WISE J080822.18-644357.3-a 45 Myr-old accreting M dwarf hosting a primordial disc

WISE J080822.18-644357.3 (WISE J0808-6443) was recently identified as a new M dwarf debris disc system and a candidate member of the 45Myr-old Carina association. Given that the strength of its infrared excess (L-IR/L-* similar or equal to 0.1) appears to be more consistent with a young protoplanetary disc, we present the first optical spectra of the star and reassess its evolutionary and membership status. We find WISE J0808-6443 to be a Li-rich M5 star with strong Ha emission (-125 < EW < -65 angstrom over 4 epochs) whose strength and broad width are consistent with accretion at a low level (similar to 10(-10)M(circle dot) yr(-1)) from its disc. The spectral energy distribution of the star is consistent with a primordial disc and is well-fitted using a two-temperature blackbody model with T-inner similar or equal to 1100K and T-outer similar or equal to 240 K. AllWISE multi-epoch photometry shows the system exhibits significant variability in the 3.4 and 4.6 mu m bands. We calculate an improved proper motion based on archival astrometry, and combined with a newradial velocity, the kinematics of the star are consistent with membership in Carina at a kinematic distance of 90 +/- 9 pc. The spectroscopic and photometric data are consistent with WISE J0808-6443 being a similar to 0.1M(circle dot) Classical T-Tauri star and one of the oldest known accreting M-type stars. These results provide further evidence that the upper limit on the lifetimes of gas-rich discs -and hence the time-scales to form and evolve protoplanetary systems -around the lowest mass stars may be longer than previously recognized, or some mechanism may be responsible for regenerating short-lived discs at later stages of pre-main sequence evolution.