1,387 research outputs found
Microscopic approach to large-amplitude deformation dynamics with local QRPA inertial masses
We have developed a new method for determining microscopically the
fivedimensional quadrupole collective Hamiltonian, on the basis of the
adiabatic self-consistent collective coordinate method. This method consists of
the constrained Hartree-Fock-Bogoliubov (HFB) equation and the local QRPA
(LQRPA) equations, which are an extension of the usual QRPA (quasiparticle
random phase approximation) to non-HFB-equilibrium points, on top of the CHFB
states. One of the advantages of our method is that the inertial functions
calculated with this method contain the contributions of the time-odd
components of the mean field, which are ignored in the widely-used cranking
formula. We illustrate usefulness of our method by applying to oblate-prolate
shape coexistence in 72Kr and shape phase transition in neutron-rich Cr
isotopes around N=40.Comment: 6pages, talk given at Rutherford Centennial Conference on Nuclear
Physics, 8 - 12 August 2011, The University of Mancheste
An X-Ray Microlensing Test of AU-Scale Accretion Disk Structure in Q2237+0305
The innermost regions of quasars can be resolved by a gravitational-lens
{\lq}telescope{\rq} on scales down to a few AU. For the purpose, X-ray
observations are most preferable, because X-rays originating from the innermost
regions, can be selectively amplified by microlensing due to the so-called
`caustic crossing'. If detected, X-ray variations will constrain the size of
the X-ray emitting region down to a few AU. The maximum attainable resolution
depends mainly on the monitoring intervals of lens events, which should be much
shorter than the crossing time. On the basis of this idea, we performe
numerical simulations of microlensing of an optically-thick, standard-type disk
as well as an optically-thin, advection-dominated accretion flow (ADAF).
Calculated spectral variations and light curves show distinct behaviors,
depending on the photon energy. X-ray radiation which is produced in optically
thin region, exhibits intensity variation over a few tens of days. In contrast,
optical-UV fluxes, which are likely to come from optically thick region,
exhibit more gradual light changes, which is consistent with the microlensing
events so far observed in Q2237+0305.
Currently, Q2237+0305 is being monitored in the optical range at Apache Point
Observatory. Simultaneous multi-wavelength observations by X-ray sattelites
(e.g., ASCA, AXAF, XMM) as well as HST at the moment of a microlens event
enable us to reveal an AU scale structure of the central accretion disk around
black hole.Comment: 10 pages LaTeX, 3 figures, accepted to ApJ Letter. e-mail:
[email protected]
Lyman Break Galaxies at : Rest-Frame UV Spectra
We report initial results for spectroscopic observations of candidates of
Lyman Break Galaxies (LBGs) at in a region centered on the Hubble Deep
Field-North by using the Faint Object Camera and Spectrograph attached to the
Subaru Telescope. Eight objects with mag, including one AGN, are
confirmed to be at . The rest-frame UV spectra of seven LBGs
commonly show no or weak Lyalpha emission line (rest-frame equivalent width of
0-10\AA) and relatively strong low-ionization interstellar metal absorption
lines of SiII 1260, OI+SiII 1303, and CII 1334 (mean
rest-frame equivalent widths of them are \AA). These
properties are significantly different from those of the mean rest-frame UV
spectrum of LBGs at , but are quite similar to those of subgroups of
LBGs at with no or weak Lyalpha emission. The weakness of Lyalpha
emission and strong low-ionization interstellar metal absorption lines may
indicate that these LBGs at are chemically evolved to some degree and
have a dusty environment. Since the fraction of such LBGs at in our
sample is larger than that at , we may witness some sign of evolution
of LBGs from to , though the present sample size is very
small. It is also possible, however, that the brighter LBGs tend to show no or
weak Lyalpha emission, because our spectroscopic sample is bright (brighter
than ) among LBGs at . More observations are required to
establish spectroscopic nature of LBGs at .Comment: 16 pages, 3 figures, accepted by Ap
Structure of Strange Dwarfs with Color Superconducting Core
We study effects of two-flavor color superconductivity on the structure of
strange dwarfs, which are stellar objects with similar masses and radii with
ordinary white dwarfs but stabilized by the strange quark matter core. We find
that unpaired quark matter is a good approximation to the core of strange
dwarfs.Comment: 8 pages 5 figures, J. Phys. G, accepte
Formation of Large-Scale Obscuring Wall and AGN Evolution Regulated by Circumnuclear Starbursts
By considering the radiative force by a circumnuclear starburst as well as an
AGN, we analyze the equilibrium configuration and the stability of dusty gas in
the circumnuclear regions. It is found that the radiative force by an intensive
starburst can support a stable gaseous wall with a scale-height of several
hundred parsecs. Moreover, by taking the simple stellar evolution in the
starburst into account, we find that the covering factor of the wall decreases
on a time-scale of several yr. The large-scale wall, if formed, works to
obscure the nucleus due to the dust opacity. Hence, it is anticipated that the
index of AGN type tends to shift from higher to lower in several yr
according as the circumnuclear starburst becomes dimmer. On the other hand, if
the AGN itself is brighter than the circumnuclear starburst (e.g. quasar case),
no stable large-scale wall forms. In that case, the AGN is highly probably
identified as type 1. The present mechanism may provide a physical explanation
for the putative correlation between AGN type and host properties that Sy2's
are more frequently associated with circumnuclear starbursts than Sy1's,
whereas quasars are mostly observed as type 1 regardless of star-forming
activity in the host galaxies.Comment: 10 pages, 3 figures, ApJ Letters in pres
Mesoscopic Stern-Gerlach spin filter by nonuniform spin-orbit interaction
A novel spin filtering in two-dimensional electron system with nonuniform
spin-orbit interactions (SOI) is theoretically studied. The strength of SOI is
modulated perpendicular to the charge current. A spatial gradient of effective
magnetic field due to the nonuniform SOI causes the Stern-Gerlach type spin
separation. The direction of the polarization is perpendicular to the current
and parallel to the spatial gradient. Almost 100 % spin polarization can be
realized even without applying any external magnetic fields and without
attaching ferromagnetic contacts. The spin polarization persists even in the
presence of randomness.Comment: 6 pages, 5 figures (2 color figures), to appear in Phys. Rev. B,
Rapid Commu
Low-Mass Star Formation, Triggered by Supernova in Primordial Clouds
The evolution of a gas shell, swept by the supernova remnant of a massive
first generation star, is studied with H_2 and HD chemistry taken into account.
When a first-generation star explodes as a supernova, H_2 and HD molecules are
formed in the swept gas shell and effectively cool the gas shell to
temperatures of 32 K - 154 K. If the supernova remnant can sweep to gather the
ambient gas, the gas shell comes to be dominated by its self-gravity, and
hence, is expected to fragment. Our result shows that for a reasonable range of
temperatures (200 K - 1000 K) of interstellar gas, the formation of
second-generation stars can be triggered by a single supernova or hypernova.Comment: 38pages, 10 figures, The Astrophysical Journal, accepted 8 Dec. 200
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