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WDS - Washington Double Star Catalog

HEASARC
Archive

Overview

The Washington Double Star Catalog (WDS), maintained by the United States Naval Observatory (USNO), is the world's principal database of astrometric double and multiple star information. The WDS Catalog contains positions, discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions and when available, Durchmusterung numbers and notes for the components of close to 100,000 systems based on ~600,000 means. The current version at the HEASARC is updated weekly and is derived from the version available online at the USNO (see http://ad.usno.navy.mil/proj/WDS/), the latter being updated nightly.

The Washington Visual Double Star Catalog (WDS) is the successor to the Index Catalogue of Visual Double Stars, 1961.0 (IDS; Jeffers & van den Bos, 1963). Three earlier double star catalogs in the 20th century, those by Burnham (BDS; 1906), Innes (SDS; 1927), and Aitken (ADS; 1932), each covered only a portion of the sky. Both the IDS and the WDS cover the entire sky, and the WDS is intended to contain all known visual double stars for which at least one differential measure has been published. The WDS is continually updated as published data become available. Prior to this, two major updates have been published (Worley & Douglass 1984, 1997). The Washington Double Star Catalog (WDS) has seen numerous changes since the last major release of the catalog. The application of many techniques and considerable industry over the past few years has yielded unprecedented gains in both the number of systems and the number of measures.


Catalog Bibcode

2001AJ....122.3466M

Bulletin

The WDS database table was last updated on 8 December 2014.

References

The Washington Double Star Catalog
    Mason, B.D., Wycoff, G.L. and Hartkopf, W.I
    http://ad.usno.navy.mil/proj/WDS/

2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star
Catalog
    Mason, B.D., Wycoff, G.L., Hartkopf, W.I., Douglass, G.G. and Worley, C.E.
    <Astronomical Journal, Volume 122, Issue 6, pp. 3466-3471.>
    =2001AJ....122.3466M.

The Washington Visual Double Star Catalog, 1996.0
    Worley C.E., Douglass G.G.
   <US Naval Observatory (1996); Astron. Astrophys. Suppl. Ser. 125, 523 (1997)>
   =1997A&AS..125..523W = CDS/ADC Catalogue I/237.

Provenance

This version of the WDS catalog was first created at the HEASARC in March 2002 based on the USNO online version (http://ad.usno.navy.mil/proj/WDS/), and is updated by the HEASARC on a weekly basis. The table schema was last revised in February 2005.

HEASARC Changes

To conform with the HEASARC database standards and to (hopefully) clarify some parameters, this version contains a few changes compared to the USNO version of the WDS catalog: (i) in the USNO version of the WDS, the parameter Notes contained both lower- and uppercase characters, whereas in the HEASARC version all characters in the parameter Notes have been uppercased: to avoid ambiguities in these two cases (characters p and P) where both upper- and lowercase values were used in the USNO version, all occurrences of lowercase 'p' in the Notes parameter have been replaced with 'A' in the HEASARC version; (ii) a Name parameter has been added to the HEASARC version of the WDS which is constructed from the 10-digit WDS identifier (based on the J2000 coordinates) and the Component_ID parameter, using the procedure recommended by the Dictionary of Nomenclature of Celestial Objects; thus, an entry with the WDS identifier of '00033+8239' and a Component_ID of 'AB' has been given the name of 'WDS J00033+8239 AB', and (iii) for many of the entries, accurate positions (0.1 seconds of time in RA, 1 arcsecond in declination) are now provided: the HEASARC has added a parameter called precision_flag that has been given a value of 'H' in such cases; the remaining stars, for which the positions in the WDS were only given to the nearest 0.1 minutes in RA, and 1 arcminutes in declination, have been given precision_flag values of 'L'.

Acknowledgement of Usage

If the WDS catalog was helpful for your research work, the following acknowledgement would be appreciated:

"This research has made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory."


