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

Benjamin L. Gerard, Christian Marois, Thayne Currie, Timothy Brandt, Jeffrey K. Chilcote, Zachary H. Draper, Tyler Groff, Olivier Guyon, Masahiko Hayashi, Nemanja Jovanovic, Gillian R. Knapp, Tomoyuki Kudo, Jungmi Kwon, Julien Lozi, Frantz Martinache, Michael McElwain, Motohide Tamura, Taichi Uyama

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


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.

Original languageEnglish (US)
Article number36
JournalAstronomical Journal
Issue number1
StatePublished - 2019


  • planets and satellites: general
  • techniques: high angular resolution
  • techniques: image processing

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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