1,166 research outputs found
Interaction and Localization of One-electron Orbitals in an Organic Molecule: Fictitious Parameter Analysis for Multi-physics Simulations
We present a new methodology to analyze complicated multi-physics simulations
by introducing a fictitious parameter. Using the method, we study quantum
mechanical aspects of an organic molecule in water. The simulation is
variationally constructed from the ab initio molecular orbital method and the
classical statistical mechanics with the fictitious parameter representing the
coupling strength between solute and solvent. We obtain a number of
one-electron orbital energies of the solute molecule derived from the
Hartree-Fock approximation, and eigenvalue-statistical analysis developed in
the study of nonintegrable systems is applied to them. Based on the results, we
analyze localization properties of the electronic wavefunctions under the
influence of the solvent.Comment: 4 pages, 5 figures, the revised version will appear in J. Phys. Soc.
Jpn. Vol.76 (No.1
Tracing the origins of permitted emission lines in RU Lupi down to AU scales
Most of the observed emission lines and continuum excess from young accreting
low mass stars (Classical T Tauri stars -- CTTSs) take place in the star-disk
or inner disk region. These regions have a complex emission topology still
largely unknown. In this paper the magnetospheric accretion and inner wind
contributions to the observed permitted He and H near infrared (NIR) lines of
the bright southern CTTS RU Lupi are investigated for the first time. Previous
optical observations of RU Lupi showed a large H-alpha profile, due to the
emission from a wind in the line wings, and a micro-jet detected in forbidden
lines. We extend this analysis to NIR lines through seeing-limited high
spectral resolution spectra taken with VLT/ISAAC, and adaptive optics (AO)
aided narrow-band imaging and low spectral resolution spectroscopy with
VLT/NACO. Using spectro-astrometric analysis we investigate the presence of
extended emission down to very low spatial scales (a few AU). The HeI 10830
line presents a P Cygni profile whose absorption feature indicates the presence
of an inner stellar wind. Moreover the spectro-astrometric analysis evidences
the presence of an extended emission superimposed to the absorption feature and
likely coming from the micro-jet detected in the optical. On the contrary, the
origin of the Hydrogen Paschen and Brackett lines is difficult to address. We
tried tentatively to explain the observed line profiles and flux ratios with
both accretion and wind models showing the limits of both approaches. The lack
of spectro-astrometric signal indicates that the HI emission is either compact
or symmetric. Our analysis confirms the sensitivity of the HeI line to the
presence of faint extended emission regions in the close proximity of the star.Comment: 11 pages, 4 figures, accepted for publication on A&
A highly-collimated SiO jet in the HH212 protostellar outflow
We mapped the HH212 Class 0 outflow in SiO(2--1, 5--4) and continuum using
the PdBI in its extended configurations. The unprecedented angular resolution
(down to 0.34") allows accurate comparison with a new, deep H2 image obtained
at the VLT. The SiO emission is confined to a highly-collimated bipolar jet
(width 0.35") along the outflow axis. The jet can be traced down to within 500
AU of the protostar, in a region that is heavily obscured in H2 images. Where
both species are detected, SiO shows the same overall kinematics and structure
as H2, indicating that both molecules are tracing the same material. We find
that the high-velocity SiO gas near the protostar is not tracing a wide-angle
wind but is already confined to a flow inside a narrow cone of half-opening
angle < 6 deg.Comment: Astronomy and Astrophysics Letter, in pres
Nuclear Tetrahedral Symmetry: Possibly Present Throughout the Periodic Table
More than half a century after the fundamental, spherical shell structure in
nuclei has been established, theoretical predictions indicate that the
shell-gaps comparable or even stronger than those at spherical shapes may
exist. Group-theoretical analysis supported by realistic mean-field
calculations indicate that the corresponding nuclei are characterized by the
('double-tetrahedral') group of symmetry, exact or approximate. The
corresponding strong shell-gap structure is markedly enhanced by the existence
of the 4-dimensional irreducible representations of the group in question and
consequently it can be seen as a geometrical effect that does not depend on a
particular realization of the mean-field. Possibilities of discovering the
corresponding symmetry in experiment are discussed.Comment: 4 pages in LaTeX and 4 figures in eps forma
On the H emission from the Cephei system
Be stars, which are characterised by intermittent emission in their hydrogen
lines, are known to be fast rotators. This fast rotation is a requirement for
the formation of a Keplerian disk, which in turn gives rise to the emission.
However, the pulsating, magnetic B1IV star Cephei is a very slow
rotator that still shows H emission episodes like in other Be stars,
contradicting current theories. We investigate the hypothesis that the
H emission stems from the spectroscopically unresolved companion of
Cep. Spectra of the two unresolved components have been separated in
the 6350-6850\AA range with spectro-astrometric techniques, using 11 longslit
spectra obtained with ALFOSC at the Nordic Optical Telescope, La Palma. We find
that the H emission is not related to the primary in Cep, but
is due to its 3.4 magnitudes fainter companion. This companion has been
resolved by speckle techniques, but it remains unresolved by traditional
spectroscopy. The emission extends from about 400 to +400 km s. The
companion star in its 90-year orbit is likely to be a classical Be star with a
spectral type around B6-8. By identifying its Be-star companion as the origin
of the H emission behaviour, the enigma behind the Be status of the
slow rotator Cep has been resolved.Comment: 4 pages, 3 figures. Accepted by A&A Letter
Collimation of a spherical collisionless particles stream in Kerr space-time
We examine the propagation of collisionless particles emitted from a
spherical shell to infinity. The number distribution at infinity, calculated as
a function of the polar angle, exhibits a small deviation from uniformity. The
number of particles moving from the polar region toward the equatorial plane is
slightly larger than that of particles in the opposite direction, for an
emission radius in extreme Kerr space-time. This means that the black
hole spin exerts an anti-collimation effect on the particles stream propagating
along the rotation axis. We also confirm this property in the weak field limit.
