The Latest Version of SiFAP: Beyond Microsecond Time Scale Photometry of Variable Objects

Technical improvements of the Silicon Fast optical Astronomical Photometer (SiFAP) allow the instrumentation to integrate photons coming from the target in time windows down to 20 mu s. Further hardware improvement has been implemented to tag the Time of Arrival (ToA) of each single photon. In addition, a new commercial GPS unit has replaced the older commercial unit improving time resolution. The latest version of SiFAP has been calibrated to check photometric sensitivity and linearity through observations of several standard stars. SiFAP has been also successfully tested by observing the HZ/Her X-1 Binary System estimating the spin period of the pulsar (Her X-1). Our results have been then compared to data available in literature.