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WDS1996: Help

WDS1996 - Washington Double Star Catalog

WDS1996 - Washington Double Star Catalog


Overview

The Washington Visual Double Star Catalog, 1996.0 (WDS), CDS/ADC Catalog I/237, is the successor to the catalog of the same name dated 1984 (CDS/ADC Catalog I/107). The WDS is intended to contain all known visual double stars for which at least one differential measure has been published through the end of 1995. It includes a discoverer code, the date of the first and last observations, the number of observations, the position angle and separation for the first and last observation, the magnitudes and spectral types of the components (when available) the proper motion of the system, Durchmusterung numbers of the components and notes for further information.

Note that the WDS is not inclusive of all pairs which have been more casually noted, although it does, in fact, include some of them. The data base upon which the present WDS rests consists of the approximately 180000 measures transferred from the Lick Observatory in 1965, which, with few exceptions, covered the interval 1927-1963, augmented by all subsequent measures (about 118000), and some 154000 pre-1927 means. These latter are the result of a continuing project to build a truly comprehensive and complete data base. Thus, approximately 452000 individual means, representing over a million individual observations, form the basic material from which the WDS is constructed. A small amount of data has not been included because of unresolved questions concerning it. The WDS contains 78100 double stars, counting (as did the Index Catalogue of Visual Double Stars or IDS, the predecessor of the WDS) multiple components in the same system as separate pairs. Comparison of the present catalog with the IDS (Jeffers et al. 1963, Publ. Lick. Obs. 21) will reveal that a considerable number (about 1000) of previously catalogued objects have been removed from the WDS in the process of editing the data. The most common reason for removal is that the object is not certainly double.

The WDS is not intended to be an "astrometric" catalog in the sense usually employed, but rather is to be considered a finding list for observers, as well as serving as a notification of which objects are known doubles or multiples, along with providing some basic astrometric and astrophysical parameters. In addition, the WDS offers information on the amount of motion and the frequency with which a given object has been observed, which is sufficient, in fact, to provide a basis for the construction of observational programs. Finally, the data can be used (with proper precautions) to analyze certain statistical properties of visual double stars.


HEASARC Changes

To conform with the HEASARC database standards and to (hopefully) clarify some parameters, this version contains a few changes compared to the CDS/ADC version of the WDS: (i) separations (the parameters Separation_Date1 and Separation_Date2) are always given in arcseconds; thus, those entries in the CDS/ADC 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; (ii) in the CDS/ADC version of the WDS the parameter Notes contained both lower and upper case characters, whereas in the HEASARC version all characters in the parameter Notes have been upper cased: to avoid ambiguities in those two cases (characters r and R, and p and P) were both upper and lower case values were used in the CDS/ADC version, occurrences of lower-case 'r' has been replaced by 'X' in the HEASARC version, and lower-case 'p' by 'C' in the HEASARC version; (iii) in the CDS/ADC version of the WDS the dates were given as (Year-1000) and thus an observation in 1932 had the value of 932; in the HEASARC version we give the date in its normal form, e.g., 1932; and (iv) we have added a Name parameter to the HEASARC version of WDS which is constructed from the J2000 coordinates (using the procedure recommended by the Dictionary of Nomenclature of Celestial Objects) and the Component_ID field. Thus, an entry with J2000 coordinates of RA = 00 hrs 03.3 mins, Declination = +82 deg 39 mins and a Component_ID of AB has been given the name of WDS J0003.3+8239 AB.

Provenence

This version of the WDS1996 catalog was created at the HEASARC in July 1998 based on the CDS/ADC Catalogue I/237. The HEASARC revised its version in February 2001.

Parameters

Name
The source designation as constructed by the HEASARC from the J2000 coordinates (using the procedure recommended by the Dictionary of Nomenclature of Celestial Objects) and the Component_ID field. Thus, an entry with J2000 coordinates of RA = 00 hrs 03.3 mins, Declination = +82 deg 39 mins and a Component_ID of AB has been given the name of WDS J0003.3+8239 AB. Note: There are a small number of double stars which have multiple corresponding entries in this database table, so a few names will appear multiple times.

