Tilting Jupiter (a bit) and Saturn (a lot) During Planetary Migration

We study the effects of planetary late migration on the gas giants obliquities. We consider the planetary instability models from Nesvorny & Morbidelli (2012), in which the obliquities of Jupiter and Saturn can be excited when the spin-orbit resonances occur. The most notable resonances occur when the $s_7$ and $s_8$ frequencies, changing as a result of planetary migration, become commensurate with the precession frequencies of Jupiter's and Saturn's spin vectors. We show that Jupiter may have obtained its present obliquity by crossing of the $s_8$ resonance. This would set strict constrains on the character of migration during the early stage. Additional effects on Jupiter's obliquity are expected during the last gasp of migration when the $s_7$ resonance was approached. The magnitude of these effects depends on the precise value of the Jupiter's precession constant. Saturn's large obliquity was likely excited by capture into the $s_8$ resonance. This probably happened during the late stage of planetary migration when the evolution of the $s_8$ frequency was very slow, and the conditions for capture into the spin-orbit resonance with $s_8$ were satisfied. However, whether or not Saturn is in the spin-orbit resonance with $s_8$ at the present time is not clear, because the existing observations of Saturn's spin precession and internal structure models have significant uncertainties.Comment: 29 pages, 8 figures, accepted for publication in The Astrophysical Journa

Emerging Trends in a Period-Radius Distribution of Close-in Planets

We analyze the distribution of extrasolar planets (both confirmed and Kepler candidates) according to their orbital periods P and planetary radii R. Among confirmed planets, we find compelling evidence for a paucity of bodies with 3 < R < 10 R_\oplus, where R_\oplus in the Earth's radius, and P < 2-3 days. We have christened this region a "sub-Jovian Pampas". The same trend is detected in multiplanet Kepler candidates. Although approximately 16 Kepler single-planet candidates inhabit this Pampas, at least 7 are probable false positives (FP). This last number could be significantly higher if the ratio of FP is higher than 10%, as suggested by recent studies. In a second part of the paper we analyze the distribution of planets in the (P,R) plane according to stellar metallicities. We find two interesting trends: (i) a lack of small planets (R < 4 R_\oplus) with orbital periods P < 5 days in metal-poor stars, and (ii) a paucity of sub-Jovian planets (4 R_\oplus < R < 8 R_\oplus) with P < 100 days, also around metal-poor stars. Although all these trends are preliminary, they appear statistically significant and deserve further scrutiny. If confirmed, they could represent important constraints on theories of planetary formation and dynamical evolution.Comment: Accepted in Ap