2,322 research outputs found
Balawyder, Aloysius, Canadian-Soviet Relations Between the World Wars, University of Toronto Press, 1972, 248 p.
Humbert-Droz, Jules, De LĂ©nine Ă Staline. Dix ans au service de lâInternationale communiste, 1921-1931, Ăd. De la BaconniĂšre, NeuchĂątel, 1971, 507 p.
The Optical Gravitational Lensing Experiment. Catalog of stellar proper motions in the OGLE-II Galactic bulge fields
We present a proper motion (\mu) catalogue of 5,080,236 stars in 49 Optical
Gravitational Lensing Experiment II (OGLE-II) Galactic bulge (GB) fields,
covering a range of -11 deg. <l< 11 deg. and -6 deg. <b<3 deg., the total area
close to 11 square degrees. The proper motion measurements are based on 138 -
555 I-band images taken during four observing seasons: 1997-2000. The catalogue
stars are in the magnitude range 11 < I < 18 mag. In particular, the catalogue
includes Red Clump Giants (RCGs) and Red Giants in the GB, and main sequence
stars in the Galactic disc. The proper motions up to \mu = 500 mas/yr were
measured with the mean accuracy of 0.8-3.5 mas/yr, depending on the brightness
of a star. This catalogue may be useful for studying the kinematic of stars in
the GB and the Galactic disk.Comment: 13 pages, 16 figures, MNRAS in pres
A boxy bulge in the Milky Way. Inversion of the stellar statistics equation with 2MASS data
Inverting the stellar statistics equation from 2MASS star counts, we obtain
the 3D density distribution of the Galactic bulge as well as its luminosity
function in the K-band. This results in a boxy bulge with axial ratios
1:0.5:0.4 and a major axis angle with respect to the Sun-galactic center of
.Comment: 5 pages, accepted to be published in A&
A Frustrated 3-Dimensional Antiferromagnet: Stacked Layers
We study a frustrated 3D antiferromagnet of stacked layers. The
intermediate 'quantum spin liquid' phase, present in the 2D case, narrows with
increasing interlayer coupling and vanishes at a triple point. Beyond this
there is a direct first-order transition from N{\' e}el to columnar order.
Possible applications to real materials are discussed.Comment: 11 pages,7 figure
Astrophysical Ionizing Radiation and the Earth: A Brief Review and Census of Intermittent Intense Sources
Cosmic radiation backgrounds are a constraint on life, and their distribution
will affect the Galactic Habitable Zone. Life on Earth has developed in the
context of these backgrounds, and characterizing event rates will elaborate the
important influences. This in turn can be a base for comparison with other
potential life-bearing planets. In this review we estimate the intensities and
rates of occurrence of many kinds of strong radiation bursts by astrophysical
entities ranging from gamma-ray bursts at cosmological distances to the Sun
itself. Many of these present potential hazards to the biosphere: on timescales
long compared with human history, the probability of an event intense enough to
disrupt life on the land surface or in the oceans becomes large. We enumerate
the known sources of radiation and characterize their intensities at the Earth
and rates or upper limits on these quantities. When possible, we estimate a
"lethal interval", our best estimate of how often a major extinction-level
event is probable given the current state of knowledge; we base these estimates
on computed or expected depletion of stratospheric ozone. In general, moderate
level events are dominated by the Sun, but the far more severe infrequent
events are probably dominated by gamma-ray bursts and supernovae. We note for
the first time that so-called "short-hard" gamma-ray bursts are a substantial
threat, comparable in magnitude to supernovae and greater than that of the
higher-luminosity long bursts considered in most past work. Given their
precursors, short bursts may come with little or no warning.Comment: to be published in Astrobiolog
Modelling the Galactic Bar Using Red Clump Giants
The color-magnitude diagrams of stars obtained for 12
fields across the Galactic bulge with the OGLE project reveal a well-defined
population of bulge red clump giants. We find that the distributions of the
apparent magnitudes of the red clump stars are systematically fainter when
moving towards lower galactic fields. The most plausible explanation of
this distinct trend is that the Galactic bulge is a bar, whose nearest end lies
at positive galactic longitude. We model this Galactic bar by fitting for all
fields the observed luminosity functions in the red clump region of the
color-magnitude diagram. We find that almost regardless of the analytical
function used to describe the 3-D stars distribution of the Galactic bar, the
resulting models have the major axis inclined to the line of sight by
, with axis ratios corresponding to . This
puts a strong constraint on the possible range of the Galactic bar models.
Gravitational microlensing can provide us with additional constrains on the
structure of the Galactic bar.Comment: submitted to the New Astronomy, 27 pages, 11 figures; also available
at ftp://www.astro.princeton.edu/stanek/Barmodel and through WWW at
http://www.astro.princeton.edu/~library/prep.htm
Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS II. The complete high resolution extinction map and implications for Bulge studies
We use the Vista Variables in the Via Lactea (VVV) ESO public survey data to
measure extinction values in the complete area of the Galactic bulge covered by
the survey at high resolution. We derive reddening values using the method
described in Paper I. This is based on measuring the mean (J-Ks) color of red
clump giants in small subfields of 2' to 6' in the following bulge area:
-10.3<b<+5.1 and -10<l<+10.4. To determine the reddening values E(J-Ks) for
each region, we measure the RC color and compare it to the (J-Ks) color of RC
stars measured in Baade's window, for which we adopt E(B-V)=0.55. This allows
us to construct a reddening map sensitive to small scale variations minimizing
the problems arising from differential extinction. The significant reddening
variations are clearly observed on spatial scales as small as 2'. We find a
good agreement between our extinction measurements and Schlegel maps in the
outer bulge, but, as already stated in the literature the Schlegel maps are not
reliable for regions within |b| < 6. In the inner regions we compare our
results with maps derived from DENIS and Spitzer surveys. While we find good
agreement with other studies in the corresponding overlapping regions, our
extinction map has better quality due to both higher resolution and a more
complete spatial coverage in the Bulge. We investigate the importance of
differential reddening and demonstrate the need for high resolution extinction
maps for detailed studies of Bulge stellar populations and structure. The
extinction variations on scales of up to 2'-6', must be taken into account when
analysing the stellar populations of the Bulge.Comment: Accepted for publication in A&
- âŠ