As has been the case in recent years, the most common topics covered were supernovae, for which 204 designations for 2004 discoveries and 22 designations for 2003 discoveries were announced on the year's Circulars (though one of those new 2003 designations, 2003lr, was found later to be two separate minor planets observed in nearly the same location on two different nights). Separately titled follow-up text on supernovae amounted to an additional 107 titles during 2004. The brightest supernova of the year, SN 2004dj in NGC 2403 (found in late July at V about 11.2 by Japanese amateur K. Itagaki), was heavily observed, with reports in the IAUCs including much discussion of a possible progenitor as well as radio and x-ray detections. The second brightest supernova of the year, SN 2004et in NGC 6946, reached magnitude R = 12.2 in late September, and it also was detected at radio wavelengths. Fully ten supernovae were reported as brighter than mag 15 at discovery during 2004, and another 13 as brighter than mag 16; the bulk of supernovae were in the magnitude range 17-19 upon discovery.
Some 68 supernovae were discovered or co-discovered by amateur astronomers during the year (led by the British trio of R. Arbour, M. Armstrong, and T. Boles with 37) --- or fully 30 percent of the total number of supernovae designated on IAUCs during 2004! --- showing the continuing highly useful impact of amateurs on supernova astronomy. The Lick Observatory Supernova Search, led by Weidong Li, made the most supernova discoveries in 2004, with a total of 85. Only 35 (or under 16 percent) of the supernovae did not have spectroscopic classification published on the Circulars --- the brightest of these being SN 2004de at mag 14.5 (with Decl. = -26 deg) --- way down from the number in 2003 (where a full third had no spectroscopic confirmation). A gamma-ray source known as GRB 031203, which had an optical afterglow, was given the supernova designation 2003lw on IAUC 8308.
The ongoing discussion by the CBAT Director with the 'supernova community' (see the 2003 annual report) has continued, resulting in the establishment of a temporary 'Possible Supernovae' CBAT webpage to handle particularly the fainter objects for which spectroscopic confirmation is not possible, awaiting the (long-delayed) establishment of a new webpage that will be hosted jointly by the new IAU Supernova Working Group and the CBAT. A preliminary-designation 'PSN' scheme based on date of discovery was established with this temporary CBAT webpage (see http://cfa-www.harvard.edu/iau/CBAT_PSN.html), and 28 such objects were designated and posted at this page in 2004.
Five Galactic novae reported on IAUCs during 2003 (the same number as in 2003), the brightest being V574 Pup, which reached visual mag 7.0 in November (V1187 Sco was only slightly fainter at mag 7.4 when discovered on Aug. 3). Seven titled items during 2004 covered novae in other galaxies, including three on novae in M31. A new CBAT webpage was established during the year to handle novae in M31, which now lists all such novae reported to the Central Bureau from 2004 Jan. 1 onwards (see http://cfa-www.harvard.edu/iau/CBAT_M31.html). As novae in M31 are relatively common (unlike their counterparts in the Magellanic Clouds or the Milky Way, which have only a few observed novae each year) --- there being roughly a couple dozen novae to be discovered (brighter than about mag 20) in M31 each year --- it has been suggested that the IAUCs only publish information on M31 novae that reach visual mag about 15 or brighter. Amateur astronomers continue to dominate the discovery of novae, whether in the Milky Way or in other galaxies --- this being the last area where discoveries are still often made on Technical Pan film, though CCD cameras are beginning to dominate this amateur area of observation, as well.
Also during 2004, separately titled items appeared more than two dozen times concerning other unusual Galactic variables, including transients observed at radio and high-energy wavelengths. Numerous IAUC reports during the year involved the outburst of what is evidently a young T-Tau-type star (brightening its association reflection nebular in Orion), for which IAUC 8354 announced the permanent variable-star designation V1647 Ori (via the on-going CBAT collaboration with N. N. Samus and the GCVS team at the Institute for Astronomy in Moscow).
Comets continued in 2004 to have a standard presence in the CBAT publications, with non-spacecraft discoveries and recoveries appearing under 52 titles, and follow-up information appearing under 60 additional titles. Three naked-eye comets produced a number of reports of observations at various wavelengths published on the IAUCs --- including comets C/2002 T7 (which peaked at total visual mag about 2.5 in May), C/2001 Q4 (which peaked at mag about 3 in May), and C/2004 F4 (which peaked at mag about 4 with a 10-deg tail as seen by ground-based observers after perihelion in late April, though it was much brighter when it appeared in the SOHO field-of-view near its April 17 perihelion date).
