860 research outputs found
Chandra Detection of the X-ray counterpart of the High-magnetic field Radio Pulsar J1119-6127 in the Supernova Remnant G292.2-0.5
We report the Chandra Advanced CCD Imaging Spectrometer detection of the
X-ray counterpart of the high magnetic field, ~1600 year-old, 407 ms radio
pulsar J1119-6127 associated with the supernova remnant G292.2-0.5. The
powerful imaging capability of Chandra also unveiled, for the first time, a
faint 3"x6" pulsar wind nebula (PWN) at energies above ~1.2 keV. The X-ray
emission from the pulsar and its associated nebula is well described by an
absorbed power law model with a photon index of 2.2 (1.9-2.8). The
corresponding 0.5-10 keV unabsorbed X-ray luminosity is 5.5(2.2-15.5)x10^32
ergs/s (at 6 kpc). When compared to two other pulsars with similar spin and
magnetic properties, J1119-6127 stands out as being the least efficient at
turning rotational kinetic energy into X-ray emission. This study shows that
high magnetic field radio pulsars can be significant X-ray emitters and Chandra
is needed to study the emission properties of the pulsars and associated faint
PWNe.Comment: 6 pages, 5 figures. To appear in ApJL July 10 2003 (submitted April
10 2003, accepted May 22 2003
Examining the Correlation between Acute Behavioral Manifestations of Concussion and the Underlying Pathophysiology of Chronic Traumatic Encephalopathy: A Pilot Study
Concussion in athletes can contribute to early neuropsychological changes that may be indicative of future neurodegenerative disease. One of the hallmark findings of chronic traumatic encephalopathy is anxiety and impulsive behavior that often develops early in the course of the disease. The behavioral dysfunction can be grouped into a broader category referred to as cognitive disruption. The current gold standard for diagnosing chronic neurodegeneration is post-mortem evaluation of tauopathy to identify neurofibrillary tau tangles in neurons. Few studies, however, have looked at clinical correlations between acute injury and chronic neurodegeneration in terms of behavior. This lack of focus towards translational study has limited advancements towards treatment. In this pilot investigation, the acute cognitive and emotional (anger, impulsivity, and anxiety) affects of concussion in a cohort of collegiate athletes (n = 30) are examined and compared to findings in the post-mortem pathologic features of chronic traumatic encephalopathy. Specifically, the role of the seroternergic system with alpha synuclein and tauopathy staining and the potential for early clinically relevant behavioral and pharmaceutical interventions was investigated. The purpose was to determine if athletes began demonstrating cognitive disruption present in post-mortem evaluation during the acute phase of injury. The acute data was collected via questionnaires within ten days of the athletesâ concussion diagnosis. Results demonstrated that 11 of 30 athletes (36%) scored in a diagnosable range of anxiety post-concussion, and athletes scored above the norm in state-anger (M = 22.9, SD = 9.99), indicating severe emotional disturbance. A limitation is that due to the long time frame from acute injury to the development of neurodegeneration individual athletes cannot be tracked in longevity thus limiting the findings to the realm of correlation. The findings from this pilot study warrant further investigation into the neuropsychological aspects for how to manage concussion and prevent degenerative disease
An analysis of the X-ray emission from the supernova remnant 3C397
The ASCA SIS and the ROSAT PSPC spectral data of the SNR 3C397 are analysed
with a two-component non-equilibrium ionization model. Besides, the ASCA SIS0
and SIS1 spectra are also fitted simultaneously in an equilibrium case. The
resulting values of the hydrogen column density yield a distance of \sim8\kpc
to 3C397. It is found that the hard X-ray emission, containing S and Fe
K lines, arises primarily from the hot component, while most of the
soft emission, composed mainly of Mg, Si, Fe L lines, and continuum, is
produced by the cool component. The emission measures suggest that the remnant
evolves in a cloudy medium and imply that the supernova progenitor might not be
a massive early-type star. The cool component is approaching ionization
equilibrium. The ages estimated from the ionization parameters and dynamics are
all much greater than the previous determination. We restore the X-ray maps
using the ASCA SIS data and compare them with the ROSAT HRI and the NRAO VLA
Sky Survey (NVSS) 20 cm maps. The morphology with two bright concentrations
suggests a bipolar remnant encountering a denser medium in the west.Comment: 20 pages, aasms4.sty, 3 figures To appear in ApJ (1999
{BOAO Photometric Survey of Galactic Open Clusters. II. Physical Parameters of 12 Open Clusters
We have initiated a long-term project, the BOAO photometric survey of open
clusters, to enlarge our understanding of galactic structure using UBVI CCD
photometry of open clusters which have been little studied before. This is the
second paper of the project in which we present the photometry of 12 open
clusters. We have determined the cluster parameters by fitting the Padova
isochrones to the color-magnitude diagrams of the clusters. All the clusters
except for Be 0 and NGC 1348 are found to be intermediate-age to old (0.2 - 4.0
Gyrs) open clusters with a mean metallicity of [Fe/H] = 0.0.Comment: 11 page
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