http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Fumihiko Usui,SUNAO HASEGAWA,Masateru Ishiguro,THOMAS G. MULLER,TAKAFUMI OOTSUBO 한국천문학회 2017 天文學論叢 Vol.32 No.1
Presently, the number of known asteroids is more than 710,000. Knowledge of size andalbedo is essential in many aspects of asteroid research, such as the chemical composition andmineralogy, the size-frequency distribution of dynamical families, and the relationship between smallbodies in the outer solar system or comets. Recently, based on the infrared all-sky survey data obtainedby \emph{IRAS}, \emph{AKARI}, and \emph{WISE}, the large asteroid catalogs containing size and albedo datahave been constructed. In this paper, we discuss the compositional distribution in the mainbelt regions based on the compiled data on size, albedo, and separately obtained taxonomic typeinformation.
DATA REDUCTION OF AKARI/IRC SPECTROSCOPIC OBSERVATIONS
Fumihiko Usui,TAKASHI ONAKA 한국천문학회 2017 天文學論叢 Vol.32 No.1
AKARI performed about 10,000 spectroscopic observations with the Infrared Camera (IRC) during its mission phase. These IRC observations provide unique spectroscopic data at near- and mid-infrared wavelengthsfor studies of the next few decades because of its high sensitivity and unique wavelength coverage. In this paper, we present the current status of the activity for improving the IRC spectroscopicdata reduction process, including the toolkit and related data packages, and also discussthe goal of this project.
AKARI/AcuA PHYSICAL STUDIES OF THE CYBELE ASTEROID FAMILY
Kasuga, Toshihiro,Usui, Fumihiko,Hasegawa, Sunao,Kuroda, Daisuke,Ootsubo, Takafumi,Mü,ller, Thomas G.,Ishiguro, Masateru American Institute of Physics 2012 The Astronomical journal Vol.143 No.6
<P>We present a study of 107 Cybele asteroids based on the archival database 'Asteroid Catalog Using AKARI (AcuA)' taken by the Infrared Astronomical Satellite. The database provides diameters D > 10 km, geometric albedos, and taxonomic information (75%) of the Cybeles. We find taxonomic diversity (mainly C-, D-, and P-type) in the population of 78 small Cybeles with diameters 10 km <D < 80 km. Their cumulative power-law size distribution index shows a shallow value of 0.86 ± 0.03. By contrast, 29 large Cybeles with D > 80 km are mostly classified as C- or P-types (90%), with a power-law index of 2.39 ± 0.18. The total mass of Cybele asteroids is estimated to be ~10<SUP>–5</SUP> M<SUB>Earth</SUB>. We also discuss the origin and formation process of the Cybele asteroid family.</P>
SPECTRAL EVOLUTION OF NOVAE IN THE NEAR-INFRARED BASED ON AKARI OBSERVATIONS
ITSUKI SAKON,TAKASHI ONAKA,Fumihiko Usui,SAYAKA SHIMAMOTO,RYOU OHSAWA,Takehiko Wada,Hideo Matsuhara,AKIRA ARAI 한국천문학회 2017 天文學論叢 Vol.32 No.1
We have carried out the near-infrared spectroscopic observations of recent classical novae (e.g., V2468Cyg, V1280Sco) within a few years from the outburst with AKARI as a part of AKARI Open Time Observing Program for Phase 3-II "Spectral Evolution of Novae in the Near-Infrared based on AKARI Observations (Proposal ID: SENNA)". The homogeneous datasets of near-infrared spectra from 2.5 $\mu$m to 5 $\mu$m with AKARI/IRC collected in this program are useful to infer the physical conditions of the shell formed by the ejected materials, to examine the chemical properties of the ejecta gas, and to examine the properties of dust formed in the nova ejecta.
HIGH-RESOLUTION IMAGING OF THE GEGENSCHEIN AND THE GEOMETRIC ALBEDO OF INTERPLANETARY DUST
Ishiguro, Masateru,Yang, Hongu,Usui, Fumihiko,Pyo, Jeonghyun,Ueno, Munetaka,Ootsubo, Takafumi,Kwon, Suk Minn,Mukai, Tadashi IOP Publishing 2013 The Astrophysical journal Vol.767 No.1
<P>We performed optical observations of the Gegenschein using a liquid-nitrogen-cooled wide-field camera, the Wide-field Imager of Zodiacal light with ARray Detector (WIZARD), between 2003 March and 2006 November. We found a narrow brightness enhancement superimposed on the smooth gradient of the Gegenschein at the exact position of the antisolar point. Whereas the Gegenschein morphology changed according to the orbital motion of the Earth, the maximum brightness coincided with the antisolar direction throughout the year. We compared the observed morphology of the Gegenschein with those of models in which the spatial density of the interplanetary dust cloud was considered and found that the volume scattering phase function had a narrow backscattering enhancement. The morphology was reproducible with a spatial distribution model for infrared zodiacal emission. It is likely that the zero-phase peak (the so-called opposition effect) was caused by coherent backscattering and/or shadow-hiding effects on the rough surfaces of individual dust particles. These results suggest that big particles are responsible for both zodiacal light and zodiacal emission. Finally, we derived the geometric albedo of the smooth component of interplanetary dust, assuming big particles, and obtained a geometric albedo of 0.06 +/- 0.01. The derived albedo is in accordance with collected dark micrometeorites and observed cometary dust particles. We concluded that chondritic particles are dominant near Earth space, supporting the recent theoretical study by dynamical simulation.</P>
MODELLING THE 3 MICRON REGION IN AKARI IRC SPECTRA
MARK HAMMONDS,TAMAMI MORI,Fumihiko Usui,TAKASHI ONAKA 한국천문학회 2017 天文學論叢 Vol.32 No.1
The existence of polycyclic aromatic hydrocarbons (PAHs) astronomically is well accepted, but the specific molecular forms observed remain uncertain. To better understand the molecular structures which may be present along a given sightline, the 3.0~--~3.6\mum\ region is modelled with careful consideration given to the underlying sub-features arising from specific structures within emitting molecules.
PHYSICAL PROPERTIES OF ASTEROIDS IN COMET-LIKE ORBITS IN INFRARED ASTEROID SURVEY CATALOGS
Kim, Yoonyoung,Ishiguro, Masateru,Usui, Fumihiko IOP Publishing 2014 The Astrophysical journal Vol.789 No.2
<P>We investigated the population of asteroids in comet-like orbits using available asteroid size and albedo catalogs of data taken with the Infrared Astronomical Satellite, AKARI, and the Wide-field Infrared Survey Explorer on the basis of their orbital properties (i.e., the Tisserand parameter with respect to Jupiter, T-J, and the aphelion distance, Q). We found that (1) there are 123 asteroids in comet-like orbits by our criteria (i.e., Q > 4.5 AU and T-J < 3), (2) 80% of them have low albedo, p(v) < 0.1, consistent with comet nuclei, (3) the low-albedo objects among them have a size distribution shallower than that of active comet nuclei, that is, the power index of the cumulative size distribution is around 1.1, and (4) unexpectedly, a considerable number (i.e., 25 by our criteria) of asteroids in comet-like orbits have high albedo, p(v) > 0.1. We noticed that such high-albedo objects mostly consist of small (D < 3 km) bodies distributed in near-Earth space (with perihelion distance of q < 1.3 AU). We suggest that such high-albedo, small objects were susceptible to the Yarkovsky effect and drifted into comet-like orbits via chaotic resonances with planets.</P>