The main target of the Besançon Observatory double and multiple star data base is to provide the international astronomical community with the most comprehensive information about all categories of double stars, namely visual, interferometric, spectroscopic, photometric (eclipsing binaries), astrometric, occultation and so forth.
The above-mentioned categories of double stars
are characterized by observational techniques set up in order to detect them.
Intrinsic separations of double stars span from one stellar radius to several
thousands astronomical units.
These classes of double stars overlap : one component of a visual double star can in turn show up as a spectrocopic binary; a spectroscopic binary can turn out to be also a photometric binary, ... Data bases specific to a given category of double stars do exist at several research centres of observatories. The Centre de Données astronomiques de Strasbourg (CDS) provides several double star catalogues besides photometric, spectral or kinematic measurements for the components. On the other hand, the user does not have at his disposal measurements specific to binaries such as, for example, orbital data of visual or spectroscopic double stars. However, angular separations and position angles are supplied for part of visual double stars (mainly through the CCDM catalogue).
The BDB double and multiple star database therefore aims at gathering in a unique place measurements specific to the different categories of double stars, setting up a computerized link between them and to put them at the disposal of anyone interested. The user will be able to find the synthesis of the different informations available in querying the database using a variety of identifiers, some being specific to double stars (see figure ).
For each catalogue entered in the database, sources and authors are clearly mentioned. No modification is made to the catalogues without the assent of the authors. On the other hand, inconsistencies are pointed out and submitted to the authors involved. Thanks to BDB, it is thus possible to know to which catalogues a given star belongs to. A figure shows the catalogues already entered in the data base and those planned in the future.
Pinpointing inconsistencies in identifiers or measurements is a crucial
problem which appears as soon as one tries to cross-identify several catalogues.
The core of the database is therefore the cross-identifier table; it is the
first milestone which allows the search from different sources of data. In
numerous cases, it allows to raise the ambiguities due to a shaky appreciation of the component, of the system and/or of their measurements.
Measurements coming from ground-based facilities as well as spacecrafts are integrated in the data base. In the future, we wish to integrate measurements other than those specific to double stars, such as proper motions, radial velocities and spectra. Interest is also being taken in non-numerical data, namely images of deep surveys such as the Digitized Sky Survey or CCD observations obtained in the framework of several observing programmes. With this aim in view, a java tool -BDBjava- has been developed to visualize this type of data. Similarly, softwares specific to binaries are integrated, allowing for instance to get complementary informations such as ephemeris calculations and orbital elements to be obtained from the data.
In order to take into account developments performed in other laboratories, automatic links are set up such as these established with the SIDONIE database in Nice, the eclipsing binary database of the Cracow Observatory, the SB9 9th catalogue of orbits of spectroscopic binaries and the CDS in Strasbourg.
The data base is managed through the /rdb database management system based mainly on UNIX macro-commands.
The developments of the data base are made under the responsability of E. OBLAK , astronomer at the Besançon Observatory, in collaboration with several local computing institutions.
Originally, BDB was started in 1995 in collaboration with D. POURBAIX
(Institut d'Astronomie et d'Astrophysique of the Université Libre
of Brussels) who laid the first computing foundations. Structural developments
were realised by T. KUNDERA from the Cracow Observatory (Poland). SInce 2000,
the computing responsability has felt to B. DEBRAY from Besançon Observatory.
A planned evolution of the BDB database is the commisioning of the
standards that will allow its interaction with the international projects
of Virtual Observatories (see e.g. the site of the International Virtual Observatory Alliance).
Since 2000, a scientific council has been set up.