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A radio continuum survey of the galactic plane has been made with the 45-m telescope of the Nobeyama Radio Observatory at 10.55 GHz, which is the highest frequency among such surveys. The sensitivity of the telescope was Tb/S = 0.47 K/Jy and the HPBW was 2!6, which was a great advantage because of the same beam size of the Bonn 5-GHz survey (Altenhoff et al. 1978). The receiver was a cooled parametric amplifier. The instantaneous bandwidth was 500 MHz, and the system noise temperature was about 100 K. The calibration source was NGC 7027, which was assumed to be 6.6 Jy. One circular polarization component was observed. The observational parameters are summarized in Table I.
It is well known that black hole candidates, Cyg X-1 and GX 339-4, have distinct high and low states, known as bimodal states. Detailed spectroscopic studies of these X-ray sources have revealed high and low states corresponding to optically thick and thin states of the surrounding accretion disks.
The maximum peak luminosity of the X-ray bursts from a burster is most likely interpreted as the Eddington luminosity of a helium-rich envelope surrounding a neutron star. If this interpretation is true, we can obtain a relation between the mass and the radius of the neutron star in terms of the maximum effective temperature of bursts. On the other hand, the most naive understanding of the origin of the 4.1 keV absorption line often detected in X-ray burst spectra gives us another relation of the neutron star mass with its radius. By solving two simultaneous equations, we can determine the values of the mass and the radius of the neutron star, respectively. However, the result is critical to every neutron star model currently considered.
The persistent emissions from X-ray bursters are also discussed.
Preliminary results of a 10-GHz radio-continuum survey of the galactic-plane region using the 45-m telescope at NRO are presented. An extensive study of a complex region at 22° ≦ ℓ ≦ 25°, |b|≳1° has been made.
An antenna in geostationary orbit was used for VLBI observations at 2.3 GHz, in combination with ground antennas in Australia and Japan. 23 of the 25 observed sources were detected on orbiter-ground baselines, with baseline lengths as large as 2.15 earth diameters. Brightness temperatures between 1012 K and 4 × 1012 K were measured for 10 sources.
Polarization measurements of the radio Arc were made with the VLA at 15 GHz. High frequency polarimetry made with high spatial resolution minimizes Faraday depolarization and reveals polarized filaments which correspond to the predominant filaments of the radio Arc. We notice a peculiar linear feature in the polarization map (“thorns”) which suggests the presence of a second magnetic field system. The total intensity maps show no evidence for an interaction between the two field systems, so the thorns may be foreground magnetized structures. However, if the two magnetic field systems do interact, it would allow a model in which the acceleration of relativistic particles takes place at their intersection. The accelerated particles would flow toward both ends of the radio Arc, and account for the intrinsic polarization observed along the entire length of the system. Thermal electrons responsible for the Faraday depolarization occuring at longer wavelengths may be supplied by the interaction of the streams of relativistic particles with relatively dense, ambient thermal clouds.
We report NH3 observations of the Sgr A complex region including Sgr A West and the 20 km/s and 50 km/s molecular clouds (M–0.13–0.08 and M–0.02–0.07) using the Nobeyama Millimeter Array and the 45m telescope. NH3(1,1) and (2,2) lines were simultaneously observed to estimate the kinetic temperature. Our results suggest strong interaction between the molecular clouds and the continuum sources in the Sgr A complex. The interaction with continuum sources might be an important factor in determining the physical conditions of molecular gas in the galactic center region.
Ginga observed 116 AGNs during its operational life from 1987 to 1991: Among them, there were 55 Seyfert galaxies, 42 quasars, 9 BL Lac objects and 10 other AGNs, although the classification is not strict. From these AGN observations, a number of fruitful results were obtained. In this review, I briefly summarize the Ginga observations of AGNs and show several similarities between the Seyfert-type AGNs and the galactic black hole candidates. I also discuss two inverse correlations between the break energy of the power law spectrum and the flux observed from the black hole candidate GS2023+338 and between the equivalent width of the iron fluorescent line and the continuum flux observed from NGC4151.
We present 22 and 49 GHz interferometric observations of Hyd A (3C218). The source was found to have a very large Faraday rotation measure (RM) (Kato et al. 1987), and to be a dominant member of a luminous X-ray cluster with a large cooling flow (David et al. 1988). These characteristics are very similar to those of Cyg A which is suggested to produce a large RM within a dense sheath around the radio lobes as a result of somehow an interaction between dense intracluster medium (ICM) and radio jets and/or lobes (Dreher et al. 1987). Hyd A is the second example of Cyg A type source. In case of Cyg A, hot spots are the place where the interaction between jets and ICM occurs (Carilli et al. 1988). We then expect in Hyd A that similar interaction also occurs to form hot spots, and consequently that high frequency observations reveal structures of the interaction.
