3,967 research outputs found
SN 1996cr: Confirmation of a Luminous Type IIn Supernova in the Circinus Galaxy
We have recently confirmed SN 1996cr as a late-time type IIn supernova (SN)
via VLT spectroscopy and isolated its explosion date to ~1 yr using archival
optical imaging. We briefly touch upon here the wealth of optical, X-ray, and
radio archival observations available for this enigmatic source. Due to its
relative proximity (3.8 +/-0.6 Mpc), SN 1996cr ranks among the brightest X-ray
and radio SNe ever detected and, as such, may offer powerful insights into the
structure and composition of type IIn SNe. We also find that SN 1996cr is
matched to GRB 4B 960202 at a 2-3 sigma confidence level, making it perhaps the
third GRB to be significantly associated with a type II SN. We speculate on
whether SN 1996cr could be an off-axis or ``failed'' GRB.Comment: 3 pages, 1 figure, poster proceeding for "Supernova 1987A: 20 Years
After: Supernovae and Gamma-Ray Bursters" AIP, New York, eds. S. Immler, K.W.
Weiler, and R. McCra
Physical activity education in the undergraduate curricula of all UK medical schools: are tomorrow's doctors equipped to follow clinical guidelines?
Physical activity (PA) is a cornerstone of disease prevention and treatment. There is, however, a considerable disparity between public health policy, clinical guidelines and the delivery of physical activity promotion within the National Health Service in the UK. If this is to be addressed in the battle against non-communicable diseases, it is vital that tomorrow's doctors understand the basic science and health benefits of physical activity. The aim of this study was to assess the provision of physical activity teaching content in the curricula of all medical schools in the UK. Our results, with responses from all UK medical schools, uncovered some alarming findings, showing that there is widespread omission of basic teaching elements, such as the Chief Medical Officer recommendations and guidance on physical activity. There is an urgent need for physical activity teaching to have dedicated time at medical schools, to equip tomorrow's doctors with the basic knowledge, confidence and skills to promote physical activity and follow numerous clinical guidelines that support physical activity promotion
Form and function in hillslope hydrology : Characterization of subsurface ow based on response observations
Acknowledgements. We are grateful to Marcel Delock, Lisei Köhn, and Marvin Reich for their support during fieldwork, as well as Markus Morgner and Jean Francois Iffly for technical support, Britta Kattenstroth for hydrometeorological data acquisition and isotope sampling, and Barbara Herbstritt and Begoña Lorente Sistiaga for laboratory work. Laurent Pfister and Jean-Francois Iffly from the Luxembourg Institute of Science and Technology (LIST) are acknowledged for organizing the permissions for the experiments and providing discharge data for Weierbach 1 and Colpach. We also want to thank Frauke K. Barthold and the two anonymous reviewers, whose thorough remarks greatly helped to improve the manuscript. This study is part of DFG-funded CAOS project “From Catchments as Organised Systems to Models based on Dynamic Functional Units” (FOR 1598). The article processing charges for this open-access publication were covered by a Research Centre of the Helmholtz Association.Peer reviewedPublisher PD
The LWA1 Radio Telescope
LWA1 is a new radio telescope operating in the frequency range 10-88 MHz,
located in central New Mexico. The telescope consists of 258 pairs of
dipole-type antennas whose outputs are individually digitized and formed into
beams. Simultaneously, signals from all dipoles can be recorded using one of
the instrument's "all dipoles" modes, facilitating all-sky imaging. Notable
features of the instrument include high intrinsic sensitivity (about 6 kJy
zenith system equivalent flux density), large instantaneous bandwidth (up to 78
MHz), and 4 independently-steerable beams utilizing digital "true time delay"
beamforming. This paper summarizes the design of LWA1 and its performance as
determined in commissioning experiments. We describe the method currently in
use for array calibration, and report on measurements of sensitivity and
beamwidth.Comment: 9 pages, 14 figures, accepted by IEEE Trans. Antennas & Propagation.
