The flux modulation of INTEGRAL

We have analyzed International Gamma-Ray Astrophysics Laboratory (INTEGRAL) data corresponding to observations of the high mass X-ray binary (HMXB) V0332+53 during its huge outburst which occurred in 2004–2005, and found that there is a quasi periodic signal with ultra low frequency of roughly 4?5×10^?5 Hz in the observation. This feature is revealed through a series of consistent analyses of imagings and fittings of the energy spectrum for each science window (SCW), and shows up in the corresponding light curves. The analysis of the power spectrum also provides a hint of a power peak located around 4×10^?5 Hz, after subtracting off the linear trend of the light curve, and shows the consistency with the previous analyses. A similar feature shows up in our analysis of the light curve of Crab in hexagonal dithering mode. Therefore, an instrumental effect on the flux modulation might exist in the INTEGRAL data product of different levels: imaging, spectral fitting and light curve analysis, at least for the observational mode of hexagonal dithering. Such an effect is, to our knowledge, not yet available in the current literature.