While the moonfree Quadrantid maximum was eagerly anticipated by SPA Meteor Section observers at the start of the Society's 50th anniversary year, January 3-4 seems not to have been especially clear across the UK. Positive results then or on January 2-3 were obtained only from parts of western and southern England, south Wales, southern East Anglia and south-west to central Scotland. A few continental European watchers also provided results, along with two regular correspondents in the USA.
People reporting data directly to the Section during the Quadrantids (visual reports where not stated) included:
Arbeitskreis Meteore (AKM) observers Juergen Rendtel and Sven Naether (Germany; results in the AKM journal Meteoros 6:3, 2003 provided by Ina Rendtel), Dirk Artoos (radio; Belgium), Belarus radio observers (Ivan Bruykhanov, Alexey Gain, Roman Grabovsky, Zahar Lapitski, Leonid Molchanov and Kiril Ushakov; data via Rainer Arlt), Jay Brausch (North Dakota, USA), Russell Cockman and several members of Falkirk Astronomical Society (visual and photo data; Falkirk, Scotland), David Entwistle (radio; Lancashire, England), Steve Evans (video; Gloucestershire, England), Kim Gowney (Pembrokeshire, Wales), Valentin Grigore (Romania), Robin Leadbeater (video; Cumbria, England), Bob Lunsford (California, USA), Edward Mallett (Suffolk, England), Tony Markham (Staffordshire, England), Tom McEwan (Ayrshire, Scotland), George Spalding (Oxfordshire, England), Enrico Stomeo (Italy), Roy Watson (Kirkintilloch, Scotland).
In addition, many more radio reports came in as Radio Meteor Observation Bulletins 114 and 115 (January and February 2003 respectively; also at website: http://www.rmob.org), provided by Chris Steyaert. These observers covering the Quadrantid epoch included:
Enric Fraile Algeciras (Spain), Mike Boschat (Nova Scotia, Canada), Walter Boschin (and colleagues Diego Ganzini, Alessandro Candolini and Giuseppe Candolini; Italy), Jeff Brower (Colorado, USA), Maurice de Meyere (Belgium), Minoru Ehara (Japan), Kenji Fujito (Japan), Valter Gennaro (Italy), Ghent University (Belgium), Patrice Guerin (France), Steve Hansen (Massachusetts, USA), Michael Krocil (Czech Republic), Toshihide Miyake (Japan), Stan Nelson (New Mexico, USA), Robert Obraz (Croatia), Hiroshi Ogawa (Japan), Sadao Okamoto (Japan), Robert Savard (Quebec, Canada), Dave Swan (England), Pierre Terrier (France), Bruce Young (Queensland, Australia), Ilkka Yrjola (Finland).
Visual Shower Review
The first graph here gives percentage magnitude distributions for the better-sky Quadrantids and early January sporadics, seen under conditions with less than 20% cloud cover, and where the limiting magnitude was at least +5.5. There were a few casual reports from the UK of several bright to fireball-class meteors, some identified as probable Quadrantids, during the evening hours of January 3-4, while the radiant was very low in the northern sky, which are not represented in this histogram.
The second graph gives an impression of how visual Quadrantid Zenithal Hourly Rate (ZHR) activity behaved on January 2-3 and 3-4. The relative paucity of observers meant a few datapoints were based on less than ideal observations (limiting magnitude of +5.4 to +5.0, radiant elevation under 20 degrees), or were the results of just one watcher. Consequently, the exact timings and strengths of the ZHRs must be treated with some caution, though the general trends shown probably give a reasonable guide to what the shower maximum produced.
With these cautions in mind, two peaks are apparent on January 3-4, a very sharp one over Europe at about 01:30 UT (ZHR =3D 90 +/- 16), the other less strongly-defined over the USA around 09:30 UT (ZHR =3D 80 +/- 17). The anticipated visual maximum was due at 00h UT or so, thus the main visual peak seems to have been a little late in 2003, if these results are correct. Observations in 2000 and 2001 suggested a second, chiefly radio, maximum may have happened some 9 to 12 hours after the usual main one. The ~09:30 UT peak falls within that window certainly.
Radio Shower Review
Checking the radio data proved a particularly complex task this time. Elements of this can be seen in the accompanying six graphs, two each giving representative observations from Japan (green), Europe (red) and North America (blue), to provide a useful overview of how different places covered the 2003 Quadrantids. Each graph shows raw hourly radio meteor echo counts across the maximum, in data collected by (in order): Sadao Okamoto; Kenji Fujito; Walter Boschin et al.; David Entwistle (longer-duration echo counts only); Robert Savard; and Stan Nelson. In all these graphs, the thicker, irregular lines, keyed to the left-hand y-axes, show the raw hourly radio echo count values, while the thinner, daily-symmetrical, magenta, curves (keyed to the right-hand y-axes) give the Quadrantid radiant elevations for each observer's site. All the illustrated radio systems were operated continuously, and drops in the echo trace to zero in general indicate times when accurate recording was affected by interference problems.
