234 research outputs found
Multiwavelength Observations of 1ES 1959+650, One Year After the Strong Outburst of 2002
In April-May 2003, the blazar 1ES 1959+650 showed an increased level of X-ray
activity. This prompted a multiwavelength observation campaign with the Whipple
10 m gamma-ray telescope, the Rossi X-ray Timing Explorer, the Bordeaux Optical
Observatory, and the University of Michigan Radio Astrophysical Observatory. We
present the multiwavelength data taken from May 2, 2003 to June 7, 2003 and
compare the source characteristics with those measured during observations
taken during the years 2000 and 2002. The X-ray observations gave a data set
with high signal-to-noise light curves and energy spectra; however, the
gamma-ray observations did not reveal a major TeV gamma-ray flare. Furthermore,
we find that the radio and optical fluxes do not show statistically significant
deviations from those measured during the 2002 flaring periods. While the X-ray
flux and X-ray photon index appear correlated during subsequent observations,
the apparent correlation evolved significantly between the years 2000, 2002,
and 2003. We discuss the implications of this finding for the mechanism that
causes the flaring activity.Comment: 17 pages, 6 figures, 2 table
Multiwavelength Observations of the Blazar Mrk 421 in December 2002 and January 2003
We report on a multiwavelength campaign on the TeV gamma-ray blazar Markarian
(Mrk) 421 performed during December 2002 and January 2003. These target of
opportunity observations were initiated by the detection of X-ray and TeV
gamma-ray flares with the All Sky Monitor (ASM) on board the Rossi X-ray Timing
Explorer (RXTE) and the 10 m Whipple gamma-ray telescope.The campaign included
observational coverage in the radio (University of Michigan Radio Astronomy
Observatory), optical (Boltwood, La Palma KVA 0.6m, WIYN 0.9m), X-ray (RXTE
pointed telescopes), and TeV gamma-ray (Whipple and HEGRA) bands.
At TeV energies, the observations revealed several flares at intermediate
flux levels, peaking between 1 and 1.5 times the flux from the Crab Nebula.
While the time averaged spectrum can be fitted with a single power law of
photon index Gamma =2.8, we find some evidence for spectral variability.
Confirming earlier results, the campaign reveals a rather loose correlation
between the X-ray and TeV gamma-ray fluxes. In one case, a very strong X-ray
flare is not accompanied by a comparable TeV gamma-ray flare. Although the
source flux was variable in the optical and radio bands, the sparse sampling of
the optical and radio light curves does not allow us to study the correlation
properties in detail.
We present a simple analysis of the data with a synchrotron-self Compton
model, emphasizing that models with very high Doppler factors and low magnetic
fields can describe the data.Comment: Accepted for publication in the Astrophysical Journa
Detection of the BL Lac Object H1426+428 at TeV Gamma Ray Energies
A very high energy (VHE) gamma-ray signal has been detected at the 5.4 sigma
level from H1426+428, an x-ray selected BL Lacertae object at a redshift of
0.129. The object was monitored from 1995 - 1998 with the Whipple 10m imaging
atmospheric Cherenkov telescope as part of a general blazar survey; the results
of these observations, although not statistically significant, were
consistently positive. X-ray observations of H1426+428 during 1999 with the
BeppoSAX instrument revealed that the peak of its synchrotron spectrum occurs
at > 100 keV, leading to the prediction of observable TeV emission from this
object. H1426+428 was monitored extensively at the Whipple Observatory during
the 1999, 2000, and 2001 observing seasons. The strongest TeV signals were
detected in 2000 and 2001. During 2001, an integral flux of 2.04 +/- 0.35
x10e-11 cm-2 s-1 above 280 GeV was recorded from H1426+428. The detection of
H1426+428 supports the idea that, as also seen in Markarian 501 and
1ES2344+514, BL Lacertae objects with extremely high synchrotron peak
frequencies produce gamma rays in the TeV range.Comment: 35 pages, 7 figures, accepted by ApJ Two upper limits in Table 3
(upper limits for 1995 and 1997) are different from the ApJ versio
The First VERITAS Telescope
The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic
Radiation Imaging Telescope Array System) has been in operation since February
2005. We present here a technical description of the instrument and a summary
of its performance. The calibration methods are described, along with the
results of Monte Carlo simulations of the telescope and comparisons between
real and simulated data. The analysis of TeV -ray observations of the
Crab Nebula, including the reconstructed energy spectrum, is shown to give
