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Proceedings Paper

Gemini planet imager observational calibration XII: photometric calibration in the polarimetry mode
Author(s): Li-Wei Hung; Sebastian Bruzzone; Maxwell A. Millar-Blanchaer; Jason J. Wang; Pauline Arriaga; Stanimir Metchev; Michael P. Fitzgerald; Anand Sivaramakrishnan; Marshall D. Perrin
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Paper Abstract

The Gemini Planet Imager (GPI) is a high-contrast instrument specially designed for direct imaging and spectroscopy of exoplanets and debris disks. GPI can also operate as a dual-channel integral field polarimeter. The instrument primarily operates in a coronagraphic mode which poses an obstacle for traditional photometric calibrations since the majority of on-axis starlight is blocked. To enable accurate photometry relative to the occulted central star, a diffractive grid in a pupil plane is used to create a set of faint copies, named satellite spots, of the occulted star at specified locations and relative intensities in the field of view. We describe the method we developed to perform the photometric calibration of coronagraphic observations in polarimetry mode using these fiducial satellite spots. With the currently available data, we constrain the calibration uncertainty to be <13%, but the actual calibration uncertainty is likely to be lower. We develop the associated calibration scripts in the GPI Data Reduction Pipeline, which is available to the public. For testing, we use it to photometrically calibrate the HD 19467 B and β Pic b data sets taken in the H-band polarimetry mode. We measure the calibrated flux of HD 19467 B and β Pic b to be 0:078±0:011 mJy and 4:87±0:73 mJy, both agreeing with other measurements found in the literature. Finally, we explore an alternative method which performs the calibration by scaling the photometry in polarimetry mode to the photometrically calibrated response in spectroscopy mode. By comparing the reduced observations in raw units, we find that observations in polarimetry mode are 1:03 0:01 brighter than those in spectroscopy mode.

Paper Details

Date Published: 9 August 2016
PDF: 13 pages
Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 99083A (9 August 2016); doi: 10.1117/12.2233665
Show Author Affiliations
Li-Wei Hung, Univ. of California, Los Angeles (United States)
Sebastian Bruzzone, Western Univ. (Canada)
Maxwell A. Millar-Blanchaer, Univ. of Toronto (Canada)
Dunlap Institute for Astronomy & Astrophysics, Univ. of Toronto (Canada)
Jason J. Wang, Univ. of California, Berkeley (United States)
Pauline Arriaga, Univ. of California, Los Angeles (United States)
Stanimir Metchev, Western Univ. (Canada)
Stony Brook Univ. (United States)
Michael P. Fitzgerald, Univ. of California, Los Angeles (United States)
Anand Sivaramakrishnan, Space Telescope Science Institute (United States)
Marshall D. Perrin, Space Telescope Science Institute (United States)

Published in SPIE Proceedings Vol. 9908:
Ground-based and Airborne Instrumentation for Astronomy VI
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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