A total of 213 IAU Circulars were published in 2000, down from the 261 published in 1999. The most popular topics covered were supernovae, which were mentioned on 71 percent of the Circulars, and comets, mentioned on 52 percent of the Circulars. These were followed by items involving gamma-ray and x-ray transients (25 percent of the year's IAUCs) and novae and other unusual galactic variable stars (23 percent).
There were 173 new supernova discoveries made in 2000 that were reported on IAUCs. The 2000 designations of extragalactic supernovae represents the second highest number of supernovae in a calendar year (the record year 1999 having some two dozen more). In addition, six supernovae found on images taken in previous years were announced and designated on IAUCs in 2000. No known supernovae became brighter than visual mag 14 during the year.
During the year, 87 comets received new 2000 designations, which are announced traditionally on the IAUCs. This figure does not include 2000 designations that have been given during the first quarter of the year 2001 to another 26 SOHO comets that were found belatedly in 2000 data, as well as a comet recovery (P/2000 Y10 = P/1992 G3) and to a November 2000 discovery of an apparently asteroidal object that was found in February 2001 to be cometary (P/2000 WT_168). Four additional objects reported in 1999 as asteroidal (and given minor-planet designations then) were found to be cometary in early 2000 and announced as comets on IAUCs during 2000 (C/1999 XS_87, P/1999 WJ_7, P/1999 XB_69, and P/1999 XN_120). And the long-awaited rediscovery of the final 'lost' minor planet, (719) Albert, was announced on May 9 (IAUC 7420). Seven additional IAUCs during the year contained items regarding other interesting minor planets (and companions or satellites to three such objects). The recoveries (or rediscoveries) of eight short-period comets (including 97P/Metcalf-Brewington in September) were also announced on IAUCs in 2000. Comet P/1963 W1 = 1963 IX, discovered by Anderson but lost since November 1963 (P = 7.9 yr), was rediscovered by the LINEAR survey in September 2000.
Numerous amateur astronomers were actively involved in searching the Solar and Heliospheric Observatory spacecraft's coronagraph images at the SOHO website, and 118 new comets detected prior to 2000 were announced on IAUCs published during 2000. Due to this large number, it was proposed and accepted at the Commission 6 meeting in Manchester (August 2000) that older SOHO comets could henceforth be announced immediately on Minor Planet Electronic Circulars, with summary listings given later on IAUCs after several SOHO comets could be collected for tabulation therein.
There were no really bright comets in 2000, though comet C/1999 S4 (LINEAR) brightened to total visual mag 6--7 in July before unexpectedly breaking apart and disappearing from view in August. Comets 2P/Encke and C/2000 W1 (Utsunomiya-Jones) reached similar brightness in September and December, respectively (with magnitude estimates given occasionally on IAUCs to aid observers). Only one comet was discovered visually during 2000 --- C/2000 W1; for this discovery, amateur astronomers Syogo Utsunomiya and Albert Jones qualify as the only recipients of the Edgar Wilson Award during the calendar year 2000. The Edgar Wilson Award for the year 1999--2000 was announced on June 29 (IAUC 7445). Despite the incentives of that Award, visual discoveries of comets continue to decline, probably due to a combination of the effects of the CCD surveys for near-earth objects that now net dozens of comet discoveries each year and of increasing light pollution worldwide.
There were also reports of two new galactic novae (V4642 Sgr and V463 Sct), of one nova in the Large Magellanic Cloud, and of five novae in other nearby galaxies. Continuing a collaboration begun a couple of years ago between the CBAT and IAU Commission 27, N. N. Samus supplies new variable-star designations for novae to be announced on IAUCs, so that the permanent designations can be used almost immediately.
The new x-ray nova XTE J1118+480 (for which an optical candidate was identified that reached visual mag 13) tallied the most reports among such objects, with information appearing on a dozen IAUCs during the year. The decline in the number of gamma-ray bursters mentioned on the IAU Circulars continued in 2000, as information on these events is being given in the GCN service of NASA's Goddard Space Flight Center. As noted by Marsden in the CBAT report for 1999, this is reasonable, given that this service disseminates the communications --- errors and all --- automatically, in contrast to the verification and editing that has traditionally been associated with the publication of the IAU Circulars.
Sixteen IAUCs during the year covered the discoveries or rediscoveries and follow-up information for three satellites of Uranus (first observed in 1999), two satellites of Jupiter (one first observed in 1999 and the second a rediscovery of the lost object S/1975 J 1), and twelve satellites of Saturn.
The number of paid subscribers to the printed edition of the IAU Circulars has continued to fall, from 267 at the end of 1999 to 235 at the end of 2000 (the latter number including 83 within North America and 152 outside of North America). In addition, there were 39 free (complimentary or exchange) subscriptions to the printed IAUCs at the end of 2000. The reduction in the number of paid subscribers to the e-mail version via the Computer Service that is shared with the Minor Planet Center is implicit in Marsden's report of the latter.
As in recent years, most of the Circulars in 2000 were prepared by the undersigned, with backup from Marsden, from Minor Planet Center Associate Director Gareth Williams (who is routinely responsible for the Bureau's presence on the WWW), and from Carl W. Hergenrother (University of Arizona) and Elizabeth O. Waagen (American Association of Variable Star Observers) --- these last two helping with CBAT and MPC functions while Marsden, Williams, and the undersigned attended the IAU General Assembly in August. Muazzez Lohmiller has efficiently taken care of the accounts, addressing of envelopes and other administrative matters.
This is my first annual report as Director of the Central Bureau for Astronomical Telegrams (having served as Associate Director since 1988, and as Assistant Director from 1981). At the IAU General Assembly in Manchester, I succeeded Brian G. Marsden in this position; after serving since 1968 as CBAT Director, Marsden was elected Director Emeritus and President of Commission 6. I take this opportunity to thank Marsden for his advice and encouragement over more than two decades in my own work with the CBAT. I look forward to continuing my service for the astronomical community and especially my involvement with the astronomers who obtain the important observations to which the CBAT attends.
Daniel W. E. Green
Director of the Bureau
IAU Commission 6 Reports
IAU Commission 6 Homepage