195 research outputs found
Observation of spin-polarized bands and domain-dependent Fermi arcs in polar Weyl semimetal MoTe
We investigate the surface electronic structures of polar 1T'-MoTe2, the Weyl
semimetal candidate realized through the nonpolar-polar structural phase
transition, by utilizing the laser angle-resolved photoemission spectroscopy
(ARPES) combined with first-principles calculations. Two kinds of domains with
different surface band dispersions are observed from a single-crystalline
sample. The spin-resolved measurements further reveal that the spin
polarizations of the surface and the bulk-derived states show the different
domain-dependences, indicating the opposite bulk polarity. For both domains,
some segment-like band features resembling the Fermi arcs are clearly observed.
The patterns of the arcs present the marked contrast between the two domains,
respectively agreeing well with the slab calculation of (0 0 1) and (0 0 -1)
surfaces. The present result strongly suggests that the Fermi arc connects the
identical pair of Weyl nodes on one side of the polar crystal surface, whereas
it connects between the different pairs of Weyl nodes on the other side.Comment: 13 pages, 4 figure
ASCA X-ray source catalogue in the Galactic Center region
The ASCA satellite made 107 pointing observations on a 5 x 5 deg^2 region
around the center of our Milky Way Galaxy (the Galactic Center) from 1993 to
1999. In the X-ray images of the 0.7--3 keV or 3--10 keV bands, we found 52
point sources and a dozen diffuse sources. All the point sources are uniformly
fitted with an absorbed power-law model. For selected bright sources, Sgr A*,
AX J1745.6-2901, A 1742-294, SLX 1744-300, GRO J1744-28, SLX 1737-282, GRS
1734-292, AX J1749.2-2725, KS 1741-293, GRS 1741.9-2853, and an unusual flare
source XTE J1739-302, we present further detailed spectral and timing analyses,
and discuss their nature.
The dozen extended X-ray sources comprise radio supernova remnants, giant
molecular clouds, and some new discoveries. Most show emission lines from
either highly ionized atoms or low-ionized irons.
The X-ray spectra were fitted with either a thin thermal or power-law model.
This paper summarizes the results and provides the ASCA X-ray source catalogue
in the Galactic Center region.Comment: 33 pages, 8 figures, Accepted for publication in ApJS, also found in
http://www.star.le.ac.uk/~mas/research/paper/#Sakano2001apj
Further studies of 1E 1740.7-2942 with ASCA
We report the ASCA results of the Great Annihilator 1E 1740.7-2942 obtained
with five pointing observations in a time span of 3.5 years. The X-ray spectrum
for each period is well fitted with a single power-law absorbed by a high
column of gas. The X-ray flux changes by a factor of 2 from period to period,
but the other spectral parameters show no significant change. The photon index
is flat with \Gamma = 0.9--1.3. The column densities of hydrogen N_H is
1.0 x 10^{23} H cm^{-2} and that of iron N_{Fe} is 10^{19} Fe cm^{-2}.
These large column densities indicate that 1E 1740.7-2942 is near at the
Galactic Center. The column density ratio leads the iron abundance to be 2
times larger than the other elements in a unit of the solar ratio. The
equivalent width of the K\alpha-line from a neutral iron is less than 15 eV in
90% confidence. This indicates that the iron column density within several
parsecs from 1E 1740.7-2942 is less than 5 x 10^{17} Fe cm^{-2}. In addition,
the derived hydrogen column density is about 1/6 of that of giant molecular
clouds in the line of sight. All these facts support that 1E 1740.7-2942 is not
in a molecular cloud, but possibly in front of it; the X-rays are not powered
by accretion from a molecular cloud, but from a companion star like ordinary
X-ray binaries.Comment: To appear in ApJ July 20, 1999 issue, Vol. 520 #1, 23 pages LaTeX
files, uses aasms4.sty and psfig.sty, also available at
http://www-cr.scphys.kyoto-u.ac.jp/member/sakano/work/paper/index-e.htm
Raman and Infrared-Active Phonons in Hexagonal HoMnO Single Crystals: Magnetic Ordering Effects
Polarized Raman scattering and infrared reflection spectra of hexagonal
HoMnO single crystals in the temperature range 10-300 K are reported.
