HEASARC Conventions for Virtual Parameters
Virtual parameters are stored in the ZZEXT metabase
table. The existence and values of these virtual parameters control how
tables are treated by the HEASARC Browse system.
The following virtual parameters are utilized and their usage is highly
recommended:
- default_search_radius
- Specfies the default for the Browse cone search radius for this
table. The value should be in arcminutes. If the table
does not have right ascension and declination columns, then this
virtual parameter should not be specified. Note that the
default search radius value may be specified as a column name
(e.g., the positional error), prefixed by "@", so that it could
vary from row to row. The existence of this entry is used by Browse
to indicate that this table can be searched by position in a
cone.
- equinox
- Specifies the epoch of the equinox of the right ascension and
declination values present in the table. This should normally be a
numeric value. In principle Browse can query tables in any equinox;
however, in order to support cross-correlations, tables should
provide default right ascension and declination columns in J2000
(FK5) coordinates. It is recommended that new tables that are to be
ingested which do not have J2000 positions have new columns added
to the table with positions in the J2000 standard coordinate frame
rather than converting the input columns. As a result, this virtual
parameter value is almost always "2000". If the table does not have
right ascension and declination columns, then this virtual parameter
should not be specified.
- right_ascension
- Specifies the name of the field in the table which contains the
right ascension values. Traditionally, this is almost always "ra".
If the table does not have a right ascension column, then this
virtual parameter should not be specified.
- declination
- Specifies the name of the field in the table which contains the
declination values. Traditionally, this is almost always "dec".
If the table does not have a declination column, then this virtual
parameter should not be specified.
- target_name
- Specifies the name of the field in the table which contains the
names of the astronomical objects or targets. This is usually
"name". If the table does not have a name column, then this virtual
parameter should not be specified.
- start_time
- Specifies the name of the field in the table which contains the
(starting) date/time of the observation or event in MJD format. If
the table does not contain temporal data, then this virtual
parameter should not be specified.
- end_time
- Specifies the name of the field in the table which contains the
date/time that the observation ended in MJD format. If the table
does not contain temporal data or if the table only contains one
time field, then this virtual parameter should not be specified.
- frequency_regime
- Specifies the frequency regime that the data in the table belongs
to. Tables may have multiple frequency_regime virtual parameters
and values if the data contained therein is multiwavelength.
Possible values:
- EUV
- Gamma-ray
- Infrared
- Optical
- Radio
- Ultraviolet
- X-ray
- Physics
"Physics" is obviously not a frequency regime, but the HEASARC has
traditionally specified this value when dealing with tables containing
physics-related data.
- observatory_name
- Specifies the name of the observatory or mission from which the
data table originated. The HEASARC convention is to use all
uppercase for these names. If the table contains
non-mission-specific or non-observatory-specific data, a generic
classification may be used. For example,
- GALAXY CATALOG
- GAMMA-RAY BURSTS
- GENERAL CATALOG
- MASTER CATALOG
- NEBULA CATALOG
- PHYSICS DATA
- RADIO CATALOG
- STAR CATALOG
- table_priority
- Specifies the order of tables within a mission/observatory grouping
in Browse table listings. Values should be
real numbers, with lower numbers meaning they are listed before
higher numbers.
- table_author
- Specifies the author(s) of the table. Use "HEASARC" for internal
tables. Use institution names such as SAO or STScI for
external project tables. Use a comma-separated list of authors'
surnames for external, non-project-related tables. For more than 4
authors or so, use "Smith et al." where "Smith" is the primary
author. Use semicolons to separate lists of authors, if the
table is a compilation of multiple sources with different sets of
authors.
- table_type
- Specifies the type of table. In Browse users can select the table
types of interest. Possible values:
- Object
- "Object" catalogs typically have one entry per astronomical
object.
- Observation
- "Observation" catalogs typically have multiple entries
per object.
- Proposal
- "Proposal" tables contain mission-specific data about the
proposals submitted by guest observers.
- Physics
- "Physics" tables contain physics data.
- System
- "System" tables comprise the metabase portion of the
Next-Generation HEASARC DBMS and their names typically
start with "zz".
- row_type
- Specifies the content of each row in the table. There is currently
no set list of possible values, but an effort should be made to
utilize existing types as much as possible. Note that multiple
row_type virtual parameter names/values may be specified, if
appropriate. Typical values:
- AGN
- Atomic Datum
- CV
- Cluster of Galaxies
- Compilation Source
- Extragalactic Source
- Extragalactic Supernova
- Extragalactic Variable Star
- GRB
- Galaxy
- Galaxy Group
- Image
- Lightcurve
- Nebula
- Nova
- Observation
- Observation Information
- Optical Counterpart
- Proposal
- Proposed Target
- Publication
- Pulsar
- Radio Counterpart
- Redshift
- SNR
- Solar Flare
- Spectrum
- Star
- Star Cluster
- Supernova
- Survey Source
- Transient
- Variable Star
- White Dwarf
- XRB
- unique_key
- Specifies the field (or fields, if multiple fields are needed, in
which case a comma-delimited list is used) which comprises the
unique (primary) key of the table. Browse
no longer utilizes this virtual parameter, so it is no longer
necessary; however, it may still be useful in understanding what
each row in the database table logically comprises. Tables now have
a special, hidden field, '_unique_id' added to them when they are
ingested which is used to provide a unique identifier.
- w3browse_display
- If the value is "N", then Browse will not
display the table in its table listings, effectively hiding the
table from users. No other value is currently recognized. Note that
queries may still be made against this table if the user
formats the URL manually or uses the batch interface.
- catalog_bibcode
- Specifies the ADS bibcode or the CDS table specifier for this
table. In the case off the latter, angle brackets ("<", ">")
are used to differentiate the CDS table specifiers from ADS
bibcodes.
All virtual parameter names are automatically converted to lowercase by
the HDBingest software, effectively making all virtual parameter names
case-insensitive; however, virtual parameter values are case-sensitive.
Documentation prepared by the
HEASARC Database Group
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Last modified: Tuesday, 18-Oct-2005 15:23:15 EDT
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