Additional giant planets in hot Jupiter systems

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Additional giant planets in hot Jupiter systems

Post by Lazarus on 13th April 2016, 5:08 pm

Possibly some more evidence towards disc migration or in situ formation of hot Jupiter planets?

Schlaufman & Winn "The Occurrence of Additional Giant Planets Inside the Water-Ice Line in Systems with Hot Jupiters: Evidence Against High-Eccentricity Migration"
http://arxiv.org/abs/1604.03107

From the abstract:
Using the current sample of giant planets discovered with the Doppler technique, we find that hot Jupiters with Porb < 10 days are no more or less likely to have exterior Jupiter-mass companions than longer-period giant planets with Porb ≥ 10 days. This result holds for exterior companions both inside and outside of the approximate location of the water-ice line.

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Re: Additional giant planets in hot Jupiter systems

Post by Shellface on 13th April 2016, 7:01 pm

(Don't think that title fits the paper, there's no new planets here)

Possibly some more evidence towards disc migration or in situ formation of hot Jupiter planets?
Mleh. That's not exactly what you should take from this, because evidence against one hypothesis is not strictly evidence for a competing one. The, eh, "proper" conclusion is that this is (fairly strong) evidence against planet-planet scattering as a significant/dominant route of formation for Hot Jupiters, and this is in turn consistent with the other models.

Pedantry aside, this is pretty interesting. Planet-planet scattering is something that has never previously had much evidence either for or against, but this and the lack of young, eccentric, intermediate period planets observed by Kepler (I forget the relevant paper) seem to clearly lean towards against.

It's both amusing and admirable that the authors chose to use simple statistical notation. Astrophysicists seem to have sub-par statistical skills overall (at least, statiscians keep saying that), so this is probably for the best.

It's also amusing that one can still find frequent references as to how Hot Jupiters are supposedly "lonely" in modern literature, despite several recent papers showing that additional companion rates for such systems is, at the least, moderate. If the extra giant planet rate for Hot Jupiters and, uh, Non-Hot Jupiters are compatible (as shown here), then by what metric are Hot Jupiters "lonely"? They certainly are if one considers low-mass, close in planets, but that is a natural result from all commonly proposed formation models for HJs, and the rarity of such systems should not really be of note by this point. Concerning only giant planets, Hot Jupiters appear no more lonely than any other type of giant planet; they are, at most, more well-spaced than multiple giant planet systems of longer period. Perhaps, then, it is merely observation bias that has caused this (apparent) misconception.

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