Electronic Telegram No. 5561 Central Bureau for Astronomical Telegrams Mailing address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network TWO METEOR SHOWER OUTBURSTS WITH POTENTIAL CONNECTION TO COMET 73P D. Vida, P. Brown, and A. Egal, University of Western Ontario; and D. Segon, Croatian Meteor Network, report on two meteor-shower outbursts with a possible connection to comet 73P/Schwassmann-Wachmann and the tau Herculid meteor shower. The first outburst occurred during 2025 May 30-June 1. Thirty-three meteors were recorded using the Global Meteor Network low-light video cameras (cf. website URL https://globalmeteornetwork.org/data/). The shower was detected by stations in Belgium, the Czech Republic, Germany, France, Croatia, Hungary, Italy, South Korea, The Netherlands, New Zealand, Russia, Slovenia, the United Kingdom, and the United States. The shower had a median geocentric radiant with coordinates R.A. = 196.4 deg, Decl. = +51.0 deg (equinox J2000.0), within a circle with a standard deviation of +/- 1.8 deg. The radiant drift in R.A. is -0.24 deg on the sky per degree of solar longitude and +1.93 in Decl., both referenced to solar longitude 69.5 deg. The geocentric, sun-centered ecliptic longitude (L-L0) was 96.89 deg, and the geocentric ecliptic latitude was +51.60 deg. The geocentric velocity was 12.1 +/- 0.1 km/s, increasing by 0.14 km/s per degree of solar longitude. The activity period spanned solar longitudes 69.01-70.71 deg, with a clear peak at 69.5 deg at at zenith hourly rate (ZHR) of about 0.2 meteors/hr. This peak of activity matches the tau Herculid meteor shower, although the radiant location is over 10 degress away from the 2022 tau Herculid outburst. The mean orbital elements of the shower meteoroids are consistent with a short-period comet origin (equinox J2000.0): q = 1.0134 +/- 0.0006 AU, e = 0.654 +/- 0.028, i = 14.6 +/- 0.6 deg, Peri. = 181.9 +/- 1.5 deg, Node = 69.8 +/- 0.4 deg, a = 2.930 +/- 0.002 AU. A search for a parent body using the Drummond D-criterion returned several matches on minor planets with D < 0.07 (2014 JL_25, 2021 GR_7, 2010 JN_71), but only one comet: 73P/Schwassmann-Wachmann (D = 0.06), the parent body of the tau Herculids, suggesting a tentative dynamical relationship. The new shower received the working designation M2025-L1 from the IAU Meteor Data Center. The second outburst began roughly simultaneously with the first one but lasted longer, until June 3. Forty-one meteors were recorded using the Global Meteor Network low-light video cameras. The shower was detected by stations in Australia, Belgium, Brazil, Canada, Germany, Greece, Croatia, Hungary, Italy, South Korea, The Netherlands, New Zealand, Slovenia, South Africa, the United Kingdom, and the United States. The radiants of the second outburst were significantly offset from the first, by around 44 degrees in equatorial coordinates. The second shower had a median geocentric radiant with coordinates R.A. = 203.0 deg, Decl. = +7.6 deg (equinox J2000.0), within a circle with a standard deviation of +/- 0.9 deg. The radiant drift in R.A. is -0.11 deg on the sky per degree of solar longitude and +0.58 in Decl., both referenced to solar longitude 71.5 deg. The geocentric, sun-centered ecliptic longitude (L-L0) was 126.89 deg, and the geocentric ecliptic latitude was +16.03 deg. The geocentric velocity was 11.7 +/- 0.1 km/s, decreasing by 0.07 km/s per degree of solar longitude. The activity period spanned solar longitudes 68.5-72.5 deg, with a broad peak between 70.7-71.5 deg. The mean orbital elements of the shower meteoroids are consistent with a short-period comet origin (equinox J2000.0): q = 0.9794 +/- 0.0031 AU, e = 0.752 +/- 0.022, i = 4.8 +/- 0.3 deg, Peri. = 202.9 +/- 1.0 deg, Node = 71.0 +/- 1.0 deg, a = 3.950 +/- 0.013 AU. The top-ten closest objects during a parent- body search using the Drummond D-criterion were all fragments of comet 73P, all with D < 0.062; the best matching fragment was component Y, with D = 0.054. The new shower received the working designation M2025-L2 from the IAU Meteor Data Center. The Canadian Meteor Orbit Radar (CMOR) did not detect any members of either outburst, suggesting that the events were dominated by larger particles, in contrast to the 2022 tau Herculid outburst, which was rich in smaller meteoroids and well observed by CMOR. The two temporally adjacent but dynamically distinct 2025 outbursts indicate the presence of separate dust filaments from comet 73P intersecting the earth's orbit within a few days of each other (M2025-L1 represented best by 73P fragment S). Although similar in timing to the 2022 tau Herculid outburst, both 2025 radiants are spatially offset, implying distinct release epochs or differing trail evolution. Notably, the 2022 tau Herculid radiant at R.A. = 209.17 deg, Decl. = +28.21 deg, lies almost equidistant between the 2025 outburst radiants (about 20 deg from each one), further supporting the interpretation of multiple discrete filaments originating from comet 73P. The complicating factor in dynamical modelling of the meteoroid complex is the high uncertainty of the comet's orbit prior to 1930. Further modelling work is required to investigate whether the observed showers are caused by older trails, ejecta from the fragments after the break-up (observed for some of them shortly after 1995), or by material released in 1995 but with different ejection velocities. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 June 6 (CBET 5561) Daniel W. E. Green