Parameters

Name
The source designation as constructed by the HEASARC from the 10-digit WDS identifier (based on the J2000 coordinates) and the Component_ID field, using the procedure recommended by the Dictionary of Nomenclature of Celestial Objects. Thus, an entry with the WDS identifier of '00033+8239' and a Component_ID of 'AB' has been given the name of 'WDS J00033+8239 AB'. Note: There are a small number of double stars which have multiple corresponding entries in the original USNO WDS Catalog, and so these names will be non-unique.

WDS
This is the WDS identifier constructed from the J2000 coordinates by the WDS creators at the USNO. Thus, a binary with a WDS identifier of '00033+8239' has (approximate) J2000 coordinates of RA = 00 hrs 03.3 mins, Declination = +82 deg 39 mins.

RA
The right ascension in the specified equinox; J2000 positions were given in the original USNO version of this catalog. The positions that are given represent the WDS authors' best estimates of these values. Where possible, these are based on the ACRS and PPM data, with proper motion incorporated (indicated by 'C' in the Notes parameter for such an entry). Notice that, for many of the entries, accurate positions (0.1 seconds of time in RA, 1 arcsecond in declination) are now provided: the HEASARC has added a parameter called precision_flag that has been given a value of 'H' in such cases. The remaining stars, for which the positions in the WDS were only given to the nearest 0.1 minutes in RA, and 1 arcminutes in declination, have been given precision_flag values of 'L'.

Also notice that the precise coordinates will be for the primary of the subsystem. For example, in the case of a system made up of A-BC and BC pairs, they will both have the same ten-digit WDS identifier, however, the precise coordinates of the respective entries would be of the A and B components, respectively.

Dec
The declination in the default equinox; J2000 positions were given in the original USNO version of this catalog. The positions that are given represent the WDS authors' best estimates of these values. Where possible, these are based on the ACRS and PPM data, with proper motion incorporated (indicated by 'C' in the Notes parameter for such an entry). Notice that, for many of the entries, accurate positions (0.1 seconds of time in RA, 1 arcsecond in declination) are now provided: the HEASARC has added a parameter called precision_flag that has been given a value of 'H' in such cases. The remaining stars, for which the positions in the WDS were only given to the nearest 0.1 minutes in RA, and 1 arcminutes in declination, have been given precision_flag values of 'L'.

Also notice that the precise coordinates will be for the primary of the subsystem. For example, in the case of a system made up of A-BC and BC pairs, they will both have the same ten-digit WDS identifier, however, the precise coordinates of the respective entries would be of the A and B components, respectively.

LII
The galactic longitude of the system.

BII
The galactic latitude of the system.

Discoverer
The discoverer, identified by a one-to-three letter code, and the discoverer's number, if assigned. The reference list (available at the USNO website as http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewref.txt) should be consulted to identify the names of the individuals corresponding to these codes.

Component_ID
The component designations, when the object has more than two components. The Lick IDS scheme has been discontinued, and components are referred to in the WDS by the traditionally employed lowercase letters. The rather awkward uppercase designations, e.g. ABXC, have been changed to the form AB-C, etc. There has been some confusion on the part of observers and students alike, as to how to designate components in multiple systems. Traditionally, these have been designated in order of separation, thus AB, AC,...., or in the cases where close pairs are observed blended, AB-C, AB-D,.... In some instances, differing resolution limits produce situations where observations are intermixed, thus AC, AB-C, and so forth. There are also many instances where later observations have revealed a closer companion; these are designated Aa, Bb, etc. In a few cases wider, later discoveries have also been so denoted.

First_Date
The date of the first observations of an object (of satisfactory accuracy), up to the current closing date, in Julian years.

Last_Date
The date of the last observation of an object (of satisfactory accuracy), up to the current closing date, in Julian years.

Number_Obs
The number of measures of the object. When there are more than 99, the number 99 is used. For smaller numbers of observations, the value in these columns is intended to accurately reflect the actual number.

