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Search Results: 1 - 10 of 789 matches for " Tetsuo Sasao "
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VLBI Observation of Microquasar Cyg X-3 during an X-ray State Transition from Soft to Hard in the 2007 May-June Flare
Jeong-Sook Kim,Soon-Wook Kim,Tomoharu Kurayama,Mareki Honma,Tetsuo Sasao,Sang Joon Kim
Physics , 2013, DOI: 10.1088/0004-637X/772/1/41
Abstract: We present a radio observation of microquasar Cyg X-3 during an X-ray state transition from ultrasoft to hard state in the 2007 May$-$June flare using the VLBI Exploration of Radio Astrometry (VERA) at 22 GHz. During the transition, a short-lived mini-flare of ${\lesssim}3$ hr was detected prior to the major flare. In such a transition, a jet ejection is believed to occur, but there have been no direct observations to support it. An analysis of Gaussian fits to the observed visibility amplitudes shows a time variation of the source axis, or a structural change, during the mini-flare. Our model fits, together with other multiwavelength observations in the radio, soft, and hard X-rays, and the shock-in-jet models for other flaring activities at GHz wavebands, suggest a high possibility of synchrotron flares during the mini-flare, indicative of a predominant contribution from jet activity. Therefore, the mini-flare with an associated structural change is indicative of a jet ejection event in the state transition from ultrasoft to hard state.
The 3-D kinematics of water masers around the semiregular variable RT Virginis
Hiroshi Imai,Katsunori M. Shibata,Kevin B. Marvel,Philip J. Diamond,Tetsuo Sasao,Makoto Miyoshi,Makoto Inoue,Victor Migenes,Yasuhiro Murata
Physics , 2003, DOI: 10.1086/374887
Abstract: We report observations of water masers around the semiregular variable RT Virginis (RT Vir), which have been made with the Very Long Baseline Array (VLBA) of the National Radio Astronomy Observatory (NRAO) at five epochs, each separated by three weeks of time. We detected about 60 maser features at each epoch. Overall, 61 features, detected at least twice, were tracked by their radial velocities and proper motions. The 3-D maser kinematics exhibited a circumstellar envelope that is expanding roughly spherically with a velocity of about 8 km/s. Asymmetries in both the spatial and velocity distributions of the maser features were found in the envelope, but less significant than that found in other semiregular variables. Systematic radial-velocity drifts of individual maser features were found with amplitudes of <= 2 km/s/yr. For one maser feature, we found a quadratic position shift with time along a straight line on the sky. This apparent motion indicates an acceleration with an amplitude of 33 km/s/yr, implying the passage of a shock wave driven by the stellar pulsation of RT Vir. The acceleration motion is likely seen only on the sky plane because of a large velocity gradient formed in the accelerating maser region. We estimated the distance to RT Vir to be about 220 pc on the basis of both the statistical parallax and model-fitting methods for the maser kinematics.
VLBI Monitoring Observations of Water Masers Around the Semi-Regular Variable Star R Crateris
Jose K. Ishitsuka,Hiroshi Imai,Toshihiro Omodaka,Munetaka Ueno,Osamu Kameya,Tetsuo Sasao,Masaki Morimoto,Takeshi Miyaji,Jun-ichi Nakajima,Teruhiko Watanabe
Physics , 2001, DOI: 10.1093/pasj/53.6.1231
Abstract: We monitored water-vapor masers around the semi-regular variable star R Crateris with the Japanese VLBI Network (J-Net) at the 22 GHz band during four epochs with intervals of one month. The relative proper motions and Doppler-velocity drifts of twelve maser features were measured. Most of them existed for longer than 80 days. The 3-D kinematics of the features indicates a bipolar expanding flow. The major axis of the asymmetric flow was estimated to be at P.A. = 136 degrees. The existence of a bipolar outflow suggests that a Mira variable star had already formed a bipolar outflow. The water masers are in a region of apparent minimum radii of 1.3 x 10^12 m and maximum radii of 2.6 x 10^12 m, between which the expansion velocity ranges from 4.3 to 7.4 km/s. These values suggest that the water masers are radially accelerated, but still gravitationally bound, in the water-maser region. The most positive and negative velocity-drifting features were found relatively close to the systemic velocity of the star. We found that the blue-shifted features are apparently accelerated and the red-shifted apparently decelerated. The acceleration of only the blue-shifted features seems to be consistent with that of the expanding flow from the star.
