If we are free to wish, we ought to have two large reflectors, one in the North and one in the South, devoted to discovery and measures of double stars.
If we look back for a century or more and ask: What do we today appreciate mostly of the observations made then? the general answer will be: observations bound to time. They can, if missed, never be recovered. Of these observations measures of double stars contribute a major part.
As far as we can judge today this will also be the case in the future.
The search for new double stars should be made with the largest instruments available in order to discover close and faint companions.
The Washington Double Star Catalog (WDS), maintained by the United States Naval Observatory, is the world's principal database of astrometric double and multiple star information. The WDS Catalog contains positions (J2000), discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions and when available, Durchmusterung numbers and notes for the components of 100,626 systems based on 690,251 means. The current version, available online, is updated nightly. This catalog is one of four USNO double star catalogs to be included on a CD-ROM now in preparation. A brief summary and statistical analysis of the contents of the catalog are presented.
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 this 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, as indicated
below.
Figure 1: Growth in the number of means in the WDS since its inception in the
early 1960's. The 1984.0 and 1996.0 editions of the WDS are indicated and at the
cutoff date for the CD-ROM production.
The growth since the 1996.0 edition is due to many sources, however the most significant additions are:
While many thousand new systems have been added, many of these observing
programs have resulted in a striking improvement in the number of observations
per system, as shown below with a specific example of USNO speckle
contributions. It is expected that with other large publications of data planned
in the future [e.g., the
Two Micron All Sky Survey, as well as the
USNO CCD Astrograph Catalog the
growth of the WDS will continue.
Figure 2: The number of means per system in the WDS. The left figure is a
histogram from late 1997 (the WDS 1996.0 with Hipparcos added) while the right
figure illustrates the same information for the 2001.0 version of the WDS. Note
that while the total number of systems has increased by more than 6300, the
number of systems with only one mean has dropped by more than 1700.
Figure 3: One source responsible for the increase in data is the prodigious
publication of USNO speckle means. The left figure illustrates a histogram of
USNO speckle means (also late 1997) binned vs. separation. The right figure
indicates the same information for the 2001.0 version of the WDS.
A comparison of the contributions of the different techniques, both in their total number and mean separation are given here. Those techniques with no measures listed are unique to the Delta-m Catalog.
Primarily of historical interest, a list of the top 25 observers (based on the total number of measures and means) is presented here. In this table, numbers are based on the WDS reference code. Totals are provided for the number of means (usually, as published --- a line of data in the WDS measurement database, each mean position often comes from several measures, usually increasing their accuracy). To the extent that it is known, multiple authors participating in a distinct group or project are counted together.
One of the largest listings in both lists above is the Washington Fundamental Catalog (WFC; Wycoff & Mason 2001). These double star measures were extracted from the WFC, a collection of 144 astrographic and transit circle catalogs covering a timebase of over one hundred years and most recently used in the computation of proper motions for the Tycho-2 project. While not intended as a double star reference, the utility of transit circle and photographic measures were known early in the 20th century, and many of the doubles in the Astrographic Catalogue were previously gleaned by Barton (1926) and others. However, there remained a plethora of double star measures in these catalogs which have now been cross-referenced with the WDS to produce these totals.
The ADS cross-reference has now been
expanded and includes the identifier from the earlier Burnham Double Star (BDS;
Burnham 1906) Catalogue as well as the later Aitken Double Star (ADS; Aitken
1932) Catalogue. BDS stars falling outside a criteria, based on magnitude and
separation (and thus a likelyhood of physicality) were dropped from the ADS.
Most of these stars were added back in the Index Catalogue of Visual Double Stars
(IDS; Jeffers, van den Bos and Greeby 1963). Some of these stars were true binaries,
and should be added back, others were added due to concerns due to common proper
motion determinations or proximity. In the three cross-reference files below there
are sorts based on BDS number (listing all BDS entries, even those not real though
these have explanations for their removal), ADS number (again, bogus binaries carry
a reason for their removal), and WDS coordinate. As before, all components associated
with the BDS or ADS system are included even if they were not known at the time of the
publication of those catalogs. As mentioned above, duplicate and bogus systems
included in the BDS or ADS have been excised for one of the following reasons:
Some detections are not included in the WDS. These include measures by long
baseline interferometry where only visibilities and baselines are published
(as opposed to a true separation and position angle) are not included. Also,
various 1-d detection data (e.g., lunar occultation and some infrared
speckle interferometry) are not included, as the measured separation is only a
projection of the true separation. These data are available in the
4th Catalog of Interferometric Measurements of Binary
Stars (Hartkopf, Mason, Wycoff, & McAlister 2001; hereafter Speckle
Catalog). The absence of separation and position angle information for the
long-baseline interferometry data is perhaps most tragic as these data cannot be
readily combined with other ``classical'' double star data for a true combined
solution.
