A total of 229 IAU Circulars were published in 2001, up from the 213 published in 2000. The most popular topics covered were supernovae (whose discoveries appeared on 55 percent of the Circulars, while at least one separately titled follow-up item on a supernova appeared on 40 percent of the year's IAUCs) and comets (with non-spacecraft discoveries appearing on 17 percent, SOHO discoveries on 14 percent, and follow-up information on comets appearing on a quarter of the 2001 Circulars). These were followed by follow-up items involving novae and other unusual Galactic variable stars, which appeared on 28 percent of the year's Circulars. Eight percent of the year's Circulars contained items on gamma-ray and x-ray transients, and 5 percent contained reports on radio transients.
There were 254 new supernova discoveries made in 2001 that were reported on IAUCs that year. However, several dozen supernovae found on 2001 images were not reported to the Central Bureau until 2002. The 2001 designations of extragalactic supernovae represents the highest number of supernovae in a calendar year, easily surpassing the previous record of 206 in 1999. In addition, seven supernovae found on images taken in previous years were announced and designated on IAUCs in 2001. Some 84 supernovae announced during the year were fainter than mag 20, attesting to the increase in searches for supernovae in distant, faint galaxies for cosmological studies. The two brightest supernovae of the year were SN 2001el in NGC 1448 (visual mag about 12.7 in September) and SN 2001ig in NGC 7424 (reaching visual mag about 12.3 in early January 2002). SN 2001bg in NGC 2608 peaked at mag about 13.7, and five other supernovae were reported between mag 14 and 15 during the year.
Nine IAUCs carried discoveries of novae and outbursts of recurrent novae or novalike variables during 2001. In addition, the year began with numerous items pertaining to V445 Pup, an apparently recurrent nova found toward the end of 2000 that initially defied classification. Three new Galactic novae announced on the Circulars during the year reached visual mag about 6.5 during a three-week period beginning mid-August (V2275 Cyg, V4739 Sgr, V4740 Sgr). Continuing a collaboration begun a few 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. There were also nine Circulars in 2001 covering reports on novae in M31, M33, and the Small Magellanic Cloud. Other unusual variables were also covered on IAUCs, and quite a number of items appeared concerning WZ Sge, which had its first outburst since 1978.
Numerous amateur astronomers were actively involved in searching the Solar and Heliospheric Observatory spacecraft's coronagraph images at the SOHO website, and many new such comets detected prior to 2001 were announced on IAUCs published during 2001. In addition to the scores of new SOHO comets announced during the year, some three dozen non-SOHO comets received new 2001 designations. Several pre-2001 non-SOHO comets also received new designations when announced on IAUCs in the year 2001. The recoveries (or rediscoveries) of three short-period comets (including 11D/Tempel-Swift, which hadn't been seen since 1908 and to which the name LINEAR was added following its independent rediscovery of this comet in December) were also announced on IAUCs in 2001. Comet 39P/Oterma was recovered in August, although there were some prerecovery observations in 1998 and 1999, the first observations since 1962.
An increasing number of objects reported as asteroidal (and given minor-planet designations) were found to be cometary and announced as comets on IAUCs during 2001. The wide-field CCD surveys are finding more comets when they are far from the sun or comets that exhibit little activity, making it more common for comets to escape proper initial classification. The new designation scheme instituted in 1995, which permits comets to assume minor-planet designations, has been most helpful in this process, and the close work of the CBAT with the Minor Planet Center (MPC) in posting many of the `asteroidal' objects with unusual motion on the NEO Confirmation Page has been invaluable in quickly sorting out and announcing such comets.
Only one comet was discovered visually during 2001 --- C/2001 Q2 (Petriew). Amateur visual discoveries of comets, particularly those from the northern hemisphere, have lessened noticeably in recent years due in part to the professional minor-planet surveys, but the case is even more pronounced for supernovae. So it is quite curious that within a span of less than three weeks following Vance Petriew's discovery, the Circulars reported visual discoveries also of a supernova (SN 2001du, by Robert Evans) and two Galactic novae (both by Alfredo Pereira). The Edgar Wilson Award for the year 2000--2001 was announced on June 29 (IAUC 7652), with only two recipients, for comet C/2000 W1 (Utsunomiya-Jones) --- a comet that, as detailed on the Circulars, faded unexpectedly over the first couple of months of 2001 into a diffuse glow, evidently disintegrating.
