tokens: V.A. acknowledges financial support from NASA/ Chandra grants GO3-14051X, AR4-15003X, NNX15AR30G, and NASA/ADAP grant NNX10AH47G. A.Z. acknowledges financial support from NASA/ADAP grant NNX12AN05G, and funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 617001. J.D., P.P., and T.G. acknowledge financial support from NASA contract NAS8-03060. M.S. acknowledges support by the the Deutsche Forschungsgemeinschaft through the Heisenberg Programme (SA 2131/3-1). S.L. acknowledges financial support from NASA/ADAP grant NNX14-AF77G. The OGLE project has received funding from the National Science Centre, Poland, Grant MAESTRO 2014/14/A/ST9/00121 to AU. We thank the anonymous referee for helpful comments and suggestions.
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