For a variety of reasons, there exist a large subset of measures contained in
the WDS database which have not been published. To make these data available to
the astronomical community they are listed below. It is anticipated that this
section will expand substantially as the data contained in the WDS are collated.
In the last 40 years, a limited group of Spanish amateurs has been systematically measuring visual double stars. Actually, they are preparing to publish all the measurements made between 1970 and 2001 --- over 10,000. This massive work has been presented at October, 2000, in the annual meeting of the Astronomic Society of France's Double Stars Commission, celebrated in Castelldefels, near Barcelona, Spain. (Josefina Ling, Circular UAI Commission-26 was in the meeting).
The first measurement catalogue entirely produced in Spain by an amateur was the Jose Luis Comellas (Doctor of Contemporaneous History, Sevilla University) one, published in 1973 (Catalogo de Estrellas Dobles Visuales 1973.0). It contained measurements from 1,200 double stars, using a simple micrometer and a 75mm aperture Polarex-Unitron refractor. Twelve years after, the same author published a second catalogue (Catalogo de Estrellas Dobles Visuales 1980.0) that included 5,104 doubles within reach of his new 102mm aperture Polarex-Unitron refractor, with a Ron Darbinian Filar Micrometer, of which he had personally measured over 3,500. For the quality and quantity of his publications, that included his exceptional Guia del Firmamento (1982) where he gathers together all his experience of more than thirty years of visual observation, as well for his extraordinary human condition, he is one of the most loved and admired authors in Spain and South America.
Since 1985 new observers have assured the continuity of J.L. Comellas work. Since 1976, I regularly collaborated with him, and in the mid 80s I had a little observatory supplied with a 102mm Polarex Unitron refractor and a filar micrometre, that enabled me to start systematic revision and update programs of the 1980.0 catalogue. In 1991, in conjunction with other colleagues, we coordinated the measurements sent to us by isolated observers, and started to publish a circular (RHO: Circular de Estrellas Dobles Visuales) for internal use, in order to coordinate our work and to make known our results.
Our equipment enhanced its measurement power with the purchase of new precision micrometers, Double Image Lyot-Chamichel-like, and CCD devices. Between 1992 and 2003 more than 5,000 new observations and measurements has been collected, provided by Spain-wide amateurs, and this has allowed to arrange a new catalogue suited to the 21st Century observers needs.
Given the huge bulk of filed data, it was necessary to develop our own database managing, analysis and ephemeris calculation software (MAIA). This job has been carried on by my colleague Jaume Planas, in collaboration with Jordi Cairol and Albert Sanchez, both members of OAG.
The evolution and development of this process has been made known in the meetings of the Astronomic Society of France's Double Stars Commission in Lyon (1995), Nice (1996), Bordeaux (1997), Tolouse (1999). This has enabled the Spanish visual double stars observers to break a certain isolation they were suffering since some decades ago.
Actually, the database and the different aplications it contains are for internal use only, but we are preparing an interactive version for Internet. In this way, our "OAG General Catalogue of 10,000 visual double stars measurements 1970-2000 (J2000.0)" wll be easily available to any worldwide observer.
Garraf Astronomical Observatory (OAG), founded in 1991 from private and public investments, develops didactic and research programs. Our observatory (1992-1998) have a 3.5m diameter dome with a 300mm aperture Newton-Cassegrain (F/3,5 and F/13,5) reflector, and 150mm F/8 refractor. Is located 30km to the south of Barcelona, inside the Garraf Natural Park, 300m over the sea. Our observatory is fully equipped for a double stars programs, with CCD, Professional Double Image Lyot-Camichel Micrometer (made by MECAPRECIS-France) and various Micrometer Reticle Eyepiece (MEADE).
OAG wishes to contact and to establish research programs specialized in visual double stars with others observers and observation teams. It has accommodation facilities for up to 55 people.
(text by : Tofol Tobal, Garraf Astronomical Observatory, e-mail: rho@arrakis.es, http:// www.oagarraf.org)
A large number of systems in the WDS may be characterized as ``neglected.'' These include unconfirmed binaries as well as systems which have not been resolved for many years. The reasons for this neglect are varied: poor coordinates or large proper motion (so the systems are ``lost''), erroneous magnitude or delta-m estimates (so the systems are skipped over or misidentified), or true neglect (too many binaries and too few observers). While the veracity of some of these systems is certainly suspect, many (if not most) of these are bona fide double stars. Three sets of lists are provided in observing list format. The first set was compiled using the following selection parameters:
A total of 6442 objects meet these criteria.
The second set of lists were compiled under the same criteria as above, but for separations under 3 arcseconds. A total of of 6632 systems fit these criteria.
