1,881 research outputs found
Swift Observations of X-ray supernovae
We present a result of X-ray supernovae (SNe) survey using the Swift
satellite public archive. An automatic searching program was designed to search
X-ray SNe among all of the Swift archival observations between November 2004
and February 2011. Using the C++ program, 24 X-ray detectable supernovae have
been found in the archive and 3 of them were newly-discovered in X-rays which
are SN 1986L, SN 2003lx, and SN 2007od. In addition, SN 2003lx is a Type Ia
supernova which may be the second X-ray detectable Type Ia after SN 2005ke
(Immler et al. 2006). Calibrated data of luminous type Ib/c supernovae was
consistent to the X-ray emission model done by Chevalier & Fransson (1994).
Statistics about the luminosities and hardness ratio have been done to purpose
of getting the X-ray emission features of the X-ray supernovae. The results
from this work help investigating the X-ray evolution of SNe and developing
similar X-ray SNe surveys in various X-rays missions
Possible TeV Source Candidates In The Unidentified EGRET Sources
We study the -ray emission from the pulsar magnetosphere based on
outer gap models, and the TeV radiation from pulsar wind nebulae (PWNe) through
inverse Compton scattering using a one-zone model. We showed previously that
GeV radiation from the magnetosphere of mature pulsars with ages of years old can contribute to the high latitude unidentified EGRET
sources. We carry out Monte Carlo simulations of -ray pulsars in the
Galaxy and the Gould Belt, assuming the pulsar birth rate, initial position,
proper motion velocity, period, and magnetic field distribution and evolution
based on observational statistics. We select from the simulation a sample of
mature pulsars in the Galactic plane () and in the high
latitude () which could be detected by EGRET. The TeV flux from
the pulsar wind nebulae of our simulated sample through the inverse Compton
scattering by relativistic electrons on the microwave cosmic background and
synchrotron seed photons are calculated. The predicted fluxes are consistent
with the present observational constraints. We suggest that strong EGRET
sources can be potential TeV source candidates for present and future
ground-based TeV telescopes.Comment: Minor changes, MNRAS in pres
Do equal land and water rights benefit the poor?: Targeted irrigation development: The case of the Andhi Khola Irrigation Scheme in Nepal
Irrigation programs / Water rights / Poverty / Households / Surveys / Water allocation / Water distribution / Water users’ associations / Farmers / Landlessness / Land ownership
The role of the state, labour policy and migrant workers' struggles in globalized China
Special issue on globalization(s) and labour in China and India, guest edited by Paul Bowles and John Harriss2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Thin accretion disks onto brane world black holes
The braneworld description of our universe entails a large extra dimension
and a fundamental scale of gravity that might be lower by several orders of
magnitude as compared to the Planck scale. An interesting consequence of the
braneworld scenario is in the nature of the vacuum solutions of the brane
gravitational field equations, with properties quite distinct as compared to
the standard black hole solutions of general relativity. One possibility of
observationally discriminating between different types of black holes is the
study of the emission properties of the accretion disks. In the present paper
we obtain the energy flux, the emission spectrum and accretion efficiency from
the accretion disks around several classes of static and rotating brane world
black holes, and we compare them to the general relativistic case. Particular
signatures can appear in the electromagnetic spectrum, thus leading to the
possibility of directly testing extra-dimensional physical models by using
astrophysical observations of the emission spectra from accretion disks.Comment: 37 pages, 14 figures, accepted for publication in PR
The Discovery of an X-ray/UV Stellar Flare from the Late-K/Early-M Dwarf LMC 335
We report the discovery of an X-ray/UV stellar flare from the source LMC 335,
captured by XMM-Newton in the field of the Large Magellanic Cloud. The flare
event was recorded continuously in X-ray for its first 10 hours from the
precursor to the late decay phases. The observed fluxes increased by more than
two orders of magnitude at its peak in X-ray and at least one in the UV as
compared to quiescence. The peak 0.1-7.0 keV X-ray flux is derived from the
two-temperature APEC model to be ~(8.4 +/- 0.6) x 10^-12 erg cm-2 s-1.
Combining astrometric information from multiple X-ray observations in the
quiescent and flare states, we identify the NIR counterpart of LMC 335 as the
2MASS source J05414534-6921512. The NIR color relations and spectroscopic
parallax characterize the source as a Galactic K7-M4 dwarf at a foreground
distance of (100 - 264) pc, implying a total energy output of the entire event
of ~(0.4 - 2.9) x 10^35 erg. This report comprises detailed analyses of this
late-K / early-M dwarf flare event that has the longest time coverage yet
reported in the literature. The flare decay can be modeled with two exponential
components with timescales of ~28 min and ~4 hours, with a single component
decay firmly ruled out. The X-ray spectra during flare can be described by two
components, a dominant high temperature component of ~40-60MK and a low
temperature component of ~10MK, with a flare loop length of about 1.1-1.3
stellar radius.Comment: 35 pages, 6 figures, 5 tables, accepted for publication in Ap
Nickel Mixing in the Outer Layers of SN 1987A
Supernova 1987A remains the most well-observed and well-studied supernova to
date. Observations produced excellent broad-band photometric and spectroscopic
coverage over a wide wavelength range at all epochs. Here, we focus on the very
early spectroscopic observations. Only recently have numerical models been of
sufficient detail to accurately explain the observed spectra. In SN 1987A, good
agreement has been found between observed and synthetic spectra for day one,
but by day four, the predicted Balmer lines become much weaker than the
observed lines. We present the results of work based on a
radiation-hydrodynamic model by Blinnikov and collaborators. Synthetic non-LTE
spectra generated from this model by the general radiation transfer code
PHOENIX strongly support the theory that significant mixing of nickel into the
outer envelope is required to maintain strong Balmer lines. Preliminary results
suggest a lower limit to the average nickel mass of 1.0 \times 10^{-5} solar
masses is required above 5000 \kmps by day four. PHOENIX models thus have the
potential to be a sensitive probe for nickel mixing in the outer layers of a
supernova.Comment: 16 pages, 7 figures, ApJ, v556 2001 (in press
INJURY INCIDENCE, DISTRIBUTION, AND SEVERITY DURING A MARATHON TRAINING SEASON AND THE IMPLICATIONS
Marathon runners and their coaches are concerned about the potential for injury during an individual season. No published studies of running injuries address this training season as a meaningful entity. This study reports the incidence of injury and the distribution of injuries for runners (n=75) on two established marathon training teams during an individual season. An injury was defined as affecting seven consecutive days or three consecutive workouts. The incidence/risks of overuse injuries, for marathon runners in a single season were found to be: anterior knee pain (20%), iliotibial band syndrome (29%), plantar fasciitis (1%), Achilles tendonitis (9%) shin splints (16%) and stress fractures (4%). This risk, overall injury distribution, severity and length of longest run prior to presentation of injury are of interest to runners, coaches and biomechanists
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