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OPTICAL AND NEAR-INFRARED POLARIMETRY FOR A HIGHLY DORMANT COMET 209P/LINEAR
Kuroda, Daisuke,Ishiguro, Masateru,Watanabe, Makoto,Akitaya, Hiroshi,Takahashi, Jun,Hasegawa, Sunao,Ui, Takahiro,Kanda, Yuka,Takaki, Katsutoshi,Itoh, Ryosuke,Moritani, Yuki,Imai, Masataka,Goda, Shuhei IOP Publishing 2015 The Astrophysical journal Vol.814 No.2
<P>We conducted an optical and near-infrared polarimetric observation of the highly dormant Jupiter-Family Comet, 209P/LINEAR. Because of its low activity, we were able to determine the linear polarization degrees of the coma dust particles and nucleus independently, that is P-n = 30.3(-0.9)(+1.3)% at alpha = 92 degrees.2 and P-n = 31.0(-0.7)(+1.0)% at alpha = 99 degrees.5 for the nucleus, and P-c = 28.8(-0.4)(+0.4)% at alpha = 92 degrees.2 and 29.6(-0.3)(+0.3)% at alpha = 99 degrees.5 for the coma. We detected no significant variation in P at the phase angle coverage of 92 degrees.2-99 degrees.5, which may imply that the obtained polarization degrees are nearly at maximum in the phase-polarization curves. By fitting with an empirical function, we obtained the maximum values of linear polarization degrees P-max = 30.8% for the nucleus and P-max = 29.6% for the dust coma. The P-max of the dust coma is consistent with those of dust-rich comets. The low geometric albedo of P-v. =. 0.05 was derived from the slope-albedo relationship and was associated with high P-max. We examined P-max-albedo relations between asteroids and 209P, and found that the so-called Umov law seems to be applicable on this cometary surface.</P>
Significantly high polarization degree of the very low-albedo asteroid (152679) 1998 KU<sub>2</sub>
Kuroda, Daisuke,Ishiguro, Masateru,Watanabe, Makoto,Hasegawa, Sunao,Sekiguchi, Tomohiko,Naito, Hiroyuki,Usui, Fumihiko,Imai, Masataka,Sato, Mitsuteru,Kuramoto, Kiyoshi EDP Sciences 2018 Astronomy and astrophysics Vol.611 No.-
<P>We present a unique and significant polarimetric result regarding the near-Earth asteroid (152679) 1998 KU2, which has a very low geometric albedo. From our observations, we find that the linear polarization degrees of 1998 KU2 are 44.6 ± 0.5% in the <I>R</I>C band and 44.0 ± 0.6% in the <I>V</I> band at a solar phase angle of 81.0°. These values are the highest of any known airless body in the solar system (i.e., high-polarization comets, asteroids, and planetary satellites) at similar phase angles. This polarimetric observation is not only the first for primitive asteroids at large phase angles, but also for low-albedo (<0.1) airless bodies. Based on spectroscopic similarities and polarimetric measurements of materials that have been sorted by size in previous studies, we conjecture that 1998 KU2 has a highly microporous regolith structure comprising nano-sized carbon grains on the surface.</P>
2014-2015 MULTIPLE OUTBURSTS OF 15P/FINLAY
Ishiguro, Masateru,Kuroda, Daisuke,Hanayama, Hidekazu,Kwon, Yuna Grace,Kim, Yoonyoung,Lee, Myung Gyoon,Watanabe, Makoto,Akitaya, Hiroshi,Kawabata, Koji,Itoh, Ryosuke,Nakaoka, Tatsuya,Yoshida, Michitos American Astronomical Society 2016 The Astronomical journal Vol.152 No.6
<P>Multiple outbursts of a Jupiter-family comet (JFC), 15P/Finlay, occurred from late 2014 to early 2015. We conducted an observation of the comet after the first outburst and subsequently witnessed another outburst on 2015 January 15.6-15.7. The gas, consisting mostly of C-2 and CN, and dust particles expanded at speeds of 1110 +/- 180 m s(-1) and 570 +/- 40 m s(-1) at a heliocentric distance of 1.0 au. We estimated the maximum ratio of solar radiation pressure with respect to the solar gravity beta(max) = 1.6 +/- 0.2, which is consistent with porous dust particles composed of silicates and organics. We found that 10(8)-10(9) kg of dust particles (assumed to be 0.3 mu m - 1 mm) were ejected through each outburst. Although the total mass is three orders of magnitude smaller than that of the 17P/Holmes event observed in 2007, the kinetic energy per unit mass (10(4) J kg(-1)) is equivalent to the estimated values of 17P/Holmes and 332P/2010 V1 (Ikeya-Murakami), suggesting that the outbursts were caused by a similar physical mechanism. From a survey of cometary outbursts on the basis of voluntary reports, we conjecture that 15P/Finlay-class outbursts occur >1.5 times annually and inject dust particles from JFCs and Encke-type comets into interplanetary space at a rate of similar to 10 kg s(-1) or more.</P>
