Misaki Mizumoto — Page 5

arXiv2015

A Warm Near-Infrared High-Resolution Spectrograph with Very High Throughput (WINERED)

WINERED is a newly built high-efficiency (throughput$ > 25-30\%$) and high-resolution spectrograph customized for short NIR bands at 0.9-1.35 ${\rm μ}$m. WINERED is equipped with ambient temperature optics and a cryogenic camera using a 1.7 ${\rm μ}$m cut-off HgCdTe HAWAII-2RG array detector. WINERED has two grating modes: one with a conventional reflective echelle grating (R$\sim$28,300), which covers 0.9-1.35 $μ$m simultaneously, the other with ZnSe or ZnS immersion grating (R$\sim$100,000). We have completed the development of WINERED except for the immersion grating, and started engineering and science observations at the Nasmyth platform of the 1.3 m Araki Telescope at Koyama Astronomical Observatory of Kyoto-Sangyo University in Japan. We confirmed that the spectral resolution ($R\sim$ 28,300) and the throughput ($>$ 40\% w/o telescope/atmosphere/array QE) meet our specifications. We measured ambient thermal backgrounds (e.g., 0.06 ${\rm [e^{-}/sec/pixel]}$ at 287 K), which are roughly consistent with that we expected. WINERED is a portable instrument that can be installed at any telescope with Nasmyth focus as a PI-type instrument. If WINERED is installed on a 10 meter telescope, the limiting magnitude is expected to be J=18-19, which can provide high-resolution spectra with high quality even for faint distant objects.

astro-ph.IM↗

arXiv2014

Interpretation of the X-ray Spectral Variation of 1H0707-495 with a Variable Double Partial Covering Model

The Narrow-line Seyfert 1 galaxy 1H0707-495 is known to exhibit significant X-ray spectral variations. Its X-ray energy spectrum is characterized by a strong soft excess emission, an extremely deep iron K-edge structure at ~7 keV, and a putative iron L-line/edge feature at ~1 keV. We have found that the energy spectrum of 1H0707-495 in 0.5-10 keV is successfully explained by a "variable double partial covering model" where the original continuum spectrum, which is composed of the soft multi-color disk blackbody component and the hard power-law component, is partially covered by two ionized absorption layers with different ionization states and the same partial covering fraction. The lower-ionized and thicker absorption layer primarily explains the iron K-edge feature, and the higher-ionized and thinner absorption layer explains the L-edge feature. We have discovered that the observed significant intensity/spectral variation within a ~ day is mostly explained by only variation of the partial covering fraction. In our model, the intrinsic luminosity and spectral shape are hardly variable within a ~ day, while some intrinsic variability above 3 keV is recognized. This is consistent with the picture that the multi-color disk blackbody spectrum is almost invariable in this timescale, and the hard power-law component is more variable. We propose that the observed spectral variation of 1H0707-495 is caused by three physically independent variations with different timescales; (1) intrinsic luminosity variation over days, (2) variation of partial covering fraction at a timescale of hours, and (3) small intrinsic hard component variation above 3 keV in a timescale of hours or less.

astro-ph.HE↗