On the "when" and "where"

[Joshua Bloom]

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Some thoughts on this, somewhat informed by Wozniak's ideas on location
reporting from the Summer school.

>
> -- If I wish to report an event that happened at given RA, Dec with a one-degree
> error disk, how simple can the STC specification be?

One can imagine reporting the position and it's uncertainty as a union of
an arbitrary set of shapes (circles, annuli, polygons), each with simple
set of parameters. Still, this does not take into account the
probabilistic nature of localization uncertainty. Localization
probabilities are not, in general, Gaussian and can form an arbitrary
mapping on the sky. To this end, it might be worth exploring the idea of
linking (or even embedding) a probability skymap which could accompany
a crude ASCII description of the error location. The author would then
provide a URI to a FITS-like image of the localization.

>
> -- Can I take a time as specified by LIGO and put it into STC? Or a time as
> specificed by GCN? Is the translation straightforward?
>

In some sense, a VOEvent does not need to have a specific time of
occurrence, so many "times"  might be associated with the same
object/event. The difficulty will be in logically associating two Events
seen by two different systems to say they are the same thing.  My own bias
is that this should happen at an abstracted layer (with humans or AI
looking at all the available information), and not part of the job of the
VOEvent backbone. For example, if both LSST and PanStarrs find the same
supernova but at different times, both are entitled to report the event as
they see fit. But it is up to the community (or some harvesting robot) to
decide how to associate the events, who gets credit for discovery, etc.

j