12,443 research outputs found
X-ray Pulsars in the Small Magellanic Cloud
XMM-Newton archival data for the Small Magellanic Cloud have been examined
for the presence of previously undetected X-ray pulsars. One such pulsar, with
a period of 202 s, is detected. Its position is consistent with an early B star
in the SMC and we identify it as a high mass X-ray binary (HMXB). In the course
of this study we determined the pulse period of the possible AXP CXOU
J010043.1-721134 to be 8.0 s, correcting an earlier report (Lamb et al 2002b)
of a 5.4 s period for this object. Pulse profiles and spectra for each of these
objects are presented as well as for a recently discovered (Haberl & Pietsch
2004) 263 s X-ray pulsar. Properties of an ensemble of 24 optically identified
HMXB pulsars from the SMC are investigated. The locations of the pulsars and an
additional 22 X-ray pulsars not yet identified as having high mass companions
are located predominately in the young (ages years) star
forming regions of the SMC as expected on the basis of binary evolution models.
We find no significant difference between the distribution of spin periods for
the HMXB pulsars of the SMC compared with that of the Milky Way. For those HMXB
pulsars which have Be companions we note an inverse correlation between spin
period and maximum X-ray flux density. (This anti-correlation has been
previously noted for all X-ray binary pulsars by Stella, White & Rosner 1986).
The anti-correlation for the Be binaries may be a reflection of the fact that
the spin periods and orbital periods of Be HMXBs are correlated. We note a
similar correlation between X-ray luminosity and spin period for the Be HMXB
pulsars of the Milky Way and speculate that exploitation of the correlation
could serve as a distance indicator.Comment: final version accepted in The Astrophysical Journa
Three New Long Period X-ray Pulsars Discovered in the Small Magellanic Cloud
The Small Magellanic Cloud is increasingly an invaluable laboratory for
studying accreting and isolated X-ray pulsars. We add to the class of compact
SMC objects by reporting the discovery of three new long period X-ray pulsars
detected with the {\it Chandra X-ray Observatory}. The pulsars, with periods of
152, 304 and 565 seconds, all show hard X-ray spectra over the range from 0.6 -
7.5 keV. The source positions of the three pulsars are consistent with known
H-alpha emission sources, indicating they are likely to be Be type X-ray binary
star systems.Comment: Accepted for publication in the Astrophysical Journa
Discovery of Pulsed X-ray Emission from the SMC Transient RX J0117.6-7330
We report on the detection of pulsed, broad-band, X-ray emission from the
transient source RX J0117.6-7330. The pulse period of 22 seconds is detected by
the ROSAT/PSPC instrument in a 1992 Sep 30 - Oct 2 observation and by the
CGRO/BATSE instrument during the same epoch. Hard X-ray pulsations are
detectable by BATSE for approximately 100 days surrounding the ROSAT
observation (1992 Aug 28 - Dec 8). The total directly measured X-ray luminosity
during the ROSAT observation is 1.0E38 (d/60 kpc)^2 ergs s-1. The pulse
frequency increases rapidly during the outburst, with a peak spin-up rate of
1.2E-10 Hz s-1 and a total frequency change 1.8%. The pulsed percentage is
11.3% from 0.1-2.5 keV, increasing to at least 78% in the 20-70 keV band. These
results establish RX J0117.6-7330 as a transient Be binary system.Comment: 17 pages, Latex, aasms, accepted for publication in ApJ Letter
Lowest Landau-level description of a Bose-Einstein condensate in a rapidly rotating anisotropic trap
A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional
trap can be described with the lowest Landau-level set of states. In this case,
the condensate wave function psi(x,y) is a Gaussian function of r^2 = x^2 +
y^2, multiplied by an analytic function P(z) of the single complex variable z=
x+ i y; the zeros of P(z) denote the positions of the vortices. Here, a similar
description is used for a rapidly rotating anisotropic two-dimensional trap
with arbitrary anisotropy (omega_x/omega_y le 1). The corresponding condensate
wave function psi(x,y) has the form of a complex anisotropic Gaussian with a
phase proportional to xy, multiplied by an analytic function P(zeta), where
zeta is proportional to x + i beta_- y and 0 le beta_- le 1 is a real parameter
that depends on the trap anisotropy and the rotation frequency. The zeros of
P(zeta) again fix the locations of the vortices. Within the set of lowest
Landau-level states at zero temperature, an anisotropic parabolic density
profile provides an absolute minimum for the energy, with the vortex density
decreasing slowly and anisotropically away from the trap center.Comment: 13 pages, 1 figur
Simultaneous IUE, EXOSAT and optical observations of the unusual AM Her type variable H058+608
Simultaneous observations of the AM Her type variable H0538+608 made with IUE, EXOSAT, and a 1.3 m ground based telescope, and subsequent optical spectrophotometry at high and low resolution are discussed. The X-ray and optical data show clear evidence of a 3.30 + or - 0.03 hr period. Three SWP spectra were taken outside of eclipse and during overlapping phase intervals. The UV spectra contain strong emission lines characteristic of this class of objects and a flat continuum which appears to be deficient, given the brightness of source at optical and X-ray wavelengths. There is evidence for intensity variations in emission lines, particularly C IV. The X-ray light curves for H0538+608 reveal behavior which may be related to irregularities in its accretion flow
Delivering organisational adaptation through legislative mechanisms: Evidence from the Adaptation Reporting Power (Climate Change Act 2008)
There is increasing recognition that organisations, particularly in key infrastructure sectors, are potentially vulnerable to climate change and extreme weather events, and require organisational responses to ensure they are resilient and adaptive. However, detailed evidence of how adaptation is facilitated, implemented and reported, particularly through legislative mechanisms is lacking. The United Kingdom Climate Change Act (2008), introduced the Adaptation Reporting Power, enabling the Government to direct so-called reporting authorities to report their climate change risks and adaptation plans. We describe the authors' unique role and experience supporting the Department for Environment, Food and Rural Affairs (Defra) during the Adaptation Reporting Power's first round. An evaluation framework, used to review the adaptation reports, is presented alongside evidence on how the process provides new insights into adaptation activities and triggered organisational change in 78% of reporting authorities, including the embedding of climate risk and adaptation issues. The role of legislative mechanisms and risk-based approaches in driving and delivering adaptation is discussed alongside future research needs, including the development of organisational maturity models to determine resilient and well adapting organisations. The Adaptation Reporting Power process provides a basis for similar initiatives in other countries, although a clear engagement strategy to ensure buy-in to the process and research on its long-term legacy, including the potential merits of voluntary approaches, is required
Very high energy gamma rays from the Crab Nebula
Observations of the Crab pulsar using the atmospheric Cerenkov technique were conducted for 22 hours. The light curve obtained shows a single peak at approximately the position of the expected main peak with a significance level of 3.2 sigma. The pulsed flux above 200 GeV is 2.5 + or - 0.8 x 10 to the 11th power cm(-2)s(-1)
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