Shadows of Multi-Black Holes: Analytic Exploration
  Shadows of multi-black holes have structures distinct from the mere
superposition of the shadow of a single black hole: the eyebrow-like structures
outside the main shadows and the deformation of the shadows. We present
analytic estimates of these structures using the static multi-black hole
solution (Majumdar-Papapetrou solution). We show that the width of the eyebrow
is related with the distance between the black holes and that the shadows are
deformed into ellipses due to the presence of the second black holes. These
results are helpful to understand qualitatively the features of the shadows of
colliding black holes. We also present the shadows of colliding/coalescing
black holes in the Kastor-Traschen solution.