Various minor changes from previous versio
Detection of Pre-Shock Dense Circumstellar Material of SN 1978K
The supernova SN 1978K has been noted for its lack of emission lines broader
than a few thousand km/s since its discovery in 1990. Modeling of the radio
spectrum of the peculiar SN 1978K indicates the existence of HII absorption
along the line of sight. To determine the nature of this absorbing region, we
have obtained a high-dispersion spectrum of SN 1978K at the wavelength range
6530--6610 \AA. The spectrum shows not only the moderately broad H-alpha
emission of the supernova ejecta but also narrow nebular H-alpha and [N II]
emission. The high [N II]6583/H-alpha ratio, 0.8-1.3, suggests that this radio
absorbing region is a stellar ejecta nebula. The expansion velocity and
emission measure of the nebula are consistent with those seen in ejecta nebulae
of luminous blue variables. Previous low-dispersion spectra have detected a
strong [N II]5755 line, indicating an electron density of 3-12x10^5 cm^{-3}. We
argue that this stellar ejecta nebula is probably part of the pre-shock dense
circumstellar envelope of SN 1978K. We further suggest that SN 1997ab may
represent a young version of SN 1978K.Comment: 12 pages, 1 figure, accepted for publication in the ApJ Letter
Creation and characterization of vortex clusters in atomic Bose-Einstein condensates
We show that a moving obstacle, in the form of an elongated paddle, can
create vortices that are dispersed, or induce clusters of like-signed vortices
in 2D Bose-Einstein condensates. We propose new statistical measures of
clustering based on Ripley's K-function which are suitable to the small size
and small number of vortices in atomic condensates, which lack the huge number
of length scales excited in larger classical and quantum turbulent fluid
systems. The evolution and decay of clustering is analyzed using these
measures. Experimentally it should prove possible to create such an obstacle by
a laser beam and a moving optical mask. The theoretical techniques we present
are accessible to experimentalists and extend the current methods available to
induce 2D quantum turbulence in Bose-Einstein condensates.Comment: 9 pages, 9 figure
Radio Spectral Index and Expansion of 3C58
We present new observations of the plerionic supernova remnant 3C58 with the
VLA at 74 and 327 MHz. In addition, we re-reduced earlier observations at 1.4
and 4.9 GHz taken in 1973 and 1984. Comparing these various images, we find
that: 1. the remnant has a flat and relatively uniform spectral index
distribution, 2. any expansion of the remnant with time is significantly less
than that expected for uniform, undecelerated expansion since the generally
accepted explosion date in 1181 A.D., and 3. there is no evidence for a
non-thermal synchrotron emission shell generated by a supernova shock wave,
with any such emission having a surface brightness of <1 x 10^(-21) W / (m^2 Hz
sr) at 327 MHz.Comment: 18 pages, 7 Figures, Latex, Accepted for publication in the
Astrophysical Journa
Determination of absolute neutrino masses from Z-bursts
Ultrahigh energy neutrinos (UHE\nu) scatter on relic neutrinos (R\nu)
producing Z bosons, which can decay hadronically producing protons (Z-burst).
We compare the predicted proton spectrum with the observed ultrahigh energy
cosmic ray (UHECR) spectrum and determine the mass of the heaviest R\nu via a
maximum likelihood analysis. Our prediction depends on the origin of the
power-like part of the UHECR spectrum: m_\nu=2.75^{+1.28}_{-0.97} eV for
Galactic halo and 0.26^{+0.20}_{-0.14} eV for extragalactic (EG) origin. The
necessary UHE\nu flux should be detected in the near future.Comment: slight rewording, revised neutrino fluxes, conclusions unchanged,
version to appear in Phys. Rev. Let
Polarization in the inner region of Pulsar Wind Nebulae
We present here the first effort to compute synthetic synchrotron
polarization maps of Pulsar Wind Nebulae (PWNe). Our goal is to highlight how
polarization can be used as an additional diagnostic tool for the flow
structure in the inner regions of these nebulae. Recent numerical simulations
suggest the presence of flow velocities ~0.5 c in the surroundings of the
termination shock, where most of the high energy emission comes from. We
construct polarization maps taking into account relativistic effects like
Doppler boosting and position angle swing. The effect of different bulk
velocities is clarified with the help of a toy-model consisting of a uniformly
emitting torus. We also present a map based on recent numerical simulations of
the entire nebula and compare it with presently available data. The comparison
with upcoming high resolution observations could provide new insight into the
inner structure of the nebula and put constraints on the geometrical properties
of the magnetic field.Comment: Accepted for publication on A&A, 6 pages, 2 figure
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