After a lull due to staffing problems at the Naval Research Laboratory, SOHO near-sun discoveries again appeared under 37 separate titles during the year (including the posting of 162 such backlogged comets from 1996, 2002, and 2003, plus 154 new objects observed in 2004). During 2004, an additional two comets were found by amateur astronomers viewing website SOHO/SWAN ultraviolet images, which were then confirmed by ground-based observations and announced on IAUCs. As noted with the announcement of the first of these on IAUC 8346, there have been numerous never-confirmed reports to the Central Bureau over the last couple of years of possible SWAN comets, and despite a great exertion of effort to have them confirmed by ground-based observers, C/2004 H6 was the first SWAN comet to have been confirmed since C/2002 O6 (cf. IAUC 7944).
The LINEAR CCD-search project again netted by far the most ground-based comet discoveries in 2004, with 25 credited finds on Circulars published during the year. The continuing close collaboration of the CBAT with the Minor Planet Center resulted in near-simultaneous announcements on IAU Circulars and Minor Planet Electronic Circulars of most of the professional-survey comets, many of which are initially reported as asteroidal but found to show cometary appearance elsewhere by follow-up observers (many of whom again are amateurs) who monitor the MPC's 'Near-Earth-Object Confirmation' webpage. The annual Edgar Wilson Award for comet discovery by amateurs was also announced by the Central Bureau in July, with only two recipients in 2004. The CBAT Director took the lead, in his role with comets names within the IAU Committee on Small Bodies Nomenclature, in getting final votes for several problematic names during the year (the results of which were announced on the IAU Circulars).
What appear to be the two largest transneptunian objects after Pluto were also noted on Circulars during the year: 2003 VB12, now known as (90377) Sedna, on IAUC 8304 and 2004 DW, now known as (90482) Orcus, on IAUC 8291. The first known southern-hemisphere feature observed on Uranus at 2.2 microns was reported on IAUC 8368, and transits of Mars I and II across the sun as viewed from the martian surface by the Mars Rover were reported on IAUC 8298. Several IAUCs during 2004 again covered the discoveries of numerous satellites of both major and minor planets, plus some purported binary nature reports of other minor planets. All of these satellites (together with novae, supernovae, and comets) are listed conveniently in chronological order (as announced on the IAUCs) at the Central Bureau's 'Headlines' webpage (http://cfa-www.harvard.edu/iau/Headlines.html).
The CBAT has continued its a notable presence on the World Wide Web, with most of its Circulars posted freely for some years until late 2004, but in November it was decided (following consultation with the officers of Commission 6) that, due to the falling revenue to the Central Bureau from falling subscriptions due to the Internet (and to the increasing expectations of the astronomical community that things be provided freely), there would be imposed immediately a block on the web-based Circulars so that they would be readable only by paying subscribers. This resulted in a dramatic spike in renewals and even new subscribers, but it also yielded much unhappiness in the astronomical community. Other sources of income are being actively sought to make up for the revenue shortfalls, and it is anticipated that older Circulars will be very soon made freely available at the CBAT website again now after a short delay (certainly those older than a year, and possibly older than several months --- noting that paying subscribers are expecting that the most recent Circulars not be made available freely). (All CBETs are also available now at the CBAT website.)
The number of paid subscribers to the printed edition of the IAU Circulars continued to fall, from 179 at the end of 2003 to 158 at the end of 2004. In addition, there were 36 free (complimentary or exchange) subscriptions to the printed IAUCs at the end of 2004. The printed IAUCs go to 66 addresses within North America and 128 outside of North America. The number of subscribers to the Computer Service (shared by the CBAT with the MPC) remained very stable, at around 464.
Assistant Director G. V. Williams has continued to serve as joint MPC/CBAT webmaster (and has been responsible for the Web CS dissemination of the IAUCs). All of the year's Circulars were prepared by the undersigned, with very helpful editorial backup by Director Emeritus B. G. Marsden, who prepared numerous CBETs during the Director's absence from Cambridge during the year (and helped to proofread many IAUCs prior to issuance and to discuss many CBAT matters from his decades of experience as CBAT Director). Aided by widespread use of 'Secure Shell' (or ssh) connectivity worldwide via the Internet, the Director has been increasingly able to handle much CBAT work during his international travels.
Numerous referees worldwide, especially some who are Commission 6 members, are also to be thanked for their great help with many items published on Circulars in 2004 (causing, unfortunately, quite a number of contributions to be rejected), continuing the long practice of the IAUCs being a refereed publication. At SAO, Muazzez Lohmiller has continued to handle the accounts, addressing of envelopes, and other administrative matters. Dan Wooldridge continues, as he has for years, with the fine printing of the IAUC cards.
Daniel W. E. Green
Director of the Bureau
IAU Commission 6 Reports
IAU Commission 6 Homepage