408 research outputs found
Identifications and SEDs of the detected sources from the AKARI Deep Field South
In order to find counterparts of the detected objects in the AKARI Deep Field
South (ADFS) in all available wavelengths, we searched public databases (NED,
SIMBAD and others). Checking 500 sources brighter than 0.0482 Jy in the AKARI
Wide-S band, we found 114 sources with possible counterparts, among which 78
were known galaxies. We present these sources as well as our first attempt to
construct spectral energy distributions (SEDs) for the most secure and most
interesting sources among them, taking into account all the known data together
with the AKARI measurements in four bands.Comment: 4 pages, 10 figures, To appear in: the proceedings of the conference
"AKARI, a light to illuminate the misty Universe", February 16-19 2009, Toky
Phase Diagram of Lattice-Spin System RbCoBr
We study the lattice-spin model of RbCoBr which is proposed by Shirahata
and Nakamura, by mean field approximation. This model is an Ising spin system
on a distorted triangular lattice. There are two kinds of frustrated variables,
that is, the lattice and spin. We obtain a phase diagram of which phase
boundary is drawn continuously in a whole region. Intermediate phases that
include a partial disordered state appear. The model has the first-order phase
transitions in addition to the second-order phase transitions. We find a
three-sublattice ferrimagnetic state in the phase diagram. The three-sublattice
ferrimagnetic state does not appear when the lattice is not distorted.Comment: 5 pages, 4 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn.
Vol.75 (2006) No.
Near-infrared Brightness of the Galilean Satellites Eclipsed in Jovian Shadow: A New Technique to Investigate Jovian Upper Atmosphere
We have discovered that Europa, Ganymede and Callisto are bright around 1.5
{\mu}m even when not directly lit by sunlight, based on observations from the
Hubble Space Telescope and the Subaru Telescope. The observations were
conducted with non-sidereal tracking on Jupiter outside of the field of view to
reduce the stray light subtraction uncertainty due to the close proximity of
Jupiter. Their eclipsed luminosity was - of their uneclipsed
brightness, which is low enough that this phenomenon has been undiscovered
until now. In addition, Europa in eclipse was <1/10 of the others at 1.5
{\mu}m, a potential clue to the origin of the source of luminosity. Likewise,
Ganymede observations were attempted at 3.6 {\mu}m by the Spitzer Space
Telescope but it was not detected, suggesting a significant wavelength
dependence. The reason why they are luminous even when in the Jovian shadow is
still unknown, but forward-scattered sunlight by haze in the Jovian upper
atmosphere is proposed as the most plausible candidate. If this is the case,
observations of these Galilean satellites while eclipsed by the Jovian shadow
provide us a new technique to investigate Jovian atmospheric composition, and
investigating the transmission spectrum of Jupiter by this method is important
for investigating the atmosphere of extrasolar giant planets by transit
spectroscopy.Comment: 7 pages, 3 figures, accepted to Ap
Kinetic construction of the high-beta anisotropic-pressure equilibrium in the magnetosphere
A theoretical model of the high-beta equilibrium of magnetospheric plasmas was constructed by consistently connecting the (anisotropic pressure) Grad–Shafranov equation and the Vlasov equation. The Grad–Shafranov equation was used to determine the axisymmetric magnetic field for a given magnetization current corresponding to a pressure tensor. Given a magnetic field, we determine the distribution function as a specific equilibrium solution of the Vlasov equation, using which we obtain the pressure tensor. We need to find an appropriate class of the distribution function for these two equations to be satisfied simultaneously. Here, we consider the distribution function that maximizes the entropy on the submanifold specified by the magnetic moment. This is equivalent to the reduction of the canonical Poisson bracket to the noncanonical one having the Casimir corresponding to the magnetic moment. The pressure tensor then becomes a function of the magnetic field (through the cyclotron frequency) and flux function, satisfying the requirement of the Grad–Shafranov equation
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