6 July 2018 Very high-sensitive NIR high-resolution spectrograph WINERED: on-going observations at NTT
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Abstract
WINERED is a highly sensitive near-infrared (NIR) high-resolution spectrograph. The spectral coverage is 0.90 to 1.35μm (z, Y, J-bands) and the spectral resolutions are R = 28,000 (WIDE-mode, covering an entire WINERED’s wavelength region with a single exposure) and R = 70,000 (HIRES-modes, covering either Y- or J-band with a single exposure). Owing to the high-throughput optics (> 0.5) and the very low noise of the system, WINERED has the potential to detect the faintest objects when attached to 10 m class telescopes as reported in the previous SPIE meeting. In the beginning of 2017, WINERED was relocated from the 1.3 m Araki telescope in Koyama Astronomical Observatory, Japan, to the ESO 3.58 m New Technology Telescope (NTT) in La Silla Observatory, Chile, and began its scientific observations. By March of 2008, 30 nights in total were allocated for observation with the WINERED at the NTT. To further improve observational efficiencies at the NTT, we upgraded and refined several units of WINERED. New slits were installed to realize a medium spectral resolution and the better correction of the distorted echellogram, the grating holder for the mosaicked high-blazed echelle gratings were modified, the ghost problems observed on the HIRES-Y mode were fixed, and the I/F mechanical parts were fabricated for easy and highlyreplicable attachment to the NTT. After verifying a few performances critical for the sensitivity of the new telescope, the background ambient radiation at the NTT, which determines the limiting magnitude because WINERED is a warm instrument with no cold stop, is very similar (~0.1 photons sec-1 pixel-1 at 290 K and ~0.04 photons sec-1 pixel1 at 280 K) to those measured at Kyoto. The stability in wavelength, which could degrade the signal-to-noise ratios (SNRs) by artificial spiky-noises generated in the subtraction and correction of telluric emission/absorption lines, is measured to be less than 0.2 pixels during an observational run, although these can be further reduced by the crosscorrelation method which are applied for spectra taken at different timings during reduction. WINERED routinely provides spectra of the SNR > 500 for bright stars, and realized the detection of those of SNR = 30 for faint objects of J = 16.4 mag (for WIDE mode) and J=15.0 (for HIRES mode) with the exposure time of 8 hours using the narrowest slit at the NTT (even without AO).
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Yuji Ikeda, Yuji Ikeda, Naoto Kobayashi, Naoto Kobayashi, Sohei Kondo, Sohei Kondo, Shogo Otsubo, Shogo Otsubo, Ayaka Watase, Ayaka Watase, Taichi Murai, Taichi Murai, Kyoko Sakamoto, Kyoko Sakamoto, Satoshi Hamano, Satoshi Hamano, Hiroaki Sameshima, Hiroaki Sameshima, Kei Fukue, Kei Fukue, Akira Arai, Akira Arai, Tomohiro Yoshikawa, Tomohiro Yoshikawa, Kei-ichi Takenaka, Kei-ichi Takenaka, Takeo Manome, Takeo Manome, Shinji Mukai, Shinji Mukai, Naoto Iida, Naoto Iida, Kentaro Yanagibashi, Kentaro Yanagibashi, Chikako Yasui, Chikako Yasui, Misaki Mizumoto, Misaki Mizumoto, Noriyuki Matsunaga, Noriyuki Matsunaga, Giuseppe Bono, Giuseppe Bono, Hideyo Kawakita, Hideyo Kawakita, } "Very high-sensitive NIR high-resolution spectrograph WINERED: on-going observations at NTT", Proc. SPIE 10702, Ground-based and Airborne Instrumentation for Astronomy VII, 107025U (6 July 2018); doi: 10.1117/12.2309605; https://doi.org/10.1117/12.2309605
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