Spectral Variability of the Nucleus of M33 in a Chandra/ACIS Observation

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.

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