Before we start Brief introduc-on of the plans and ideas for the planetary group (Links with Chilean Universi-es JC/One Day WS; Planetary Systems II) Visitors encouraged Members to provide cross‐training to PAO members (PAO is a place to talk about science! Planets is a key driver for the future of ESO, we should to grow exper-se and interest on the field) Frequency of the mee-ngs – Every two weeks seems a good number
Spin‐orbit angle measurements for six southern transiting planets Amaury Triaud et al http://www.superwasp.org/documents/triaud2010_rossiter.pdf
“This is a real bomb we are dropping into the field of exoplanets,” says Amaury Triaud, a PhD student at the Geneva Observatory who, with Andrew Cameron and Didier Queloz, leads a major part of the observa-onal campaign. WHY???
Rossiter‐McLaughlin effect We all know how a photometric transit looks like How about the spectroscopic transit?
Radial velocity
The transi/ng object blocks the stellar disk producing a shi: in the RV The amplitude of this effect is related to the geometry and to the rota/onal velocity
Ohta et al. (2005)
Ohta et al. (2005)
Gaudi & Winn 2006, ApJ λ (or β in Triaud’s paper) is the projected spin orbit misalignment angle. Thus: • for β =0 the planetary orbit is perpendicular to the stellar rota/on axis; • For β =90 the orbit is along the rota/on axis • For β >90 the orbital mo/on is retrograde
Measurements Amaury Triaud et al Global fiang of photometric transit, RV curve and spectroscopic transit 6 transi-ng planets found by WASP were studied in the paper 3 of them have β > 90 (retrograde orbits) 3 others have β ~ 0 WASP‐5b; β ~ 0 WASP‐15b; β = 139
The real misalignment Amaury Triaud et al They measured the sky‐ projected spin‐orbit angle The real angle ψ is es-mated using the argument that the spin axis is isotropically distributed cos ψ = cos I cosi + sin I cos β I is the inclina-on of the stellar spin axis and I the inclina-on of the planet’s orbital axis.
Discussion Amaury Triaud et al 26 RM effects have been observed so far 14 have β < 22 and are considered aligned They find that there is a 82% probability that ψ is >22deg (Solar System case)
Kozai Mechanism In a presence of a 3 rd distant body, if the orbital plane of the inner binary is not aligned with the outer orbit, the e_in and the inclina-on between the two orbits will oscillate in cycles. KC+Tidal fric-on the e_in becomes large so that in the periastron passage -des take over for a while working towards a circular orbit.
Theoretical prediction The predic-on for the misalignment spin‐planetary orbit For systems with a third companion. (Fabrycky and Tremaine 2007)
It matches beau-fully the observa-ons!
Conclusions RM measurements obtained with high accuracy RV data suggest that >80% of the hot‐jupiters are misaligned with angles some-mes > 90% Forma-on of hot‐jupiters via migra-on requires interac-ons with the disc and therefore coplanarity Kozai mechanism would cause the inner orbit to oscillate (e_in, inclina-on) and reduce the orbital period. The predicted distribu-on of spin‐orbit angle is very similar to the one drawn from sta-s-cal arguments transforming the β distribu-on.
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