The quadrupole moment of the central object produces a force toward the
equatorial plane. For a smaller emission radius , the absorption of
particles into the black hole, the non-uniformity and/or the anisotropy of the
emission distribution become much more important.Comment: 11 pages, 8 figures; accepted for publication in CQ
The E-ELT Multi-Object Spectrograph: latest news from MOSAIC
There are 8000 galaxies, including 1600 at z larger than 1.6, which could be
simultaneously observed in an E-ELT field of view of 40 sq. arcmin. A
considerable fraction of astrophysical discoveries require large statistical
samples, which can only be obtained with multi-object spectrographs (MOS).
MOSAIC will provide a vast discovery space, enabled by a multiplex of 200 and
spectral resolving powers of R=5000 and 20000. MOSAIC will also offer the
unique capability of more than 10 "high-definition" (multi-object adaptive
optics, MOAO) integral-field units, optimised to investigate the physics of the
sources of reionization. The combination of these modes will make MOSAIC the
world-leading MOS facility, contributing to all fields of contemporary
astronomy, from extra-solar planets, to the study of the halo of the Milky Way
and its satellites, and from resolved stellar populations in nearby galaxies
out to observations of the earliest "first-light" structures in the Universe.
It will also study the distribution of the dark and ordinary matter at all
scales and epochs of the Universe. Recent studies of critical technical issues
such as sky-background subtraction and MOAO have demonstrated that such a MOS
is feasible with state-of-the-art technology and techniques. Current studies of
the MOSAIC team include further trade-offs on the wavelength coverage, a
solution for compensating for the non-telecentric new design of the telescope,
and tests of the saturation of skylines especially in the near-IR bands. In the
2020s the E-ELT will become the world's largest optical/IR telescope, and we
argue that it has to be equipped as soon as possible with a MOS to provide the
most efficient, and likely the best way to follow-up on James Webb Space
Telescope (JWST) observations.Comment: 10 pages, 3 Figures, in Ground-based and Airborne Instrumentation for
Astronomy VI, 2016, Proc. SPI
Structure of Excited States of 10Be studied with Antisymmetrized Molecular Dynamics
We study structure of excited states of 10Be with the method of variation
after spin parity projection in the framework of antisymmetrized molecular
dynamics. Present calculations describe many excited states and reproduce the
experimental data of E2 and E1 transitions and the new data of the
transition strength successfully. We make systematic discussions on the
molecule-like structures of light unstable nuclei and the important role of the
valence neutrons based on the results obtained with the framework which is free
from such model assumptions as the existence of inert cores and clusters.Comment: 15 pages, RevTex, seven postscript figures (using epsf.sty
Adaptive Optics Spectroscopy of the [Fe II] Outflows from HL Tauri and RW Aurigae
We present new results of [Fe II] 1.644-micron spectroscopy toward the jets
from HL Tau and RW Aur carried out with the Subaru Telescope combined with the
adaptive optics system. We observed the regions within 2" - 3" from the stars
with the sub-arcsecond resolutions of 0."5 and 0."2 for HL Tau and RW Aur,
respectively. In addition to the strong, high velocity emission extended along
each jet, we detected a blueshifted low velocity emission feature seen as a
wing or shoulder of the high velocity emission at each stellar position.
Detailed analysis shows that the position-velocity diagrams (PVDs) of HL Tau
and RW Aur show a characteristic similar to those of the cold disk wind and
X-wind models in that the [Fe II] line width is broad in the vicinity of the
stellar position and is narrower at the extended jet. A closer comparison
suggests, however, that the disk wind model tends to have too large line width
at the jet while the X-wind model has excess emission on the redshifted side at
the stellar position. The narrow velocity width with symmetric line profiles of
the observed high velocity emission supports an X-wind type model where the
launching region is localized in a small radial range, while the low velocity
emission located away from the star favors the presence of a disk wind. The [Fe
II] emission from the HL Tau jet shows a gap of 0."8 between the redshifted jet
and the star, indicating the presence of an optically thick disk of ~ 160 AU in
radius. The [Fe II] emission from the RW Aur jet shows a marked drop from the
redshifted peak at Y ~ -0."2 toward the star, suggesting that its disk radius
is smaller than 40 AU.Comment: Accepted in the ApJ (October 2006, v649n2), AAS LaTEX macros v 5.2,
Total 25 pages with 7 figure
The origin of ultra high energy cosmic rays
We briefly discuss some open problems and recent developments in the
investigation of the origin and propagation of ultra high energy cosmic rays
(UHECRs).Comment: Invited Review Talk at TAUP 2005 (Zaragoza - September 10-14, 2005).
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