Emanom is a general tool for determining whether an EPIC MOS chip is
likely to be in an anomalous state, that is, having an anomalously
high quiescent particle background(QPB) below 
keV. It is
part of the goflib library of functions, subroutines, and tasks. It is
generally used with Extended Source Analysis Software (ESAS)
analyses. The algorithm is based on an updated version of Kuntz &
Snowden (2008) which relies upon the 2.5-5.0 keV/0.4-0.8 keV hardness
ratio to identify observations where the low energy band is
anomalously high. The object of this routine is to identify the chips
whose QPB spectrum, for this observation, is significantly different
from their normal QPB spectrum. This routine uses rather restrictive
criteria and may not be suitable for other uses. The work upon which
this algorithm is based will be published shortly.
For each chip experiencing anomalous states (currently MOS1-4, MOS1-5,
MOS2-2, and MOS2-5) this algorithm calculates the 2.5-5.0 keV/0.4-0.8
keV hardness ratio and compares that values to the noan_lim and
anom_lim values for that chip. If the hardness ratio is 
noan_lim the chip is considered good (G), and the QPB background
spectrum should be well characterised. If the hardness ratio is
anom_lim then the chip is considered bad (B), and the QPB
background spectrum cannot be constructed for this chip. If the
hardness ratio falls between noan_lim and anom_lim, then
the chip is considered intermediate (I), and the standard method for
constructing the QPB spectrum may be sufficient, but the user
should exercise caution. If there are so few counts in the spectrum
that the hardness ratio is not defined then the chip is considered to
be in an unknown state (U), and if the chip is not active it is
considered to be off (O).
The values for anom_lim and noam_lim are as follows:
MOS1, CCD4, anom_lim: 2.75 MOS1, CCD4, noam_lim: 3.00
MOS1, CCD5, anom_lim: 2.25 MOS1, CCD5, noam_lim: 3.60
MOS2, CCD2, anom_lim: 2.10 MOS2, CCD2, noam_lim: 2.50
MOS2, CCD5, anom_lim: 2.00 MOS2, CCD5, noam_lim: 4.00
The hardness ratios, the uncertainty in the hardness ratios, and the flag (B, G, I, O, or U) are recorded in the header keywords ANOMHRn, ANOMHEn, and ANOMFLn respectively if writekeys is true.
Note that chips that are in anomalous states still have useable spectra at energies greater than 1 keV.
