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The HEASARC On-line Service

An Update

K. L. Rhode, Patricia Tyler,

and Karen M. Smale


One of the primary objectives of the HEASARC is to provide a user-friendly, multi-mission, multi-wavelength environment in which to access the data that it archives. An On-line Service has been established to help accomplish that objective. Users who log in to the Service can access data from orbiting observatories (the list of which currently includes Cos-B, HEAO-1, Einstein, EXOSAT, Ginga, IUE, and ROSAT) along with many well-known astronomical catalogs. The database system and software within the On-line Service allow users to search and locate data, and then to either analyze it remotely, or to export it to their home computers for analysis there.

Introduction to the XOBSERVER environment

The HEASARC On-line Service resides on the NSSDC Data Archive and Distribution Service, (NDADS), a VAX cluster at GSFC. A captive account called XRAY has been set up on the NDADSA VAX to provide secure remote access to the database system and software. A program called XOBSERVER controls the use of the XRAY account. XOBSERVER provides:

  • automatic registration of users,
  • a user directory where files can be stored and manipulated,
  • TCP/IP, DECnet and PSI access (plus a gateway option),
  • runtime execution of database access and analysis tasks, and
  • tasks to transfer files to the user's computer.

    A user logs in remotely to XRAY and then runs database and analysis tasks to search through astronomical catalogs, locate data files, and analyze or transfer data. The XOBSERVER program originated from the EXOSAT Database System, which was written by the European Space Agency's (ESA's) Space Science Department between 1986 and 1990 to provide remote access to archival data obtained by EXOSAT. Recently the HEASARC, the ESA, and the University of Leicester, UK, have been jointly developing the system to provide a generic environment for on-line astrophysics archival access and analysis. The system was renamed XOBSERVER in recognition of its multi-mission nature and to distinguish the controlling environment from the analysis and database tasks.

    Logging in

    The first issue of Legacy and the HEASARC "On-line Users Guide" describe in detail how to use the captive account. Briefly, users can log in to the HEASARC On-line Service 24 hours a day by setting host to or telnetting to NDADSA.

    $ set host ndadsa (set host 15761)
    $ telnet

    Once the user has connected, NDADSA will signal its presence and ask for a username. The user enters XRAY at the USERNAME prompt, and is logged in to the On-line Service captive account. A new user, or one who is logging in from a different location than usual, will be asked to type a HEASARC username. This should be the user's first initial and last name, (e.g., INEWTON).

    Once the user has successfully logged in to the captive account, the HEASARC> prompt appears; this indicates that HEASARC XOBSERVER is ready to receive input. At this point there are a number of options available to the user, including accessing the databases or the bulletin board, running data analysis programs, or transferring files. On-line help can be accessed by simply typing help at the HEASARC> prompt.

    The BROWSE databases

    Typically, a user will begin by running the database access program, BROWSE, to search through and display the available data and catalogs. BROWSE is a command-driven program that uses a database management system to select data from tables of information and results, and access any associated data product files. The analysis tasks available within the XOBSERVER environment can be executed from within BROWSE, or outside of it, whichever the user prefers.

    BROWSE is started by typing

    HEASARC> browse [dbname]

    The optional parameter dbname specifies the name of the database to be accessed; if no dbname is given, BROWSE will prompt for one. Typing a ? or carriage return will display a list of all the available HEASARC databases. Once a user chooses a database to "browse", that database is loaded as the current database, and the user enters commands to manipulate the database entries. Users can sort, search, display and plot entries in the database, and can also cross-correlate the data with entries in other databases. In addition, the data can be passed to other programs for spectral, timing, and image analysis, and interactive plotting and fitting.

    Note that here the word "database" simply means a collection of information or results which has been organized into a table. The rows in the table are called "entries", and the columns are "parameters". HEASARC databases typically contain observation logs, astronomical catalogs, bibliographies, file names and locations, and/or data analysis results. In the case of an observation log, the database may contain one entry for each observation, with the associated parameters being the observation date, time, and duration, pointing coordinates, and instrument used. Catalog databases often are organized with one entry (or row) for each source, and parameters (or columns) such as source names, coordinates, count rates, magnitudes, and classifications.

    At present, there are more than 80 HEASARC databases on line. A listing of some of the available databases appears in Table 1. The databases can be accessed separately, or cross-correlated with one another to find matches in common parameter fields. For example, celestial coordinates can be used to find all matching sources in two databases, based on positional coincidences within a specified radius. Some of the 30 new databases since the last issue of Legacy are described in the section Recent Additions to the HEASARC On-line Service.

