Revised astrometric calibration of the Gemini Planet Imager

Robert J. de Rosa , Meiji M. Nguyen , Jeffrey Chilcote , Bruce Macintosh , Marshall D. Perrin , Quinn Konopacky , Jason J. Wang , Gaspard Duchêne (1) , Eric L. Nielsen , Julien Rameau , S. Mark Ammons , Vanessa P. Bailey , Travis Barman , Joanna Bulger , Tara Cotten , Rene Doyon , Thomas M. Esposito , Michael P. Fitzgerald , Katherine B. Follette , Benjamin L. Gerard , Stephen J. Goodsell , James R. Graham , Alexandra Z. Greenbaum , Pascale Hibon , Li-Wei Hung , Patrick Ingraham , Paul Kalas , James E. Larkin , Jérôme Maire , Franck Marchis , Mark S. Marley , Christian Marois , Stanimir Metchev , Maxwell A. Millar-Blanchaer , Rebecca Oppenheimer , David Palmer , Jennifer Patience , Lisa Poyneer , Laurent Pueyo , Abhijith Rajan , Fredrik T. Rantakyrö , Jean-Baptiste Ruffio , Dmitry Savransky , Adam C. Schneider , Anand Sivaramakrishnan , Inseok Song , Remi Soummer , Sandrine Thomas , J. Kent Wallace , Kimberly Ward-Duong , Sloane Wiktorowicz , Schuyler Wolff

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

We present a revision to the astrometric calibration of the Gemini Planet Imager (GPI), an instrument designed to achieve the high contrast at small angular separations necessary to image substellar and planetary-mass companions around nearby, young stars. We identified several issues with the GPI data reduction pipeline (DRP) that significantly affected the determination of the angle of north in reduced GPI images. As well as introducing a small error in position angle measurements for targets observed at small zenith distances, this error led to a significant error in the previous astrometric calibration that has affected all subsequent astrometric measurements. We present a detailed description of these issues and how they were corrected. We reduced GPI observations of calibration binaries taken periodically since the instrument was commissioned in 2014 using an updated version of the DRP. These measurements were compared to observations obtained with the NIRC2 instrument on Keck II, an instrument with an excellent astrometric calibration, allowing us to derive an updated plate scale and north offset angle for GPI. This revised astrometric calibration should be used to calibrate all measurements obtained with GPI for the purposes of precision astrometry.

Keywords: Astrophysics - Instrumentation and Methods for Astrophysics

Domains: Sciences of the Universe [physics]

Robert J. de Rosa, Meiji M. Nguyen, Jeffrey Chilcote, Bruce Macintosh, Marshall D. Perrin, et al.. Revised astrometric calibration of the Gemini Planet Imager. Journal of Astronomical Telescopes, Instruments, and Systems, 2020, 6, ⟨10.1117/1.JATIS.6.1.015006⟩. ⟨insu-03705228⟩