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A space VLBI satellite is planed to be launched in 1995 by the Institute of Space and Astronautical Science (ISAS), Japan. Together with this satellite, a worldwide collaborative project named the VLBI Space Observatory Program (VSOP) is under developed. Although the project is oriented to imaging mission for compact cores of active galactic nuclei and maser sources, it will open new aspect on all of VLBI applications. The basic design and parameters of VSOP project are reviewed.
Optical and radio behaviours of OJ 287 in the recent outburst are presented. The light curve is similar to that in the previous outburst in 1970–1971, although the maximum brightness is about 1 mag fainter. The intraday variations are found in both optical and radio regions. We find no periodicity of time scales less than 0.2 days.
We report on the first space-VLBI observations of the OH masers in two main-line OH transitions at 1665 and 1667 MHz. The observations involved the space radio telescope on board the Japanese satellite HALCA and an array of ground radio telescopes. The maps of the maser region and images of individual maser spots were produced with an angular resolution of 1 mas, which is several times higher than the angular resolution available on the ground. The maser spots were only partly resolved and a lower limit to the brightness temperature 6 × 1012 K was obtained. The masers seem to be located in the direction of low interstellar scattering.
We present high resolution studies of the nuclear region in NGC 3079 with phase-referenced VLBI monitoring between its water maser and continuum emission. From results of the observations, NGC 3079 showed relative motion between core-jet-like continuum components. One of the components (A) relative to the reference maser feature moved with an apparent subluminal velocity along the SE-NW direction, almost parallel to alignment of the components. On the other hand, the position of the other component (B) did not show such a significant change. If the maser gas is associated with a rotating disk, the maser gas should be gravitationally bound to the central mass. This suggests that B and A are the nucleus and jet, respectively.
We have examined a relativistic beaming model using a VLBI survey by Preston et al. (1985). Our statistical study of a ratio R of the flux density for the beamed compact core to that for unbeamed components of a source shows Lorentz factor γ to be ≅ 6 and RT (R at transverse alignment) to be ≅ 10−2 for a sample of 222 QSO's. In addition, we find that a sample of 60 radio galaxies show the beaming effect with γ ≅ 4. It should be emphasized here that the beaming effect strongly affects the source counts (Log N - Log S) especially at high frequencies.
Intrinsic large rotation measures (RM) were searched for 128 extragalactic sources based on polarization data obtained at the NRO 45–m telescope. The number of sources with RM > 500 rad m−2 is only seven.
We present results of the first space VLBI observations of PKS 1921-293. An inner jet component about 1.5 mas north of the core is revealed for the first time. The compact core is partially resolved, but still has a brightness temperature (at the source rest frame) of 3.0×1012 K. A spectral index map made by combining the 1.6 GHz VSOP image with the 5.0 GHz VLBA+Y image at the first epoch is also presented.
In order to investigate the genesis of powerful radio jet, we have mapped the central 10 pc region of the nearby radio galaxy NGC 6251 with a 0.2 pc resolution using VLBI at two radio frequencies, 5 GHz and 15 GHz, we have found the sub-parsec-scale counterjet for the first time in this radio galaxy. This discovery allows us to investigate the jet acceleration based on the relativistic beaming model.
Millimeter-wave continuum sources in NGC 7538 region were observed with the NRO 45-m telescope and Nobeyama Millimeter Array. NRO 45-m telescope observations showed that the compact region which includes IRS1, IRS2, and IRS3 has a strong millimeter-wave intensity excess, cf. figures 1, and 2.
VLBI observations of millimeter wavelengths can probe the broad line emission and jet forming regions of quasars, and the scale of an accretion disk around massive black holes in nearby active galaxies, which are self-absorbed at longer wavelengths. Therefore, the extension of the mm-VLBI network is timely and urgent problem. We are now planning to move Nobeyama 6 m mm VLBI telescope to Kagoshima. The telescope will be placed at Kinkohwan park in Kagoshima City in late 1992 and will be operated in 1993. The frequencies for VLBI observations will range from 22 GHz to 100 GHz.
To date, there are two mm-VLBI facilities in Japan: Nobeyama 45 m and Kashima 34 m, However, the longest baseline is only about 200km EW which provides a fringe separation of 17 mas. This is not sufficient for high resolution mapping. A 10 m telescope which is under construction at Mizusawa, 400 km north from Kashima which will be usable up to 43 GHz and will add a north-south baseline, which is very important for astrometrie measurement.
