1. P.N.Lebedev Physical Institute , Leninsky prospekt 53, Moscow 119991 , Russia
2. Moscow Institute of Physics and Technology (State Research University) , Institutsky per. 9, Dolgoprudny 141700 , Russia
3. National Research Center ‘Kurchatov Institute’ , Kurchatov sqr. 1, Moscow 123182 , Russia
4. Black Hole Initiative at Harvard University , 20 Garden Street, Cambridge, MA 02138 , USA
5. Harvard-Smithsonian Center for Astrophysics , 60 Garden Street, Cambridge, MA 02138 , USA