Group-theoretical analysis is performed and scattering selection rules for the
second order scattering processes are presented. Based on the results of
lattice dynamics calculations, performed within the shell model, the observed
lines in the spectra are assigned to definite lattice vibrations. The magnetic
ordering of Mn ions, which occurs below T=76 K, is shown to effect both
Raman- and infrared-active phonons, which modulate Mn-O-Mn bonds and,
consequently, Mn exchange interaction.Comment: 8 pages, 6 figure
Log N - Log S Relations and Spectral Properties of Sources from the ASCA Large Sky Survey --- their Implications for the Origin of the Cosmic X-ray Background (CXB)
We carried out the first wide-area unbiased survey with the ASCA satellite in
the 0.7-10 keV band around a north Galactic-pole region covering a continuous
area of 7 square degrees (Large Sky Survey; LSS). To make the best use of ASCA
capability, we developed a new source-detection method where the complicated
detector responses are fully taken into account. Applying this method to the
entire LSS data independently in the total (0.7-7 keV), hard (2-10 keV), and
soft (0.7-2 keV) band, we detected 107 sources altogether with sensitivity
limits of 6 x 10E-14 (0.7-7 keV), 1 x 10E-13 (2-10 keV), and 2 x 10E-14 erg
sE-1 cmE-2 (0.7-2 keV), respectively. A complete list of the detected sources
is presented. Based on detailed studies by Monte Carlo simulations, we
evaluated effects of the source confusion and accurately derived Log N - Log S
relation in each survey band. The Log N - Log S relation in the hard band is
located on the extrapolation from the GINGA and HEAO1 results with the
Euclidean slope of -3/2, while that in the soft band is consistent with the
results by ROSAT. At these flux limits, 30 (+/- 3) percent of the CXB in the
0.7-7 keV band and 23 (+/- 3) percent in the 2-10 keV band have been resolved
into discrete sources. The average spectrum of faint sources detected in the
total band shows a photon index of 1.63 +/- 0.07 in the 0.7-10 keV range,
consistent with the comparison of source counts between the hard and the soft
energy band. Those detected in the hard band show a photon index of 1.49 +/-
0.10 in the 2-10 keV range. These spectral properties suggest that contribution
of sources with hard energy spectra become significant at a flux of 10E-13 erg
sE-1 cmE-2 (2-10 keV). The most plausible candidates are type-II AGNs, as
indicated by on-going optical identifications.Comment: 28 pages, 11 figures, to appear in ApJ 518, 1999; figure 1 replaced,
minor errors in text correcte
Optical Identification of the ASCA Large Sky Survey
We present results of optical identification of the X-ray sources detected in
the ASCA Large Sky Survey. Optical spectroscopic observations were done for 34
X-ray sources which were detected with the SIS in the 2-7 keV band above 3.5
sigma. The sources are identified with 30 AGNs, 2 clusters of galaxies, and 1
galactic star. Only 1 source is still unidentified. The flux limit of the
sample corresponds to 1 x 10^{-13} erg s^{-1} cm^{-2} in the 2-10 keV band.
