2007ApJ...669..106K

Using 400 days of new X-ray monitoring of M82, we confirm the 62 day periodicity previously reported. In the full data set spanning 1124 days, we find a period of 62.0±0.3 days and a coherence, Q=22.3, that is consistent with a strictly periodic signal. We estimate that the probability of chance occurrence of our observed signal is 6x10^–7. The light curve folded at this period is roughly sinusoidal and has a peak-to-peak amplitude of (0.99±0.10)x10^–11 erg/cm2/s. Confirmation of the periodicity strengthens our previous suggestion that the 62 day modulation is due to orbital motion within an X-ray binary.