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Register a new userNear-Infrared Imaging of a Spiral in the CQ Tau Disk
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We present $L^prime$-band Keck/NIRC2 imaging and $H$-band Subaru/AO188+HiCIAO polarimetric observations of CQ Tau disk with a new spiral arm. Apart from the spiral feature our observations could not detect any companion candidates. We traced the spiral feature from the $r^2$-scaled HiCIAO polarimetric intensity image and the fitted result is used for forward modeling to reproduce the ADI-reduced NIRC2 image. We estimated the original surface brightness after throughput correction in $L^prime$-band to be $sim126$ mJy/arcsec$^2$ at most. We suggest that the grain temperature of the spiral may be heated up to $sim$200 K in order to explain both of the $H$- and $L^{prime}$-bands results. The $H$-band emission at the location of the spiral originates from the scattering from the disk surface while both scattering and thermal emission may contribute to the $L^{prime}$-band emission. If the central star is only the light source of scattered light, the spiral emission at $L^prime$-band should be thermal emission. If an inner disk also acts as the light source, the scattered light and the thermal emission may equally contribute to the $L^prime$-band spiral structure.
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