results consistent with earlier measurements. The telescope is operating as
expected and has met or exceeded all design specifications.Comment: Accepted by Astroparticle Physic
VERITAS: the Very Energetic Radiation Imaging Telescope Array System
The Very Energetic Radiation Imaging Telescope Array System (VERITAS)
represents an important step forward in the study of extreme astrophysical
processes in the universe. It combines the power of the atmospheric Cherenkov
imaging technique using a large optical reflector with the power of
stereoscopic observatories using arrays of separated telescopes looking at the
same shower. The seven identical telescopes in VERITAS, each of aperture 10 m,
will be deployed in a filled hexagonal pattern of side 80 m; each telescope
will have a camera consisting of 499 pixels with a field of view of 3.5 deg
VERITAS will substantially increase the catalog of very high energy (E >
100GeV) gamma-ray sources and greatly improve measurements of established
sources.Comment: 44 pages, 16 figure
National survey of variations in practice in the prevention of surgical site infections in adult cardiac surgery, United Kingdom and Republic of Ireland
Background: Currently no national standards exist for the prevention of surgical site infection (SSI) in cardiac surgery. SSI rates range from 1% to 8% between centres. Aim: The aim of this study was to explore and characterize variation in approaches to SSI prevention in the UK and the Republic of Ireland (ROI). Methods: Cardiac surgery centres were surveyed using electronic web-based questionnaires to identify variation in SSI prevention at the level of both institution and consultant teams. Surveys were developed and undertaken through collaboration between the Cardiothoracic Interdisciplinary Research Network (CIRN), Public Health England (PHE) and the National Cardiac Benchmarking Collaborative (NCBC) to encompass routine pre-, intra- and postoperative practice. Findings: Nineteen of 38 centres who were approached provided data and included responses from 139 consultant teams. There was no missing data from those centres that responded. The results demonstrated substantial variation in over 40 aspects of SSI prevention. These included variation in SSI surveillance, reporting of SSI infection rates to external bodies, utilization of SSI risk prediction tools, and the use of interventions such as sternal support devices and gentamicin impregnated sponges. Conclusion: Measured variation in SSI prevention in cardiac centres across the UK and ROI is evidence of clinical uncertainty as to best practice, and has identified areas for quality improvement as well as knowledge gaps to be addressed by future research
A data-driven synthesis of research evidence for domains of hearing loss, as reported by adults with hearing loss and their communication partners
A number of assessment tools exist to evaluate the impact of hearing loss, with little consensus among researchers as to either preference or psychometric adequacy. The item content of hearing loss assessment tools should seek to capture the impact of hearing loss on everyday life, but to date no one has synthesized the range of hearing loss complaints from the perspectives of the person with hearing loss and their communication partner. The current review aims to synthesize the evidence on person with hearing loss- and communication partner-reported complaints of hearing loss. Searches were conducted in Cos Conference Papers Index, the Cumulative Index to Nursing and Allied Health Literature, Excerpta Medica Database, PubMed, Web of Science, and Google Scholar to identify publications from May 1982 to August 2015. A manual search of four relevant journals updated the search to May 2017. Of the 9,516 titles identified, 78 records (comprising 20,306 participants) met inclusion criteria and were taken through to data collection. Data were analyzed using meta-ethnography to form domains representing the person with hearing loss- and communication partner-reported complaints of hearing loss as reported in research. Domains and subdomains mutual to both perspectives are related to ââAuditoryââ (listening, communicating, and speaking), ââSocialââ (relationships, isolation, social life, occupational, and interventions), and ââSelfââ (effort and fatigue, emotions, identity, and stigma). Our framework contributes fundamental new knowledge and a unique resource that enables researchers and clinicians to consider the broader impacts of hearing loss. Our findings can also be used to guide questions during diagnostic assessment and to evaluate existing measures of hearing loss
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