A Spin-Orbit Alignment for the Hot Jupiter HATS-3b

TL;DR

This study measures the spin-orbit alignment of the Hot Jupiter HATS-3b, finding it aligned with its host star's spin axis, supporting trends observed in similar exoplanet systems.

Contribution

First measurement of spin-orbit angle for a HATSouth-discovered exoplanet, using spectroscopic Rossiter-McLaughlin effect observations.

Findings

HATS-3b's orbit is aligned with its star's spin axis.

Results support the trend of hot stars having randomly oriented planetary orbits.

The measurement was achieved with the UCLES spectrograph on the Anglo-Australian Telescope.

Abstract

We have measured the alignment between the orbit of HATS-3b (a recently discovered, slightly inflated Hot Jupiter) and the spin-axis of its host star. Data were obtained using the CYCLOPS2 optical-fiber bundle and its simultaneous calibration system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The sky-projected spin-orbit angle of $\lambda = 3\pm25^{\circ}$ was determined from spectroscopic measurements of Rossiter-McLaughlin effect. This is the first exoplanet discovered through the HATSouth transit survey to have its spin-orbit angle measured. Our results indicate that the orbital plane of HATS-3b is consistent with being aligned to the spin axis of its host star. The low obliquity of the HATS-3 system, which has a relatively hot mid F-type host star, agrees with the general trend observed for Hot Jupiter host stars with effective temperatures $>6250$K to have randomly distributed spin-orbit angles.