Fourth Planet at Upsilon Andromedae

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Fourth Planet at Upsilon Andromedae

Post by Edasich on 2nd December 2010, 4:42 am

ArxiV seems offline, but A&A displays this as highlighted content

A fourth planet orbiting υ Andromedae

We present a 4-planet Keplerian fit for the radial velocity curve of the F8V star υ Andromeda, indicating the presence of a fourth planet in the system. We detect an additional fifth coherent signal in the radial velocity curve which we attribute to stellar activity. The discovery of a new planet around υ Andromedae makes this system the fifth to contain, at least, four planets. These four planets have minimum masses of 0.69, 1.98, 4.13 and 1.06 MJup and orbital periods of 4.62, 241.26, 1276.46 and 3848.9 days, respectively. We have numerically integrated the orbital solution for these four planets and find that the system is stable for at least 10 Myr. The orbit of the fourth planet coincides with an island of stability reported by Rivera & Haghighipour (2007, MNRAS, 374, 599). We find that the characteristics of the new fourth planet are very similar to those of Jupiter and that the planets in this system have very strong interactions with each other. As previously found, υ Andb and υ Andc are in apsidal alignment, while the orbit of the new planet (υ Ande) is close to an external 3:1 resonance with υ Andc.

M4=1.059 Mj, a=5.24588 AUs, e=0.005. Quite Jupiter-like.

Also masses of inner planets seem not revised according to McArthur et al. (2010), giving c as 1.98 Mj and d as 4.13 Mj planets.

Detected also fifth signal (183 days), but likely due to stellar activity.

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Re: Fourth Planet at Upsilon Andromedae

Post by Lazarus on 2nd December 2010, 4:45 am

If you have signed up to the A&A EDPS service (which is free), you can download this article under the "latest articles free" service.

Interestingly enough, absolutely no reference is made to the astrometric results and it appears the system is being treated as coplanar with true masses being the minimum masses.

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Re: Fourth Planet at Upsilon Andromedae

Post by Sirius_Alpha on 15th August 2011, 8:19 pm

Dynamical Analysis of the 3:1 Resonance in the upsilon-Andromedae System
http://arxiv.org/abs/1108.2736

We study the dynamics of the upsilon-Andromedae planetary system proposed by Curiel et al. (2011). We focus on the study of the 3:1 Mean Motion Resonance between upsilon-Andromedae-d and the recently discovered upsilon-Andromedae-e (hereafter upsilon-And-d and upsilon-And-e). Numerical simulations of the dynamics of the four planet system are conducted. The previously reported apsidal resonance between upsilon-And-c and upsilon-And-d is confirmed. In addition, we find that upsilon-And-d and upsilon-And-e are also in an apsidal resonance condition. Our results further indicate that the upsilon-Andromedae planetary system configuration is in the middle of a stability island in the semimajor axis-eccentricity domain. Additionally, we performed numerical integrations of the planetary configuration over 500 Myr and found it to be stable. We conclude that, within the uncertainties in the value of the orbital parameters, it is likely that upsilon-Andromedae planetary system will remain stable for a long timescale.

Resonances in a system that has evidence of scattering... hmm....

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Re: Fourth Planet at Upsilon Andromedae

Post by Lazarus on 16th August 2011, 2:45 am

Not entirely sure what the point of this analysis is. The system is treated as coplanar with masses equal to the radial velocity minimum masses. The astrometric results from McArthur et al. (2011) are not mentioned, indeed that paper is not even in the references list.

Given the astrometric analysis gives much larger mass values for the planets, inverts the mass hierarchy of planets c and d, and alters the apsidal alignment, taking this into account would probably have a significant effect on the conclusions about the system dynamics.

Still waiting for an analysis of the four-planet system with the astrometry taken into account...

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