GammaLib

Performing further cross checks between the fermi science tools and ctools the following problem came up:

If one takes the xmlfile from the science tools and tries to analyse it with gammalib/ctools the following happens:

input example:

<pre>
&lt;spectrum normPar=&quot;norm&quot; type=&quot;LogParabola&quot;&gt;
<spectrum normPar="norm" type="LogParabola">
<parameter error="0.0403546564" free="1" max="100000" min="1e-05" name="norm" scale="6.664498894e-12" value="0.330797703"/>
<parameter error="0.1932913856" free="1" max="5" min="-0" name="alpha" scale="1" value="2.762437733"/>
<parameter error="0.9494770106" free="1" max="10" min="-10" name="beta" scale="0.1" value="3.304939119"/>
<parameter free="0" max="300" min="0.02" name="Eb" scale="1000" value="1.444281016"/>
</spectrum>
</pre>

this means if the source is fitted also the Pivotenergy is free, which leads to the huge errors on the fitted parameters ( I think due to problem of correlated parameters) an example shown here:
<pre>
<spectrum type="LogParabola">
<parameter name="Prefactor" value="0.001" error="0.0510866" scale="1e-09" min="0.001" max="1000" free="1" />
<parameter name="Index" value="-3.71444e-05" error="878492" scale="1" min="-10" max="10" free="1" />
<parameter name="Curvature" value="-0.319421" error="0.108217" scale="1" min="-10" max="10" free="1" />
<parameter name="Scale" value="511.743" error="7.03715e+08" scale="1" min="20" max="10000" free="1" />
</spectrum>
</pre>

But also fixing the Pivotenergy does not solve the problem at the moment since the definitions of the parameters in the fermi science tools and gammalib/ctools are not completely compatible. This leads to a fit result like this:

<pre>
<spectrum type="LogParabola">
<parameter name="Prefactor" value="1.13197" error="0.0615543" scale="6.6645e-12" min="1e-05" max="100000" free="1" />
<parameter name="Index" value="-4.18061" error="0.0833878" scale="1" min="-5" max="5" free="1" />
<parameter name="Curvature" value="-10" error="0" scale="0.1" min="-10" max="10" free="1" />
<parameter name="Scale" value="1.44428" scale="1000" min="0.02" max="300" free="0" />
</spectrum>

</pre>