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Published July 2019 | Submitted + Published
Journal Article Open

A Chromaticity Analysis and PSF Subtraction Techniques for SCExAO/CHARIS Data


We present an analysis of instrument performance using new observations taken with the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instrument and the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system. In a correlation analysis of our data sets (which use the broadband mode covering the J band through the K band in a single spectrum), we find that chromaticity in the SCExAO/CHARIS system is generally worse than temporal stability. We also develop a point-spread function (PSF) subtraction pipeline optimized for the CHARIS broadband mode, including a forward modeling-based exoplanet algorithmic throughput correction scheme. We then present contrast curves using this newly developed pipeline. An analogous subtraction of the same data sets using only the H-band slices yields the same final contrasts as the full JHK sequences; this result is consistent with our chromaticity analysis, illustrating that PSF subtraction using spectral differential imaging (SDI) in this broadband mode is generally not more effective than SDI in the individual J, H, or K bands. In the future, the data processing framework and analysis developed in this paper will be important to consider for additional SCExAO/CHARIS broadband observations and other ExAO instruments which plan to implement a similar integral field spectrograph broadband mode.

Additional Information

© 2019 The American Astronomical Society. Received 2019 February 18; revised 2019 May 9; accepted 2019 May 14; published 2019 July 1. The data in this paper was obtained through 2017B open use Canadian and US Gemini exchange time (Gerard 2017). We gratefully acknowledge research support of the Natural Sciences and Engineering Council of Canada through the Postgraduate Scholarships-Doctoral discovery grant (DG), and Technologies for Exo-Planetary Science Collaborative Research and Training Experience programs. The development of SCExAO was supported by the JSPS (Grant-in-Aid for Research #23340051, #26220704 #23103002), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt. Cuba Foundation and the directors contingency fund at Subaru Telescope. CHARIS was built at Princeton University under a Grant-in-Aid for Scientific Research on Innovative Areas from MEXT of the Japanese government (# 23103002). We thank Jason Wang and Jean-Baptiste Ruffio for helpful discussions and suggestions about forward modeling. The authors thank the anonymous referee for the comments and suggestions that have significantly improved this manuscript. The authors acknowledge and support the cultural and spiritual importance of the summit of Maunakea to the Hawaiian native community. We are grateful to share and respect this land with the community.

Attached Files

Published - Gerard_2019_AJ_158_36.pdf

Submitted - 1905.05821.pdf


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