Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 1, 2013 | Submitted + Published
Journal Article Open

The Stellar Obliquity and the Long-period planet in the HAT-P-17 Exoplanetary System

Abstract

We present the measured projected obliquity – the sky-projected angle between the stellar spin axis and orbital angular momentum – of the inner planet of the HAT-P-17 multi-planet system. We measure the sky-projected obliquity of the star to be λ = 19^(+14)_( −16) degrees by modeling the Rossiter- McLaughlin (RM) effect in Keck/HIRES radial velocities (RVs). The anomalous RV time series shows an asymmetry relative to the midtransit time, ordinarily suggesting a nonzero obliquity – but in this case at least part of the asymmetry may be due to the convective blueshift, increasing the uncertainty in the determination of λ. We employ the semi-analytical approach of Hirano et al. (2011) that includes the effects of macroturbulence, instrumental broadening, and convective blueshift to accurately model the anomaly in the net RV caused by the planet eclipsing part of the rotating star. Obliquity measurements are an important tool for testing theories of planet formation and migration. To date, the measured obliquities of ∼50 Jovian planets span the full range, from prograde to retrograde, with planets orbiting cool stars preferentially showing alignment of stellar spins and planetary orbits. Our results are consistent with this pattern emerging from tidal interactions in the convective envelopes of cool stars and close-in planets. In addition, our 1.8 years of new RVs for this system show that the orbit of the outer planet is more poorly constrained than previously thought, with an orbital period now in the range of 10–36 years.

Additional Information

© 2013 The American Astronomical Society. Received 2013 January 25; accepted 2013 May 24; published 2013 July 9. We thank the referee for a prompt response, careful reading, and useful comments, Jason Eastman for providing the EXOFAST code to community, and the many observers who contributed to the measurements reported here. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff, especially Scott Dahm, Greg Doppman, Hien Tran, and Grant Hill for support of HIRES and Greg Wirth for support of remote observing. Finally, we extend special thanks to those of Hawaiian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible. Facilities: Keck:I (HIRES), Keck:II (NIRC2)

Attached Files

Published - 0004-637X_772_2_80.pdf

Submitted - 1301.6289v1.pdf

Files

0004-637X_772_2_80.pdf
Files (999.8 kB)
Name Size Download all
md5:c942240daf65b520ae52b705fa585216
588.4 kB Preview Download
md5:bdd3acbb86d923a041ad7172ab9422e4
411.4 kB Preview Download

Additional details

Created:
August 22, 2023
Modified:
February 2, 2024