NED object is NGC 0253; Reference is  1992ApJS...80..531F

   Fig. 7. -Isointensity contour maps of the X-ray emission of detected
 galaxies superposed onto optical plates.  Galaxies are ordered by increasing
 RA.  The galaxy name(s) and the Einstein sequence number are given for each
 overlay.  The energy band used for the IPC contour maps is also indicated (S,
 H, or B; see text).  For galaxies observed with both instruments, we give the
 IPC map first, and then the HRI map.  The lowest contour level corresponds to
 a 2{sigma} enhancement over the background level.  Subsequent contours
 correspond to 3, 4, 5, and 6{sigma}.  Above this, contours may be skipped in
 strong sources to avoid crowding.  A straight solid line represents the edge
 of the x-ray field of view.  Dashed lines indicate the boundaries of the IPC
 ribs.