There were no really bright comets in 2001, though comet C/2001 A2 reached total visual mag about 3.5 in June and C/2000 WM_1 reached m_1 about 5 in December. A comet discovered in August at a heliocentric distance of about 10 AU, C/2001 Q4 (NEAT), is likely to become a naked-eye object when near perihelion in May 2004. Numerous items regarding spectral observations from optical to radio wavelengths appeared on IAUCs during the year for C/2001 A2 and C/1999 T1, the latter being at m_1 about 8 in January. C/2001 A2 fragmented into at least five pieces. Such cometary fragmenting is becoming noticed more frequently now with increased CCD observation and has become a fairly common topic on the Circulars. The short-period comet 51P/Harrington was noted to have split in December, for example.
Seven IAUCs during the year covered the discoveries and follow-up information for numerous satellites of both major and minor planets. Companions were reported for various classes of dynamic objects, including a near-earth minor planet, main-belt asteroids, a Jupiter Trojan, and transneptunian objects (TNOs). Eight Circulars in 2001 each carried information on TNOs and on other minor planets, and four IAUCs in 2001 contained items on other solar-system objects (including an unusual near-earth object that was determined eventually to be an operational artificial spacecraft). Of note were observations reported in January and February on IAUCs that suggest a diameter for one TNO, (20000), that is about half that of Pluto. In April, the second TNO (after Pluto) to have a companion was announced, followed later in the year by two additional TNO cases.
It is frequently mentioned by astronomers that they appreciate having magnitudes of comets, novae, and supernovae published on IAUCs to aid in observing plans, and such data have been included for decades now. In addition, for the last several years, an interlinked website involving the CBAT, the MPC, and the International Comet Quarterly has included posting of total CCD and visual magnitude estimates of comets. The CBAT maintains its own ``Headlines" webpage that lists conveniently the recent discoveries of comets, novae, supernovae, and satellites of major and minor planets. Other aspects of the CBAT website were modified during the year (an ongoing process of website development) to add information at the request of astronomers and members of the news media and general public.
The number of paid subscribers to the printed edition of the IAU Circulars has continued to fall, from 243 at the end of 2000 to 216 at the end of 2001. In addition, there were 38 free (complimentary or exchange) subscriptions to the printed IAUCs at the end of 2001. The printed IAUCs go to 77 addresses within North America and 139 outside of North America. There were 501 paid subscribers to the CBAT/MPC electronic service at the end of 2001, compared with 498 at the end of 2000. The on-line IAUCs posted at the CBAT website now routinely are delayed by some days to non-subscribers, following complaints by paying subscribers when they were posted for all to view soon after issuance.
As in recent years, most of the Circulars in 2001 were prepared by the undersigned, with very helpful editorial backup by Director Emeritus B. G. Marsden (who prepared 13 Circulars during the year and helped to proofread and critique most of the rest prior to issuance). Minor Planet Center Associate Director Gareth Williams also maintains a strong presence, essentially as an acting Assistant Director to the Bureau, by also helping to proofread Circulars, contributing to many comet announcements that appear on the Circulars after appearing first on the MPC's NEO Confirmation Page, being ready to issue IAUCs if Green and Marsden are travelling, and helping to maintain the Bureau's presence on the World Wide Web. Many members of the astronomical community serve each year as referees for items submitted for publication on IAUCs, especially members of Commission 6, and we are grateful to them for their sometimes-considerable time spent in helping to assure the high quality of the published content on the Circulars. At SAO, Muazzez Lohmiller has continued to handle the accounts, addressing of envelopes, and other administrative matters; Judy Terry has also handled numerous CBAT administrative matters.
Daniel W. E. Green
Director of the Bureau