Based on the sample, the paper discusses optical and X-ray spectral
properties of the AGNs, contribution of the sources to the Cosmic X-ray
Background, and redshift and luminosity distributions of the AGNs. An
interesting result is that the redshift distribution of the AGNs suggests a
deficiency of high-redshift (0.5 10^{44}
erg s^{-1}) absorbed narrow-line AGNs (so called type 2 QSOs).Comment: Accepted for publication in ApJ. 57 pages with 13 figures, 9 JPG
plates, 5 additional PS tables. Original EPS plates (gzipped format
~1Mbyte/plate) and TeX tables are available from
ftp://ftp.kusastro.kyoto-u.ac.jp/pub/akiyama/0001289
Insulin-Insulin-like Growth Factors Hybrids as Molecular Probes of Hormone : Receptor Binding Specificity
Insulin, insulin-like growth factors 1 and 2 (IGF-1 and -2, respectively), and their receptors (IR and IGF-1R) are the key elements of a complex hormonal system that is essential for the development and functioning of humans. The C and D domains of IGFs (absent in insulin) likely play important roles in the differential binding of IGF-1 and -2 to IGF-1R and to the isoforms of IR (IR-A and IR-B) and specific activation of these receptors. Here, we attempted to probe the impact of IGF-1 and IGF-2 D domains (DI and DII, respectively) and the IGF-2 C domain (CII) on the receptor specificity of these hormones. For this, we made two types of insulin hybrid analogues: (i) with the C-terminus of the insulin A chain extended by the amino acids from the DI and DII domains and (ii) with the C-terminus of the insulin B chain extended by some amino acids derived from the CII domain. The receptor binding affinities of these analogues and their receptor autophosphorylation potentials were characterized. Our results indicate that the DI domain has a more negative impact than the DII domain does on binding to IR, and that the DI domain Pro-Leu-Lys residues are important factors for a different IR-A versus IR-B binding affinity of IGF-1. We also showed that the additions of amino acids that partially "mimic" the CII domain, to the C-terminus of the insulin B chain, change the binding and autophosphorylation specificity of insulin in favor of the "metabolic" IR-B isoform. This opens new venues for rational enhancement of insulin IR-B specificity by modifications beyond the C-terminus of its B chain
Analysis of Shot Noise at Finite Temperatures in Fractional Quantum Hall Edge States
We investigate shot noise at {\it finite temperatures} induced by the
quasi-particle tunneling between fractional quantum Hall (FQH) edge states. The
resulting Fano factor has the peak structure at a certain bias voltage. Such a
structure indicates that quasi-particles are weakly {\it glued} due to thermal
fluctuation. We show that the effect makes it possible to probe the difference
of statistics between FQH states where quasi-particles have the
same unit charge.Finally we propose a way to indirectly obtain statistical
angle in hierarchical FQH states.Comment: 5 pages, 3 figure
The XMM-Newton serendipitous survey. VII. The third XMM-Newton serendipitous source catalogue
Thanks to the large collecting area (3 x ~1500 cm at 1.5 keV) and wide
field of view (30' across in full field mode) of the X-ray cameras on board the
European Space Agency X-ray observatory XMM-Newton, each individual pointing
can result in the detection of hundreds of X-ray sources, most of which are
newly discovered. Recently, many improvements in the XMM-Newton data reduction
algorithms have been made. These include enhanced source characterisation and
reduced spurious source detections, refined astrometric precision, greater net
sensitivity and the extraction of spectra and time series for fainter sources,
with better signal-to-noise. Further, almost 50\% more observations are in the
public domain compared to 2XMMi-DR3, allowing the XMM-Newton Survey Science
Centre (XMM-SSC) to produce a much larger and better quality X-ray source
catalogue. The XMM-SSC has developed a pipeline to reduce the XMM-Newton data
automatically and using improved calibration a new catalogue version has been
produced from XMM-Newton data made public by 2013 Dec. 31 (13 years of data).
Manual screening ensures the highest data quality. This catalogue is known as
3XMM. In the latest release, 3XMM-DR5, there are 565962 X-ray detections
comprising 396910 unique X-ray sources. For the 133000 brightest sources,
spectra and lightcurves are provided. For all detections, the positions on the
sky, a measure of the quality of the detection, and an evaluation of the X-ray
variability is provided, along with the fluxes and count rates in 7 X-ray
energy bands, the total 0.2-12 keV band counts, and four hardness ratios. To
identify the detections, a cross correlation with 228 catalogues is also
provided for each X-ray detection. 3XMM-DR5 is the largest X-ray source
catalogue ever produced. Thanks to the large array of data products, it is an
excellent resource in which to find new and extreme objects.Comment: 23 pages, version accepted for publication in A&
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