    Table 1: Sample of HEASARC On-line Service Databases

    20CMNORTH   Catalog: 20cm radio
    3ARIEL      Catalog: 3A (Ariel-V)
    RC3         Catalog: 3rd Ref Cat of Galaxies
    4UHURU      Catalog: 4th Uhuru X-ray
    6CMNORTH    Catalog: 6cm radio
    ABELL       Catalog: Abell Clusters
    KUEHR       Catalog: Extragal. Radio Sources
    CNS3        Catalog: Gliese Nearby Stars 3
    SNRGREEN    Catalog: Green SNRs
    GSC         Catalog: HST guide stars
    HD          Catalog: Henry Draper
    QSO         Catalog: Hewitt & Burbidge QSO
    ZCAT        Catalog: Huchra CfA Redshift
    IRASID      Catalog: IRAS FSC Associations
    IRASFSC     Catalog: IRAS Faint Sources
    IRASPSC     Catalog: IRAS Point Sources
    KONUS       Catalog: Konus 11 & 12
    PULSAR      Catalog: Lyne Pulsar
    MCKSION     Catalog: McCook & Sion WD's
    MRC         Catalog: Molonglo Radio Sources
    PVOTRIG     Catalog: PVO gamma-ray bursts
    RITTER      Catalog: Ritter CVs & LMXRBs
    SAO         Catalog: SAO stars
    HXRBS       Catalog: SMM HXRBS
    WOOLLEY     Catalog: Stars <25 pc from Sun
    TD1         Catalog: Stellar UV Fluxes
    VSTARSUSP   Catalog: Suspected Variables
    VSTARS      Catalog: Variable Stars, 4th ed.
    VERON89     Catalog: Veron Quasars & AGN
    DOCUMENTS   Documents: HEASARC
    LE          EXOSAT CMA (central 6 arc min)
    CMA         EXOSAT CMA Database
    GS          EXOSAT GS database
    ME          EXOSAT ME database
    PR          EXOSAT PR database

    TGS EXOSAT TGS L and R orders TGS2 EXOSAT Transmission Grating EXOPUBS EXOSAT bibliography EXOLOG EXOSAT observation log EMSS Einstein EMSS catalog HRICFA Einstein HRI CfA Source List HRIEXO Einstein HRI EXOSAT source list HRIIMAGE Einstein HRI Image Database HRIPHOT Einstein HRI Photon Event Data IPCIMAGE Einstein IPC Image Database IPC Einstein IPC Source List IPCSLEW Einstein IPC slew catalog SSS Einstein SSS database SSSHME Einstein SSS dbase-IBM listing EINLOG Einstein observation log GROLOG GRO Phase I Viewing Plan GINGALOG Ginga LAC Log Catalog GINGAMODE Ginga LAC Mode Catalog A1 HEAO 1 A1 X-ray Catalog A2LED HEAO 1 A2 LED Sky Catalog A2PIC HEAO 1 A2 Piccinotti Catalog A2POINT HEAO 1 A2 Point Catalog A3 HEAO 1 MC LASS Catalog A4 HEAO 1 A4 X-ray catalog

    IUE IUE ULDA database COSB COS-B Photon Catalog SMMGRS SMM GRS Gamma-Ray Burst D'base

    XRAY Master Catalog: X-ray XCOLL Master Catalog: X-ray Collimators OPTICAL Master Catalog: optical RADIO Master Catalog: radio

    ROSTL1 ROSAT AO1 long-term timeline ROSTL2 ROSAT AO2 long-term timeline ROSTL3 ROSAT AO3 long-term timeline WFCBSC ROSAT WFC Bright Source Cat. ROSAO ROSAT accepted AO proposals ROSATLOG ROSAT log of observations ROSOBS ROSAT observations status ROSSTL ROSAT short-term timeline

    Recent Additions to the HEASARC On-line Service

    Since publication of the first edition of Legacy, there have been many additions to the list of Browse databases available within the HEASARC On-line Service. Several new catalogs and datasets have been placed on-line, while others have been updated to newer and more complete versions. The following databases have been recently acquired or updated and are now accessible through Browse:

    KUEHR - Catalog of Extragalactic Radio Sources

    The catalog is a compilation of 518 extragalactic radio sources with flux densities greater than 1 Jy at 5 GHz. It contains sources from the NRAO-MPI 5 GHz Strong Source Surveys and from re-observation at 5 GHz of sources found in the Parkes 2.7 GHz surveys. Included are radio flux densities, radio positions, object classes, visual magnitudes, redshifts, and spectral indices.

