Enhanced quick look facility for XMM spectra with a Datalink service

[Laurent Michel]

Dear all,

I put online a prototype of a datalink service providing an enhanced quick look facility for XMM EPIC spectra.
The detail of this implementation will be published in an IVOA note very soon.


DataLink Service
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This Datalink service has been implemented on the development bench of the interface of the 3rd XMM catalogue.
This database contains 63 spectra published in a TAP service (not in any registry). There are 5 links attached to each spectra:
1) A preview generated by the XMM pipeline
2) A Zipball containing the FITS spectrum file with all ancillary data needed to reprocess it.
3-5) Pointers on 3 Web services fitting a model on the spectrum (based on Xspec)
When the user clicks on a Datalink icon a popup show out all links. Links 1 & 2 return directly the requested data files. Links 
3-5 run each a self described service which work in 2 steps. A description of the parameters supported by the service is is 
first returned. TapHandle builds then an HTML form which returns the data generated by the link service.

Client side
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A Javascript widget has been added to TapHandle to process the content of the Datalink columns.

Service Access
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1) Open http://saada.unistra.fr/taphandle?url=http%3A//saada.unistra.fr/3xmm/tap
3) Open the EPIC node on the data tree.
2) Clickclick on the EPIC_SPECTRUM node
3) CLick on any entry of the DataLink column (far right)

Scientific context (extract from the note to be published)
------------------
There is a real need for tools helping HE astronomers to evaluate online the spectral characteristics of sources of interest. 
That is not easy yet because source spectra are delivered as raw data. They have often a statistic too poor to be simply 
calibrated by an automated process. Usually, users download the FITS spectra with calibration data to do their own local 
processing. This heavy operation could be often skipped if there was a quick look facility. That can be achieved by a Webservice 
running on selected spectra with a few parameters given by the user. 2 use cases have been identified by the HE team of the 
Observatory of Strasbourg.
1) Preview: The previews of XMM-Newton spectra are currently precomputed by the mission pipeline. They are only available for 
sources for which an EPIC spectra has been computed.
2) Model fit: This service helps users to get the spectral characteristics of sources to evaluate if they are or not good 
candidates for the studied class of objects. The purpose of the demonstrator is to fit online some standard models on candidate 
spectra. Three models are proposed here, a power law, a power law including Z and an emission spectrum from hot diffuse (mekal).

Important:
---------
This service is a technical demonstrator. The model parameters are still under definition with a pool of astronomers.
In other words, don't consider the pictures returned by this service as valuable scientific documents.


See you in Heidelberg
Laurent

-- 

---- Laurent MICHEL              Tel  (33 0) 3 68 85 24 37
      Observatoire de Strasbourg  Fax  (33 0) 3 68 85 24 32
      11 Rue de l'Universite      Mail laurent.michel at astro.unistra.fr
      67000 Strasbourg (France)   Web  http://astro.u-strasbg.fr/~michel
---