Additional Planets at WASP-47

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Additional Planets at WASP-47

Post by Sirius_Alpha on 11th August 2015, 8:35 pm

A super-earth and a Neptune at WASP-47.
http://arxiv.org/abs/1508.02411

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Re: Additional Planets at WASP-47

Post by Lazarus on 12th August 2015, 2:23 am

Well that's new: WASP-47b seems like a rather typical hot Jupiter, and given the lack of nearby companions to HJs so far, this seems quite unexpected. Implications for HJ migration mechanisms?
This compact set of planets in nearly circular, coplanar orbits demonstrates that at least a subset of Jupiter-size planets can migrate in close to their host star in a dynamically quiet manner.
Presumably this system will end up getting a K2 number in due course.
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Re: Additional Planets at WASP-47

Post by tommi59 on 12th August 2015, 5:44 am

Of course it will get K2 number and is really surprising .Mass of the inner planet 1.817 earth radius is less than 8.9 earth mass but being so close to host surely planet has no volatiles and for sure is rocky with mass at least 7.5 earths.I wonder what results would bring exploring other WASP, HAT and COROT planets
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Re: Additional Planets at WASP-47

Post by Shellface on 12th August 2015, 1:51 pm

Huzzah!

This was something picked out by Hans, a Planet Hunters member, in the raw K2 data. It got picked up by Vanderburg (who does the lightcurve processing), and then after some consultation it got quickly analysed and written up in just over a week. They were quite devoted to being firt to the call, I guess. I did have some minor input (I was first to point out that the star was WASP-47), but nothing much.

At first, I was skeptical that the extra signals were real. b appears to be a completely normal clump Hot Jupiter, and for all of those found by K1, none of them show any extra signals as here. However, everything seemed fine after detrending, and the professionals agreed that they looked bona-fide. One must wonder, then, why such systems are so rare…

c appears to be quite similar to 55 Cancri e, to the extent that they ought to have similar abundances as they both orbit super-metal-rich stars. If they were to have similar densities, then c's RV semi-amplitude would be ~7 m/s, which is definitely achievable with current spectrographs. d would be difficult, with a semi-amplitude of ~3 m/s, but improving the TTV mass measurement is certainly a possibility - indeed, I expect that a combined RV + TTV analysis would be highly applicable to this system.

Anyway… this is a very interesting system, and it will likely be seeing a fair bit of attention in the near future. It'll probably be one of K2's most remarkable discoveries, as well.

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Re: Additional Planets at WASP-47

Post by Lazarus on 12th August 2015, 2:55 pm

Quite a change from the WASP-47b discovery paper, which it shared with six other systems. In that paper, the section dedicated to the system was all of two paragraphs long, of which the first was a brief summary of stellar properties and the second consisted of the following sentence:
With an orbital period of 4.16 d, a mass of 1.14 MJup and a radius of 1.15 RJup WASP-47b is an entirely typical hot Jupiter.
There were 19 RVs and it isn't clear how many transits were observed. I have to wonder how many similar systems are hiding in sparse RV data and small transit sets, particularly if they are typically more misaligned than the WASP-47 configuration and/or produce weaker TTVs.
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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 12th August 2015, 4:06 pm

Whenever we come across a system like this, I always keep in mind a sort of anthropic principle: There are going to be outliers, and no single outlier is necessarily cause to reexamine planet formation mechanisms. WASP-47's unusual set-up may be a fluke, which is why nothing similar was found in the Kepler dataset. It's worth noting that the system is generally similar to the inner planetary system at 55 Cancri.

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Re: Additional Planets at WASP-47

Post by tommi59 on 18th September 2015, 4:14 am

I am not sure if anybody noticed but we have another gas giant planet in this system with 571 days period
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Re: Additional Planets at WASP-47

Post by tommi59 on 18th September 2015, 4:18 am

http://www.iap.fr/col2015/talks/wednesday/neveu_vanmalle.pdf
Quite curious paper .Hot Jupiters have siblings another example besides WASP 47 is WASP-41


Last edited by tommi59 on 18th September 2015, 9:11 am; edited 1 time in total
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Re: Additional Planets at WASP-47

Post by Stalker on 18th September 2015, 7:33 am

tommi59 wrote:I am not sure if anybody noticed but we have another gas giant planet in this system with 571 days period
Hu?

