Astrometric orbit for Gamma Cephei Ab

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Astrometric orbit for Gamma Cephei Ab

Post by Lazarus on 20th April 2018, 1:37 pm

Benedict et al. (2018) "A Mass for γ Cep Ab"

HST Fine Guidance Sensor results for Gamma Cephei. The planetary orbit has an inclination of 169.5 giving a true mass of 9.4 Jupiter masses. The mutual inclination with respect to the stellar orbit is around 70.

The mutual inclination exceeds the critical angle for Kozai oscillations. This would likely have implications for the stability of the system. If Kozai oscillations are occurring, it is interesting that we are observing the planetary orbit at such a low eccentricity.
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Re: Astrometric orbit for Gamma Cephei Ab

Post by Lazarus on 28th July 2018, 10:55 am

So finally got round to setting up integration for this system. Assuming I haven't made mistakes in the integrator, looks like the Kozai oscillations drive the eccentricity up to around 0.9, with a period of about 6000 years. Roughly 20% of the time is spent with eccentricities at or below the current value, so not massively unlikely to observe such a state.

It seems unlikely that any other planets could survive in the system.
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