D. E. Harris, C. S. Grant
Center for Astrophysics, 60 Garden St., Cambridge, MA 02138
Observatoire de Lyon, F--69561 Saint-Genis-Laval Cedex, France
Current address: IUE Observatory/Villafranca, Apartado 50727, E--28080 Madrid, Spain
In 1989 January, SAO established an on-line service to help astronomers prepare ROSAT proposals by providing access to the preliminary source list from the `` Einstein Observatory Catalog of IPC X-ray Sources.'' In the intervening years, we have updated the source list, added to the documentation, included many more Einstein databases as well as a number of tables from other wavebands, provided access to images for downloading from all of the Einstein CD-ROMs, and installed new software for more sophisticated filtering and retrieval. Although we have improved the functionality and made significant additions to the databases, we still maintain a simple menu interface accessible from any type of terminal. An instruction manual does not exist: the on-line help facility provides the necessary information.
The EOLS provides three options for data retrieval. The ``database query'' is a menu-driven system which allows users to build their own query and select which output columns should be retrieved. The ``quick query'' provides an output format which requires only one specification of selection criteria, and returns up to 79 characters per row (pre-selected by us). The ``multiple quick query'' is a positional search on several tables. We have endeavored to make the selection process simple and the easiest option is to select one or more affinity groups. However, the user can specify particular tables from different groups by choosing the ``Custom'' option or choose to select all tables.
Here are six of the 30 rows retrieved from 105 catalogs with a single query:
All of our Einstein CD-ROMs are permanently available for downloading images. They may be obtained with ftp or with the VMS ``copy'' command. As of 1994 June 30, we have:
There are several important features of the EOLS service, including a low maintenance operation, and the ADS connection. The EOLS provides all of our databases to the ADS, and our documents that describe each table are written in the ADS format. Documentation is available for each database table and provides extensive detail in some areas (e.g., Vol. 1 of the IPC catalog), archival material such as the `` Einstein Revised User's Manual,'' and ``help'' files which provide information on system operations. A communication facility is also available, and features a bulletin board (including ROSAT news) and an e-mail facility for sending yourself documents and the results of database searches. Finally, a set of tools for precessing coordinates and column densities of galactic H I (north of Dec = -40^o) are available.
There are four methods to log onto the EOLS:
Once successful, the login name is ``einline''; no password is required. Note: since UNIX is case sensitive, make sure you use lower case when logging in!
For many years we have noticed the difficulty of finding radio source data in public archives or on-line databases. In 1991, the IAU Working Group on ``Radioastronomical Databases'' was formed with one of us (H.A.) as the chair. By now the Working Group has secured some 130 catalogs of radio sources with a total of entries. Although the working group recognized that a long term solution to this problem should be provided by an on-going commitment from the National Radio Astronomy Observatory (NRAO) or the Strasbourg Astronomical Data Center (CDS), the EOLS volunteered to serve as an experimental platform for access to the catalog collection. This ``provisional'' solution is now by far the most complete on-line facility for radio source data, offering access to 63 radio catalogs with 520,000 searchable entries. Contributions of new data tables are welcome, but can only be incorporated into the system if authors provide proper documentation and formatted ASCII tables.
The histogram in Figure 1 shows the average number of logins per month from outside the Center for Astrophysics from 1989 to mid-1994.
Figure: Logins per month from outside CfA: 1989--1994. Original PostScript figure (76 kB)