Ishiguro, Masateru,Kuroda, Daisuke,Hanayama, Hidekazu,Takahashi, Jun,Hasegawa, Sunao,Sarugaku, Yuki,Watanabe, Makoto,Imai, Masataka,Goda, Shuhei,Akitaya, Hiroshi,Takagi, Yuhei,Morihana, Kumiko,Honda, IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.798 No.2
<P>We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a heliocentric distance r(h) = 1.6AU and showed weak activity at r(h) <= 1.4AU. We found an active region of <0.001% of the entire nuclear surface during the comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with an uncertainty of factor 3-5) were ejected following a differential power-law size distribution with index q = -3.25 +/- 0.10. We derived a mass-loss rate of 2-10 kg s(-1) during the active phase and a total mass of approximate to 5 x 10(7) kg during the 2014 return. The ejection terminal velocity of millimeter- to centimeter-sized particles was 1-4ms(-1), which is comparable to the escape velocity from the nucleus (1.4ms(-1)). These results imply that such large meteoric particles marginally escaped from the highly dormant comet nucleus via the gas drag force only within a few months of the perihelion passage.</P>
Ishiguro, Masateru,Kuroda, Daisuke,Hasegawa, Sunao,Kim, Myung-Jin,Choi, Young-Jun,Moskovitz, Nicholas,Abe, Shinsuke,Pan, Kang-Sian,Takahashi, Jun,Takagi, Yuhei,Arai, Akira,Tokimasa, Noritaka,Hsieh, He IOP Publishing 2014 The Astrophysical journal Vol.792 No.1
<P>We investigated the magnitude-phase relation of (162173) 1999 JU3, a target asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed the International Astronomical Union's H-G formalism but found that it fits less well using a single set of parameters. To improve the inadequate fit, we employed two photometric functions: the Shevchenko and Hapke functions. With the Shevchenko function, we found that the magnitude-phase relation exhibits linear behavior in a wide phase angle range (alpha = 5 degrees-75 degrees) and shows weak nonlinear opposition brightening at alpha < 5 degrees, providing a more reliable absolute magnitude of H-V = 19.25 +/- 0.03. The phase slope (0.039 +/- 0.001 mag deg(-1)) and opposition effect amplitude (parameterized by the ratio of intensity at alpha = 0 degrees.3 to that at alpha = 5 degrees, I(0 degrees.3)/I(5 degrees) = 1.31 +/- 0.05) are consistent with those of typical C-type asteroids. We also attempted to determine the parameters for the Hapke model, which are applicable for constructing the surface reflectance map with the Hayabusa 2 onboard cameras. Although we could not constrain the full set of Hapke parameters, we obtained possible values, w = 0.041, g = -0.38, B-0 = 1.43, and h = 0.050, assuming a surface roughness parameter <(theta)over bar> = 20 degrees. By combining our photometric study with a thermal model of the asteroid, we obtained a geometric albedo of p(v) = 0.047 +/- 0.003, phase integral q = 0.32 +/- 0.03, and Bond albedo A(B) = 0.014 +/- 0.002, which are commensurate with the values for common C-type asteroids.</P>
Polarimetric Study of Near-Earth Asteroid (1566) Icarus
Ishiguro, Masateru,Kuroda, Daisuke,Watanabe, Makoto,Bach, Yoonsoo P.,Kim, Jooyeon,Lee, Mingyeong,Sekiguchi, Tomohiko,Naito, Hiroyuki,Ohtsuka, Katsuhito,Hanayama, Hidekazu,Hasegawa, Sunao,Usui, Fumihik American Institute of Physics 2017 The Astronomical journal Vol.154 No.5