    SNRGREEN - Catalog of Galactic SNRs

    This catalog contains information on 174 galactic supernova remnants as published in Green 1988, Astrophys. Space Sci., 148, 3, and updated by Green 1990, PASP (in press).

    ZCAT - CfA Redshift Catalog

    The CfA Redshift Catalog incorporates velocity data from the Whipple Observatory and other sources, as well as velocities from earlier compilations. It includes BT magnitudes, some UGC numbers, and increased "accuracy" in the velocity source information. The data were assembled mainly for the study of the large scale structure of the universe; thus the catalog is nearly complete in redshift information, but not necessarily complete in categories such as diameter, magnitude, and cross-references to other catalogs.

    IRASFSC - IRAS Faint Source Catalog

    The IRASFSC database contains the IRAS Faint Source Catalog (FSC) non-associations data. (The associations data for the IRAS FSC is contained in the IRASID database.) Version 2.0 of the FSC, released in September 1990, is a highly reliable catalog which is 2.5 to 3 times more sensitive than the IRAS Point Source Catalog (PSC). The FSC also contains 99,973 infrared sources which are not in the PSC.

    IRASID - IRAS FSC Associations Catalog

    The IRASID database contains the associations data for the IRAS Faint Source Catalog (FSC). The main catalog of non-associations data is contained in the IRASFSC database.

    KONUS - Konus 11 & 12 Gamma-ray Burst Catalog

    This catalog contains gamma-ray burst data from the KONUS instruments, which were flown on pairs of Venera spacecraft. Veneras 11/12 were launched in September 1978; bursts were recorded through January 1980. Veneras 13/14 were launched in November 1981 and were operational through March 1983. The Veneras were interplanetary spacecraft which flew to Venus, and thus each spacecraft had whole sky coverage for most of its mission.

    PVOTRIG - Pioneer Venus Orbiter Triggered Gamma Ray Bursts

    This catalog gives information on the triggered events detected by the PVO instrument from September 14, 1978 to July 21, 1988. The catalog comes from the Ph.D. thesis of Kuan-Wen Chuang (UC Riverside, 1990).

    VERON89 - Catalog of Quasars and AGN

    This catalog is the 4th edition of Veron-Cetty and Veron, "A Catalogue of Quasars and Active Galactic Nuclei". It contains data for quasars, active galaxies, and BL Lac objects.

    GROLOG - Gamma Ray Observatory Viewing Plan

    This database contains the Phase 1 viewing plan for the Compton Gamma Ray Observatory. It gives target names and coordinates, instrument used, and start and end times for each Phase 1 observation.

    COSB - COS-B Photon Catalog

    This is a catalog of photon data from the European Space Agency satellite Cos-B. Cos-B was dedicated to gamma-ray astronomy in the energy range 50 MeV to 5 GeV, and carried a single experiment, a spark chamber telescope, developed in a collaboration by six European institutes. The experiment became operational on August 17, 1975, and was switched off on April 25, 1982, when on-board resources were exhausted. During this period, 65 observations, typically of a month's duration, were performed. Circular sky regions of about 40 degrees in diameter were covered in each observation. The majority of the pointings were distributed along the galactic equator, but 15 observations were devoted to regions at high (>20 degree) galactic latitudes. Several regions of specific interest were repeatedly observed.

    RC3 - Third Reference Catalogue of Bright Galaxies

    The RC3 database contains the machine-readable version of the Third Reference Catalogue of Bright Galaxies (RC3.9) by G. de Vaucouleurs, A. de Vaucouleurs, H.G. Corwin, R.J. Buta, P. Fouque, and G. Paturel, 1991.

    CNS3 - Catalog of Gliese Nearby Stars

    This catalog is a preliminary version of the Third Catalogue of Nearby Stars (CNS3) compiled by Wilhelm Gliese and Hartmut Jahreiss (Astronomisches Rechen-Institut, Heidelberg, Germany). It contains information about every known star within 25 parsecs of the Sun.

    HRIPHOT - Einstein HRI Images in Event List Format

    The HRIPHOT database contains information in Event List format from the High Resolution Imager (HRI) aboard the Einstein Observatory. The Einstein HRI detector provided an arrival time and position for each X-ray event occurring within its 24-arcmin field-of-view and within the energy range 0.15 keV to 3.5 keV. The HRIPHOT database points to 870 HRI photon events files, stored in FITS format.

