DPS Pasadena Meeting 2000, 23-27 October 2000
Session 31. Extra-Solar Planets
Oral, Chairs: W. Cochran, G. Wuchterl, Wednesday, 2000/10/25, 10:30am-12:10pm, Little Theater (C107)

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[31.07] Stability of the Upsilon Andromedae System. II: Simulations Using the New Lick Observatory Fits

E. J. Rivera (NASA Ames & SUNY Stony Brook), J. J. Lissauer (NASA Ames)

We present results of long-term numerical orbital integrations designed to test the stability of the three-planet system orbiting \upsilon Andromedae. Our initial conditions are based on the February 2000 and July 2000 fits to the radial velocity data obtained by the Marcy-Butler-Fischer planet-search group at Lick Observatory. In comparison with the fit they presented last year (Butler et al. 1999, ApJ 526, 916), the fit for the outer planet has significantly changed; the eccentricity has changed from 0.36 to 0.31 to 0.35 and the period has increased from 1269 to 1309 to 1313 days. Assuming that the middle planet is inclined by 1\circ with respect to the plane containing the other two bodies, we multiplied the planetary masses by some mass factor mf \equiv 1/\sin{i}. Our integrations involving all three planets show that the system is typically stable for at least 100 Myr for mf \le 4 for the February 2000 fit. Systems based on the July 2000 fit are stable for at least 50 Myr for mf \le 2.5. In comparison, our analysis using the initially announced observed orbital elements (Rivera & Lissauer 2000, ApJ 530, 454), resulted in analogous systems which became unstable on time scales less than 1 Myr for mf \ge 2.25. We observed a secular resonance between the outer two planets in both our previous and current analyses.

This research was supported in part by NASA's OSSRP under grant NAG 5-9680.

The author(s) of this abstract have provided an email address for comments about the abstract: rivera@epimethius.arc.nasa.gov

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