8,307 research outputs found
Database of Molecular Masers and Variable Stars
We present the database of maser sources in H2O, OH and SiO lines that can be
used to identify and study variable stars at evolved stages. Detecting the
maser emission in H2O, OH and SiO molecules toward infrared-excess objects is
one of the methods of identification long-period variables (LPVs, including
Miras and Semi-Regular), because these stars exhibit maser activity in their
circumstellar shells. Our sample contains 1803 known LPV objects. 46% of these
stars (832 objects) manifest maser emission in the line of at least one
molecule: H2O, OH or SiO. We use the database of circumstellar masers in order
to search for long-periodic variables which are not included in the General
Catalogue of Variable Stars (GCVS). Our database contains 4806 objects (3866
objects without associations in GCVS catalog) with maser detection in at least
one molecule. Therefore it is possible to use the database in order to locate
and study the large sample of long-period variable stars. Entry to the database
at http://maserdb.netComment: Accepted for publication in RA
A homogeneous heat pipe design code
A computer program was developed to facilitate parametric performance evaluation of heat pipes in lightweight heat rejection systems. A description of the code, user's manual, and sample inputs are provided. The emphasis is placed on the analysis and design of homogeneous wick heat pipes. The analysis of the annular heat pipe is included as part of the heat pipe radiator subroutine
Nuclear radiation problems, unmanned thermionic reactor ion propulsion spacecraft
A nuclear thermionic reactor as the electric power source for an electric propulsion spacecraft introduces a nuclear radiation environment that affects the spacecraft configuration, the use and location of electrical insulators and the science experiments. The spacecraft is conceptually configured to minimize the nuclear shield weight by: (1) a large length to diameter spacecraft; (2) eliminating piping penetrations through the shield; and (3) using the mercury propellant as gamma shield. Since the alumina material is damaged by the high nuclear radiation environment in the reactor it is desirable to locate the alumina insulator outside the reflector or develop a more radiation resistant insulator
Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines
We present the results of SiO millimeter-line observations of a sample of
known SiO maser sources covering a wide dust-temperature range. A cold part of
the sample was selected from the SiO maser sources found in our recent SiO
maser survey of cold dusty objects. The aim of the present research is to
investigate the causes of the correlation between infrared colors and SiO maser
intensity ratios among different transition lines. In particular, the
correlation between infrared colors and SiO maser intensity ratio among the
J=1-0 v=1, 2, and 3 lines are mainly concerned in this paper. We observed in
total 75 SiO maser sources with the Nobeyama 45m telescope quasi-simultaneously
in the SiO J=1-0 v=0, 1, 2, 3, 4 and J=2-1 v=1, 2 lines. We also observed the
sample in the 29SiO J=1-0 v=0 and J=2-1 v=0, and 30SiO J=1-0 v=0 lines, and the
H2O 6(1,6)-5(2,3) line. As reported in previous papers, we confirmed that the
intensity ratios of the SiO J=1-0 v=2 to v=1 lines clearly correlate with
infrared colors. In addition, we found possible correlation between infrared
colors and the intensity ratios of the SiO J=1-0 v=3 to v=1&2 lines. Two
overlap lines of H2O (i.e., 11(6,6) nu_2=1 -> 12(7,5) nu_2=0 and 5(0,5) nu_2=2
-> 6(3,4) nu_2=1) might explain these correlation if these overlap lines become
stronger with increase of infrared colors, although the phenomena also might be
explained by more fundamental ways if we take into account the variation of
opacity from object to object.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ. Full
resolution version available at
http://www.asiaa.sinica.edu.tw/~junichi/paper
The Music of the Aetherwave - B-mode Polarization in Einstein-Aether Theory
We study how the dynamical vector degree of freedom in modified gravity
affects the CMB B-mode polarization in terms of the Einstein-aether theory. In
this theory, vector perturbations can be generated from inflation, which can
grow on superhorizon scales in the subsequent epochs and thereby leaves
imprints on the CMB B-mode polarization. We derive the linear perturbation
equations in a covariant formalism, and compute the CMB B-mode polarization
using the CAMB code modified so as to incorporate the effect of the aether
vector field. We find that the amplitude of the B-mode signal from the aether
field can surpass the contribution from the inflationary gravitational waves
for a viable range of model parameters. We also give an analytic argument
explaining the shape of the spectrum based on the tight coupling approximation.Comment: 12 pages, 6 figure
Anisotropic magnetic properties of CeAgGe single crystal
In order to investigate the anisotropic magnetic properties of
CeAgGe, we have successfully grown the single crystals, for the first
time, by high temperature solution growth (flux) method. We have performed a
detailed study of the grown single crystals by measuring their electrical
resistivity, magnetic susceptibility, magnetization, specific heat and
magnetoresistance. A clear anisotropy and an antiferromagnetic transition at
= 4.6 K have been observed in the magnetic properties. The magnetic
entropy reaches ln 4 at 20 K indicating that the ground state and the first
excited state are very closely spaced (a quasi-quartet state). From the
specific heat measurements and crystalline electric field (CEF) analysis of the
magnetic susceptibility, we have found the level splitting energies as 5 K and
130 K. The magnetization measurements reveal that the a-axis is the easy axis
of magnetization and the saturation moment is = 1.6 /Ce, corroborating the previous neutron diffraction measurements on a
polycrystalline sample.Comment: Submitted to Phys. Rev.
Prolific pair production with high-power lasers
Prolific electron-positron pair production is possible at laser intensities
approaching 10^{24} W/cm^2 at a wavelength of 1 micron. An analysis of electron
trajectories and interactions at the nodes (B=0) of two counter-propagating,
circularly polarised laser beams shows that a cascade of gamma-rays and pairs
develops. The geometry is generalised qualitatively to linear polarisation and
laser beams incident on a solid target.Comment: 4 pages, 1 figure, minor revisions, accepted for publication in
Physical Review Letter
Galactic-Center Hyper-Shell Model for the North Polar Spurs
The bipolar-hyper shell (BHS) model for the North Polar Spurs (NPS-E, -W, and
Loop I) and counter southern spurs (SPS-E and -W) is revisited based on
numerical hydrodynamical simulations. Propagations of shock waves produced by
energetic explosive events in the Galactic Center are examined. Distributions
of soft X-ray brightness on the sky at 0.25, 0.7, and 1.5 keV in a +/-50 deg x
+/-50 deg region around the Galactic Center are modeled by thermal emission
from high-temperature plasma in the shock-compressed shell considering
shadowing by the interstellar HI and H2 gases. The result is compared with the
ROSAT wide field X-ray images in R2, 4 and 6 bands. The NPS and southern spurs
are well reproduced by the simulation as shadowed dumbbell-shaped shock waves.
We discuss the origin and energetics of the event in relation to the starburst
and/or AGN activities in the Galactic Center. [ High resolution pdf is
available at http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/2016bhs/ ]Comment: 13 pages, 20 figures; To appear in MNRA
New Algorithms for Position Heaps
We present several results about position heaps, a relatively new alternative
to suffix trees and suffix arrays. First, we show that, if we limit the maximum
length of patterns to be sought, then we can also limit the height of the heap
and reduce the worst-case cost of insertions and deletions. Second, we show how
to build a position heap in linear time independent of the size of the
alphabet. Third, we show how to augment a position heap such that it supports
access to the corresponding suffix array, and vice versa. Fourth, we introduce
a variant of a position heap that can be simulated efficiently by a compressed
suffix array with a linear number of extra bits
- …