研究者業績

森井 幹雄

モリイ ミキオ  (Mikio Morii)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 主任研究開発員

研究者番号
90392810
J-GLOBAL ID
202201019169253149
researchmap会員ID
R000042142

論文

 13
  • Mikio Morii, Yoshitomo Maeda, Hisamitsu Awaki, Kouichi Hagino, Manabu Ishida, Koji Mori
    Publications of the Astronomical Society of Japan 2024年2月9日  
    Abstract We develop a new deconvolution method to recover the precise Crab Nebula image taken by the Hitomi HXT, suppressing the artifact due to the bright Crab pulsar. We extend the Richardson–Lucy method, introducing two components corresponding to the nebula and pulsar with regularization for smoothness and flux, respectively, and performing simultaneous deconvolution of multi-pulse-phase images. The structures, including the torus and jets, seen in the deconvolved nebula image at the lowest energy band of 3.6–15 keV appear consistent with those identified in the high-resolution Chandra X-ray image. Above 15 keV, we confirm NuSTAR’s findings that the nebula size decreases in higher energy bands. We find that the north-east side of the nebula is fainter in higher energy bands. Our deconvolution method is applicable for any telescope images of faint diffuse objects containing a bright point source.
  • Tomoki Omama, Makoto Uemura, Shiro Ikeda, Mikio Morii
    Publications of the Astronomical Society of Japan 73(3) 716-727 2021年6月13日  査読有り
    Simultaneous X-ray and optical observations of black hole X-ray binaries have shown that the light curves contain multiple correlated and anti-correlated variation components when the objects are in the hard state. In the case of the black hole X-ray binary GX 339−4, the cross correlation function (CCF) of the light curves suggests a positive correlation with an optical lag of 0.15 s and anti-correlations with an optical lag of 1 s and X-ray lag of 4 s. This indicates that the two light curves have some common signal components with different delays. In this study we extracted and reconstructed those signal components from the data for GX 339−4. The results confirmed that correlation and anti-correlation with the optical lag are two common components. However, we found that the reconstructed light curve for the anti-correlated component indicates a positively correlated variation with an X-ray lag of ∼+1 s. In addition, the CCF for this signal component shows anti-correlations not only with the optical lag, but also with the X-ray lag, which is consistent with the CCF for the data. Therefore, our results suggest that the combination of the two positively correlated components, that is, the X-ray preceding signal with the 0.15 s optical lag and the optical preceding signal with the 1 s X-ray lag, can make the observed CCF without anti-correlated signals. The optical preceding signal may be caused by synchrotron emission in a magnetically dominated accretion flow or in a jet, while further study is required to understand the mechanism of the X-ray time lag.
  • Yasuda, Naoki, Tanaka, Masaomi, Tominaga, Nozomu, Jiang, Ji-an, Moriya, Takashi J., Morokuma, Tomoki, Suzuki, Nao, Takahashi, Ichiro, Yamaguchi, Masaki S., Maeda, Keiichi, Sako, Masao, Ikeda, Shiro, Kimura, Akisato, Morii, Mikio, Ueda, Naonori, Yoshida, Naoki, Lee, Chien-Hsiu, Suyu, Sherry H., Komiyama, Yutaka, Regnault, Nicolas, Rubin, David
    Publications of the Astronomical Society of Japan 2019年6月24日  査読有り
    <jats:title>Abstract</jats:title> <jats:p>We present an overview of a deep transient survey of the COSMOS field with the Subaru Hyper Suprime-Cam (HSC). The survey was performed for the 1.77 deg2 ultra-deep layer and 5.78 deg2 deep layer in the Subaru Strategic Program over six- and four-month periods from 2016 to 2017, respectively. The ultra-deep layer reaches a median depth per epoch of 26.4, 26.3, 26.0, 25.6, and 24.6 mag in g, r, i, z, and y bands, respectively; the deep layer is ∼0.6 mag shallower. In total, 1824 supernova candidates were identified. Based on light-curve fitting and derived light-curve shape parameter, we classified 433 objects as Type Ia supernovae (SNe); among these candidates, 129 objects have spectroscopic or COSMOS2015 photometric redshifts and 58 objects are located at z &gt; 1. Our unique data set doubles the number of Type Ia SNe at z &gt; 1 and enables various time-domain analyses of Type II SNe, high-redshift superluminous SNe, variable stars, and active galactic nuclei.</jats:p>
