Multiple Planets at GJ 676A

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Multiple Planets at GJ 676A

Post by Sirius_Alpha on 1st July 2012, 8:16 pm

A planetary system with gas giants and super-Earths around the nearby M dwarf GJ 676A. Optimizing data analysis techniques for the detection of multi-planetary systems
http://arxiv.org/abs/1206.7118

Several M dwarfs are targets of systematical monitoring in searches for Doppler signals caused by low mass exoplanet companions. As a result, an emergent population of high multiplicity planetary systems around low mass stars starts to show up as well. We optimize classic data analysis methods and develop new ones to enhance the sensitivity towards lower amplitude planets in high multiplicity systems. We re-derive Doppler measurements from public HARPS spectra of GJ 676A using the recently developed template matching method (HARPS-TERRA software). We use refined versions of periodograms to assess the presence of additional low mass companions. We also analyse the same dataset using Bayesian statistics tools and compare the performance of both methods. We confirm the known massive gas giant candidate and the presence of a trend in the RVs. In addition to that, we find very secure evidence in favor of two new candidates in close-in orbits and masses in the super-Earth mass regime. Also, the increased time-span of the observations allows the detection of curvature in the ltrend suggesting the presence of a massive outer companion whose nature is still unclear. Even though the increased sensitivity of our new periodogram tools, we find that Bayesian methods are significantly more sensitive and reliable in the early detection of candidate signals but more works is needed to properly quantify their robustness against false positives. These new planetary system holds the record of minimum mass range (from 4.5Me to 5 Mjup) and period range (from 3.6 days to more than 10 years), being the first exoplanetary system with a general architecture similar to our Solar System. GJ 676A can be happily added to the family of high multiplicity planetary systems around M dwarfs.

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Re: Multiple Planets at GJ 676A

Post by Daniel on 2nd July 2012, 1:54 pm

the EPE it's too lazy to update this new planets in this days...
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Re: Multiple Planets at GJ 676A

Post by Sirius_Alpha on 2nd July 2012, 2:49 pm

Schneider could be away. He's a human with his own life to tend to like the rest of us.

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Re: Multiple Planets at GJ 676A

Post by Daniel on 2nd July 2012, 3:09 pm

Yeah I would agree with you,but it's happen often many times, normally not long ago,he leave a warning that will update it in some date in the future

Is there any problem to question this odd things that happen in the EPE? or he is some kind of god that can't be questioning?

like you said he is only human a scientist,and we can question him and the EPE mistakes
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Re: Multiple Planets at GJ 676A

Post by Lazarus on 2nd July 2012, 5:03 pm

Remember he is providing this stuff for free, he is not obligated to follow your demands at all unless you have some kind of contract with him. Why exactly do you feel entitled to make demands?

EPE has no real official status in the way that e.g. the IAU does. If you feel you can do better by all means feel free to make your own website.
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Re: Multiple Planets at GJ 676A

Post by Daniel on 2nd July 2012, 5:09 pm

Just Ask now is make Demands... alright we can't asking,questioning anything more, people take as offence on this days

And by the way sorry for my ignorance, for me EPE was like IAU, something official
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Re: Multiple Planets at GJ 676A

Post by tommi59 on 3rd July 2012, 2:48 am

He is on holiday besides these planets are confirmed or not?
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Re: Multiple Planets at GJ 676A

Post by jyril on 3rd July 2012, 2:51 am

EPE has been something like a hobby for Schneider since the spring of 1995, before the discovery of 51 Pegasi b. How many of us can boast having a useful website so long?

Remember the number of extrasolar planet discoveries are growing rapidly, which also means much more work.

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Re: Multiple Planets at GJ 676A

Post by Sirius_Alpha on 5th July 2012, 11:39 pm

Schneider may not have read the same paper we did.
http://exoplanet.eu/star.php?st=GJ+676A

He lists the b planet as unconfirmed and only shows three planets.

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Re: Multiple Planets at GJ 676A

Post by Lazarus on 6th July 2012, 2:01 am

Also the d and e planets are not actually in the catalogue list, looks like whatever is used to make the planets appear in the lists has not been switched on for recently-added planets.
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Re: Multiple Planets at GJ 676A

Post by Sirius_Alpha on 2nd August 2016, 8:25 pm

The mass of planet GJ676A b from ground-based astrometry: A planetary system with two mature gas giants suitable for direct imaging
http://arxiv.org/abs/1608.00918

GJ676A is an M0 dwarf hosting both gas-giant and super-Earth-type planets discovered with radial-velocity measurements. Using FORS2/VLT, we obtained position measurements of the star in the plane of the sky that tightly constrain its astrometric reflex motion caused by the super-Jupiter planet `b` in a 1052-day orbit. This allows us to determine the mass of this planet to Mb=6.7+1.8−1.5MJ, which is ∼40 \% higher than the minimum mass inferred from the radial-velocity orbit. Using new HARPS radial-velocity measurements, we improve upon the orbital parameters of the inner low-mass planets `d` and `e` and we determine the orbital period of the outer giant planet `c` to Pc=7340 days under the assumption of a circular orbit. The preliminary minimum mass of planet `c` is Mcsini=6.8MJ with an upper limit of ∼39MJ that we set using NACO/VLT high-contrast imaging. We also determine precise parallaxes and relative proper motions for both GJ676A and its wide M3 companion GJ676B. Despite the probably mature age of the system, the masses and projected separations (∼0.1" -- 0.4") of planets `b` and `c` make them promising targets for direct imaging with future instruments in space and on extremely large telescopes. In particular, we estimate that GJ676A b and GJ676A c are promising targets for directly detecting their reflected light with the WFIRST space mission. Our study demonstrates the synergy of radial-velocity and astrometric surveys that is necessary to identify the best targets for such a mission.

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Re: Multiple Planets at GJ 676A

Post by Lazarus on 3rd August 2016, 1:31 pm

Nice result, always good to have the sin(i) pinned down. Seems there may be some doubts about planet "e", possibly an artefact of stellar rotation?
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Re: Multiple Planets at GJ 676A

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