PA_Date1
The position angle (PA) in degrees for the date listed in the parameter first_date. Position angles are unprecessed in this catalog (i.e., they are for the mean date of the observation).

PA_Date2
The position angle (PA) in degrees for the date listed in the parameter last_date. Position angles are unprecessed in this catalog (i.e., they are for the mean date of the observation).

Separation_Date1
The angular distances, in seconds of arc, between the specified components, for the date listed in the parameter first_date. Those entries in the USNO version of the WDS for which the separation(s) were given in arcminutes (entries having the character '6' in the parameter Notes) have had their values multiplied by 60 to convert them into arcseconds. In those cases where there has been no appreciable motion observed over the duration of observations, only one position angle and separation is listed (in the parameters pa_date1 and separation_date1).

Separation_Date2
The angular distances, in seconds of arc, between the specified components, for the date listed in the parameter last_date. Those entries in the USNO version of the WDS for which the separation(s) were given in arcminutes (entries having the character '6' in the parameter Notes) have had their values multiplied by 60 to convert them into arcseconds. In those cases where there has been no appreciable motion observed over the duration of observations, only one position angle and separation is listed (in the parameters pa_date1 and separation_date1)

Comp1_Mag
The V magnitude of the primary component. The magnitudes were obtained from many sources, the most important of which were the Bright Star Catalogue, the Michigan Spectral Survey, and the SIMBAD data base. In the latter case, all of the Durchmusterung stars have been individually compared with SIMBAD data. The most commonly found datum was the combined V magnitude. In such instances the observational data base was examined in order to define a more reliable "mean" magnitude difference. This was then used, together with the total magnitude, to determine the individual values. The WDS authors state that the magnitudes presented in this version of WDS are the most inhomogeneous parameters, and urge users who are interested in statistical studies to allow for this fact.

Comp2_Mag
The V magnitude of the secondary component. The magnitudes were obtained from many sources, the most important of which were the Bright Star Catalogue, the Michigan Spectral Survey, and the SIMBAD data base. In the latter case, all of the Durchmusterung stars have been individually compared with SIMBAD data. The most commonly found datum was the combined V magnitude. In such instances the observational data base was examined in order to define a more reliable "mean" magnitude difference. This was then used, together with the total magnitude, to determine the individual values. The WDS authors state that the magnitudes presented in this version of WDS are the most inhomogeneous parameters, and urge users who are interested in statistical studies to allow for this fact.

Spect_Type
The spectral type of the primary component, and/or of both components, space permitting. MK spectral types have been obtained from many sources, most important of which have been the Bright Star Catalogue, the Michigan Spectral Survey, and the SIMBAD data base. In the latter case, all of the Durchmusterung stars have been individually compared with SIMBAD data.

Primary_PM_RA
The component of the proper motion of the primary in seconds of arc per 1000 years (or milliarcseconds per year), in right ascension reduced to great circle, except if the parameter Notes contains a 'P', in which case the unit is seconds of arc per 100 years. Specifically, this catalog lists for pm_ra the quantity 15*mu(alpha)*cos(delta), where mu(alpha) is the proper motion in seconds of time, and delta is the declination. A positive (negative) value for primary_pm_ra indicates an eastward (westward) motion in Right Ascension.

Primary_PM_Dec
The component of the proper motion of the primary in seconds of arc per 1000 years (or milliarcseconds per year), in declination, except if the parameter Notes contains a 'P', in which case the unit is seconds of arc per 100 years. Specifically, this catalog lists for pm_dec the quantity mu(delta), where mu(delta) is the proper motion in arcseconds. A positive (negative) value for primary_pm_dec indicates a northward (southward) motion in declination.