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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 18th September 2015, 9:05 am

The b-planet is well aligned.
http://arxiv.org/abs/1509.05337

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Re: Additional Planets at WASP-47

Post by Lazarus on 18th September 2015, 12:33 pm

That 571-day period for WASP-47 looks interesting but the phase coverage isn't ideal. Interesting configuration if real though.

EDIT: though apparently there's a forthcoming paper about it (a submitted paper by Neveau-VanMalle et al. is mentioned in the Sanchis-Ojeda et al. paper)
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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 27th September 2015, 11:23 pm


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Re: Additional Planets at WASP-47

Post by Edasich on 28th September 2015, 12:14 pm

Sirius_Alpha wrote:Here's the paper.
http://arxiv.org/abs/1509.07750

Well, so does WASP-41 harbour a multiplanet system:

http://exoplanet.eu/catalog/wasp-41_c/

Glad to see the number of transiting exoplanet hosts with additional planets/(sub)stellar companions increase. Smile
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Re: Additional Planets at WASP-47

Post by Lazarus on 29th September 2015, 2:41 pm

Looks like WASP-47couter is in the HZ (WASP-47cinner definitely isn't), though probably not a good candidate for sufficiently massive satellites to maintain habitable conditions. Have to wonder what (if anything) is in the gap between the outer two planets...
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Re: Additional Planets at WASP-47

Post by Stalker on 30th September 2015, 3:06 am

Should'nt we change the title?

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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 30th September 2015, 11:28 am

What to?

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Re: Additional Planets at WASP-47

Post by Lazarus on 13th October 2015, 4:31 pm

The original paper has now been updated to version 2, and the planets redesignated.
http://arxiv.org/pdf/1508.02411v2.pdf

The 0.8-day planet is now WASP-47e, while the 9-day planet is WASP-47d.
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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 14th October 2015, 12:01 am

Doppler spectroscopy masses for all three inner planets.
http://arxiv.org/abs/1510.03811

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Re: Additional Planets at WASP-47

Post by Lazarus on 14th October 2015, 3:24 pm

So WASP-47e turns out to be a 1.8 Earth radii rocky planet, which is consistent with there being a dependence of the super-Earth/sub-Neptune transition on the incident flux.
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Re: Additional Planets at WASP-47

Post by Edasich on 14th October 2015, 4:18 pm

WASP-47 e appears a "cannonball" with nearly 1.5 times the gravity of Jupiter then, whereas WASP-47 d is a lesser gas giant with gravity lower than the Earth, more similar to Uranus or Neptune. Really an interesting system, somehow vaguely similar to Rho1 Cancri. I wonder if other WASP transiting planet hosts are harbouring multiplanet systems as much peculiar.

I'm thinking of WASP-3, 4, 5 and 10 with controversial transit timing variations and so are WASP-8 Ab, 22 and 34 b suspected to host long-period substellar companions, likely massive gas giants.
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Re: Additional Planets at WASP-47

Post by Lazarus on 24th October 2016, 3:43 pm

New paper about the system up on A&A forthcoming: Almenara et al. (2016) "Absolute densities, masses, and radii of the WASP-47 system determined dynamically"

Orbital eccentricity of c seems to be slightly higher but still consistent with the previous results. Planet e appears to be a massive rocky planet, again confirming previous results for the system.
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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 31st October 2016, 10:09 pm


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Re: Additional Planets at WASP-47

Post by Sirius_Alpha on 15th December 2016, 9:52 pm

Updated parameters and formation hypotheses.

Mass Constraints of the WASP-47 Planetary System from Radial Velocities
https://arxiv.org/abs/1612.04851

Mass and Eccentricity Constraints in the WASP-47 Planetary System from a Simultaneous Analysis of Radial Velocities & Transit Timing Variations
https://arxiv.org/abs/1612.04856

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Re: Additional Planets at WASP-47

Post by Lazarus on 3rd October 2017, 3:23 pm

Vanderburg et al. "Precise Masses in the WASP-47 System"
https://arxiv.org/abs/1710.00026

The mass of WASP-47e is decreased relative to previous estimates (see the discussion in section 3.4), the composition is now inconsistent with being Earthlike at approximately 3.3-sigma. While it could be a rocky planet with an extremely low iron fraction, this seems unlikely given the high [Fe/H] of the star, so like 55 Cnc e it likely has a volatile-rich envelope.
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