The absence of a thin disc in M81

We present the results of simultaneous Suzaku and NuSTAR observations of the nearest low-luminosity active galactic nucleus (LLAGN), M81*. The spectrum is well described by a cut-off power law plus narrow emission lines from Fe K alpha, Fe xxv, and Fe xxvi. There is no evidence of Compton reflection from an optically thick disc, and we obtain the strongest constraint on the reflection fraction in M81* to date, with a best-fitting value of R = 0.0 with an upper limit of R < 0.1. The Fe Ka line may be produced in optically thin, N-H = 1 x 10(23) cm(-2), gas located in the equatorial plane that could be the broad line region. The ionized iron lines may originate in the hot, inner accretion flow. The X-ray continuum shows significant variability on similar to 40 ks time-scales suggesting that the primary X-ray source is similar to 100 s of gravitational radii in size. If this X-ray source illuminates any putative optically thick disc, the weakness of reflection implies that such a disc lies outside a few x 10(3) gravitational radii. An optically thin accretion flow inside a truncated optically thick disc appears to be a common feature of LLAGN that are accreting at only a tiny fraction of the Eddington limit.