ASCA Observation of the Quiescent X-Ray Counterpart to SGR 1627-41

We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux approximately 5x10-12 ergs cm-2 s-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations.     

Three-dimensional image of the anisotropic bodies beneath central Honshu, Japan

Shear-wave splitting from local deep earthquakes is investigated to clarify the volume and the location of two anisotropic bodies in the mantle wedge beneath central Honshu, Japan. We observe a spatial variation in splitting parameters depending on the combination of sources and receivers, nearly N–S fast in the northern region, nearly E–W fast in the southern region and small time delays in the eastern region. Using forward modelling, two models with 30 and 10 per cent anisotropy are tested by means of a global search for the locations of anisotropic bodies with various volumes. The optimum model is obtained for 30 per cent anisotropy, which means a 5 per cent velocity difference between fast and slow polarized waves. The northern anisotropic body has a volume of 1.00° (longitude) × 0.5° (latitude) × 75 km (depth), with the orientation of the symmetry axis being N20°E. The southern anisotropic body has a volume of 1.25° × 1.25° × 100 km with the symmetry axis along N95°E. Our results show that the anisotropic bodies are located in low-velocity and low- Q regions of the mantle. This, together with petrological data and the location of volcanoes in the arc, suggests that the possible cause of the anisotropy is the preferred alignment of cracks filled with melt.     

Source mechanisms and tectonic significance of historical earthquakes along the nankai trough,Japan

Two recent and three historical earthquakes which occurred along the Nankai trough, marking the northern plate boundary between the Philippine Sea and the Asian Plate, are studied mainly on the basis of the data of crustal deformations and tsunami waves. These earthquakes are the 1946 Nankaido, the 1944 Tonankai, the 1854 Ansei I, II and the 1707 Hoei earthquakes. They are all interpreted as low-angle thrust faults at the plate boundary, with the oceanic side underthrusting northwestward against southwestern Japan. The fault parameters of the historical earthquakes are assumed here to be common to those of the recent two earthquakes, except for the magnitude of dislocation.The entire fault region, which extends for 530 km from western Shikoku Island in the west to the Tokai district in the east, is divided into four fault planes, which are denoted the planes A, B, C and D, from west to east, respectively. Then, the five earthquakes may be attributed to the planes A, B, C and D, in the following manner: the Nankaido earthquake, A + B; the Tonankai earthquake, C; the Ansei II earthquake, A + B; the Ansei I earthquake, C + D; and the Hoei earthquake, A + B + C + D.The latest cycle of earthquake migration seems incomplete as proved by the recent inactivity in D. Consequently, the future major earthquake next to occur is expected there, off the Tokai district. Eight further ancient earthquakes from A.D. 684 to 1605 are also discussed. Taking the results of the foregoing studies into consideration, their sequence is well interpreted by the four migration cycles. Topographical data, tilt of coastal terraces and location of hinge lines, prove that the thrusting has continued all along the extension of the Nankai trough for at least 300,000 years.     

VIDEO AND PHOTOGRAPHIC SPECTROSCOPY OF 1998 AND 2001 LEONID PERSISTENT TRAINS FROM 300 TO 930 nm

Spectra of persistent meteor trains were observed at wavelength between 300 and 930 nm. Two obtained train spectra during the 1998 and 2001 Leonid meteor showers are reported here. During the 1998 Leonids, one train was detected by a photographic camera with a spectrograph covering 370–640 nm region. On the other hand, during the 2001 Leonids, video observations were carried out using image intensified cameras in ultraviolet (UV), visible and near infrared (near-IR) wavelengths. Temperatures in persistent trains have been measured by atmospheric O₂ A(0,1) band at the wavelength near 864.5 nm. From a video spectrum obtained just 7 s after parent fireball’s flare, a rotational temperature of 250 K at altitude of 88.0±0.5 km was estimated. We can say that the cooling time scale of train strongly depends on the initial mass of its fireball at least for Leonids. Based on cooling constant calculated from our results, we estimated a temperature of ∼ ∼130 K as a final exothermic temperature at early stage of persistent trains.     

Resonant excitation of the solarg-modes through coupling of 5-min oscillations

It is proposed that the interacting solarg-modes are driven by the beat forcing ofg-modes by two 5-min oscillations, excited by ak-mechanism. The observational implications of the proposed mechanism are discussed.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

A planetary companion orbiting the intermediate-mass G Giant HD 173416

The discovery of a planetary companion to the intermediate-mass late-type giant star HD173416 from precise Doppler surveys of G and K giants at Xingiong station and Okayama Astrophysical Observatory (OAO) is presented in this letter. The planet has a minimum mass of 2.7 MJ an eccentricity of 0.21, a semimajor axis of 1.16 AU and an orbital period of 324 days.     

Gamma-ray probe of cosmic ray pressure in galaxy clusters and cosmological implications

Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic ray ions in the ICM is still lacking, they produce γ-ray emission through the decay of neutral pions produced in their collisions with ICM nucleons. We investigate the capability of the Gamma-ray Large Area Space Telescope ( GLAST ) and imaging atmospheric Čerenkov telescopes (IACTs) for constraining the cosmic ray pressure contribution to the ICM. We show that GLAST can be used to place stringent upper limits, a few per cent for individual nearby rich clusters, on the ratio of pressures of the cosmic rays and thermal gas. We further show that it is possible to place tight (≲10 per cent) constraints for distant  ( z ≲ 0.25)  clusters in the case of hard spectrum, by stacking signals from samples of known clusters. The GLAST limits could be made more precise with the constraint on the cosmic ray spectrum potentially provided by IACTs. Future γ-ray observations of clusters can constrain the evolution of cosmic ray energy density, which would have important implications for cosmological tests with upcoming X-ray and Sunyaev–Zel'dovich effect cluster surveys.     

Purely physical separation of a small fraction of the Allende meteorite that is highly enriched in noble gases

Abstract— Fine material that floats during freeze-thaw disaggregation of the Allende meteorite is greatly enriched in noble gases compared to the bulk meteorite. Not only the elemental concentrations, but also most isotopic ratios of the noble gases in this fraction, strongly suggest that this material is very similar to the gas-rich carbonaceous residue isolated from the bulk meteorite by chemical treatment. The only significant difference in noble gas signature between our separated fraction and the chemical residues is that the ¹²⁹Xe/¹³²Xe ratio in the former is significantly lower than that in the latter, which suggests readsorption of ¹²⁹Xe released from the dissolved minerals during the chemical treatment. This is the first time that a gas-rich residue of a meteorite has been separated by a purely physical method alone. We also show that noble gases in phase Q and presolar diamond may be separable physically, although both are closely associated.     

Sea-floor positioning with global positioning system–acoustic link system

The present study describes a new system designed and developed for observing crustal deformation on the sea floor. The system consists of two parts, the kinematic positioning by global positioning system (GPS) and acoustic ranging techniques. Since the location of a site at the ocean bottom relative to a reference site on land cannot be determined directly, the procedure was divided into two steps. First, the position of a vessel was determined using differential and kinematic GPS techniques, and then the position of a reference point at the ocean bottom was located relative to the vessel using the acoustic ranging technique. Thus, the location of the ocean-bottom station is determined relative to the reference sites on land in the global reference system. The accuracy was tested in several ways. In one experiment, a buoy was used as the surface station which linked the positions of a GPS receiver to the acoustic transponder. Assuming a simple sound velocity profile of the seawater, the position of an ocean-bottom reference point was estimated with an accuracy of several meters. Thus, with the present system, it is difficult to observe ocean-bottom crustal deformations generated by typical plate motions. Methods are being investigated to improve the observation system for more accurate sea floor positioning.