Gain Notes for Revolution 1555

This is one of the later revolutions in the mission where the calibration
sources have become so weak that for the best energy determination and
IC Gain History table is needed.

NB: This revolution is strongly affected by the effects of grey filtering that
occurred because of the presence of the strong and active source V404 Cyg in the
field of view. It has not been possible to garantee good gain calibration for
the Science windows for which there is significant loss of events due to grey
filtering. It is possible that a new IC table will be created at a later date
i.e. after 2nd July 2015. The calibration data is also compromised by sky source
photons swamping the calibration source areas so that the reduced flow of
calibration photons is fatally contaminated with target photons.

For this revolution only Xe line results are shown in the range 20 to 38 keV to
demonstrate the goodness of the energy determination where it can be validated
at all, and to show the extent of the scatter in the data where the Xe line is
swamped by the V404 source points and the effect of grey filtering.
 

To get optimal results with this revolution it is necessary to use the IC gain history.
See notes in revolutions prior to revolution 1433 to find out how to do this
if you don't already know.

All offline gain/energy corrections (including the IC tables) are based on the
two Fe calibration sources in JEM-X1, for both units.

Latest OSA software (version 10 and higher) automatically cuts out the first
Science windows of data from each revolution to ensure that people do not use data
from the instrument-settling period. This process can be overruled, but only by
experienced users.
	
JEM-X1: 

The Xe line analysis performed using the IC table shows enormous scattering
in the Xe line data, some of which may  be real, but most of which is
due to having far too few counts in the Xe data during periods of grey
filtering. The gain correction correction done with the IC table provided has aimed
to get all useable Xe line points within a few percent of the ideal value, and for
those points not showing huge scatter, this has worked out at around 4% of ideal, except for
one point.Whether any of the many points outside the usual figures are indicative of
actual gain correction falling well beyond the usual range is still being investigated. 
As usual, it is recommended that users avoid the first few science 
windows for energy-sensitive applications (automatically removed by OSA 10.0).

The lack of a visible revolution-integrated Xe line is worrying and being
investigated.

JEM-X2: 

All the same comments apply to JEM-X2 as to JEM-X1. The only difference is that there
is a very faint Xe line centered at 29.82keV which indicates that overall calibration
is good even though it can't be verified for many SCWs.

The JEM-X2 corrections are based on the JEM-X1 Fe calibration sources, since
all the Cd sources are now to weak to use.

CAO 2/7/2015