Kepler-64 (KIC 4862625) - Circumbinary Planet in a Quadruple System (PH1)

A quadruple system with a transiting circumbinary planet.

Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System
http://arxiv.org/abs/1210.3612

Quote :

We report the discovery and confirmation of a transiting circumbinary planet (PH1) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ~137 days, with seven transits identified in Quarters 1-11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities and the Kepler light curve of KIC 4862625.The 6.18 $\pm$ 0.17 Earth radii planet orbits outside the 20-day orbit of an eclipsing binary consisting of an F dwarf (1.734 +/- 0.044 Solar radii, 1.528 +/- 0.087 Solar masses) and M dwarf (0.378 +/0 0.023 Solar radii, 0.408 +/- 0.024 solar masses). For the planet, we find an upper mass limit of 169 Earth masses(0.531 Jupiter masses) at the 99.7& confidence level. With a radius and mass less than that of Jupiter, PH1 is well within the planetary regime. Outside the planet's orbit, at ~1000 AU, a previously unknown visual binary has been identified that is bound to the planetary system, making this the first known case of a quadruple star system with a transiting planet.

Nice, been wondering if exoplanets would be found in systems with more than 3 stars.

The Ba/Bb binary seems quite wide (~60 AU), wonder if any S-type planets could have formed there, but I guess it's going to be hard to do an RV-search.

So what would the designation for the planet be - the paper seems to prefer to use PH1, but I guess it would be KIC 4862625 A(ab) b?

Wow. Noteworthy. Circumbinary planets are growing in number

Lazarus wrote:

So what would the designation for the planet be - the paper seems to prefer to use PH1, but I guess it would be KIC 4862625 A(ab) b?

I was wondering about that, too. I would use KIC 4862625 Ab or (A)b myself.

Right we've got a 4-star system with planets, now let's go do a deep-imaging search of Castor! We must have more multiplicity!

Lazarus wrote:

Right we've got a 4-star system with planets, now let's go do a deep-imaging search of Castor! We must have more multiplicity!

Haha

Independent discovery of KIC 4862625 and Kepler-47 systems:

A Gas Giant Circumbinary Planet Transiting an Evolved F Star Primary of the Eclipsing Binary Star KIC 4862625 and the Independent Discovery and Characterization of the two transiting planets in the Kepler-47 System
http://arxiv.org/abs/1210.3850

Great success of the Planet Hunters initiative, maybe in future transiting missions the sharing of data with the public will become the norm.

On the other hand circumbinary planets deserve a dedicated topic, they are a different class of planetary systems in every sense.

Lazarus wrote:

Right we've got a 4-star system with planets, now let's go do a deep-imaging search of Castor! We must have more multiplicity!

Well Castor System a 6 star system each group of the binary star by analogy of other circumbinary planetary systems can very possess they own planetary system,by the distance between stars in group can each of 3 binary star system have your own planetary system...

About deep-imaging search I don't know,but would be interesting search for planetary transit and TTV in the eclipsing binary system of Castor Ca and Cb,would be possible such study? if so would be a fascinating study on this 6 multiple star system personally my favorite

Daniel wrote:

About deep-imaging search I don't know,but would be interesting search for planetary transit and TTV in the eclipsing binary system of Castor Ca and Cb,would be possible such study? if so would be a fascinating study on this 6 multiple star system personally my favorite

Actually YY Geminorum (=Castor C) is one of the target systems for the DWARF project which aims to do just that...

Wow I can't wait the results, very interesting to know that Part of the Castor star system is now been search for planets

Well, once they claimed period change in the eclipsing pair YY Geminorum, indicative of the presence of a brown dwarf or a giant planet in 10 or more years orbit...

Lazarus wrote:

So what would the designation for the planet be - the paper seems to prefer to use PH1, but I guess it would be KIC 4862625 A(ab) b?

EPE decided that just 'b' was sufficient.
http://exoplanet.eu/catalog/kic_4862625_b/

Overview of the detection and confirmation of PH-1 on the Planet Hunters Blog

Part 1, Part 2, Part 3, Part 4

PH1 ABCD a should be named but because the first planet starts as b not a what is wrong in my opinion so PH1 ABCD b

Should it not be PH1 ABbCD? Did I get it wrong or does the planet go around only A and B and not ABC and D.

Just a thought.

If PH1 is the star's name, the designation could be PH1(AB) b. The CD pair has nothing to do with it (unless the planet orbited both pairs, in which case it would be PH1(ABCD) b).

The paper refers to the stars as AA, AB, BA and BB. So I would expect (AB)b to be a circumquartinary planet in this case.

Right jyril planet is not orbiting distant pair of stars only AB

Sirius_Alpha wrote:

The paper refers to the stars as AA, AB, BA and BB. So I would expect (AB)b to be a circumquartinary planet in this case.

I see. Don't stars in hierarchical binaries usually have lowercase letter designations (i.e. Aa+Ab, Ba+Bb?) In this case the planet would be PH1(AaAb)b. A planet around a single star would be PH1Aab... confusing.

PH1Ab where "A" refers to the binary doesn't work either because it mixes up with the designation of secondary companion of the primary binary star...

jyril wrote:

PH1Ab where "A" refers to the binary doesn't work either because it mixes up with the designation of secondary companion of the primary binary star...

That's why I propose PH1 (A)b. If we denote circumbinary planets by placing the host star(s) in parentheses, then either PH1 (A)b or PH1 (AA,AB)b would work.

jyril wrote:

Don't stars in hierarchical binaries usually have lowercase letter designations (i.e. Aa+Ab, Ba+Bb?)

I've seen it both ways, but I think it would be confusing to start using lower-case letters for stars when planets already use them.

jyril wrote:

I see. Don't stars in hierarchical binaries usually have lowercase letter designations (i.e. Aa+Ab, Ba+Bb?)

Yes, the paper uses these Aa/Ab, Ba/Bb. This is the normal binary star convention, which would be even more confusing to change. Planet designations can be viewed as being part of this system with an implied "A", as described here.

I'm not such a fan of using (A), here's why: suppose we find another star in the system converting the A subsystem into a triple:

((Aa-Ab)-Ac)-(Ba-Bb)

The designation then has to reflect the fact the planet orbits Aa and Ab but not Ac.

My preference is A(ab)b for the planet, it indicates which stars are orbited, doesn't needlessly repeat the fact that the planet is in the A subsystem, and is stable if an outer stellar companion is found in the A subsystem.

If on the other hand we find that star Ab is binary, for example:

(Aa-(Ab1-Ab2))-(Ba-Bb)

The designation will still reflect the hierarchy of the system.

Good point about the (A)b idea. I hadn't thought of that.

PH1= Kepler-64b

Kepler Mission Manager Update

http://www.nasa.gov/mission_pages/kepler/news/keplerm-20121026.html

Oh, nice. It was getting difficult to memorize that ID