∼3.3 kpc (after submission of the first version of this manuscript), we find a mass accretion rate more in line with the estimate of Patterson et al., of the order of 10^-7 M _o yr^-1. Our results predict powerful soft X-ray or extreme ultraviolet emission from the hot inner region of the high accretion rate disk. Using constraining X-ray observations and assuming that the accretion disk does not depart too much from the standard model, we are left with two possible scenarios. The disk either emits mainly extreme ultraviolet radiation, which, at a distance of 4.8 kpc, is completely absorbed by the interstellar medium, or the hot inner disk, emitting soft X-rays, is masked by the bulging disk seen at a higher inclination.