These flags indicate conditions which cast serious doubt upon the quality of the event as an X-ray detection:
At least one pixel included in the event is found in the bad pixel table.
The pixel under the event centroid shares an edge with a pixel from the bad pixel table.
The pixel under the event centroid lies in the first or last row or column of the telemetered window.
The calibrated energy of every pixel included in the event lies below the acceptance threshold.
The event does not lie entirely within a two-by-two pixel region.
The pixel under the event centroid shares an edge with the oposing node.
These flags provide information about the composition of the event:
At least one pixel included in the event lies in node zero.
At least one pixel included in the event lies in node one.
At least one pixel included in the event represents an on-board reconstruction.