I have in my notes that it is 6:1, not 5:1. I also have that the sunspots shift in positions which is why only some light curves have the sunspots, and that the shifting positions is likely similar to the butterfly diagram of the sun (I assume you know more about this than I do since you did Solar System). Besides that, I don't know, maybe you found a flaw in their research? I'll leave it to syo_astro if he would know anything about this.There's one slight thing that made me hesitant to answer though that I want to bring up too. Looking at the blips in your picture, they seem to come at intervals of 5 transits, making it seem like the ratio of orbits and star's rotations is 5:1. However, according to Bécky et al. this ratio should be 6:1 (http://arxiv.org/pdf/1403.7526v1.pdf), as illustrated by Figure 3 on page 3. It shows various transit light curves, with every sixth light curve having the same sunspot. Similarly, in Figure 6, there's a big spike in the height of the bar every 6th transit. Although a minor detail, this actually threw me off a lot because I assumed that it must have been a different star. Do you know anything about this, or is it just a differeing result from experimentation?
1. Faster 2. Before, since they accrete mass faster 3a. Frost line 3b. Past the frost line, volatile 'gasses' are solid and can accrete into planetesimals whereas before the frost line they cannot 3c. Negative, since gas giants are the heaviest type of planet and they typically consist primarily of hydrogen and helium 3d. Positive, since although gas giants have lower metallicities than terrestrial planets and ice giants, they have large metallic cores heavier than terrestrial planets 4. A higher surface density correlates to higher planetesimal mass and faster planetesimal growth