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(Ballet) I have nothing against splitting at 300 MeV rather than 3162 MeV.
I don't think it is useful to extend down to 20 MeV. The events measured below 30 MeV are for a large part coming from above 30 MeV (the effective area increases steeply with energy there) and they have very bad spatial resolution.
On the other hand, it may be useful to add another band above 3 GeV (split 3 to 10 GeV and > 10 GeV). This will add another piece of information for bright hard sources and will not really change anything for faint sources (most photons above 3 GeV will be in the 3 to 10 GeV band).
It is true that for many sources the only useful bands will be 300 MeV to 1 GeV and 1 to 3 GeV, but I don't see that as a problem.
5. Flux_History
(Ballet) Did anybody study what was the best energy interval (in particular the lower boundary) to look for variability? Is 100 MeV indeed the best trade-off between number of source photons and number of background photons plus contamination by other sources ?
(Digel) This has not been studied, to my knowledge. Certainly 100 MeV is not the best in terms of being able to distinguish sources. Quoting fluxes for the range >100 MeV, though, is common.
The variability index can apply to whatever energy interval we choose, presumably specified along with the definition of the index
6. Hist_Start/End
(Ballet) If I understood correctly the ideas developed in the September 2002 review of how to obtain a light curve, this will be done by running likelihood in each time bin (fixing the diffuse emission and the spectral indices). That document implied that this would be done in smaller time bins for brighter sources.
It would be much more homogeneous to do that in the same time intervals for all sources. It would ensure that the likelihood results for closeby sources would be obtained consistently, and would also be easier to use for systematic studies.
(Atwood, 31 Dec 2005) On the selection energy bands - one might consider that the background rejection analysis is done in quasi-logarithmic energy bands as well. However the definition of the bands is a little different with break points at < 100, 100-350, 350-1000, 1000-3500, 3500-10000, > 10000.
(Digel, 4 Jan 2006) No one else has weighed in on Bill's comment. I was going to say that the 30-100, 100-300, 300-1000, 1000-3000, and >3000 MeV ranges correspond to what was used for EGRET, but they don't really. (Above 1 GeV, the standard energy ranges used for EGRET analysis were 1-2, 2-4, and 4-10 GeV.) So I can't say that tips the balance one way or the other. I would hope that especially for point sources (as opposed to diffuse sources) we'll be essentially immune to any trouble (systematic errors, I guess) from residual background. But in case the character of the residual changes a lot between the bands used for the background rejection analysis, we may be better off using them to start with. Does anyone else have a strong opinion about this?
5. Flux_History
(Ballet) Did anybody study what was the best energy interval (in particular the lower boundary) to look for variability? Is 100 MeV indeed the best trade-off between number of source photons and number of background photons plus contamination by other sources ?
(Digel) This has not been studied, to my knowledge. Certainly 100 MeV is not the best in terms of being able to distinguish sources. Quoting fluxes for the range >100 MeV, though, is common.
The variability index can apply to whatever energy interval we choose, presumably specified along with the definition of the index
6. Hist_Start/End
(Ballet) If I understood correctly the ideas developed in the September 2002 review of how to obtain a light curve, this will be done by running likelihood in each time bin (fixing the diffuse emission and the spectral indices). That document implied that this would be done in smaller time bins for brighter sources.
It would be much more homogeneous to do that in the same time intervals for all sources. It would ensure that the likelihood results for closeby sources would be obtained consistently, and would also be easier to use for systematic studies.
I would like to propose that we do that in large time intervals (like one month) for all sources. So I would like to propose that we do that in large time intervals (like one month) for all sources. So the time interval (not the number of bins) would be fixed. In addition, we could add specific files (one per source) for bright sources where much more detailed information can be obtained (including spectral variability for example, or going beyond 100 bins).
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I've left the flux history and peak flux entries specified as corresponding to the range >100 MeV. I'd prefer to leave it that way for the purposes of the Catalog - the same energy range for every source and every time range.
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Additional issues (starting 31 Dec 2005)
12. Galactic coordinates
(Strong) Hesitating to add comments at this stage, but I see that there are no Galactic coordinates.
With INTEGRAL catalogs it's always a pain to plot the catalogs as a Galactic distribution with eg fv since they also miss (l,b). Of course it can easily be done with e.g. an idl program but Galactic is so fundamental why not include it?
The EGRET catalogs DO have it which is very convenient! (Maybe all this was already discussed before).
(Digel) I think in Galactic coordinates, too, and would like to second this nomination. We are already at 34 columns, so what is a couple more? Regarding the error ellipses, we should keep the position angles (Conf_68_PosAng and Conf_95_PosAng) as degrees East of North, i.e., with respect to celestial coordinates.