For example, how to retrieve all the spectra of stars with spectral type between A0 and A2? It is a very general question. You may wish to select the members of the Hyades, or AGB stars, or whatever class of objects may be present in the catalogue of the ELODIE archive and/or download the corresponding spectra with an apropriate on-the-fly processing.
There are two different cases. Either you may select your sample by putting constraints on some physical parameters or you may want to access a sample made by yourself or taken from the litterature.
1. Making a sample from constraints on physical parameters
There are to types of information on which we plan to allow selections to be made: (1) observational parameters and (2) physical parameters.
The observational parameters, generated when the observations were done and included in the FITS header (meta-data) are stored in a table of the database and we will provide, after completion of phase 2 of development (September 2004), an advanced selection menu to put constraints on signal-to-noise, date of observation, name of observer or other parameters (suggestions are welcome).
The selection on physical parameters will rely on the availability of these parameters and actually there is a project of a "server of fundamental parameters of stars" to be opened next year at Observatoire de Bordeaux. This server will provide the effective temperature, surface gravity and metallicity (extension of the Cayrel et al. catalogue) and will also give estimates of absolute magnitude, plus an indication of spectral classification, photometry...
The latter parameters are now available from the Simbad database and we are currently studying improvements of cross-access with Simbad. Possibly, in the future, Simbad will give direct access to the entries in the ELODIE archive.
We hope that basic physical parameters will be included in the version to be released in September 2004, to allow selection of samples from physical parameters.
2. Using a pre-defined sample or loading your own sample
3. Getting the spectra for a sample
We recommend to read the document: "Other ways of accessing the Elodie archive".