0620062

The discovery of persistent hard X-ray emission from anomalous X-ray pulsars (AXPs) is one of the most remarkable discoveries by INTEGRAL to date! The spectral-shape transition of these AXPs around ~10 keV is drastic and not understood: from soft to extremely hard. These AXPs are detected up to at least 150 keV and their non-thermal emissions contain the bulk of the total energy emitted.These remarkable AXP spectra have led to several theoretical attempts to explain the non-thermal hard X-ray emission using e.g. magnetar corona and/or exotic QED processes in the most extreme magnetic fields. The current measurements are inssufficient to distinguish between several physically very different models. Using all available INTEGRAL archival data on these sources we collected good statistics on their time-averaged (years)n spectra and pulse profiles. However we know from the soft X-ray NIR and even radio bands that AXPs show dramatic variability behaviour in a wide variety of forms. What causes these dramatic events and how variations in one energy range relate to another is still a major puzzle in AXP astrophysics and is clearly intimately connected to determining the origin of AXP emission across the spectrum.We propose an INTEGRAL ToO program to follow up any (known or new) AXP not detected by INTEGRAL which shows significant increase in the persistent flux in soft X-rays (2-10 keV) till above 2E-11 erg cm-2 s-1. This can be easily measured with RXTE with which the AXPs are regularly monitored.We ask for 800 ks to determine accurately changes in parameters. To optimize the available INTEGRAL time we ask for the first 400 ks observation followed by near-real-time analysis searching for evidence fo the expected changes. After justification to the Proj. Scientist we request the remaining 400 ks. [truncated! Please see actual data for full text]