Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

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Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Post by Sirius_Alpha on 9th December 2008, 9:05 pm

Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Abstract wrote:We present the latest velocities for 10 multi-planet systems, including a re-analysis of archival Keck and Lick data, resulting in improved velocities that supersede our previously published measurements. We derive updated orbital fits for ten Lick and Keck systems, including two systems (HD 11964, HD 183263) for which we provide confirmation of second planets only tentatively identified elsewhere, and two others (HD 187123, and HD 217107) for which we provide a major revision of the outer planet's orbit. We compile orbital elements from the literature to generate a catalog of the 28 published multiple-planet systems around stars within 200 pc. From this catalog we find several intriguing patterns emerging: - Including those systems with long-term radial velocity trends, at least 28% of known planetary systems appear to contain multiple planets. - Planets in multiple-planet systems have somewhat smaller eccentricities than single planets. - The distribution of orbital distances of planets in multi-planet systems and single planets are inconsistent: single-planet systems show a pile-up at P ~ 3 days and a jump near 1 AU, while multi-planet systems show a more uniform distribution in log-period. In addition, among all planetary systems we find: - There may be an emerging, positive correlation between stellar mass and giant-planet semi-major axis. - Exoplanets more massive than Jupiter have eccentricities broadly distributed across 0 < e < 0.5, while lower-mass exoplanets exhibit a distribution peaked near e = 0.

It's interesting that they suggest an eccentricity of 55 Cnc e of 0.264, and for 55 Cnc f, an eccentricity of zero.

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Re: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Post by Edasich on 10th December 2008, 6:36 am

Updated yes, new no. Except for HD 183263c.
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Re: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Post by Lazarus on 10th December 2008, 4:11 pm

Well HD 183263c does make it a new multi-planet system, no?

Regarding the 55 Cnc system, the data is from the Newtonian fit in the discovery paper for the fifth planet (table 4).

What's weird is the way that the orbital parameters of the Mu Arae planets are taken from two contradictory references: the outer two planets are taken from the eccentric solution, the inner two planets are taken from the more circular 4-planet solution.
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Re: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Post by Lazarus on 14th December 2008, 2:37 pm

Also, so much for the third planet in HD 11964...
Gregory (2007) also noted the 38 d period in a Bayesian periodgram of the published velocities (as well as a 360 d signal which is not apparent in the re-reduced data presented here).
(btw since you didn't include the link to the paper in the original post, here it is)
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Re: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Post by Sirius_Alpha on 14th December 2008, 7:06 pm

Oh, wow. Thanks. A completely mindless mistake on my part.

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Re: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

Post by Lazarus on 18th December 2008, 6:52 am

Also note the reference to a forthcoming paper about 47 UMa, which is presumably the source of the parameters that currently appear on CNE and EPE... yet more re-reduced data.
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Re: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

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