Alpha Aurigids

Observer's Synopsis

This shower's duration seems to persist from August 25 to September 6. Maximum occurs from RA=85 deg, DECL=+41 deg on September 1 (Solar Longitude=158 deg). The annual maximum ZHR may be as high as 9, but outbursts of over 30 occurred in 1935 and 1986.

History

The Alpha Aurigids were discovered by Cuno Hoffmeister and A. Teichgraeber (Sonneberg, Germany) on the night of August 31/September 1, 1935 (Solar Longitude=158 deg). The maximum hourly rate was reported as 30, while the radiant was determined as RA=84.2 deg, DECL=+42.0 deg. The meteors possessed an average magnitude of 2.62, while 74% of those brighter than magnitude 3.5 left trains. V. Guth immediately noted the similarity between this radiant and the predicted radiant of RA=90.2 deg, DECL=+39.3 deg for comet Kiess (1911 II).
In his 1948 book, Meteorstrome, Hoffmeister noted that the link with comet Kiess made the circumstances of the 1935 observations curious. He pointed out that the comet's orbit was nearly parabolic, making the shower's sudden appearance 24 years after its perihelion passage difficult to explain. Hoffmeister examined his own annual observations made near the end of August and in early September, and noted probable detections of this shower in 1911, 1929, and 1930. In the former year, 5 of the 55 meteors he had plotted on September 2 (Solar Longitude=159.2 deg) converged at RA=84 deg, DECL=+43 deg. During 1929, he found radiants of RA=85 deg, DECL=+38 deg on September 1 (Solar Longitude=158.1 deg), RA=87 deg, DECL=+38 deg on September 3 (Solar Longitude=159.8 deg), and RA=89 deg, DECL=+39 deg on September 4 (Solar Longitude=161.0 deg). In 1930, one radiant was found at RA=82 deg, DECL=+38 deg on August 31 (Solar Longitude=156.4 deg). Hoffmeister concluded that, although activity seems to have been present since the comet's perihelion passage, there is no evidence that the Alpha Aurigids are a permanent shower. He added that the strong 1935 shower was probably due to an isolated meteor group in the comet's orbit. Hoffmeister's conclusion seemed well founded, as additional observations failed to appear in the records of American, European, or Russian observers in the four decades following 1935, however, three significant observations have been made in recent years.
During 1979 and 1980 members of the Western Australia Meteor Section (WAMS) succeeded in observing the Alpha Aurigids. In the former year, observations were made over the period of August 25-September 2. Maximum activity came on September 2, when the ZHR reached 8.52+/-1.87 from a radiant of RA=87 deg, DECL=+42 deg. In 1980, observations were made during August 31-September 6. Maximum came on the 6th, when the ZHR reached 9.11+/-0.96, from RA=82 deg, DECL=+38 deg.
The latest detection of this shower came on September 1, 1986, when I. Tepliczky (Hungary) observed 24 meteors from RA=94 deg, DECL=+36.4 deg between 00:47 and 02:11 (UT). Around 01:25 (Solar Longitude=158.34 deg), the ZHR reached 39.6+/-8.1. The meteors ranged in brightness from magnitude -4 to +4, with an average of +0.5.

Orbit

The Author has determined the following average orbit from the six visual radiants listed in Hoffmeister's Meteorstrome and the two radiants given by the WAMS.
AOP AN i q e a
126.7 158.7 149.0 0.807 1.0 ---

The orbit of comet Kiess (1911 II) was calculated by Brian G. Marsden in 1978, and is

AOP AN i q e a
1911 II 110.4 158.0 148.4 0.684 0.996 184.6

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