32 planets from HARPS

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Re: 32 planets from HARPS

Post by Sirius_Alpha on 16th February 2011, 8:38 pm

Red dwarfs are something like ≥ 80 - 100 MJ.

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Re: 32 planets from HARPS

Post by Edasich on 17th February 2011, 5:58 am

Preprint

http://arxiv.org/abs/1102.3372

And the worst is we're likely going to lo lose another one or two. HD 195019 b would be a star and HD 81040 b another brown dwarf. On the other hand Rho1 Cancri d's "planethood" seems not to be discussed.
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Re: 32 planets from HARPS

Post by Lazarus on 17th February 2011, 8:13 am

I guess the early results from astrometric analyses will contain more cases where planet candidates turn out to be brown dwarfs or stars, because these are easier to detect via astrometry and will thus give more certainty about the results.

As for 55 Cnc d it has the advantage of being a member of a planetary system (so if it turns out to be 20 Jupiter masses that would be strong evidence in favour of deuterium-fusing planets), and the current data suggests a mass in the non-fusion domain anyway...
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Re: 32 planets from HARPS

Post by Edasich on 17th February 2011, 2:29 pm

However are we sure astrometry is really an attendible tool to determine true masses?

I remember of VB 10 where it claimed to find something massive and then nothing actually...
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Re: 32 planets from HARPS

Post by Sirius_Alpha on 17th February 2011, 2:33 pm

It's just as good a tool to measure mass as radial velocity is a tool to measure the orbital period.

Both detection methods will suffer if you don't have adequate data or aren't sampling around the orbital period very well.

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Re: 32 planets from HARPS

Post by Lazarus on 17th February 2011, 6:02 pm

I don't see why a few spurious results should cast the entire technique into doubt. Astrometry is already well-established for the study of binary stars, this is essentially an extension of that to more extreme mass ratios.

There is also the point that this is not a search for new planets, but attempting to detect already-known examples. You therefore have the advantage of knowing the orbital period, phase, eccentricity and argument of pericentre from the radial velocity measurements, so you will have a good idea of whether you are detecting the orbit or not.
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Re: 32 planets from HARPS

Post by Sirius_Alpha on 5th May 2011, 9:08 pm

Edasich wrote:A second (unconfirmed) planet pops up around HIP 5158:
http://exoplanet.eu/star.php?st=HIP+5158

HIP 5158 c is now confirmed, though the parameters are rather unconstrained.

Bayesian evidence for two companions orbiting HIP 5158
http://arxiv.org/abs/1105.1150

We present results of a Bayesian analysis of radial velocity (RV) data for the star HIP 5158, confirming the presence of two companions and also constraining their orbital parameters. Assuming Keplerian orbits, the two-companion model is found to be e^{48} times more probable than the one-planet model, although the orbital parameters of the second companion are only weakly constrained. The derived orbital periods are 345.6 +/- 2.0 d and 9017.8 +/- 3180.7 d respectively, and the corresponding eccentricities are 0.54 +/- 0.04 and 0.14 +/- 0.10. The limits on planetary mass (m \sin i) and semimajor axis are (1.44 +/- 0.14 M_{J}, 0.89 +/- 0.01 AU) and (15.04 +/- 10.55 M_{J}, 7.70 +/- 1.88 AU) respectively. Owing to large uncertainty on the mass of the second companion, we are unable to determine whether it is a planet or a brown dwarf. The remaining `noise' (stellar jitter) unaccounted for by the model is 2.28 +/- 0.31 m/s. We also analysed a three-companion model, but found it to be e^{8} times less probable than the two-companion model.

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Re: 32 planets from HARPS

Post by Lazarus on 8th May 2011, 7:46 am

Have to wonder how these systems with inner eccentric giants but outer near-circular Jupiter-analogues (23 Librae being another example) get that way...
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Re: 32 planets from HARPS

Post by Sirius_Alpha on 8th May 2011, 9:32 am

Similarly, Mercury is much more eccentric than the other inner planets.
Perhaps in cases like HIP 5158 and 23 Lib, some differential migration occurs. The outer planet doesn't come inward much, but inner planets do migrate further inward significantly. This can lead to scattering down the road if they get too near each other. I suppose under this idea, 55 Cancri would be a system whose inner migraters didn't scatter. If so, I'd expect the gap between f and d (and between these inner eccentric planets and their outer Jupiter-analogues for systems like like HIP 5158 and 23 Lib) to be fairly clear of planets.

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Re: 32 planets from HARPS

Post by tommi59 on 9th May 2011, 4:00 am

I can not fully agree because in HIP 5158 system is brown dwarf on eccentric orbit causing big disruption in that system.55 cancri d orbit is circular and is some space for stable orbit between f and d. It does mean any planet between d and f is much more likely than between b and c in HIP5158..Personally I think there is one planet.
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Re: 32 planets from HARPS

Post by Lazarus on 5th July 2011, 12:55 am

HD 63765b, HD 104067b, HD 125595b and HIP 70849b

The HARPS search for southern extrasolar planets. XXV. Four new planets in orbit around the moderatly active dwarfs HD 63765, HD 104067, HD 125595, and HIP 70849

A planet around HD 9578 was mentioned in the original message but appears not to be in this paper...

Table updated
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Re: 32 planets from HARPS

Post by Edasich on 5th July 2011, 3:20 am

Well, at last! Now there area only GJ 433 and 667 C left to be released (+ HD 9578 then).
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Re: 32 planets from HARPS

Post by Lazarus on 5th July 2011, 3:45 pm

Yes it has been a while hasn't it, starting to close in on 2 years since the press release.

Personally I'm wondering when there will be a publication of the Gliese 581 update...
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Re: 32 planets from HARPS

Post by lodp on 11th July 2011, 8:31 pm

Then they go and issue "The HARPS search for southern extrasolar planets. XXX"! (Several Papers yet to come?) - See arxiv.

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Re: 32 planets from HARPS

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