<P>We conducted a polarimetric observation of the fast-rotating near-Earth asteroid (1566) Icarus at large phase (Sun-asteroid-observer's) angles alpha = 57 degrees-141 degrees around the 2015 summer solstice. We found that the maximum values of the linear polarization degree are P-max = 7.32 +/- 0.25% at phase angles of alpha(max) = 124 degrees +/- 8 degrees in the V-band and P-max = 7.04 +/- 0.21% at alpha(max) = 124 degrees +/- 6 degrees in the RC-band. Applying the polarimetric slope-albedo empirical law, we derived a geometric albedo of p(V) = 0.25 +/- 0.02, which is in agreement with that of Q-type taxonomic asteroids. amax is unambiguously larger than that of Mercury, the Moon, and another near-Earth S-type asteroid (4179) Toutatis but consistent with laboratory samples with hundreds of microns in size. The combination of the maximum polarization degree and the geometric albedo is in accordance with terrestrial rocks with a diameter of several hundreds of micrometers. The photometric function indicates a large macroscopic roughness. We hypothesize that the unique environment (i.e., the small perihelion distance q = 0.187 au and a short rotational period of T-rot = 2.27 hr) may be attributed to the paucity of small grains on the surface, as indicated on (3200) Phaethon.</P>
KISO/KWFC Observation of the Dust Ejecta Associated with the 2007 Outburst of 17P/Holmes
Masateru Ishiguro,Yuki Sarugaku,Daisuke Kuroda,Hidekazu Hanayama,Yoonyoung Kim,Yuna Kwon,Hiroyuki Maehara,Jun Takahashi,Tsuyoshi Terai,Fumihiko Usui,Jeremie J.Vaubaillon,Tomoki Morokuma,Naoto Kobayash 한국천문학회 2015 天文學會報 Vol.40 No.2
( Takehiko Matsushita ),( Shu Watanabe ),( Daisuke Araki ),( Kanto Nagai ),( Yuichi Hoshino ),( Noriyuki Kanzaki ),( Tomoyuki Matsumoto ),( Takahiro Niikura ),( Ryosuke Kuroda ) 대한슬관절학회 2021 대한슬관절학회지 Vol.33 No.-
Introduction: Previous studies have reported that alignment changes depend on the patient’s position in orthopedic surgery. However, it has not yet been well examined how the patient’s position affects the preoperative planning in high-tibial osteotomy (HTO). Therefore, the aim of this study was to investigate the effects of the patient’s position on preoperative planning in HTO. Materials and methods: A total of 60 knees in 55 patients who underwent HTO were retrospectively examined. Virtual preoperative planning for medial open-wedge HTO (OWHTO), lateral closed-wedge HTO (CWHTO), and hybrid CWHTO were performed by setting the percentage of the weight-bearing line (%WBL) at 62% as an optimal alignment. The correction angle differences between the supine and standing radiographs were measured. The virtual %WBL (v%WBL) was determined by applying the correction angle obtained from the standing radiograph to the supine radiograph. The %WBL discrepancy (%WBLd) was calculated as v%WBL - 62 (%) to predict the possible correction errors during surgeries. A single regression analysis was performed to examine the correlation between the correction angle difference and %WBLd. Results: The mean correction angle was significantly higher when the preoperative planning was based on standing radiographs than when based on supine radiographs (P < 0.001), and the mean difference was 2.2 ± 1.5°. The difference between the two conditions in the medial opening gaps for OWHTO, lateral wedge sizes (mm) for CWHTO, and hybrid CWHTO were 2.6 ± 2.0, 2.3 ± 1.6, and 1.9 ± 1.4, respectively. The mean v%WBL was 71.2% ± 7.3%, and the mean %WBLd was 10.1% ± 7.4%. A single regression analysis revealed a linear correlation between the correction angle difference and %WBLd (%WBLd = 4.72 × correction angle difference + 0.08). No statistically significant difference in the parameters was found between the supine and standing radiographs postoperatively. Conclusions: We found significant differences in the estimated correction angles between the supine and standing radiographs in the planning for HTO. Therefore, surgeons should carefully consider the difference between supine and standing radiographs and estimate the possible correction error during surgery when planning a HTO.