▁ 0 . 2 5 ▁or ▁ 0 . 5 ▁s ▁integr ations ▁and ▁ 4 ▁energy ▁channels ▁( with ▁short est ▁integration ▁time ▁being ▁ 8 ▁s ). ▁Again , ▁the ▁outputs ▁of ▁the ▁ 2 ▁detect ors ▁were ▁sum med . ▁ ▁The ▁U ly ss es ▁soft ▁X - ray ▁detect ors ▁consisted ▁of ▁ 2 . 5 - mm ▁thick ▁× ▁ 0 . 5   cm 2 ▁area ▁Si ▁surface ▁bar rier ▁detect ors . ▁A ▁ 1 0 0   m g / cm 2 ▁b ery l li um ▁fo il ▁front ▁window ▁rejected ▁the ▁low ▁energy ▁X - ray s ▁and ▁defined ▁a ▁con ical ▁FO V ▁of ▁ 7 5 ° ▁( half - angle ). ▁These ▁detect ors ▁were ▁pass ively ▁co o led ▁and ▁operate ▁in ▁the ▁temperature ▁range ▁− 3 5 ▁to ▁− 5 5   ° C . ▁This ▁det ector ▁had ▁ 6 ▁energy ▁channels , ▁covering ▁the ▁range ▁ 5 – 2 0 ▁ke V . ▁ ▁The oret ical ▁X - ray ▁astronom y ▁The oret ical ▁X - ray ▁astronom y ▁is ▁a ▁branch ▁of ▁theoretical ▁astronom y ▁that ▁de als ▁with ▁the ▁theoretical ▁ast ro physics ▁and ▁theoretical ▁ast ro chem istry ▁of ▁X - ray ▁generation , ▁emission , ▁and ▁detection ▁as ▁applied ▁to ▁astronom ical ▁objects . ▁ ▁Like ▁theoretical ▁ast ro physics , ▁theoretical ▁X - ray ▁astronom y ▁uses ▁a ▁wide ▁variety ▁of ▁tools ▁which ▁include ▁analyt ical ▁models ▁to ▁approximate