Calibration of the instrumental polarization effects of SCExAO-CHARIS' spectropolarimetric mode
Rob G. van Holstein, Steven P. Bos, Jasper Ruigrok, Julien Lozi, Olivier Guyon, Barnaby Norris, Frans Snik, Jeffrey Chilcote, Thayne Currie, Tyler D. Groff, Joo… 展开作者
Rob G. van Holstein, Steven P. Bos, Jasper Ruigrok, Julien Lozi, Olivier Guyon, Barnaby Norris, Frans Snik, Jeffrey Chilcote, Thayne Currie, Tyler D. Groff, Joost 't Hart, Nemanja Jovanovic, Jeremy Kasdin, Tomoyuki Kudo, Frantz Martinache, Ben Mazin, Ananya Sahoo, Motohide Tamura, Sébastien Vievard, Alex Walter, Jin Zhang
SCExAO at the Subaru telescope is a visible and near-infrared high-contrast imaging instrument employing extreme adaptive optics and coronagraphy. The instrument feeds the near-infrared light (JHK) to the integral field spectrograph CHARIS. Recently, a Wollaston prism was added to CHARIS' optical path, giving CHARIS a spectropolarimetric capability that is unique among high-contrast imaging instruments. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. The 22 wavelength bins of CHARIS provide a unique opportunity to investigate in detail the wavelength dependence of the instrumental polarization effects. From measurements with the internal light source, we find that the image derotator (K-mirror) produces strong wavelength-dependent crosstalk, in the worst case converting ~95% of the incident linear polarization to circularly polarized light that cannot be measured. Theoretical calculations show that the magnitude of the instrumental polarization of the telescope varies with wavelength between approximately 0.5% and 0.7%, and that its angle is exactly equal to the altitude angle of the telescope. We plan to more accurately determine the instrumental polarization of the telescope with observations of a polarization standard star, and fit more comprehensive physical models to all experimental data. In addition, we plan to integrate the complete Mueller matrix model into the existing CHARIS post-processing pipeline, with the aim to achieve a polarimetric accuracy of <0.1% in the degree of linear polarization. Our calibrations of CHARIS' spectropolarimetric mode will enable unique quantitative polarimetric studies of circumstellar disks and planetary and brown dwarf companions.
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 datasets (which use the broadband mode covering J through 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 modelling-based e…
We describe a new high-contrast imaging capability well suited for studying planet-forming disks: near-infrared (NIR) high-contrast spectropolarimetric imaging with the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) integral field spectrograph (IFS). The advent of extreme adaptive optics (AO) systems, like SCExAO, has enabled recovery of planet-mass companions at the expected locations of gas-giant formation in young disks alongside disk structures (such as gaps or spirals) that may indicate prot…
We present first results from a new exoplanet direct imaging survey being carried out with the Subaru Coronagraphic Extreme Adaptive Optics project (SCExAO) coupled to the CHARIS integral field spectrograph and assisted with Keck/NIRC2, targeting stars showing evidence for an astrometric acceleration from the Hipparcos and Gaia satellites. Near-infrared spectra from CHARIS and thermal infrared photometry from NIRC2 constrain newly-discovered companion spectral types, temperatures, and gravities. Relative astrometry of companions from SCExAO/CHARIS and NIRC2 and absolute astrometry of the star …
SCExAO at the Subaru telescope is a visible and near-infrared high-contrast imaging instrument employing extreme adaptive optics and coronagraphy. The instrument feeds the near-infrared light (JHK) to the integral-field spectrograph CHARIS. The spectropolarimetric capability of CHARIS is enabled by a Wollaston prism and is unique among high-contrast imagers. We present a detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument. From measurements with the internal light source, we find that the image derotator…
We present new, near-infrared (1.1--2.4 $μm$) high-contrast imaging of the bright debris disk surrounding HIP 79977 with the Subaru Coronagraphic Extreme Adaptive Optics system (SCExAO) coupled with the CHARIS integral field spectrograph. SCExAO/CHARIS resolves the disk down to smaller angular separations of (0.11"; $r \sim 14$ au) and at a higher significance than previously achieved at the same wavelengths. The disk exhibits a marginally significant east-west brightness asymmetry in $H$ band that requires confirmation. Geometrical modeling suggests a nearly edge-on disk viewed at a position …
We report the direct imaging discovery of a low-mass companion to the nearby accelerating A star, HIP 109427, with the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument coupled with the MKID Exoplanet Camera (MEC) and CHARIS integral field spectrograph. CHARIS data reduced with reference star PSF subtraction yield 1.1-2.4 $μ$m spectra. MEC reveals the companion in $Y$ and $J$ band at a comparable signal-to-noise ratio using stochastic speckle discrimination, with no PSF subtraction techniques. Combined with complementary follow-up $L_{\rm p}$ photometry from Keck/NIRC2, the SCEx…