Secondary_PM_RA
The component of the proper motion of the secondary in seconds of arc per 1000 years (or milliarcseconds per year), in right ascension reduced to great circle, except if the Notes parameter contains a 'P', in which case the unit is seconds of arc per 100 years. Specifically, this catalog lists for pm_ra the quantity 15*mu(alpha)*cos(delta), where mu(alpha) is the proper motion in seconds of time, and delta is the declination. A positive (negative) value for secondary_pm_ra indicates an eastward (westward) motion in Right Ascension.

Secondary_PM_Dec
The component of the proper motion of the secondary in seconds of arc per 1000 years (or milliarcseconds per year), in declination, except if the Notes parameter contains a 'P', in which case the unit is seconds of arc per 100 years. Specifically, this catalog lists for pm_dec the quantity mu(delta), where mu(delta) is the proper motion in arcseconds. A positive (negative) value for secondary_pm_dec indicates a northward (southward) motion in declination.

DM
The Durchmusterung number of the object in the system used by the Henry Draper Catalogue: Bonn (BD) from +89 degrees to -22 degrees inclusive, Cordoba (CoD) from -23 degrees to -51 degrees inclusive, and Cape Photographic (CPD) from -52 degrees to -89 degrees inclusive. When a star is not contained in the Durchmusterung proper to its declination zone, but is contained in another Durchmusterung, this is so indicated in the Notes file (http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewnotes_main.txt) at the USNO WDS website. Other components having different Durchmusterung numbers are also indicated in this same file.

Notes
The codes listed below are contained in this parameter. The following files are available at the USNO WDS website: the Notes file is at http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewnotes_main.txt the Delta-m Catalog is at http://ad.usno.navy.mil/wds/dm/deltam2.html the Synonyms list is at http://ad.usno.navy.mil/proj/WDS/misc/wds_synonyms.txt

         N: Notes found in the Notes file at
            http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewnotes_main.txt
         B: Summary line gives blue (Johnson U or B, blue
            photographic, etc.) magnitudes.
         C: Orbit and Linear solution. A published orbit exists
            and this system has a Linear Solution as well. A "C"
            code, then, indicates both an "O" and an "L" code.
         D: Has measure in Delta-M catalog.
         I: Identification uncertain. Match of object at precise
            position with WDS pair may or may not be correct.
            Currently under examination.
         K: Summary line gives K-band or other infrared (>1
            micron) magnitudes
         L: Linear solution. Linear elements for this pair have
            been determined. Linear Elements Catalog is
            currently under devlopement.
         M: Magnitude modified. Magnitudes have been corrected
            to the Tycho-V scale based on other systems measured
            by the discoverer and Tycho.
         O: Orbit, briefly described in the notes file and has
            entry in Orbit Catalog
         P: 100-year proper motion in right ascension and declination
         R: Summary line gives red (Johnson R or I, red
            photographic, etc.) magnitudes
         X: A "dubious double" (or "bogus binary"). This pair may
            represent a positional typo in the original publication
            (so we're looking in the wrong location), an optical
            double disappearing due to radically different proper
            motions, a plate flaw, or simply a pair not at a
            magnitude, separation, etc., sufficiently similar to
            those noted when the first measure was added (making
            it too faint, too close, etc.). Please contact the authors
            of the catalog if you know about any circumstances where you
            have found or have ascertained the mystery behind these pairs.
         A: Coordinates and proper motions from ACRS, PPM, IRS,
            FK5 catalogs.
  

Precision_Flag
For many of the entries, accurate positions (0.1 seconds of time in RA and 1 arcsecond in declination) are now provided. This parameter has been created by the HEASARC to indicate the accuracy of the positional data: it has been given a value of 'H' for those stars which have positions of the above-quoted accuracy; the remaining stars, for which the positions in the WDS were only given to the nearest 0.1 minutes in RA and 1 arcminutes in declination, have been given values of 'L'.

Class
Browse object classification, derived from the spectral type parameter (spect_type). In cases where spectral types of two components are given, the class is based on the first (primary) spectral type.


Contact Person

Questions regarding the WDS database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 28-Aug-2012