    IPCSLEW - The Einstein IPC Slew Survey source list

    The IPCSLEW database contains the most recent version of the list of sources detected by the IPC Slew Survey. It was created in March 1992 and contains 819 entries. The original IPC Slew Survey source list was released on CD-ROM and contained 1067 sources. The list was updated in 1991 to remedy a software bug which omitted a thin slice of RA near 24h; the bug fix yielded 8 additional sources, to bring the total to 1075. The list, however, was found to contain a large fraction (10 to 15 percent) of unreliable sources, especially those sources with o(<,~) 5 photons. The unreliable sources were rejected in producing the latest version of the source list, so that it now has an estimated false source rate of only 2 percent, and contains 256 fewer sources than the previous version.

    OPTICAL - Master Optical Catalog

    The OPTICAL database is a newly-revised master catalog containing selected parameters from several optical source catalogs. OPTICAL was created by copying all of the entries and common parameters from the HEASARC databases which contain the following catalogs:

    Abell Catalog of Galaxy Clusters (1989)
    Ritter Catalog of CV's, X-Ray Binaries & Related Objects (1990)
    General Catalog of Variable Stars, 4th ed. (Kholopov 1985-88)
    Smithsonian Astrophysical Observatory Star Catalog (1989)
    McCook & Sion White Dwarf Catalog (1987)
    Hewitt & Burbidge Catalog of Quasi-Stellar Objects (1987)
    Woolley Catalog of Stars within 25 Parsecs of the Sun (1970)
    Veron-Cetty & Veron Catalog of Quasars and AGN (1989)
    Green Catalog of Supernova Remnants (1988, updated 1990)
    CfA Redshift Catalog (Huchra 1989)

    ROSTL3 - The ROSAT AO3 Long-term Timeline

    The ROSTL3 database is based on the ROSAT AO-3 (part 1) long-term timeline (MPE number 1000). The first half of the AO-3 timeline was made in June 1992, and covers the interval June 15 to December 7, 1992. The ROSTL3 database, provided by the ROSAT U.K. Data Center, contains details of all scheduled pointed observations on a one entry per slot basis, where a "slot" is an interval of constant celestial pointing with detectors on.

    WFCBSC - ROSAT Bright Source Catalog

    The WFCBSC database contains the ROSAT Wide Field Camera Bright Source Catalogue. It contains 384 bright EUV sources found during the ROSAT all-sky survey of July 1990 to January 1991. The information in this pre-publication database is based on what will be published by Pounds et al. in MNRAS.

    The HEASARC continues to collect catalogs and data from various sources and ingest them into the database system in the HEASARC On-line Service. The current listing of available SYSTEM databases may be obtained on-line by typing Browse at the HEASARC> prompt and then entering either a ? or just a carriage return at the Database: prompt.

    File transfer options

    Files that are created during an XOBSERVER session are stored in the user's directory, including any extracted data products, and log and history files created by the XOBSERVER programs. (A complete record of all output from a user's BROWSE session and XOBSERVER session is written to log files called BROWSE.LOG and XOBSERVER.LOG.) These files can be transferred from the user's directory to his or her home computer. The transfer can be made either from the XRAY account using the mail or send commands, or from the user's computer using the VMS copy command. The file transfer method used depends on whether the file is ASCII or binary, and whether it is a VMS-to-VMS or VMS-to-UNIX transfer.

    Help documentation, which describes what each file transfer command is suitable for, is contained in the XOBSERVER User's Guide. Type help at the HEASARC> prompt to access the guide.

    Spectral, timing and image analysis

    Users can access various analysis programs from within the XOBSERVER environment. The spectral, timing and image analysis packages are all part of the XANADU analysis package and are called XSPEC, XRONOS and XIMAGE, respectively.

    All three of these analysis programs can be run within BROWSE or as a stand-alone procedure. More details about how to run these programs are available in the first issue of Legacy. Full documentation is available upon request from


    On-line help documentation on XSPEC can be accessed from a number of places. Users can type help when inside XSPEC for descriptions of commands. Also, both the BROWSE and the XOBSERVER on-line documentation contain information about XSPEC and examples of how to use it; the former can be accessed by typing help within BROWSE, and the latter by typing help at the HEASARC> prompt.