  • T. Kawamuro, Y. Ueda, M. Shidatsu, T. Hori, M. Morii, S. Nakahira, N. Isobe, N. Kawai, T. Mihara, M. Matsuoka, T. Morita, M. Nakajima, H. Negoro, S. Oda, T. Sakamoto, M. Serino, M. Sugizaki, A. Tanimoto, H. Tomida, Y. Tsuboi, H. Tsunemi, S. Ueno, K. Yamaoka, S. Yamada, A. Yoshida, W. Iwakiri, Y. Kawakubo, Y. Sugawara, S. Sugita, Y. Tachibana, T. Yoshii
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 238(2) 2018年10月  
    We present the third MAXI/GSC catalog in the high Galactic latitude sky (vertical bar b vertical bar > 10 degrees) based on the 7-year data from 2009 August 13 to 2016 July 31, complementary to that in the low Galactic latitude sky (vertical bar b vertical bar < 10 degrees) (Hori et al. 2018). We compile 682 sources detected at significances of s(D,4-10 keV) >= 6.5 in the 4-10 keV band. A two-dimensional image fit based on the Poisson likelihood algorithm (C-statistics) is adopted for the detections and constraints on their fluxes and positions. The 4-10 keV sensitivity reaches approximate to 0.48 mCrab, or approximate to 5.9 x 10(-12) erg cm(-2) s(-1), over half of the survey area. Compared with the 37-month Hiroi et al. (2013) catalog, which adopted a threshold of s(D,4-10) (keV) >= 7, the source number increases by a factor of similar to 1.4. The fluxes in the 3-4 keV and 10-20 keV bands are further estimated, and hardness ratios (HRs) are calculated using the 3-4 keV, 4-10 keV, 3-10 keV, and 10-20 keV band fluxes. We also make the 4-10 keV light curves in 1-year bins for all the sources and characterize their variabilities with an index based on a likelihood function and the excess variance. Possible counterparts are found from five major X-ray survey catalogs by Swift, Uhuru, RXTE, XMM-Newton, and ROSAT, as well as an X-ray galaxy cluster catalog (MCXC). Our catalog provides the fluxes, positions, detection significances, HRs, 1-year bin light curves, variability indices, and counterpart candidates.
  • T. Hori, M. Shidatsu, Y. Ueda, T. Kawamuro, M. Morii, S. Nakahira, N. Isobe, N. Kawai, T. Mihara, M. Matsuoka, T. Morita, M. Nakajima, H. Negoro, S. Oda, T. Sakamoto, M. Serino, M. Sugizaki, A. Tanimoto, H. Tomida, Y. Tsuboi, H. Tsunemi, S. Ueno, K. Yamaoka, S. Yamada, A. Yoshida, W. Iwakiri, Y. Kawakubo, Y. Sugawara, S. Sugita, Y. Tachibana, T. Yoshii
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 235(1) 2018年3月  
    We present the first MAXI/GSC X-ray source catalog in the low-Galactic-latitude sky vertical bar b vertical bar < 10 degrees outside the Galactic center region (vertical bar b vertical bar < 5 degrees, l < 30 degrees, and l > 330 degrees) based on 7-year data from 2009 August 13 to 2016 July 31. To overcome source confusion in crowded regions, we have accurately calibrated the position-dependent shape of the point-spread function of the MAXI/GSC by analyzing onboard data. We have also taken into account the Galactic ridge X-ray emission. Using a maximum likelihood image fitting method, we have detected 221 sources with a significance threshold >6.5 sigma, 7 of which are transients only detected in 73-day time-sliced images. The faintest source has a flux of 5.2 x 10(-12) erg cm(-2) s(-1) (or an intensity of 0.43 mCrab) in the 4-10 keV band. We have identified the counterparts for about 81% of the detected sources, by cross-matching with the Swift, Uhuru, RXTE, XMM-Newton, MCXC, and ROSAT all-sky survey catalogs. Our catalog contains the source name, position and its error, flux and detection significance in the 3-4. keV, 4-10. keV, and 10-20. keV bands, hardness ratios, and information on the likely counterpart for the individual detected sources. We have obtained 73-day bin light curves of all the cataloged sources over 7 years and have calculated their periodograms. On the basis of the mean properties of time variability and spectral hardness, we suggest that the majority of the unidentified sources are low-mass X-ray binaries or blazars. Finally, we present the log N-log S relations at different Galactic longitudes and for different source populations.
