Extrasolar binary planets

Ochiai, Nagasawa & Ida "Extrasolar Binary Planets I: Formation by tidal capture during planet-planet scattering"
http://arxiv.org/abs/1406.6780

Apparently binary gas giants can be formed during planet scattering, judging by table 1 it looks like the formation rate is similar to the HJ formation rate (assuming that HJs are formed through scattering)
Some of them may even survive for the main sequence lifetime provided they are not too close to the star: the survival limit is estimated at ~0.3 AU.
The promised paper II will cover how to detect them.

Paper II:

Lewis, Ochiai, Nagasawa & Ida "Extrasolar Binary Planets II: Detectability by Transit Observations"
http://arxiv.org/abs/1504.06365

Investigates the possibility of finding them in the CoRoT and Kepler data. Suggests that CoRoT SRc01 E2 1066 matches the binary planet model but is not conclusive. Binary planets should be detectable in the Kepler dataset.