We report the discovery of a bright X-ray transient , CXOU J132527.6-430023 , in the nearby early-type galaxy NGC 5128 .
The source was first detected over the course of five Chandra observations in 2007 , reaching an unabsorbed outburst luminosity of { 1 - 2 \times 10 ^ { 38 } } { erg~ { } s ^ { -1 } } in the 0.5-7.0 keV band before returning to quiescence .
Such luminosities are possible for both stellar-mass black hole and neutron star X-ray binary transients .
Here , we attempt to characterize the nature of the compact object .
No counterpart has been detected in the optical or radio sky , but the proximity of the source to the dust lanes allows for the possibility of an obscured companion .
The brightness of the source after a > 100 fold increase in X-ray flux makes it either the first confirmed transient non-ULX black hole system in outburst to be subject to detailed spectral modeling outside the Local Group , or a bright ( > 10 ^ { 38 } ~ { } { erg~ { } s ^ { -1 } } ) transient neutron star X-ray binary , which are very rare .
Such a large increase in flux would appear to lend weight to the view that this is a black hole transient .
X-ray spectral fitting of an absorbed power law yielded unphysical photon indices , while the parameters of the best-fit absorbed disc blackbody model are typical of an accreting { \sim 10 ~ { } M _ { \odot } } black hole in the thermally dominant state .