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

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 $\hat{I}»={-7^{\circ }}_{-12^{\circ }}^{+11^{\circ }}$, $\hat{I}»={79^{\circ }}_{-10^{\circ }}^{+19^{\circ }}$, and $\hat{I}»={99^{\circ }}_{-9^{\circ }}^{+10^{\circ }}$ 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 $T_{\mathrm{eff}}=6250\pm 120$K). WASP-100b and WASP-109b are highly irradiated bloated hot Jupiters orbiting hot early-mid F stars (F2 with $T_{\mathrm{eff}}=6900\pm 120$K and F4 with $T_{\mathrm{eff}}=6520\pm 140$K), making them consistent with the trends observed for the majority of stars hosting planets on high-obliquity orbits.

10 pages, 10 figures, 6 tables. Has been accepted for publication in The Astronomical Journal