Here we discuss requirements for high performance and solution processable organic semiconductors, by presenting a systematic investigation of 7-alkyl-2-phenylbenzothieno[3,2-b]benzothiophenes (Ph-BTBT-Cn’s). We found that the solubility and thermal properties of Ph-BTBT-Cn’s depend systematically on the substituted alkyl-chain length n. The observed features are well understood in terms of the change of molecular packing motif with n: The compounds with n ≤ 4 do not form independent alkyl chain layers, whereas those with n ≥ 5 form isolated alkyl chain layers. The latter compounds afford a series of isomorphous bilayer-type crystal structures that form two-dimensional carrier transport layers within the crystals. We also show that the Ph-BTBT-C10 afford high performance single-crystalline field-effect transistors the mobility of which reaches as high as 15.9 cm2/Vs. These results demonstrate a crucial role of the substituted alkyl chain length for obtaining high performance organic semiconductors and field-effect transistors.
ASCA, the fourth Japanese X-ray astronomy satellite, was launched by the Institute of Space and Astronautical Science (ISAS) on 1993 February 20. ASCA is designed to be a high-capability X-ray observatory (Tanaka et al. 1994). It is equipped with nested thin-foil mirrors which provide a large effective area over a wide energy range from 0.5 to 10 keV. Two different types of detectors, CCD cameras (SIS) and imaging gas scintillation proportional counters (GIS) are employed as the focal plane instruments.
Cygnus X-1 was in the Soft State between May and September 1996 for the first time in more than 20 years creating an opportunity to study the thermal component, its spectral evolution, time variability and its relation to the hard component during intensity variations. We will show how the luminosity of the thermal component changes in relation to its temperature and attempt to determine whether the emitting area varied during the variations.
ASCA DSS was intended to carry out unbiased surveys in wide energy range of 0.5-10 keV. The strategy of this project is to survey small sky region with extremely high sensitivity reaching to the source confusion limit of ASCA XRT, in contrast to the Large Sky Survey project (Ueda 1996) which covers much larger sky area with relatively shallow exposure.
The origin of the Cosmic X-ray Background (CXB) radiation has been investigated extensively by soft X-ray deep survey imaging observations with Einstein and ROSAT. In contrast, the lack of telescopes capable of detecting hard X-rays has prevented us from extensive study of the nature of the CXB in the energy range above 2 keV before ASCA.
About 10 X-ray binaries in our Galaxy and LMC/SMC are considered to contain black hole candidates (BHCs). Among these objects, Cyg X-1 was identified as the first BHC, and it has led BHCs for more than 25 years(Oda 1977, Liang and Nolan 1984). It is a binary system composed of normal blue supergiant star and the X-ray emitting compact object. The orbital kinematics derived from optical observations indicates that the compact object is heavier than ~ 4.8 M⊙ (Herrero 1995), which well exceeds the upper limit mass for a neutron star(Kalogora 1996), where we assume the system consists of only two bodies. This has been the basis for BHC of Cyg X-1.
Absorption line features were detected at 4.1 keV from X 1636-536 with the Tenma satellite in the spectra of X-ray bursts (Waki et al., 1984). Similar features were also detected from X 1608-52 and EXO 1747-214 during bursts (Nakamura et al., 1988; Magnier et al., 1989). These features at 4.1 keV may be interpreted as the redshifted Kα absorption line of helium-like iron atoms. However, such interpretation requires extremely soft equation of state for the nuclear matter, and confirmation with high resolution detectors is urged (Lewin et al., 1993). To investigate the line features, we observed X 1636-536 with ASCA for ~ 240 ksec.
The X-ray background in the energy range above 2 keV is highly uniform except for an excess component along the Galactic plane. The excess along the plane is considered to be associated with our Galaxy, whereas the rest of the emission is believed to be of extragalactic origin. In this paper, the X-ray background at high Galactic latitude is discussed and is designated as the CXB (cosmic X-ray background) to distinguish it from the Galactic origin.
The VLBI Space Observatory Programme (VSOP) is the first dedicated Space-VLBI mission. We report here on the planning for a second generation mission which builds on and extends the successful collaborations established for the VSOP mission, and which aims to improve both resolution and sensitivity by a factor of ∼10.