Simultaneous X-ray and optical timing observations of GX 339-4

GX 3394 is an unusual galactic black hole candidate extremely variable in boththe optical and Xray bands during its lowhard state. Only a very short simultaneous opticalXray study has been performed, which suggested that the opticalvariations are strongly coupled with Xray variations. We propose to perform acomprehensive simultaneous opticalXray rapid variability study with EPICPNand the OM. We will also use EPICMOS and RGS to study the weak soft componentand the 6.4 keV iron line detected in this state. We expect to detect edges andpossibly other emission lines in the RGS energy range. With these observations,we hope to make significant progress in the understanding of the coupled inflow outflow system around a persistently accreting stellar mass black hole. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]