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21.
Turatto M Suzuki T Mazzali PA Benetti S Cappellaro E Danziger IJ Nomoto K Nakamura T Young TR Patat F 《The Astrophysical journal》2000,534(1):L57-L61
The extraordinary SN 1997cy associated with GRB 970514 has been observed photometrically and spectroscopically for nearly 2 yr. At the time of discovery, SN 1997cy was the brightest supernova (SN) ever observed (MV=-20.1, vhel=19,140 km s-1, H0=65 km s-1 Mpc-1). Up to the last available observations (600 days after the gamma-ray burst), the total time-integrated flux was equal to or larger than that expected from the complete thermalization of the gamma-rays produced by 2.3 M middle dot in circle of 56Co. However, starting already on day 60 the luminosity decline is slower than the 56Co decay rate, indicating that the SN ejecta was interacting with circumstellar material (CSM). The interaction appeared to weaken around day 550. The spectra of SN 1997cy are dominated at all epochs by Halpha emission, which shows at least three components of different widths, as in SN 1988Z. Several other lines with different widths are also visible, especially at early epochs. The entire light curve of SN 1997cy is reproduced by a model of the interaction of the very energetic (E=3x1052 ergs) ejecta of a massive star (25 M middle dot in circle) with the CSM, with some contribution from radioactive decays. The CSM could have been ejected with a mass-loss rate of M&d2; approximately 4x10-4 M middle dot in circle yr-1 as the progenitor star evolved from a blue to a red supergiant about 104 yr before the explosion. The lack of oxygen and magnesium lines in the spectra at nebular phases poses a problem for models requiring high-mass progenitors. The possibility that most of the core material of the progenitor has fallen onto a massive black hole so that the reverse shock dies at the inner edge of the H/He envelope is discussed. 相似文献
22.
More and more small bodies are found to be porous. Laboratory impact experiments of various porous materials have been performed, which increased our understanding of the impact process of porous bodies. In this review, we classify porous targets according to the internal structure, describe the physical properties that characterize these materials, and summarize some results of impact strength and the general tendency upon impact condition and material properties. The material property presented here includes a relation between applied load and distension although measured in static condition. Further investigation is required to clarify the role of crack growth and compaction in the time evolution of physical properties of porous materials upon impact. Laboratory experiments with detailed material properties will be useful as a database that can serve as a reference for numerical modeling and theoretical scaling considerations. 相似文献
23.
Masanobu Shimada Hiromi Oaku Yasushi Mitomi Hiroshi Murakami Akira Mukaida Yasuhisa Nakamura Joji Ishizaka Hiroshi Kawamura Tasuku Tanaka Motoaki Kishino Hajime Fukushima 《Journal of Oceanography》1998,54(5):401-416
We present calibration and validation results of the OCTS’s ocean color version-3 product, which mainly consists of the chlorophyll-a concentration (Chl-a) and the normalized water-leaving radiance (nLw). First, OCTS was calibrated for the inter-detector sensitivity difference, offset, and absolute sensitivity using external
calibration source. It was also vicariously calibrated using in-situ measurements for water (Chl-a andnLw) and atmosphere (optical thickness), which were acquired synchronously with OCTS under cloud-free conditions. Second, the
product was validated using selected 17 in-situ Chl-a and 11 in-situnLw measurements. We confirmed that Chl-a was estimated with an accuracy of 68% for Chl-a less than 2 mg/m3, andnLw from 94% (band 2) to 128% (band 4). Geometric accuracy was improved to 1.3 km. Stripes were significantly reduced by modifying
the detector normalization factor as a function of input radiance. 相似文献
24.
Mingyu Wu Quanming Lu Martin Volwerk Rumi Nakamura Tielong Zhang 《Astrophysics and Space Science》2018,363(2):22
In this paper, with the in-situ observations from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes we report a wavy dipolarization front (DF) event, where the DF has different magnetic structures and electron distributions at different \(y\) positions in the Geocentric Solar Magnetospheric (GSM) coordinates. At \(y \sim2.1R_{E}\) (\(R_{E}\) is the radius of Earth), the DF has a relatively simple structure, which is similar to that of a conventional DF. At \(y \sim3.0R_{E}\), the DF is revealed to have a multiple DF structure, where the plasma exhibits a vortex flow. Such a wavy DF could be the results of the interchange instability. The different structure of such a wavy DF at different sites has a great effect on electron acceleration. Fermi acceleration can occur at the site of the DF with a simple or multiple DF structure, while betatron acceleration as a local process has the contribution to energetic electrons only at the site of the DF with a simple structure. 相似文献
25.