  • 根來 均, 上野 史郎, 冨田 洋, 中平 聡志, 木村 公, 石川 真木, 中川 友進, 三原 建弘, 杉崎 睦, 芹野 素子, 志達 めぐみ, 松岡 勝, 河合 誠之, 常深 博, 吉田 篤正, 坂本 貴紀, 中島 基樹, 上田 佳宏, 坪井 陽子, 山内 誠, 森井 幹雄, 山岡 和貴, MAXIチーム
    日本物理学会講演概要集 71 502-502 2016年  
  • 有元 誠, 河合 誠之, 谷津 陽一, 池田 博一, 原山 淳, 米徳 大輔, 澤野 達哉, 冨田 洋, 木村 公, 上野 史郎, 三原 建弘, 芹野 素子, 森井 幹雄, 吉田 篤正, 坂本 貴紀, 常深 博, 幸村 孝由, 根来 均, 上田 佳宏, 坪井 陽子, 海老沢 研, 中村 卓史, 田中 貴浩, 吉田 道利, 神田 展行, Vagins Mark
    日本物理学会講演概要集 70 504-504 2015年  
  • Motoko Serino, Takanori Sakamoto, Nobuyuki Kawai, Atsumasa Yoshida, Masanori Ohno, Yuji Ogawa, Yasunori Nishimura, Kosuke Fukushima, Masaya Higa, Kazuto Ishikawa, Masaki Ishikawa, Taiki Kawamuro, Masashi Kimura, Masaru Matsuoka, Tatehiro Mihara, Mikio Morii, Yujin E. Nakagawa, Satoshi Nakahira, Motoki Nakajima, Yuki Nakano, Hitoshi Negoro, Takuya Onodera, Masayuki Sasaki, Megumi Shidatsu, Juri Sugimoto, Mutsumi Sugizaki, Fumitoshi Suwa, Kazuhiko Suzuki, Yutaro Tachibana, Toshihiro Takagi, Takahiro Toizumi, Hiroshi Tomida, Yohko Tsuboi, Hiroshi Tsunemi, Yoshihiro Ueda, Shiro Ueno, Ryuichi Usui, Hisaki Yamada, Takayuki Yamamoto, Kazutaka Yamaoka, Makoto Yamauchi, Koshiro Yoshidome, Taketoshi Yoshii
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 66(5) 2014年10月  
    The Monitor of All-sky X-ray Image (MAXI) Gas Slit Camera (GSC) detects gamma-ray bursts (GRBs), including bursts with soft spectra, such as X-ray flashes (XRFs). MAXI/GSC is sensitive to the energy range from 2 to 30 keV. This energy range is lower than other currently operating instruments which are capable of detecting GRBs. Since the beginning of the MAXI operation on 2009 August 15, GSC observed 35 GRBs up to the middle of 2013. One third of them were also observed by other satellites. The rest of them show a trend to have soft spectra and low fluxes. Because of the contribution of those XRFs, the MAXI GRB rate is about three times higher than those expected from the BATSE logN-log P distribution. When we compare it to the observational results of the Wide-field X-ray Monitor on the High Energy Transient Explorer 2, which covers the the same energy range as that of MAXI/GSC, we find the possibility that many of the MAXI bursts are XRFs with E-peak lower than 20 keV. We discuss the source of soft GRBs observed only by MAXI. The MAXI logN-log S distribution suggests that the MAXI XRFs are distributed over a closer distance than hard GRBs. Since the distributions of the hardness of galactic stellar flares and X-ray bursts overlap with those of MAXI GRBs, we discuss the possibility of confusion of such galactic transients with the MAXI GRB samples.
