Stellar Obliquities & Planetary Alignments (SOPA) I. Spin-Orbit measurements of Three Transiting Hot Jupiters: WASP-72b, WASP-100b, & WASP-109b

TL;DR

This study measures the spin-orbit angles of three transiting hot Jupiters, revealing diverse orbital inclinations and contributing to understanding planetary migration and system dynamics.

Contribution

First measurements of the sky-projected spin--orbit angles for three hot Jupiters, including nearly polar and aligned orbits, using high-resolution spectroscopy.

Findings

WASP-72b has a well-aligned orbit with λ ≈ -7°.

WASP-100b and WASP-109b are on highly inclined, nearly polar orbits.

Results support trends of high-obliquity orbits around hot, irradiated stars.

Abstract

We report measurements of the sky-projected spin--orbit angles for three transiting hot Jupiters: two of which are in nearly polar orbits, WASP-100b and WASP-109b, and a third in a low obliquity orbit, WASP-72b. We obtained these measurements by observing the Rossiter--McLaughlin effect over the course of the transits from high resolution spectroscopic observations made with the CYCLOPS2 optical fiber bundle system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The resulting sky-projected spin--orbit angles are $\lambda = {-7^{\circ}}^{+11^{\circ}}_{-12^{\circ}}$, $\lambda = {79^{\circ}}^{+19^{\circ}}_{-10^{\circ}}$, and $\lambda = {99^{\circ}}^{+10^{\circ}}_{-9^{\circ}}$ for WASP-72b, WASP-100b, and WASP-109b, respectively. These results suggests that WASP-100b and WASP-109b are on highly inclined orbits tilted nearly $90^{\circ}$ from their host star's equator while the orbit of WASP-72b appears to be well-aligned. WASP-72b is a typical hot Jupiter orbiting a mid-late F star (F7 with $T_\mathrm{{eff}}=6250\pm120$K). WASP-100b and WASP-109b are highly irradiated bloated hot Jupiters orbiting hot early-mid F stars (F2 with $T_\mathrm{{eff}}=6900\pm120$K and F4 with $T_\mathrm{{eff}}=6520\pm140$K), making them consistent with the trends observed for the majority of stars hosting planets on high-obliquity orbits.