690 research outputs found
Anomalous population of He states in reactions with Li
Structure with the lowest energy observed in the He spectrum populated
in the proton knockout reaction with Li beam has a peak at
MeV. This peak is usually interpreted as a resonant ground state of
He. Our theoretical calculations indicate that this peak is likely to be
a pileup of , , and excitations with very similar shapes. %We
predict a very specific nature of the excitation in He. Moreover,
the ``soft'' excitation appears to be the lowest one in energy. Such an
anomalous continuum response is traced to the halo structure of Li
providing extreme low energy shift to all the expected continuum excitations.
Competitions of the initial state structure (ISS) and the final state
interaction (FSI) effects on the spectrum and three-body correlations in
He are discussed. Analogous effect of the extreme low-energy shift could
also be expected in other cases of emitters populated in reactions with
halo nuclei. Simplified example of the He spectrum in knockout
from Be, is given. We also discuss limits on the properties of He
stemming from the observed He spectrum.Comment: 10 pages, 13 figure
Pauli-principle driven correlations in four-neutron nuclear decays
Mechanism of simultaneous non-sequential four-neutron () emission (or
`true' -decay) has been considered in phenomenological five-body approach.
This approach is analogous to the model of the direct decay to the continuum
often applied to - and -decays. It is demonstrated that -decay
fragments should have specific energy and angular correlations reflecting
strong spatial correlations of `valence' nucleons orbiting in their
-precursors. Due to the Pauli exclusion principle, the valence neutrons are
pushed to the symmetry-allowed configurations in the -precursor structure,
which causes a `Pauli focusing' effect. Prospects of the observation of the
Pauli focusing have been considered for the -precursors H and O.
Fingerprints of their nuclear structure or/and decay dynamics are predicted
Variable Star Candidates in an ACS Field of M31
A search for variable stars is performed using two epochs of Hubble Space
Telescope (HST) Advanced Camera for Surveys (ACS) imaging data for a 9.28
square arcminute portion of M31. This data set reveals 254 sources that vary by
at least 4-sigma between epochs. The positions and 2-epoch B-band (equivalent)
photometry of these sources are presented. The photometry suggests that this
catalog includes most of the RR Lyrae population of this portion of M31.Comment: 22 pages, 3 tables, 5 figures, accepted for publication in A
Spectroscopy of Globular Clusters in M81
We present moderate-resolution spectroscopy of globular clusters (GCs) around
the Sa/Sb spiral galaxy M81 (NGC 3031). Sixteen candidate clusters were
observed with the Low Resolution Imaging Spectrograph on the Keck I telescope.
All are confirmed as bona fide GCs, although one of the clusters appears to
have been undergoing a transient event during our observations. In general, the
M81 globular cluster system (GCS) is found to be very similar to the Milky Way
(MW) and M31 systems, both chemically and kinematically. A kinematic analysis
of the velocities of 44 M81 GCS, (the 16 presented here and 28 from previous
work) strongly suggests that the red, metal-rich clusters are rotating in the
same sense as the gas in the disk of M81. The blue, metal-poor clusters have
halo-like kinematics, showing no evidence for rotation. The kinematics of
clusters whose projected galactocentric radii lie between 4 and 8 kpc suggest
that they are rotating much more than those which lie outside these bounds. We
suggest that these rotating, intermediate-distance clusters are analogous to
the kinematic sub-population in the metal-rich, disk GCs observed in the MW and
we present evidence for the existence of a similar sub-population in the
metal-rich clusters of M31. With one exception, all of the M81 clusters in our
sample have ages that are consistent with MW and M31 GCs. One cluster may be as
young as a few Gyrs. The correlations between absorption-line indices
established for MW and M31 GCs also hold in the M81 cluster system, at least at
the upper end of the metallicity distribution (which our sample probes). On the
whole, the mean metallicity of the M81 GCS is similar to the metallicity of the
MW and M31 GCSs. The projected mass of M81 is similar to the masses of the MW
and M31. Its mass profile indicates the presence of a dark matter halo.Comment: 35 pages, including 11 figures and 9 tables. Accepted for publication
in the Astronomical Journa
Hadronic Regge Trajectories: Problems and Approaches
We scrutinized hadronic Regge trajectories in a framework of two different
models --- string and potential. Our results are compared with broad spectrum
of existing theoretical quark models and all experimental data from PDG98. It
was recognized that Regge trajectories for mesons and baryons are not straight
and parallel lines in general in the current resonance region both
experimentally and theoretically, but very often have appreciable curvature,
which is flavor-dependent. For a set of baryon Regge trajectories this fact is
well described in the considered potential model. The standard string models
predict linear trajectories at high angular momenta J with some form of
nonlinearity at low J.Comment: 15 pages, 9 figures, LaTe
The M31 Globular Cluster Luminosity Function
We combine our compilation of photometry of M31 globular cluster and probable
cluster candidates with new near-infrared photometry for 30 objects. Using
these data we determine the globular cluster luminosity function (GCLF) in
multiple filters for the M31 halo clusters. We find a GCLF peak and dispersion
of V_0^0=16.84 +/-0.11, sigma_t=0.93 +/- 0.13 (Gaussian sigma = 1.20 +/- 0.14),
consistent with previous results. The halo GCLF peak colors (e.g., B^0_0 -
V^0_0) are consistent with the average cluster colors. We also measure V-band
GCLF parameters for several other subsamples of the M31 globular cluster
population. The inner third of the clusters have a GCLF peak significantly
brigher than that of the outer clusters (delta V =~ 0.5mag). Dividing the
sample by both galacticentric distance and metallicity, we find that the GCLF
also varies with metallicity, as the metal-poor clusters are on average 0.36
mag fainter than the metal-rich clusters. Our modeling of the catalog selection
effects suggests that they are not the cause of the measured differences, but a
more complete, less-contaminated M31 cluster catalog is required for
confirmation. Our results imply that dynamical destruction is not the only
factor causing variation in the M31 GCLF: metallicity, age, and cluster initial
mass function may also be important.Comment: AJ, in press. 36 pages, including 7 figure
Модель механізму антикризового управління в адміністративно-територіальному утворенні
The model of the crisis-mechanism for administrative-territory unit is descript including aim-setting, projects of the risk-oriented strategy formation, the structure institutionalization of the crisis-assignment, crisis-management during strategy realization, diagnostic and identification of the crisis-threats. The approach to management for the system of the strategy realization based on the crisis-group creation, which exist on dual virtual-real status. The approach delivers such differs: accented proactive management; integration of the strategic and crisis functions without the special institution creation; the matrix structure integrates the functional and aimed activity; adaptively opportunities; stimulate of the project management implementation; opportunities to create the inter-organizational crisis-cell under crisis-threat..Описано модель механізму антикризового управління в адміністративно-територіальному утворенні, яка включає процеси цілепокладання, формування проектів ризик-орієнтованої стратегії, структурну інституціоналізацію антикризової відповідальності, управління ризиками на етапах реалізації стратегії, діагностику та ідентифікацію кризових небезпек. Підхід до побудови системи управління реалізацією стратегії передбачає створення кризових груп, які можуть існувати у подвійному віртуально-реальному режимі, і має такі принципові ознаки: виражений проактивний характер; інтеграція стратегічних та антикризових функцій без створення спеціальної антикризової структури; матрична структура вправління поєднує функціональну і цільову діяльність; гнучкість; сприяння упровадженню проектного підходу; можливість в умовах кризової ситуації розгорнути міжорганізаційну мережу кризового управління
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