Electronic Telegram No. 1108 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://www.cfa.harvard.edu/iau/cbat.html ORIONID METEORS 2007 [this text replaces that on CBET 1107] Following last year's elevated rates (cf. CBET 698), P. Jenniskens, SETI Institute, reports that the annual Orionid shower has again been stronger and brighter than expected in 2007. In the period 2007 Oct. 4-23, Orionid shower rates reported by the International Meteor Organization were 80 percent higher than normal, peaking at ZHR = 45 per hour on Oct. 22d11h UT. Furthermore, a 1-day-wide outburst occurred with a peak rate of ZHR = 25/hr, centered on solar longitude 208.15 +/- 0.05 deg (equinox 2000.0; Oct. 22d01h), similar to other such outbursts observed in 1993 and 2006. The total rate peaked at 65 +/- 3 per hour, stronger than in 2006. From single-station video observations, I. Yrjola, Kuusankoski, Finland, measured radiant positions at R.A. = 94.7 deg, Decl. = +16.0 deg on Oct. 21.03 (55 meteors); R.A. = 95.7 deg, Decl. = +16.0 deg on Oct. 22.04 (96 meteors); and R.A. = 96.9 deg, Decl. = +14.0 deg on Oct. 23.03 (57 meteors). From three-station video observations, E. Lyytinen (Helsinki, Finland) reports mean radiants of R.A. = 94.9 deg, Decl. = +15.7 deg on Oct. 21.0; R.A. = 95.8 deg, Decl. = +15.6 deg on Oct. 22.0; and R.A. = 96.4 deg, Decl. = +15.9 deg on Oct. 23.0. J. M. Trigo-Rodriguez, Institute of Space Sciences (Consejo Superior Investigaciones Cientificas) and Institut d'Estudis Espacials de Catalunya, reports that high-resolution CCD all-sky and wide-field CCD imagery recorded by the Spanish Meteor and Fireball Network (SPMN) showed an outburst of the Orionid shower during Oct. 19d02h00m-19d03h30m UT. Observations were made from the Montsec Astronomical Observatory and Montseny stations, and activity was mainly composed of bright meteors and fireballs with ZHR = 40 +/- 10, peaking at 3h00m +/- 30m UT (solar longitude 205.47 deg). Additional confirmation of the outburst was obtained by three SPMN video stations operated by J. M. Madiedo (Universidad de Huelva) located in Seville and Huelva. Video and small-field CCD imagery shows the presence of fainter meteors than those imaged from all-sky CCD cameras. Video data and parallel visual observations suggest that the outburst was also composed of meteors as faint as mag 6. On Oct. 19, all meteors (except for a weak background) were coming from a very compact radiant located at R.A. = 90.2 +/- 0.1 deg, Decl. = 14.8 +/- 0.1 deg (equinox 2000.0, from 12 CCD meteors). The magnitude distribution index (chi) was 1.5 +/- 0.4. On Oct. 19-20, Orionid activity decreased to ZHR = 25 +/- 5, still exhibiting bright meteors in all-sky CCD and video cameras. Video and visual data indicate that the activity was dominated by fainter meteors than on the previous night (chi = 1.8 +/- 0.4). On Oct. 20-21, Orionid activity increased to ZHR = 60 +/- 10, produced by bright meteors and abundant fireballs from a compact radiant located at R.A. = 95.3 +/- 0.4 deg, Decl. = 15.7 +/- 0.2 deg (from 18 video meteors). Consequently, the magnitude distribution decreased to chi = 1.5 +/- 0.4. On that night, several very bright (mag -8 to -12) fireballs were recorded over Spain before sunrise, and their emission spectra were obtained with high-sensitivity video devices. The brightest recorded event was a daylight Orionid bolide recorded by J. M. Madiedo (Universidad de Huelva) on Oct. 21, at 6h07m54s UT over the province of Huelva. During the following nights, increased activity of bright Orionid meteors by SPMN cameras has been still ongoing. According to Jenniskens, annual Orionid shower rates should continue to be elevated in the next two weeks, when the shower activity declines. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2007 CBAT 2007 October 25 (CBET 1108) Daniel W. E. Green