    For users who wish to copy spectral files back to their home computers to analyze them, XSPEC and its associated programs are available for local installation. Both the VAX/VMS and Sun-UNIX versions can be obtained by sending e-mail to, or Karen Smale at


    Each of the XRONOS tasks is explained in the on-line help documentation within the program itself; the documentation is accessed by typing help at the XRONOS> prompt, or replying help to any question asked by a XRONOS application. Information about XRONOS can be found in the on-line help for BROWSE and XOBSERVER as well.

    At present, XRONOS is available for remote installation on VAX/VMS machines, and will soon be available in Sun-UNIX and HP-UX versions as well. Information can be obtained from Lorella Angelini at


    Detailed help documentation for XIMAGE can be accessed from within the program by typing help. Information on XIMAGE and associated image analysis routines is also contained in the XOBSERVER help and in the BROWSE help.

    XIMAGE can be installed locally on the user's computer. Currently, only a VAX-VMS version is available; Sun-UNIX and HP-UX versions are under development. Contact Lorella Angelini at for more information.


    The plotting and function-fitting package that is used within the XOBSERVER environment is called QDP. The QDP package is used by the BROWSE, XSPEC and XRONOS programs to plot light curves and spectra. From each of these programs, a QDP file can be generated, and later input to QDP for plotting and fitting. Users can also generate QDP files in the XRAY account, and then transfer them to their home computer, where they can replot and manipulate them locally.

    Users who wish to install a copy of QDP on their home computers can contact the HEASARC (write to QDP is available in VMS, UNIX and MS-DOS versions. A full help facility is available within QDP. There is also information about QDP in the on-line documentation for XOBSERVER and BROWSE.

    Obtaining user's guides and information

    In addition to the extensive on-line help in the XRAY account, a variety of documentation is available from the HEASARC. Table 2 contains a list of the currently available documents. Please see the BROWSE database called DOCUMENTS for a more up-to-date list. Requests for documentation should be sent to NDADSA::REQUEST, or

    In addition to the above documents, the CD-ROM "The Einstein Observatory SSS, MPC, and FPCS Data Products" is available from the HEASARC by contacting

    User questions or problems with any of the XOBSERVER software or the database system should also be reported to Comments are welcome, and user suggestions will be implemented when possible.

    Table 2


    Available HEASARC Databases CAT 91 Jun BROWSE User's Guide UG 91 Feb Definition Panel Report RPT 89 Jul File Struct & Format of Processed Einstein UG 88 Dec Guidelines for PDMP's RPT 91 Feb HEAO 1 A-2 Analysis UG 87 Jul HEAO A-2 Catalog of Pre-HEAO X-ray sources CAT HEASARC Implementation Plan RPT 90 Jan HEASARC Online Service/XOBSERVER Ref Guide BRO 91 Dec HUG Recommendations RPT 91 Jun Interoperability Gateway Guide UG 90 Mar Legacy - The HEASARC Journal (Number 1) JOU 92 May Legacy - The HEASARC Journal (Number 2) JOU 92 Nov List of Approved ROSAT Observations (AO-1) CAT 90 Jan List of ROSAT Observations (thru April 92) CAT 91 Nov MIPS Flyer BRO 91 Jan MIPS User's Guide UG 90 Dec PGPLOT Graphics Subroutine Library UG 86 Jan PROS Description (NRA 91-OSSA-3 Append. H) RPT 90 Dec PROS: Data Analysis for ROSAT PPR 91 May QDP/PLT User's Guide UG 91 Jun ROSAT Data Products Guide 2.0 UG 91 Jul ROSAT Mission Description (91-OSSA-3App.F) RPT 91 Jan ROSAT Mission Description Addendum RPT 91 Nov ROSAT Newsletter (Number 1) NL 89 Feb ROSAT Newsletter (Number 2) NL 89 Sep ROSAT Newsletter (Special Edition) NL 90 Jan ROSAT Newsletter (Number 4) NL 90 Jul ROSAT Newsletter (Number 5) NL 91 Jun ROSAT Newsletter (Number 6) NL 91 Nov ROSAT Newsletter (Number 7) NL 92 Sep ROSAT brochure BRO 90 Oct ROSAT-PROS User's Guide UG 91 Aug User Manual for SAOimage UG 91 Jan User's Guide to HEAO A-2 Data Analysis Sys UG 88 Jun XIMAGE - X-ray Astron Image Analysis Facil UG XOBSERVER Available Databases UG 91 Dec XOBSERVER Online User's Guide UG 91 Dec XRONOS - Timing Analysis Software Package 2.0 UG 91 Oct XSPEC - X-ray Spectral Fitting Package 7.0 UG 90 Nov XSPEC User's Guide UG 91 Feb

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