We report very long baseline array (VLBA) observations at 2.3, 8.4, and 15.4 GHz towards nine gigahertz peaked spectrum (GPS) sources. One Seyfert 1 galaxy, one Seyfert 2 galaxy, three radio galaxies, and four quasars were included in our survey. We obtained spatial distributions of the free–free absorption (FFA) opacity with milliarcsecond resolution for all sources. It is found that type 1 (Seyfert 1 and quasars) and type 2 (Seyfert 2 and radio galaxies) sources showed different distributions of the FFA opacities. The type 1 sources tend to show more asymmetric opacity distributions towards a double lobe, while those of the type 2 sources are rather symmetric. Our results imply that the different viewing angle of the jet causes the difference of FFA opacity along the external absorber. This idea supports the unified scheme between quasars and radio galaxies, proposed by Barthel (1989).
We report results from nearly simultaneous pentachromatic VLBI observations towards a nearby GPS galaxy NGC 1052. The observations at 1.6 and 4.8 GHz with the VSOP, and at 2.3, 8.4, and 15.4 GHz with VLBA, provide linear resolutions of ∼0.1 pc. Convex spectra of a double-sided jet imply that synchrotron emission is obscured through foreground cold dense plasma, in terms of free–free absorption (FFA). We found a central condensation of the plasma which covers about 0.1 and 1 pc of the approaching and receding jets, respectively. A simple model with a geometrically thick plasma torus perpendicular to the jets is established to explain the asymmetric distribution of FFA opacities.
We are deploying a new station for sub-millimeter Very Long Baseline Interferometry (VLBI) to obtain shadow images of Supermassive Black Hole (SMBH). Sub-mm VLBI is thought to be the only way so far to get the direct image of SMBH by its shadow, thanks to the superb angular resolution and high transparency against dense plasma around SMBH. At the Summit Station on Greenland, we have started monitoring the opacity at sub-mm region. The Summit Station subtends long baselines with the Atacama Large Milimeter/submillimeter Array (ALMA) in Chile and Submillimeter Array (SMA) in Hawaii. In parallel, we started retrofitting the ALMA North America prototype telescope (renamed as Greenland Telescope: GLT) for the cold environment.
Control of crystal orientation of vertically grown epitaxial Si (111) and (110) nanowire arrays on Si substrate has been demonstrated using a combination of an anodic aluminum oxide (AAO) template and vapor – liquid – solid (VLS) growth method. The crystal orientation of the nanowire was investigated by transmission electron microscopy. A growth direction of the nanowire arrays was guided perpendicular to the surface of the substrate by the AAO template, and the crystal orientation of the nanowire arrays was selected using the single crystal Si substrate properly cut in desired orientation.
We report results of our European VLBI Network observations towards M 87 jet at 1.6 GHz in order to study the velocity field. We revealed continuous jet up to 500 mas from the core and HST-1 component. We have not detected any proper motion for the components within first 160 mas from the core and significant superluminal motions from 2.5 to 3.5 c for the HST-1 components. Those are in good agreement with previous observations. We derived proper motions for the components about 160 to 500 mas from the core. Interestingly, the measured proper motions are faster than that of the inner components and slower than that of HST-1 components. It may suggest the possible acceleration region for superluminal features of M 87 jet.
The first dedicated space-VLBI project, the VLBI Space Observatory Programme (VSOP), commenced with the successful launch of radio-astronomical satellite HALCA in 1997. Plans for a second generation space-VLBI project have been made by a working group over a number of years. This project, VSOP-2, has now been approved by Japan's space agency, JAXA, as the ASTRO-G project. It is planned for the spacecraft to observe in the 8, 22 and 43 GHz bands with cooled receivers for the two higher bands, which include important maser lines. It will have a maximum angular resolution at 43 GHz (7 mm) of about 40 micro-arcseconds. Although the VSOP project mainly observed continuum emission from active galactic nuclei (AGN), VSOP-2/ASTRO-G is expected to enable a variety of high angular resolution maser line observations.
Porous Pd42.5Cu30Ni7.5P20 bulk glassy alloy rods with porosities up to 71% were successfully prepared by water quenching in a 15 MPa hydrogen atmosphere, followed by heat treatment in a supercooled liquid state. Pores with sizes up to 80 μm were homogeneously distributed over the whole cross-sectional area. Under compressive deformation, the porous alloys with porosities exceeding 41% did not show macroscopic fracture in a wide compressive strain range up to 0.6. Mechanical tests with porous alloy rods whose pores are anisotropically oriented indicate that the plasticity of the porous alloy is strongly affected by stress concentration factor.
High-energy protons are generated by focusing an ultrashort pulsed
high intensity laser at the Advanced Photon Research Center, JAERI-Kansai
onto thin (thickness <10 μm) Tantalum targets. The laser
intensities are about 4 × 1018 W/cm2. The
prepulse level of the laser pulse is measured with combination of a PIN
photo diode and a cross correlator and is less than 10−6.
A quarter-wave plate is installed into the laser beam line to create
circularly polarized pulses. Collimated high energy protons are observed
with CH coated Tantalum targets irradiated with the circularly polarized
laser pulses. The beam divergence of the generated proton beam is measured
with a CR-39 track detector and is about 6 mrad.