Shigehisa Nakamura 《Marine Geodesy》2013,36(3):265-272
Abstract Tsunami occurrence and invasive tsunami at a local area in the circum‐Pacific seismic zone were studied as a Poisson process. The tsunami height at Osaka, Japan, was related to tsunami magnitude. The exceedence frequency of invaded tsunami at Osaka showed a good fitness to the Poisson process. However, an adapted process should be introduced for exceedence frequency of tsunami occurrence in the western Pacific. The exceedence probability of invasive tsunami at Osaka was shown as a function of tsunami magnitude on a diagram with a parameter of the time period. The obtained result might be useful for the planning of coastal area, warning of invasive tsunami, and designing coastal structures as protection within the scope of tsunami economics. 相似文献
26.
Wang Tan K. McIntosh Kirk Nakamura Yosio Liu Char-Shine Chen How-Wei 《Marine Geophysical Researches》2001,22(4):265-287
A wide-angle seismic survey, combining ocean-bottom seismometers (OBS) and multi-channel seismic (MCS) profiling, was implemented
in the southwestern Ryukyu subduction zone during August and September 1995. In this paper, we present the data analysis of
eight OBSs and the corresponding MCS line along profile EW9509-1 from this experiment. Seismic data modeling includes identification
of refracted and reflected arrivals, initial model building from velocity analysis of the MCS data, and simultaneous and layer-stripping
inversions of the OBS and MCS arrivals. The velocity-interface structure constructed along profile EW9509-1 shows that the
northward subduction of the Philippine Sea Plate has resulted in a northward thickening of the sediments of the Ryukyu Trench
and the Yaeyama accretionary wedge north of the trench. The boundary between the subducting oceanic crust and the overriding
continental crust (represented by a velocity contour of 6.75 km/s) and a sudden increase of the subducting angle (from 5 degrees
to 25 degrees) are well imaged below the Nanao Basin. Furthermore, velocity undulation and interface variation are found within
the upper crust of the Ryukyu Arc. Therefore, the strongest compression due to subduction and a break-off of the slab may
have occurred and induced the high seismicity in the forearc region.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
27.
Shigehisa Nakamura 《Marine Geodesy》2013,36(4):305-312
A note is presented on tsunami bore front. This tsunami bore front is an old dynamical problem but also a new problem to be understood. The tsunami event on 2004 December 26 has raised this is an urgent problem. The author introduces here a model in order to see a hydrodynamical specific property of the tsunami bore front. This modeling gives us a new understanding about what mechanics is for the interested tsunami bore front, especially, around a coastal zone. This work adds a new understanding about mechanics of water motions as the tsunamis generated by the earthquake undersea at a distant area from the coast. The model in this work points out a specific transitional pattern as a function of time and space of tsunami bore front. This modeling gives what is essential at considering tsunami bore front. 相似文献
28.
Arata Sugimura Tokihiko Matsuda Kiyotaka Chinzei Kazuaki Nakamura 《Bulletin of Volcanology》1963,26(1):125-140
The late Cenozoic orogeny in Japan is briefly reviewed. Amounts of volcanic materials in the three periods of the orogeny are estimated at: early Neogene 150 × 103 km3 (mafic 40 %, salic 60 %), middle and late Neogene 20 × 103 km3 (mafic 70 %, salic 30 %), Quaternary 5 × 103 km3 (mafic 80 %, salic 20 %). The largest volume per unit time is in the early Neogene, and the smallest in the middle and late Neogene. Volume per unit area becomes larger towards the southeastern margin or «front» of the volcanic belt. Thermal energy transported by volcanic materials is compared with the terrestrial heat flow in the belt. 相似文献
29.
Shallow intrusion of magma caused phreatic explosions and mud flows at the snow-covered summit of Chokai volcano, northeast Honshu, Japan, after 153 years of dormancy. Total heat emission by the eruption is estimated at more than 3.0 × 1021 erg. Equivalent amount of magma is about 2.2 × 108 ton. Focal mechanisms of the associated volcanic earthquakes, which had been variable during the period of eruption. became stable after the cessation of the surface activity with pressure axis in a NW direction which is also the strike of the epicenter distribution. This temporal change of focal mechanisms may be interpreted as the result of propagation of increased pore pressure in the direction of the maximum pressure in the post eruptive period. The magmatic pressure which certainly predominated during the eruption period and caused carthquakes with variable mechanisms, decreased through surface activity. 相似文献
30.