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Astron. Astrophys. 335, 351-362 (1998)

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Orbital evolution of asteroidal fragments into the [FORMULA]6 resonance via Yarkovsky effects

D. Vokrouhlický 1 and P. Farinella 2

1 Institute of Astronomy, Charles University, V Holeovikách 2, CZ-180 00 Prague 8, Czech Republic (e-mail: vokrouhl@mbox.cesnet.cz)
2 Gruppo di Meccanica Spaziale, Dipartimento di Matematica, Università di Pisa, Via Buonarroti 2, I-56127 Pisa, Italy (e-mail: paolof@dm.unipi.it)

Received 28 September 1997 / Accepted 24 February 1998

Abstract

We analyze the dynamical evolution of asteroidal fragments released in the Flora region, near the inner edge of the main asteroid belt, and drifting into the [FORMULA] secular resonance due to Yarkovsky non-gravitational effects. We find that fragments 5 to 20 m in size evolve under the "seasonal" Yarkovsky effect which causes a secular semimajor axis decay; they reach [FORMULA] after a time shorter than their collisional lifetime when they start within about 0.05 to 0.2 AU out of the resonance. Metal-rich fragments drift slower but have have much longer lifetimes than stony ones, so they drift farther from their formation site and sample a wider portion of the inner belt. Fragments around 100 m in size are mainly influenced by the "diurnal" Yarkovsky effect if their surface is covered by a (thin) regolith layer; this causes a random walk in semimajor axis controlled by impacts which reorient the spin axis. Within their lifetime of [FORMULA] Myr these fragments can move throughout the inner part of the asteroid belt, episodically crossing [FORMULA]. Meter-sized stony fragments, which probably deliver most meteorite falls, may also drift into the resonance under the "diurnal" effect, provided their surfaces have low thermal conductivities and/or their rotation is unusually slow. According to our dynamical model, which is truncated to 15 degree in the fragment's orbital eccentricity, [FORMULA] resonance effects typically result into large eccentricity increases, such that main-belt orbits rapidly become Earth-crossing when the resonance is reached and/or crossed. This confirms the idea that the interplay of resonant dynamics and Yarkovsky-related semimajor axis mobility is crucial in the transport of meteorites and small near-Earth asteroids from the main asteroid belt to the near-Earth space.

Key words: celestial mechanics, stellar dynamics – minor planets, asteroids – meteors, meteoroids

Send offprint requests to: D. Vokrouhlický

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© European Southern Observatory (ESO) 1998

Online publication: June 12, 1998

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