Exosat studies of dips in Hercules X‐1

Abstract

EXOSAT observations of three absorption dips in Hercules X‐1 are presented. A partial covering model is employed, and qualitative differences between the three dips are highlighted. The behavior of the pulse profile during the dips is discussed. A transition between different phase states of the absorbing medium is observed within one dip, consistent with the cooling and condensation of an ionized cloud into discrete absorbing clumps.