Yasushi Muraki

CCD uVJIC photometry was obtained for three eclipsing binaries in the Magellanic Clouds and the preliminary analyses of their light curves has been made using a modified Wilson code. The LMC system, MACHO*05:36:48.7-69:17:00, is detached and eccentric, most likely comprising of two similar stars. The system has apsidal motion with a period of 100 ± 5 years. Initial results for two other systems in the SMC, MOA J005018.4–723855 and MOA J005623.5–722123, indicate circular orbits with the former semi-detached and the latter detached with two stars of very similar temperature.

A new accelerator experiment to study very forward particle emission in the LHC collider, LHCf, is presented. Because a collision of 7 TeV protons corresponds to eV in the laboratory system, our experiment can give a rm base for simulating air showers generated from ultra high energy cosmic rays. This is indispensable information for the ongoing large experiments like TA, Auger and EUSO for the near future. The LHCf detector is composed of three tower electromagnetic calorimeters and scintillating bers (SciFi) to measure core position of the shower. To avoid multi particle hits, each tower has a small cross section (2cm 2cm, 3cm 3cm and 4cm 4cm). We have conrmed that we can measure shower energy with 5% resolution even using such small calorimeters. A project overview and the results of a beam test carried out in August 2004 at CERN SPS are presented.

Solar neutrons observed by a solar neutron telescope, a neutron monitor and a muon telescope on June 6th 1991 indicate that ions are accelerated a few minutes later than electrons. We propose that ions are accelerated by the shock wave which has been induced by the flux of electrons in the solar atmosphere. In other cases such as May 24, 1990, March 22, 1991 and June 4th, 1991, the same features have been seen.

ABSTRACT We have investigated ion acceleration mechanisms in solar flares by observing solar neutrons produced by in association with these solar flares. Solar neutrons are observed by means of ground-based neutron monitors and solar neutron telescopes which form an international network for solar neutron observations. Observations of solar neutrons have been made during solar cycle 23 using this network. More than a hundred X class flares have been recorded in solar cycle 23. Corresponding to these, five solar neutron events were observed by ground-based neutron monitors from the flares of November 24, 2000, August 25, 2001, October 28, November 2 and 4, 2003. The statistical significances of all these events were, very significant (more than 5 σ), and the excesses were clear. These solar neutron events observed in solar cycle 23 were detected in association with strong emissions of hard X-rays and γ -rays. The occurrence of solar neutrons appears to be correlated with the intensity of hard X-rays and γ -rays emitted by the associated solar flare as observed by the Yohkoh, RHESSI and INTEGRAL satellites. Assuming that solar neutrons are produced at the same time as the emission of these γ -rays, a good correlation is found between the production times of solar neutrons and the observed excesses of neutron monitors. The corresponding energy spectra of solar neutrons at the solar surface is well described by a power law. The spectral indexes of the solar neutron events we have observed in solar cycle 23 are typical for the solar neutron events observed so far, being between -3 and -4, although the fluxes are fainter than those observed in earlier events. From the spectra of solar neutrons, the energy spectra of accelerated ions can be deduced and these are found to be softer than the neutron spectra, which have spectral indexes between -4 and -5. The corresponding number of protons above 30 MeV was estimated to be between 1030 and 1033 for these events.

Simultaneous Observations of Solar Neutrons on June 6, 1 991 at Mt. Haleakala and Mt. Norikura Y. Muraki, S. Sakakibara, S. Shibata 1), K. Murakami 2) K. Takahashi 3), KR Pyle 4), T. Sakal 5), K. Mitsui 6) MA Shea 7) and DF Smart 7) Solar-Terrestrial-Environmental ...

ABSTRACT Before 1995, measurements with use of large area detectors could not find clear evidence of strong particle beams coming from Cygnus X-3 in 100 TeV region (CASA, Cygnus, Tibet and Hegra groups). On the contrary, observation by the EGRET detector on board CGRO satellite has found three bright sources of gamma-rays in Cygnus region and one of them corresponds to the position of Cygnus X-3. In this paper, the authors examine the possibility that cosmic-rays in UHE region are really coming from Cygnus region using the experimental data themselves taken by Ohya airshower detector which have been operated in a duration during between 1986 and 1994. This detector has a prominent character in comparison with other experiment in the following point since it has a large muon detectorwith an area of 500m^2 which is located under 33m tunnel from the ground level. There is no contamination of punch-through electrons inside the muon detector being penetrated through the rock. Only genuine muons are counted by the muoun detector. This paper may become our final results on Ohya air shower experiment. We have found two points of excess of photon-like showers from Cygnus region. One of the peaks coincides with the peak given by EGRET observation, but the other does not fit exactly to the position of Cygnus X-3. Recently (2013) ,the groups of Tibet-AS array and MILAGRO have observed an excess of UHE cosmic rays from Cygnus region and their results may coincide with our early observation during 1986 and 1994.