Last bin in light curves overlaps the next-to-the-last bin in time

[jasercion]

Ported from jira STGEN-107.

Hi,
I have found a bug in the evtbin package. When producing a light curve
using gtbin, the last bin in the output FITS file starts before the
end of the previous bin, in other words TIME of the last bin is less
than (TIME+TIMEDEL) of the previous one. See for example the attached
light curve "prova.lc". These are the last three rows:

Row TIME TIMEDEL
(TIME+TIMEDEL)
10823 241779317.787482 0.0300000011920929 (241779317.81748200119)
10824 241779317.817482 0.0300000011920929 (241779317.84748200119)
10825 241779317.837992 0.0110200047492981

I attach also the parameters file used to produce "prova.lc", and the
events file (a GBM Time-Tagged-Event file).
I don't know if this problem with the binner (i think) impacts only
the last bin of the light curves (that should not be a big issue), or
other things as well.

I have used one of the last SCons version available (contained in
ScienceTools-LATEST-1-3154), as well as other older version, and the
problem shows out in every version.

[jasercion]

Response from @joeastro:

I've retested for this issue by following the "LAT Aperture Photometry" analysis thread, and I confirm that it is still present. It seems that for N time bins, the TIMEDEL of the last bin is actually twice the difference in time between the last and second-last bins. For the other bins, the TIMEDEL keyword accurately reflects the difference in time between adjacent bins. I will need to look at the LIN algorithm that GTBIN uses to figure out how it is treating the last bin.