Remarks on the Erroneous Dispersion Surfaces From a Pair of a Hyperbolic Branch and An Elliptical Arc of the Intersected Two Laue Spheres Based on the Usual Crude Approximation  [PDF]
Tetsuo Nakajima
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.23022
Abstract: In almost all previous works, the hyperbolic dispersion surfaces of the central proper quadrics have been crudely derived from the degree of reduction from the bi-quadratic equation by use of some roughly indefinable approximate relations. Moreover, neglecting the high symmetry of the hyperbola, both the branches have been approximated on the asymmetric surfaces composed of a pair of a branch of the hyperbola and a vertex of the ellipse without the presentation of reasonable evidence. Based upon the same dispersion surfaces equation, a new original gapless dispersion surfaces could be rigorously introduced without crude omission of even a term in the bi-quadratic equation based upon usual analogy with the extended band theory of solid as the close approximation to the truth.
Japanese Social Expenditure under Rapid Population Ageing  [PDF]
Tetsuo Fukawa
Open Journal of Social Sciences (JSS) , 2015, DOI: 10.4236/jss.2015.311018
Abstract: Japan is suffering from low fertility for more than two decades, and Japanese social security system needs a structural reform to be more effective and sustainable. In this paper, we discussed structural issues in the Japanese social security system, which will provide the basis for containing social expenditure in Japan. Some Japanese benefits, such as child-rearing support and benefit for low income families as well as long-term care benefit, need to be increased. On the other hand, it is important to incorporate right incentives in the system for healthcare and LTC services, and new forms of solidarity are indispensable to make Japanese social security system sustainable.
Distributive Impact of Low-Income Support Measures in Japan  [PDF]
Tetsuo Fukawa
Open Journal of Social Sciences (JSS) , 2016, DOI: 10.4236/jss.2016.412002
Abstract:
Population decline together with rapid aging has a strong cost push pressure on social security systems in Japan. Effective measures to support low-income families are quite important to mitigate income inequality and to overcome low fertility in Japan. Using the micro-data of the Basic Household Survey 2010, we analyse various measures to support low income families through various simulations concerning child allowance, social security contributions, and income taxes. Based on the simulation results, we discussed distributive impact of such measures and their policy implications.
Elderly Population Projection and Their Health Expenditure Prospects in Japan  [PDF]
Tetsuo Fukawa
Modern Economy (ME) , 2017, DOI: 10.4236/me.2017.811085
Abstract: By using a dynamic micro-simulation model named INAHSIM-II, we conducted a population-household projection in Japan (INAHSIM 2017) for the period of 2015-2065. Due to rapid aging of the population, the distribution of the elderly (65 years old or older) by dependency level has a profound impact on health expenditure (namely medical expenditure and long-term care expenditure) of the elderly. In this paper, we estimated health expenditure of the elderly in 2025-2065, using the results of the projection of the elderly by dependency level.
Radiative emission of neutrino pair from nucleus and inner core electrons in heavy atoms
M. Yoshimura,N. Sasao
Physics , 2013, DOI: 10.1103/PhysRevD.89.053013
Abstract: Radiative emission of neutrino pair (RENP) from atomic states is a new tool to experimentally investigate undetermined neutrino parameters such as the smallest neutrino mass, the nature of neutrino masses (Majorana vs Dirac), and their CP properties. We study effects of neutrino pair emission either from nucleus or from inner core electrons in which the zero-th component of quark or electron vector current gives rise to large coupling. Both the overall rate and the spectral shape of photon energy are given for a few cases of interesting target atoms. Calculated rates exceed those of previously considered target atoms by many orders of magnitudes.
Photonic soliton and its relevance to radiative neutrino pair emission
M. Yoshimura,N. Sasao
Physics , 2009,
Abstract: We consider atomic system of $\Lambda-$type 3-level coupled to 2 mode fields, and derive an effective Maxwell-Bloch equation designed for two photon emission between two lower levels. We find axially symmetric, topologically stable soliton solutions made of condensed fields. Immediate implication of soliton formation to radiative neutrino pair emission is to enhance its rate, larger than the usual $\propto N^2$ factor of target number dependence, along with another merit of increasing the signal to the background photon emission.
Determination of CP violation parameter using neutrino pair beam
M. Yoshimura,N. Sasao
Physics , 2015, DOI: 10.1016/j.physletb.2015.12.040
Abstract: Neutrino oscillation experiments under neutrino pair beam from circulating excited heavy ions are studied. It is found that detection of double weak events has a good sensitivity to measure CP violating parameter and distinguish mass hierarchy patterns in short baseline experiments in which the earth-induced matter effect is minimized.
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