WDS
This field is constructed from the J2000 coordinates using the procedure recommended by the Dictionary of Nomenclature of Celestial Objects. Thus, an entry with J2000 coordinates of RA = 00 hrs 03.3 mins, Declination = +82 deg 39 mins has been given the value J0003.3+8239.

RA
The right ascension in the default equinox. The positions 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 the positions in the WDS were only given to the nearest 0.1 minutes in RA, and 1 arcminutes in Declination.

Dec
The declination in the default equinox. The positions 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 the positions in the WDS were only given to the nearest 0.1 minutes in RA, and 1 arcminutes in Declination.

LII
The galactic longitude of the object.

BII
The galactic latitude of the object.

Discoverer
The discoverer, identified by a one-to-three letter code, and the discoverer's number, if assigned. The reference list (available as the file "wdsref.dat" from the HEASARC's anonymous FTP area in the directory ftp://legacy.gsfc.nasa.gov/heasarc/dbase/misc_files/wds) should be consulted first to identify individuals. However, some discoverer designations do not appear in this list, for various reasons, and a supplementary list is provided (available as the file "wdsrefa.dat" in the HEASARC's anonymous FTP area in the directory ftp://legacy.gsfc.nasa.gov/heasarc/dbase/misc_files/wds/).

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 lower-case letters. The rather awkward upper-case 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 closing date of 1996.0, in Julian years.

Last_Date
The date of the last observation of an object (of satisfactory accuracy), up to the closing date of 1996.0, 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, except for some pairs for which the discoverers only gave crude estimates, such as NF or SP, where these estimates are listed. Position angles are unprecessed in this catalog (i.e. they are for the mean date of observation).

PA_Date2
The position angle (PA) in degrees for the date listed in the parameter last_date, except for some pairs for which the discoverers only gave crude estimates, such as NF or SP, where these estimates are listed. Position angles are unprecessed in this catalog (i.e. they are for the mean date of 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 CDS/ADC 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 CDS/ADC 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. 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.

PM_RA
The component of the proper motion 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' or an 'R', 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 pm_ra indicates an eastward (westward) motion in Right Ascension.

PM_Dec
The component of the proper motion in seconds of arc per 1000 years (or milliarcseconds per year), in declination, except if the parameter Notes contains a 'Q' or an 'R', 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 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 the file "notes.dat" (available in the HEASARC's anonymous FTP area in the directory ftp://legacy.gsfc.nasa.gov/heasarc/dbase/misc_files/wds). Other components having different Durchmusterung numbers are also indicated in this same ancillary file "notes.dat".

Notes
The following codes are contained in these columns:

         N: Notes found in the Notes table: see the file "notes.dat" (available
            in the HEASARC's anonymous FTP area in the directory
            ftp://legacy.gsfc.nasa.gov/heasarc/dbase/misc_files/wds).
         O: Orbit. Where motion has exceeded 360 degrees, no
            values are listed in the position angle and separation
            columns. Orbits may be found in the "Fourth
            Catalog of Orbits of Visual Binary Stars" (Worley
            and Heintz, 1983), and in the Information Circulars
            published by Commission 26 of the IAU, as well as
            in the literature.
         P: 100 year proper motion in right ascension is given in pm_ra.
         Q: 100 year proper motion in declination in pm_dec.
         R: 100 year proper motion in right ascension (pm_ra) and
            declination (pm_dec)
         A: Pair appears in an appendix list, not part of the
            discoverer's regular numbering system.
         X: Pair was listed, but in a "rejected" list, not part
            of the discoverer's regular numbering sequence.
         S: Pair has other discoverer's designations and numbers
            in the literature due to duplicate discovery.
            Credit is given to the earliest discovery
            observation (and correct identification) reported
            in the literature. The List of Synonyms "notesyns.dat" and
            the List of Additional Discoverers "wdsrefa.dat" are available
            at ftp://legacy.gsfc.nasa.gov/heasarc/dbase/misc_files/wds.
         C: Coordinates and proper motions from the ACRS, PPM,
            IRS, and FK5 catalogs.
         6: Separation given in minutes of arc rather than arcseconds in
            the original CDS/ADC version of this catalog.
  

Class
Browse classification, derived from the spectral type parameter (spect_type).


References

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.

Contact Person

Questions regarding the WDS1996 database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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