2003ApJ...583..758L

We have analyzed a 90 ks long observation of the bright nucleus of M33 made with Chandra/ACIS. We detected low-amplitude (∼10%) highly significant variability on timescales of ∼5000 s. We also found associated spectral variability. The two main spectral components [a power law with Γ∼2 and a multicolor disk (MCD) with kT∼0.9-1.2 keV] vary in relative flux. The MCD temperature also increases with increasing MCD flux. The pattern of variability is reminiscent of (but not identical to) Galactic black hole binaries. An ≳5 M_☉ accreting black hole may explain this source.