  • 三原 建弘, 河合 誠之, 森井 幹雄, 吉田 篤正, 山岡 和貴, 根来 均, 中島 基樹, 坪井 陽子, 上田 佳宏, 廣井 和雄, 常深 博, 松岡 勝, 木村 公, 山内 誠, 杉崎 睦, 芹野 素子, 中平 聡志, 山本 堂之, 冨田 洋, 上野 史郎, 小浜 光洋
    日本物理学会講演概要集 66 112-112 2011年  査読有り
  • 三原 建弘, 石川 真木, 河合 誠之, 森井 幹雄, 吉田 篤正, 山岡 和貴, 中平 聡志, 根来 均, 中島 基樹, 坪井 陽子, 上田 佳宏, 松岡 勝, 磯部 直樹, 廣井 和雄, 常深 博, 木村 公, 山内 誠, 杉崎 睦, 芹野 素子, 中川 友進, 山本 堂之, 冨田 洋, 上野 史郎, 小浜 光洋
    日本物理学会講演概要集 66 106-106 2011年  査読有り
  • M. Morii, S. Kitamoto, N. Shibazaki, D. Takei, N. Kawai, M. Arimoto, M. Ueno, Y. Terada, T. Kohmura, S. Yamauchi
    AIP Conference Proceedings 983 268-270 2008年  査読有り
    Anomalous X-ray pulsars (AXPs) are thought to be magnetars, which are neutron stars with ultra strong magnetic field of 1014-10 15G. Their energy spectra below ∼10keV are modeled well by two components consisting of a blackbody (BB) (∼0.4keV) and rather steep power-law (POW) function (photon index ∼2-4). Kuiper et al. (2004) discovered hard X-ray component above ∼10keV from some AXPs. Here, we present the Suzaku observation of the AXP 1E 1841-045 at the center of supernova remnant Kes 73. By this observation, we could analyze the spectrum from 0.4 to 50 keV at the same time. Then, we could test whether the spectral model above was valid or not in this wide energy range. We found that there were residual in the spectral fits when fit by the model of BB + POW. Fits were improved by adding another BB or POW component. But the meaning of each component became ambiguous in the phase-resolved spectroscopy. Alternatively we found that NPEX model fit well for both phase-averaged spectrum and phase-resolved spectra. In this case, the photon indices were constant during all phase, and spectral variation seemed to be very clear. This fact suggests somewhat fundamental meaning for the emission from magnetars. © 2008 American Institute of Physics.
  • Hiroshi Tomida, Masaru Matsuoka, Kazuyoshi Kawasaki, Shiro Ueno, Yasuki Adachi, Mitsuhiro Kohama, Motoko Suzuki, Masaki Ishikawa, Haruyoshi Katayama, Tatehiro Mihara, Mutsumi Sugizaki, Naoki Isobe, Hiroshi Tsunemi, Emi Miyata, Nobuyuki Kawai, Jun Kataoka, Atsumasa Yoshida, Kazutaka Yamaoka, Hitoshi Negoro, Motoki Nakajima, Yoshihiro Ueda, Satochi Eguchi, Mikio Morii
    Proceedings of SPIE - The International Society for Optical Engineering 7011 2008年  
    MAXI (Monitor of All-sky X-ray Image) is a payload on board the International Space Station, and will be launched on April 2009. We report on the current development status on MAXI, in particular on the two types of X-ray camera (GSC and SSC), and the simulation results of the MAXI observation. SSC is a CCD camera. The moderate energy resolution enables us to detect the various emission peak including 0.5 keV oxygen line. The averaged energy resolution at the CCD temperature of -70 deg is 144.5 eV (FWHM) for 5.9 keV X-ray. GSC includes proportional gas counters, which have large X-ray detection area (5350cm2). The averaged position resolution of 1.1mm at 8 keV enable us to determined the celestial position of bright sources within the accuracy of 0.1 degree. The simulation study involving the results of performance test exhibits the high sensitivity of MAXI as designed.
