Hi All

It's an interesting paper with a suggestion for a possible mechanism too, that the efficiency of orbital migration may depend on the relative size of the preplanetary nebula - higher mass stars have denser nebula, and that brown dwarfs are perhaps too big to undergo major inwards migration. There also seems to be a dearth of brown dwarf companions at wider separations too.

The statistics for planets with periods < 5 years is a frequency of about ~ 4 (+/- 2) %. Lineweaver & Grether have previously estimated a ~ 25% likelihood of planets in wider orbits, but the Marcy & Butler statistics suggests about ~ 1/2 that at 12% (up to 21% for high metallcitiy stars though.)

Interesting.

Adam