We describe the current on-sky performance of the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument on the Subaru telescope on Maunakea, Hawaii. SCExAO is continuing to advance its AO performance, delivering H band Strehl ratios in excess of 0.9 for bright stars. We describe new advances with SCExAO's wavefront control that lead to a more stable corrected wavefront and diffraction-limited imaging in the optical, modifications to code that better handle read noise suppression within CHARIS, and tests of the spectrophotometric precision and accuracy within CHARIS. We outline steps…
We present SCExAO/CHARIS high-contrast imaging/$JHK$ integral field spectroscopy of $κ$ And b, a directly-imaged low-mass companion orbiting a nearby B9V star. We detect $κ$ And b at a high signal-to-noise and extract high precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo (2016). $κ$ And b's spectrum best resembles that of a low-gravity L0--L1 dwarf (L0--L1$γ$). Its spectrum and luminosity are very well matched by 2MASSJ0141-4633 and several other 12.5--15 $M_{\rm J}$ free floating members of the 40 $Myr$-old Tuc-Hor Ass…
We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of $\sim$ 20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5$σ$ astrometric acceleration on the star as detected with the $Gaia$ and $Hipparcos$ satellites. SCExAO/CHARIS $JHK$ (1.1--2.4 $μ$m) spectra and Keck/NIRC2 $L_{\rm p}$ (3.78 $μ$m) photometry are best matched by a field L/T transition object: an older, higher gravity, and less dusty counterpart to …
We describe the expected scientific capabilities of CHARIS, a high-contrast integral-field spectrograph (IFS) currently under construction for the Subaru telescope. CHARIS is part of a new generation of instruments, enabled by extreme adaptive optics (AO) systems (including SCExAO at Subaru), that promise greatly improved contrasts at small angular separation thanks to their ability to use spectral information to distinguish planets from quasistatic speckles in the stellar point-spread function (PSF). CHARIS is similar in concept to GPI and SPHERE, on Gemini South and the Very Large Telescope,…
We describe the current performance of the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument on the Subaru telescope on Maunakea, Hawaii and present early science results for SCExAO coupled with the CHARIS integral field spectrograph. SCExAO now delivers H band Strehl ratios up to $\sim$ 0.9 or better, extreme AO corrections for optically faint stars, and planet-to-star contrasts rivaling that of GPI and SPHERE. CHARIS yield high signal-to-noise detections and 1.1--2.4 $μm$ spectra of benchmark directly-imaged companions like HR 8799 cde and kappa And b that clarify their atmosp…
Updating the SCExAO/CHARIS polarimetric calibration following the Nasmyth beam-switcher upgrade
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）；National Astronomical Observatory of Japan, Subaru Telescope（日本国立天文台 昴星团望远镜）；Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究所）；Department of Physics and Astronomy, University of Notre Dame（圣母大学物理与天文系）；Department of Physics and Astronomy, University of Texas at San Antonio（德克萨斯大学圣安东尼奥分校物理与天文系）；Optical Sharpeners；National Astronomical Observatory of Japan（日本国立天文台）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；European Southern Observatory（欧洲南方天文台）；College of Optical Sciences, University of Arizona（亚利桑那大学光学科学学院）；Astrobiology Center（天体生物学中心）；Space Science and Engineering Initiative, College of Engineering, University of Hawaii（夏威夷大学工程学院太空科学与工程倡议项目）；Institute for Astronomy, University of Hawaii（夏威夷大学天文学研究所）；Center for Space Sciences and Technology, University of Maryland, Baltimore County（马里兰大学巴尔的摩郡太空科学与技术中心）；Astrophysics Science Division, NASA-GSFC（美国国家航空航天局戈达德太空飞行中心天体物理学科学部）；Center for Research and Exploration in Space Science and Technology, NASA-GSFC（美国国家航空航天局戈达德太空飞行中心太空科学与技术研究与探索中心）
The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) project is an instrument on the Subaru telescope that is pushing the frontiers of what is possible with ground-based high-contrast imaging of extrasolar planets. The system features key breakthroughs in wavefront sensing and coronagraphy to yield extremely high Strehl ratio corrections and deep planet-to-star contrasts, even for optically faint stars. SCExAO is coupled to a near-infrared integral field spectrograph -- CHARIS -- yielding robust planet spectral characterization. In its first full year of operations, SCExAO has already cla…
We present $H$-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from $r$ $\sim$ 0.3" to $r$ $\sim$ 1" (34--114 au). The disk is oriented in a near east-west direction (PA $\sim$ 75$^{o}$), is inclined by $i$ $\sim$ 70--75$^{o}$ and is strongly forward-scattering ($g$ $>$ 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disk's east…
The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is an extremely modular high-contrast instrument installed on the Subaru telescope in Hawaii. SCExAO has a dual purpose. Its position in the northern hemisphere on a 8-meter telescope makes it a prime instrument for the detection and characterization of exoplanets and stellar environments over a large portion of the sky. In addition, SCExAO's unique design makes it the ideal instrument to test innovative technologies and algorithms quickly in a laboratory setup and subsequently deploy them on-sky. SCExAO benefits from a first…