  • Shiro Ueno, Masaru Matsuoka, Kazuyoshi Kawasaki, Hiroshi Tomida, Yasuki Adachi, Mitsuhiro Kohama, Motoko Suzuki, Masaki Ishikawa, Haruyoshi Katayama, Tatehiro Mihara, Mutsumi Sugizaki, Naoki Isobe, Hiroshi Tsunemi, Emi Miyata, Nobuyuki Kawai, Jun Kataoka, Atsumasa Yoshida, Kazutaka Yamaoka, Hitoshi Negoro, Motoki Nakajima, Mikio Morii, Yoshihiro Ueda, Satoshi Eguchi
    Proceedings of SPIE - The International Society for Optical Engineering 7011 2008年  
    Monitor of All-sky X-ray Image (MAXI) is an X-ray all-sky monitor, which will be delivered to the International Space Station (ISS) by a space shuttle crew in early 2009, to scan almost the entire sky once every 96 minutes for a mission life of two to five years. The detection sensitivity will be 5 mCrab (5σ level) for a one-day MAXI operation, 2 mCrab for one week, and 1 mCrab for one month, reaching a source confusion limit of 0.2 mCrab in two years. In this paper, brief descriptions are presented for the MAXI mission and payload, and three operation phases, 1) the launch-to-docking phase, 2) the initial in-orbit calibration phase, and 3) the routine operation phase. We also describes the MAXI data product and its release plan for public users.

MISC

 69
  • Ryou Ohsawa, Akira Hirota, Kohei Morita, Shinsuke Abe, Daniel Kastinen, Johan Kero, Csilla Szasz, Yasunori Fujiwara, Takuji Nakamura, Koji Nishimura, Shigeyuki Sako, Jun-ichi Watanabe, Tsutomu Aoki, Noriaki Arima, Ko Arimatsu, Mamoru Doi, Makoto Ichiki, Shiro Ikeda, Yoshifusa Ita, Toshihiro Kasuga, Naoto Kobayashi, Mitsuru Kokubo, Masahiro Konishi, Hiroyuki Maehara, Takashi Miyata, Yuki Mori, Mikio Morii, Tomoki Morokuma, Kentaro Motohara, Yoshikazu Nakada, Shin-ichiro Okumura, Yuki Sarugaku, Mikiya Sato, Toshikazu Shigeyama, Takao Soyano, Hidenori Takahashi, Masaomi Tanaka, Ken’ichi Tarusawa, Nozomu Tominaga, Seitaro Urakawa, Fumihiko Usui, Takuya Yamashita, Makoto Yoshikawa
    Planetary and Space Science 194 105011 2020年12月  
  • Michael W Richmond, Masaomi Tanaka, Tomoki Morokuma, Shigeyuki Sako, Ryou Ohsawa, Noriaki Arima, Nozomu Tominaga, Mamoru Doi, Tsutomu Aoki, Ko Arimatsu, Makoto Ichiki, Shiro Ikeda, Yoshifusa Ita, Toshihiro Kasuga, Koji S Kawabata, Hideyo Kawakita, Naoto Kobayashi, Mitsuru Kokubo, Masahiro Konishi, Hiroyuki Maehara, Hiroyuki Mito, Takashi Miyata, Yuki Mori, Mikio Morii, Kentaro Motohara, Yoshikazu Nakada, Shin-Ichiro Okumura, Hiroki Onozato, Yuki Sarugaku, Mikiya Sato, Toshikazu Shigeyama, Takao Soyano, Hidenori Takahashi, Ataru Tanikawa, Ken’ichi Tarusawa, Seitaro Urakawa, Fumihiko Usui, Junichi Watanabe, Takuya Yamashita, Makoto Yoshikawa
    Publications of the Astronomical Society of Japan 72(1) 2019年12月6日  
