Hot/Warm Jupiter formation, effects on planetary systems

Investigating whether it is possible that the observed hot and warm Jupiters actually formed in situ rather than migrating inwards.

A. C. Boley, A. P. Granados Contreras, B. Gladman "The In Situ Formation of Giant Planets at Short Orbital Periods"
http://arxiv.org/abs/1510.04276

A second study of hot Jupiter formation in the inner regions of planetary systems, instead of via planet migration from beyond the ice line.

Batygin, Bodenheimer & Laughlin "In Situ Formation and Dynamical Evolution of Hot Jupiter Systems"
http://arxiv.org/abs/1511.09157

There's also an accompanying Oklo.org post.
http://oklo.org/2015/11/30/how-did-they-get-there/

Warm Jupiters are less lonely than hot Jupiters: close neighbours
http://arxiv.org/abs/1601.05095

Quote :

Exploiting the Kepler transit data, we uncover a dramatic distinction in the prevalence of sub-Jovian companions, between systems that contain hot Jupiters (periods inward of 10 days) and those that host warm Jupiters (periods between 10 and 200 days). Hot Jupiters as a whole, with the singular exception of WASP-47b, do not have any detectable inner or outer planetary companions (with periods inward of 50 days and sizes down to 2REarth). Restricting ourselves to inner companions, our limits reach down to 1REarth. In stark contrast, half of the warm Jupiters are closely flanked by small companions. Statistically, the companion fractions for hot and warm Jupiters are mutually exclusive, in particular in regard to inner companions.
The high companion fraction of warm Jupiters also yields clue to their formation. The warm Jupiters that have close-by siblings should have low orbital eccentricities and low mutual inclinations. The orbital configurations of these systems are reminiscent of those of the low-mass, close-in planetary systems abundantly discovered by the Kepler mission. This, and other arguments, lead us to propose that these warm Jupiters are formed in-situ. There are indications that there may be a second population of warm Jupiters with different characteristics. In this picture, WASP-47b could be regarded as the extending tail of the in-situ warm Jupiters into the hot Jupiter region, and does not represent the generic formation route for hot Jupiters.

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:

Quote :

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

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

Quote :

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.

A possible explanation for why hot Jupiters typically don't seem to have close companions: secular resonance involving the stellar quadrupole moment tends to result in the systems becoming misaligned (possibly with the result of destabilising additional nearby planets).

Spalding & Batygin "A Secular Resonant Origin for the Loneliness of Hot Jupiters"
https://arxiv.org/abs/1707.06370

(Wasn't sure whether to put this in this thread or this one, maybe worth merging them and possibly also this one too?)

Good idea. Definitely helps clean up the clutter! Merged.