The third and final set of lists includes those neglected systems not covered by the previous lists. These include systems with large magnitude differences, or fainter primary or secondary magnitudes, as well as systems whose magnitudes or separations are either unknown or unpublished. A total of 45,768 systems fit these criteria.
Set three contains thirteen doubles since excised by the Tycho team. These have been marked on the observing lists.
These lists, especially the last, can be tailored to your specific observing needs. To have a custom-made observing list prepared with parameters different than those above, please fill out an observing list request form:
The current edition of the WDS contains the most recent, observational data available and includes systems newly discovered by the Hipparcos mission. While Hipparcos did not provide discovery designations, these are the primary system identifiers in visual double star astronomy. A cross reference file of these 3,406 systems first resolved by Hipparcos (HDS = Hipparcos Double Star) containing the abbreviated coordinate, as well as the HDS and HIP numbers is provided as are cross references of WDS entries which had Hipparcos problem solutions (i.e., the G, X, O, V double star solutions as well as those which were suspected non-single). Systems with only one measure in the WDS which are Hipparcos problem stars (thus, providing a quasi-confirmation) are indicated in the notes file.
The current version of the WDS also contains measures of 12,770 systems from the Tycho-2 Catalogue. These include 11,536 known systems as well as 1,220 newly determined (TDS = Tycho Double Star) systems from the Tycho-2 database. The previous total of 1,234 new systems, has been changed to 1,220 following retraction of some new double stars by the Tycho team. These numbers are presented as blank lines in the TDS cross reference file. Also, notes have been added for 1,130 systems of dubious veracity (N < 3) having a ``failed double'' or ``photocenter'' solution. Some of these are being reconsidered as further processing of the Tycho-2 data for double stars continues (Fabricius et al. 2001). A cross-reference of double stars measured by Tycho-2 is available here. A cross-reference of new TDS systems is available here.
In 2001 an effort led by Claus Fabricius was begun to extract from the Tycho pixel data as many double stars, both new and known, as possible. This effort has resulted in the Tycho Double Star Catalogue. A total of 25,232 additional double star measures (in addition to those enumerated above) were found. The numbering of new Tycho doubles (the TDS stars) includes the original set of 1,234 (subsequently reduced to 1,220) described above plus additional systems found in the Tycho Double Star Catalogue reduction. This second set of new doubles begins with TDS1235 (the retracted TDS numbers are not reused). A complication arose as a result of the magnitude of this work --- what to do when the number is 10,000 or more (i.e., after TDS9999, what next?). A makeshift strategy was employed by taking the next available designation, TDT (Tycho Doubles, too?), thus the next system after TDS9999 is TDT 1. The known and new doubles listings includes both analyses of the Tycho data. In addition, precise coordinates (better than arcsecond) are available for another subset of double stars seen as single by Tycho (due to the magnitude of the secondary and/or separation of the system). The improvements in the precision of the WDS is discussed below.
In addition, we now also provide custom-made observing lists. If the user
provides limitations as to RA, Dec, separation, magnitudes, number of
observations, and date of last observation, it is possible to prepare observing
lists. Both data requests and observing list requests are available online.
The Second Delta-m Catalog:
New to
the WDS is an additional indicator in columns 100-102. This ``D'' note code
indicates the system has additional Delta-m information tabulated in the Delta-m
Catalog (in addition to those determined during astrometric measures). These
results will eventually be incorporated in a weighted scheme for the magnitude
listings of the WDS data line.
Examples of the first are the binaries first resolved by W. Herschel and both F.G.W. Struve and O. Struve. William Herschel published seven lists (I - VI, plus ``new'', or N), with stars of each list starting at number 1. In addition to their original discovery lists, each of the Struve's published an appendix, as well as a list of ``rejected'' doubles. These multiple lists were completely spelled out in the Aitken Double Star Catalogue (e.g., H IV 48), but when the Index (IDS) Catalogue was compiled at Lick all of these other designators were dropped for lack of space. As a result there are, for example, five components with the designation H 48! The source Herschel list was given in the notes file to the IDS. Appended and rejected stars from the lists of the Struve's were handled with an ``a'' or ``r'' towards the end of the WDS data line in most cases.
In the second (and fortunately rare) case, systems found quite near to known ones were given the same designation plus trailing character(s) (e.g., ES 1293a or BU 885 1/2). Sometimes both components were assigned these additional characters, sometimes only one; occasionally two pairs in an entirely different section of the sky were given the same designation by the author (probably by mistake).
Each of these cases is being handled in a different manner. For the William Herschel discoveries, a list identifier is added to column three of each designation. For example:
H 19 (at 16 hours) was originally H II 19 and is now known as H 2 19, H 7 (at 18 hours) was originally H V 7 and is now known as H 5 7, and H 111 (at 06 hours) was originally H N 111 and is now known as H N 111.
