A 2004 Geminid meteor spectrum in the visible–ultraviolet region - Extreme Na depletion?

Free access article

Issue		A&A Volume 438, Number 2, August I 2005


Page(s)		L17 - L20
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:200500142

A&A 438, L17-L20 (2005)
DOI: 10.1051/0004-6361:200500142

Letter

A 2004 Geminid meteor spectrum in the visible-ultraviolet region

Extreme Na depletion?

T. Kasuga^{1, 2}, J. Watanabe² and N. Ebizuka³

¹ Department of Astronomical Science, School of Physical Science, The Graduate University for Advanced Studies (Sokendai), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
    e-mail: kasugats@cc.nao.ac.jp
² National Astronomical Observatory of the Japan (NAOJ), National Institute of Natural Science, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
    e-mail: jun.watanabe@nao.ac.jp
³ RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan
    e-mail: ebizuka@riken.go.jp

(Received 8 March 2005 / Accepted 4 June 2005)

Abstract
This paper shows the first result of a Geminid meteor spectrum in the visible-ultraviolet region. Wavelengths between 300-600 nm were observed on the meteor which appeared at $17^{\rm h} 41^{\rm m} 24^{\rm s}$ UT on 2004 December 14, and strong emissions of neutral atoms such as mainly MgI, FeI, CaI and NaI were identified. The abundances of metallic atoms and their excitation temperature were obtained on the assumption that a Boltzmann distribution for the population of each energy level.

The results suggest the possibility that the abundances of Geminid meteors are slightly different from solar abundances. Na/Mg = 0.0036 $\pm$ 0.0005, which is much lower than other meteor showers. On the other hand, the Ni/Mg ratio is 0.078 $\pm$ 0.012, which is larger than solar abundance, and that of meteors of other showers. Extreme Na depletion, and moreover, excess Ni are derived for a Geminid meteor. The excitation temperature value, 4640.6 $\pm$ 1.5 K is consistent with their moderate velocity.

Key words: ultraviolet wavelength region -- Geminid meteor spectrum -- solar abundance -- 3200 Phaethon

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