0840021

We propose to perform long-term INTEGRAL observations ($sim 600$~ks) of transient bright X-ray pulsars during their powerful outbursts. The observations will be focused on the study of: 1) the cyclotron absorption line behavior at the low luminosities (search for the transition between the direct and reversal correlations of the cyclotron energy and luminosity and determination of the critical luminosity) 2) the corresponding evolution of the pulse profile with the luminosity and photon energy especially near the cyclotron line. The distinctive feature of our proposal in a comparison with previously performed X-ray pulsar TOO observations is that to cover the low luminosity part of the outburst with maximal exposure and minimal amount of data gaps. Such observations will provide enough statistics to trace the behavior of the cyclotron absorption line at low luminosities as well as for the study of corresponding changes of the pulse profile. [truncated! Please see actual data for full text]