In Japan, for some unidentified reason, observers failed to record as strong a radio response after the Quadrantid radiant had culminated on January 3-4 UT as before, though as the European and North American data revealed, this should not have been the case. For much of the time between ~23h to Quadrantid radiant-set from Japan, between 09h-10h UT, there is an almost total absence of obvious Quadrantid activity in some datasets. A few showed a possible partial recovery for a time around 02h-04h UT, but nothing more.
In Europe, the problem was an on-going one increasingly prevalent over the last few years, that of the number of transmitters shutting down for several hours over midnight UT, coupled with that of fewer suitable transmitters continuing generally. This meant that in many European datasets, echo count numbers which should have been improving as the Quadrantid radiant pulled away from the horizon, actually fell, in some cases to virtually negligible levels, from approximately 22h-03h UT. The overlap with the timing of the mysterious lack of Quadrantid echoes over Japan was extremely unfortunate, further compounded when one realizes this period coincided with the lower radiant elevations for North America!
A first analysis of the radio data revealed four potential Quadrantid maxima, with mean UT timings centred at January 3, 12h +/- 1h (but in only 33% of the results, and of relatively minor strength) and 21h +/- 2h, January 4, 03h +/- 1h and 10h +/- 2h. The strongest maximum occurred in 70% of the datasets between January 3-4, 19h-05h UT. The longer-duration echo counts sometimes give additional guidance to major shower maxima especially, but very few suitable datasets were available. Some of the Japanese results could support a longer-duration echo peak around January 3, 22h +/- 1h UT, though this may be less significant, as it was around one of the times of best radio-visibility for the Quadrantids from Japan. Only two European longer-duration datasets were available for examination, and these favoured a mean peak time of 01:30 +/- 1.5h UT on January 4. This is a more plausibly interesting event, as the shower radiant was still relatively low for these observers. This could indicate this was the more likely longer-duration radio peak, which was at least conveniently coincident with the preliminary visual findings!
Reinterpreting the radio data, trying to allow for the various reception difficulties outlined above, could imply the main Quadrantid maximum happened at a mean time of January 3, 23:15 +/- 4h UT. There are however considerable uncertainties in doing so. The problems around the midnight UT interval on January 3-4 certainly suggest strongly that the two "central" radio peaks of the four found should be treated as parts of a single, reception-affected, period, rather than two separate ones at least, even if the main maximum cannot be better defined than this.
The other two radio peaks, January 3, ~12h and January 4, ~10h UT, also need further discussion. The first, though relatively poorly reported, may be a rare retrieval of the radio-telescopic Quadrantid maximum known from previous results as happening up to 14 hours before the visual peak. If we take the main radio-visual peak in 2003 as falling sometime between roughly 23h-02h UT on January 3-4, this earlier peak preceded the main one by some 11 to 14 hours or so, exactly what would be expected. If correct, this is quite an achievement, as this earlier peak was not found in radio reports from most of the recent Quadrantid returns. The second peak was found in all the available datasets where the Quadrantid radiant was above the horizon, and again assuming the same main peak times as above, trailed that maximum by about 8 to 11 hours, very similar to the 9 to 12 hour gap seen previously, and very close to the probable "USA" visual maximum, as discussed earlier. Few other visual results have become available since the event, so these peak timings remain unconfirmed possibilities, but with the results from recent years in addition, it may be that two such main peaks are indeed currently happening within the Quadrantids. A good, clear moonless spell over a future Quadrantid epoch may tell us much more.
From the observers' perspective, the 2003 Quadrantids were not as successful as had been hoped-for overall. In the UK, several people reported seeing a few Quadrantids casually during the evening hours of January 3-4, including the bright meteors and fireballs referred to earlier, but the near and post-midnight periods seem to have had generally poorer skies, typically timed for the increasingly favourable radiant elevations! Despite this, some observers had a reasonably good night, including Steve Evans, who managed almost 6.25h of video observing on January 3-4, picking up 24 Quadrantids and a dozen sporadics. One of Steve's composite video-still images is given here, along with one of Robin Leadbeater's.
In continental Europe, very few observers had much luck on Quadrantid maximum night. Valentin Grigore in Romania reported most positively, with generally clear skies from midnight onwards, but in Italy and Belgium (information from Hendrik Vandenbruaene of the VVS meteor group), conditions were useless. Bob Lunsford in California had the best skies from the North American reporters, a mostly clear night on January 3-4, with clouds coming up only towards the end of the night to spoil the view.
Despite the uncooperative winter weather in too many places, and difficulties in interpreting the radio data for sometimes unknown reasons, this was an interesting return of the Quadrantids. It seems to fit the pattern of those of recent years which have apparently produced a double maximum, although until we enjoy another well-observed Quadrantid epoch, this aspect is liable to remain unconfirmed. For now, it is important to try to make thorough observations of the shower at every return, as sky conditions allow, that is. The last really well-seen Quadrantid return was back in 1992, so we may have quite a wait for another good one yet! My grateful thanks are extended as always to everyone who sent in data, comments and other correspondence, allowing an early preliminary report by the end of 2003 February, and this report now. Good luck, and clear skies for your next watching!
Report prepared by SPA Meteor Director Alastair McBeath, 2003 July 8.