    <jats:title>Abstract</jats:title> <jats:p>Using a prototype of the Tomo-e Gozen wide-field CMOS mosaic camera, we acquire wide-field optical images at a cadence of $2\:$Hz and search them for transient sources of duration 1.5 to $11.5\:$s. Over the course of eight nights, our survey encompasses the equivalent of roughly two days on one square degree, to a fluence equivalent to a limiting magnitude of about $V = 15.6$ in a 1-s exposure. After examining by-eye the candidates identified by a software pipeline, we find no sources which meet all our criteria. We compute upper limits to the rate of optical transients consistent with our survey, and compare those to the rates expected and observed for representative sources of ephemeral optical light.</jats:p>
  • Ko Arimatsu, Ryou Ohsawa, George L. Hashimoto, Seitaro Urakawa, Jun Takahashi, Miyako Tozuka, Yoichi Itoh, Misato Yamashita, Fumihiko Usui, Tsutomu Aoki, Noriaki Arima, Mamoru Doi, Makoto Ichiki, Shiro Ikeda, Yoshifusa Ita, Toshihiro Kasuga, Naoto Kobayashi, Mitsuru Kokubo, Masahiro Konishi, Hiroyuki Maehara, Noriyuki Matsunaga, Takashi Miyata, Mikio Morii, Tomoki Morokuma, Kentaro Motohara, Yoshikazu Nakada, Shin-ichiro Okumura, Shigeyuki Sako, Yuki Sarugaku, Mikiya Sato, Toshikazu Shigeyama, Takao Soyano, Hidenori Takahashi, Ken’ichi Tarusawa, Nozomu Tominaga, Jun-ichi Watanabe, Takuya Yamashita, Makoto Yoshikawa
    The Astronomical Journal 158(6) 236 2019年11月20日  
  • Yoshitomo Maeda, Ryo Iizuka, Takayuki Hayashi, Toshiki Sato, Nozomi Nakaniwa, Mai Takeo, Hitomi Suzuki, Manabu Ishida, Shiro Ikeda, Mikio Morii
    Publications of the Astronomical Society of Japan 71(5) 2019年9月17日  
    <jats:title>ABSTRACT</jats:title> <jats:p>We present a concept for an X-ray imaging system with a high angular resolution and moderate sensitivity. In this concept, a two-dimensional detector, i.e., an imager, is put at a slightly out-of-focus position of the focusing mirror, rather than just at the mirror focus, as in the standard optics, to capture miniature images of objects. In addition, a set of multi-grid masks (or a modulation collimator) is installed in front of the telescope. We find that the masks work as a coded aperture camera and that they boost the angular resolution of the focusing optics. The major advantage of this concept is that a much better angular resolution, having an order of 2–3 or more than in the conventional optics, is achievable, while a high throughput (large effective area) is maintained, which is crucial in photon-limited high-energy astronomy, because any type of mirrors, including lightweight reflective mirrors, can be employed in our concept. If the signal-to-noise ratio is sufficiently high, we estimate that angular resolutions at the diffraction limit of 4″ and 0.″4 at ∼7 keV can be achieved with a pair of masks at distances of 1 m and 100 m, respectively.</jats:p>
  • Toshiki Sato, John P. Hughes, Brian J. Williams, Mikio Morii
    The Astrophysical Journal 879(2) 64 2019年7月8日  

共同研究・競争的資金等の研究課題

 7