In the case of the O. Struve appendix an A is added following STT in the name. For F. Struve, he provided two appendices. Those from the shorter list (Appendix II) are designated STFB. For example:
STF 11 (appendix I) is now STFA 11. STF 11 (appendix II) is now STFB 11. STT 252 (appendix) is now STTA252.
Stars of the second type are given the same 3-letter discovery designation but a new number, starting with 9001, to indicate that they originally had a different designation. For example:
BAL2356b is now BAL9001. BU 885 1/2 is now BU 9001.A complete list of stars of the second type is provided in the error correction file. All changes in designation are described in the notes file. In addition to these, designations for 271 W. Herschel (H ), 110 F. Struve (STF) and 227 O. Struve (STT) systems have been changed. Note that for some of these systems, the former three character, four digit reference (a3i4) has been replaced by a four character, three digit reference (a4i3). Although, for all USNO applications (e.g., data or observing list request) an a7 read will see no difference.
For observations of double stars it is often necessary and beneficial to observe single stars. These can serve as an idealized point-source-function (psf) to determine the behavior of various elements in the optical chain, characterize various reduction algorithms, or be used to generate artificial double stars or other more complicated morphologies by use of calcite crystals, slit masks, aperture masks, etc.
Unfortunately, finding a good list of these calibrator sources is more difficult than it sounds. Generally speaking, the more that stars are studied the higher their multiplicity fraction. Erroneously labeled ``single stars'' can render vital calibration data useless through the discovery of a previously unknown companion or the slight modification of the psf by an unresolved component.
The basic data for this list come from the Speckle Catalog, which tabulates null detections from various duplicity surveys in addition to double star measures obtained by speckle interferometry and other high-resolution techniques. Stars from the Bright Star Catalog (Hoffleit & Warren 1991) are checked against the WDS, the Speckle Catalog, and the Hipparcos Catalog (ESA 1997) and only considered to be ``single'' stars if all the following criteria are met:
The final all-sky list contains 1,170
systems fulfilling these criteria. In the future, it is planned to update this
list to include systems which would be unresolved by optical interferometry.
Measures in the Washington Double Star Catalog have been collected, collated, and maintained since the early 1960's when the original IDS (Jeffers & van den Bos, 1963) was transferred from Lick Observatory to the U.S. Naval Observatory. Presented in order are the WDS J2000 coordinates, the discovery and component designation, the first and last measured epoch, the number of means, the first and last measured position angle (theta) in degrees, the first and last measured separation (rho) in arcseconds, the magnitudes of the primary and secondary, the spectral type of one or both components (if known), proper motion in RA and Dec (milliarcseconds/yr), the Durchmusterung (DM) number (The DM of the object in the system used by the Henry Draper Catalogue: Bonn from +89 to -22 inclusive, Cordoba from -23 to -51 inclusive, Cape Photographic from -52 to -89 inclusive), and a notes column. It should be noted that the WDS is not a photometric or spectral type catalog, and while the catalogers strive to provide the most correct values for these parameters, they should not be considered definitive. Some characters in the notes column indicate specific entries in another file (i.e., an N indicates an entry in the notes file), catalog (an O in the Orbit Catalog, and a D in the Delta-m Catalog), or are referenced in the format file. The full Catalog (8.7Mb) is available below as are format, note, reference and other ancillary files. The WDS 2001.0 is also available on a CD-ROM of USNO double star catalogs. Copies of this CD-ROM can be obtained from the authors.
Addition of the delta-m information as well as other more significant changes to the WDS database is currently under consideration. The input from regular users of the database and other interested parties is greatly appreciated in our efforts to make the WDS as helpful and user-friendly as possible. Please provide comments on the format of the WDS, missed references, or any other items of interest to you on our Comment form.
Information is being added to the database on a continuing basis, and this edition of the WDS will also be updated regularly.
You may request a reasonable amount of information from the double star catalog, a custom observing list, a copy of the Double Star CD, or make a comment by e-mail.
We are in debt to Geoff Douglass for his
work on the WDS database and his leadership in the speckle program at the USNO.
The Washington Double Star Catalogs and USNO speckle program were conceived and
nurtured by Charles Worley. Providing data in WDS
format (or at least electronic format) has allowed the WDS to grow
significantly. We would here like to acknowledge the contributions of Bob
Argyle, Wulff Heintz, Elliott Horch, Josefina Ling, Francisco Manuel Rica
Romero, and Walt Sanders.
``This research has made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory.''
A notification of references to relevant papers is appreciated.
This page is maintained by Brian Mason
Updated: 14 December 2004
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