2,268 research outputs found
Canada and the Korean War: Fifty Years On
In September 1998, the Canadian War Museum initiated a visiting speaker series to make available to the general public the latest research, debate and opinion on Canadian and international military history. Like the Museum’s highly popular film series, the talks were usually held on week nights and carried no admission fee. They have proven highly successful, both with Museum visitors and invited speakers. The latter have included eminent Canadian historians like Terry Copp, David Bercuson and Bill McAndrew, and international scholars like John Keegan, Paul Gough, and Christopher Pugsley. In the autumn of 2000, the Museum will welcome world-renowned First World War scholar Jay Winter and Pulitzer Prize winner James McPherson.
The Museum staged one of these events to coincide with the 50th anniversary of the outbreak of the Korean War. In addition to hosting several hundred Korean War veterans during the anniversary weekend of June 24–25, updating its Korean War permanent gallery, and mounting a travelling exhibit of contemporary war photographs, the Museum invited Dalhousie University professor Denis Stairs to comment on Canada’s diplomatic role in the crisis from the perspective of 50 years. This, in effect, amounted to a reconsideration of the arguments first presented in Professor Stairs’ seminal work, The Diplomacy of Constraint, which, twenty five years after its publication, remains the standard work in the field. Speaking on Sunday, 25 June 2000, fifty years to the day after North Korean forces first crossed the 38th parallel to invade the American-supported Republic of Korea in the south, the text of his address follows. Like the monograph on which it comments, the article constitutes a critical component of Canada’s Korean War literature, a tour de force by one of Canada’s most gifted scholars
The Formation of the Double Pulsar PSR J0737-3039A/B
Recent timing observations of the double pulsar J0737-3039A/B have shown that
its transverse velocity is extremely low, only 10 km/s, and nearly in the Plane
of the Galaxy. With this new information, we rigorously re-examine the history
and formation of this system, determining estimates of the pre-supernova
companion mass, supernova kick and misalignment angle between the pre- and
post-supernova orbital planes. We find that the progenitor to the recently
formed `B' pulsar was probably less than 2 MSun, lending credence to
suggestions that this object may not have formed in a normal supernova
involving the collapse of an iron core. At the same time, the supernova kick
was likely non-zero. A comparison to the history of the double-neutron-star
binary B1534+12 suggests a range of possible parameters for the progenitors of
these systems, which should be taken into account in future binary population
syntheses and in predictions of the rate and spatial distribution of short
gamma-ray burst events.Comment: To appear in MNRAS Letters. Title typo fix only; no change to pape
Radiation pattern of the isolated pulsar PSR B1828-11
Based on the free precession model of the isolated pulsar PSR B1828-11, Link
& Epstein 2001) showed that the observed pulse durations require the radio beam
to have a non-standard shape: the beam duration is larger for beam sweeps
farthest from the dipole axis. In their analysis they assumed that the actual
precession period is ~ 500 d. Recent theoretical studies suggested that the
actual precession period might be ~ 1000 d as seen in observations (Rezania
2002, Wasserman 2002). In this paper, in a good agreement with the observed
data (Stairs et al. 2000), we model the changes of the pulse shape in a
precession cycle with period ~ 1000 d and find that the variation of the pulse
duration follows from a {\it standard} beam pattern in each cycle.Comment: 9 pages, 3 figures, Accepted for publication in A&
Testing Lorentz violation with binary pulsars: constraints on standard model extension
Under the standard model extension (SME) framework, Lorentz invariance is
tested in five binary pulsars: PSR J0737-3039, PSR B1534+12, PSR J1756-2251,
PSR B1913+16 and PSR B2127+11C. By analyzing the advance of periastron, we
obtain the constraints on a dimensionless combination of SME parameters that is
sensitive to timing observations. The results imply no evidence for the break
of Lorentz invariance at level, one order of magnitude larger than
previous estimation.Comment: 4 pages, no figure, accepted for publication in RA
Neutron Stars in Globular Clusters
Dynamical interactions that occur between objects in dense stellar systems
are particularly important for the question of formation of X-ray binaries. We
present results of numerical simulations of 70 globular clusters with different
dynamical properties and a total stellar mass of 2*10^7 Msun. We find that in
order to retain enough neutron stars to match observations we must assume that
NSs can be formed via electron-capture supernovae. Our simulations explain the
observed dependence of the number of LMXBs on ``collision number'' as well as
the large scatter observed between different globular clusters. For millisecond
pulsars, we obtain good agreement between our models and the numbers and
characteristics of observed pulsars in the clusters Terzan 5 and 47 TucComment: 5 pages, 3 figures, to appear in "Dynamical Evolution of Dense
Stellar Systems", IAUS 246, ed. E. Vesperin
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