Commission 26: Double and Multiple Stars
(Etoiles Doubles et Multiples)

Report of July 2003 Business Meeting


This is the report of the Commission 26 business meeting which took place on 2003 July 18 during the twenty-fifth General Assembly of the IAU in Sydney, Australia. The meeting was chaired by C. Scarfe, the outgoing president, and was attended by the following members: C. Allen, F. Arenou, R. Argyle, A. Boden, J. Davis, F. Fekel, W. Hartkopf, J. Kub'at, J. Ling, B. Mason, T. Oswalt, T. Pauls, D. Pourbaix, W. Tango, T. ten Brummelaar, A. Tokovinin, N. Turner, W. van Altena, E. Weis, and H. Zinnecker.

President's report

Commission website

W. Hartkopf gave a short report on the Commission's website. It includes an address list for members and others interested in double star astronomy, a bibliography of recent papers (mostly from J. Ling and colleagues), copies of IAU Commission 26 Circulars dating back to 1993, particulars on upcoming meetings, and links to double star catalogs, other IAU Commissions, and other related sites. Suggestions for improving the site were requested. The website's url is

Special Session 3

B. Mason summarized the discussions of Special Session 3 on A New Classification Scheme for Double Stars, which had taken place in the morning of the same day. Commission 26 ratified the C Type Resolution which is described in the proceedings of Special Session 3, on the subject of double star nomenclature (refer to Highlights of Astronomy article).

Information Circulars

J. Ling reported on the current status of the Information Circulars. She gave a brief review of their history, which now spans almost fifty years. Until 1993 they were published in French, but since then, in English. Their distribution has been successfully converted to electronic mail in the past triennium, and they are posted on the Commission's website. The back issues of the past ten years are also available there.

New orbits and new discoveries of double stars are the primary material of the Circulars, but their contents have become increasingly diverse in recent years. They include reports of Commission meetings, announcements of Symposia, Colloquia and other meetings, announcements about preparation and publication of new catalogues, and an annual list of papers published on double stars. They also include occasional obituaries and historical notes.

Since 1998 the Circulars have had ISSN number 1024-7769. They are also now included in the NASA Astrophysics Data System (ADS) with the bibliographic code IAUDS, which should be used in bibliographic references to them.

The possibility was raised of using the Circulars to draw attention to binaries nearing periastron or requiring special action for other reasons, and this was met with general approval. Also discussed was the idea of making the annual reference list more complete, but it was noted that this would be too large a job for one person and would require the active collaboration of several people, as is the case for Commission 42's semiannual Bibliography of Close Binaries.

The next three years

W. Hartkopf then took the floor. He thanked C. Scarfe for his service as Commission president for the past triennium. Thanks were also given to retiring Organizing Committee members T. Armstrong, R. Mathieu, and M. Valtonen. New OC members J. Davis, E. Oblak, and T. Oswalt were welcomed. Goals mentioned for the upcoming three years included a colloquium in 2005 or thereabouts (with possible topics and sites discussed later in the meeting), improvements to the website, more involvement by amateurs, and recruitment of new members. Several upcoming catalogs were mentioned, as well as a planned second CDROM of double star catalogs to be published in early 2004.

Observing facilities under development

Reports were then presented on development of some new major observing facilities, and additions to established ones.

Catalogues and databases

Amateur work on double stars

R. Argyle spoke about amateur projects in double star measurement during the 2000-2003 triennium. Measurement of visual double stars by amateur observers is becoming more widespread. During the period under report some 11,000 mean measurements were added to the USNO Observations Catalogue. These consist mainly of micrometer measures, CCD astrometry and graticule eyepiece observations. In addition, A. Alzner has contributed 17 orbits to refereed publications and Commission 26 Circulars. A very large project, by M. Nicholson, consisting of astrometry and photometry of 80,000 wide and faint pairs taken from archive Schmidt plate astrometry, is being assessed. At least one large database of 10,000 measures by Spanish observers is being prepared for publication. The work done by USNO in pointing out systems which require attention is vital to focus future activity. The almost complete lack of observations in the southern hemisphere was noted.

Planets in binary systems

H. Zinnecker reported about a recent list of 16 giant planets in 12 wide binary systems, discovered by the radial-velocity method and compiled by Eggenberger, Udry and Mayor. In each case the host star's membership in the system has been confirmed by orbital or common proper motion. A famous example is 16 Cyg B; however no giant planet has been found around 16 Cyg A. The semi-major axis of the 16 Cyg system is 850 AU. Two other systems, 55 Cyg and Upsilon And, with similar component separations, host systems of three planets, all around the primary in the latter case and around the secondary in the former.

Searches for giant planets around the components of about 100 single-lined binaries with periods longer than about two years are also under way by the same Geneva group.

Availability of observing facilities

A letter was read from P. Lampens, who was unable to attend the General Assembly, expressing concern about the increasing lack of access to telescopes by double star observers, and about publication of data, and requesting a statement on these matters. The following was accepted by the meeting as such an expression from the Commission.

Commission 26 views with concern the severe difficulty, faced by members in recent years, in obtaining access to telescopes with which to continue long-term observing programmes. Those programmes have in the past been highly productive, with scientifically valuable publication records, and their discontinuance will cause gaps in the coverage of many orbits, some of them at critical phases. Moreover, lack of telescope access will discourage currently active workers and impede recruitment of new ones, who will be needed to take advantage of the large databases now under development and those anticipated from future major ground- and space-based surveys.

Commission 26 is concerned to ensure that high-quality data are accepted for publication in widely read journals, even before those data provide orbit coverage adequate for detailed analysis and the derivation of astrophysically useful results. Double-star studies are often very long-term, and such publication makes the data accessible to others who use them for such purposes as planning observing programmes.


The meeting was adjourned at approximately 5:30 p.m.


Thanks are due to all who contributed to the meeting, and especially to those who summarized their presentations for this report.

C. D. Scarfe
President of the Commission