Rapid optical and X-ray timing observations of GS1826-238

We propose to carry out a rapid optical timing observations of the LMXB GS1826238, which should be performed simultaneously with XMM telescope. The mainobjective of the proposed observations is to estimate reprocessing time delay inthe accretion disk and make a detailed analysis of the optical response to theXray burst. The proposed observations of the short orbital period binary GS1826238 is of high importance because it might help to unambiguously detect thefinite time delay due to reprocessing of illuminating Xrays within hotaccretion disk corona. In addition, we plan to perform a series of opticalspectra in order to spectroscopically confirm the 2.25h photometric period anddetermine the exact orbital ephemerides for GS 1826238. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]