5,542 research outputs found

    Broadband Spectral Analysis of PKS 0528+134: A Report on Six Years of EGRET Observations

    Get PDF
    The multiwavelength spectra of PKS 0528+134 during six years of observations by EGRET have been analyzed using synchrotron self-Compton (SSC) and external radiation Compton (ERC) models. We find that a two-component model, in which the target photons are produced externally to the gamma-ray emitting region, but also including an SSC component, is required to suitably reproduce the spectral energy distributions of the source. Our analysis indicates that there is a trend in the observed properties of PKS 0528+134, as the source goes from a gamma-ray low state to a flaring state. We observe that during the higher gamma-ray states, the bulk Lorentz factor of the jet increases and the ERC component dominates the high-energy emission. Our model calculations indicate the trend that the energies of the electrons giving rise to the synchrotron peak decreases, and the power-ratio of the gamma-ray and low energy spectral components increases, as the source goes from a low to a high gamma-ray state.Comment: 36 pages, 13 figures, final version accepted for publication in ApJ; includes minor modification

    Gemini/GMOS Transmission Spectral Survey: Complete Optical Transmission Spectrum of the hot Jupiter WASP-4b

    Full text link
    We present the complete optical transmission spectrum of the hot Jupiter WASP-4b from 440-940 nm at R ~ 400-1500 obtained with the Gemini Multi-Object Spectrometers (GMOS); this is the first result from a comparative exoplanetology survey program of close-in gas giants conducted with GMOS. WASP-4b has an equilibrium temperature of 1700 K and is favorable to study in transmission due to a large scale height (370 km). We derive the transmission spectrum of WASP-4b using 4 transits observed with the MOS technique. We demonstrate repeatable results across multiple epochs with GMOS, and derive a combined transmission spectrum at a precision about twice above photon noise, which is roughly equal to to one atmospheric scale height. The transmission spectrum is well fitted with a uniform opacity as a function of wavelength. The uniform opacity and absence of a Rayleigh slope from molecular hydrogen suggest that the atmosphere is dominated by clouds with condensate grain size of ~1 um. This result is consistent with previous observations of hot Jupiters since clouds have been seen in planets with similar equilibrium temperatures to WASP-4b. We describe a custom pipeline that we have written to reduce GMOS time-series data of exoplanet transits, and present a thorough analysis of the dominant noise sources in GMOS, which primarily consist of wavelength- and time- dependent displacements of the spectra on the detector, mainly due to a lack of atmospheric dispersion correction.Comment: 23 pages, 12 figures, accepted for publication in AJ, 2017 July

    EGRET Observations of the Diffuse Gamma-Ray Emission in Orion: Analysis Through Cycle 6

    Get PDF
    We present a study of the high-energy diffuse emission observed toward Orion by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory. The total exposure by EGRET in this region has increased by more than a factor of two since a previous study. A simple model for the diffuse emission adequately fits the data; no significant point sources are detected in the region studied (l=195l = 195^\circ to 220220^\circ and b=25to10b = -25^\circ to -10^\circ) in either the composite dataset or in two separate groups of EGRET viewing periods considered. The gamma-ray emissivity in Orion is found to be (1.65±0.11)×1026ssr1(1.65 \pm 0.11) \times 10^{-26} {s sr}^{-1} for E > 100 MeV, and the differential emissivity is well-described as a combination of contributions from cosmic-ray electrons and protons with approximately the local density. The molecular mass calibrating ratio is N(H2)/WCO=(1.35±0.15)×1020cm2(Kkm/s)1N(H_2)/W_{CO} = (1.35 \pm 0.15) \times 10^{20} cm^{-2} (K km/s)^{-1}.Comment: 16 pages, including 5 figures. 3 Tables as three separate files. Latex document, needs AASTEX style files. Accepted for publication in Ap

    Multiplicity of Galactic Cepheids from long-baseline interferometry I. CHARA/MIRC detection of the companion of V1334 Cygni

    Get PDF
    We aim at determining the masses of Cepheids in binary systems, as well as their geometric distances and the flux contribution of the companions. The combination of interferometry with spectroscopy will offer a unique and independent estimate of the Cepheid masses. Using long-baseline interferometry at visible and infrared wavelengths, it is possible to spatially resolve binary systems containing a Cepheid down to milliarcsecond separations. Based on the resulting visual orbit and radial velocities, we can then derive the fundamental parameters of these systems, particularly the masses of the components and the geometric distance. We therefore performed interferometric observations of the first-overtone mode Cepheid V1334 Cyg with the CHARA/MIRC combiner. We report the first detection of a Cepheid companion using long-baseline interferometry. We detect the signature of a companion orbiting V1334 Cyg at two epochs. We measure a flux ratio between the companion and the Cepheid f = 3.10+/-0.08%, giving an apparent magnitude mH = 8.47+/-0.15mag. The combination of interferometric and spectroscopic data have enabled the unique determination of the orbital elements: P = 1938.6+/-1.2 days, Tp = 2 443 616.1+/-7.3, a = 8.54+/-0.51mas, i = 124.7+/-1.8{\deg}, e = 0.190+/-0.013, {\omega} = 228.7+/-1.6{\deg}, and {\Omega} = 206.3+/-9.4{\deg}. We derive a minimal distance d ~ 691 pc, a minimum mass for both stars of 3.6 Msol, with a spectral type earlier than B5.5V for the companion star. Our measured flux ratio suggests that radial velocity detection of the companion using spectroscopy is within reach, and would provide an orbital parallax and model-free masses.Comment: Published in A&

    GeV Gamma-Ray Sources

    Get PDF
    We report on the preliminary extension of our work on cataloging the GeV sky to approximately 7 years of CGRO/EGRET observations with special emphasis on a search for transient sources. The search method and significance levels are presented. Our initial results on 13 possible transients indicate that 3 may be new gamma-ray sources. Sixteen new steady GeV sources are also detected, 3 of which have never been reported as gamma-ray sources

    Individual correlates of podoconiosis in areas of varying endemicity: a case-control study

    Get PDF
    BACKGROUND Podoconiosis is a non-filarial form of elephantiasis resulting in lymphedema of the lower legs. Previous studies have suggested that podoconiosis arises from the interplay of individual and environmental factors. Here, our aim was to understand the individual-level correlates of podoconiosis by comparing 460 podoconiosis-affected individuals and 707 unaffected controls. METHODS/PRINCIPAL FINDINGS This was a case-control study carried out in six kebeles (the lowest governmental administrative unit) in northern Ethiopia. Each kebele was classified into one of three endemicity levels: 'low' (prevalence 5%). A total of 142 (30.7%) households had two or more cases of podoconiosis. Compared to controls, the majority of the cases, especially women, were less educated (OR = 1.7, 95% CI = 1.3 to 2.2), were unmarried (OR = 3.4, 95% CI = 2.6-4.6) and had lower income (t = -4.4, p<0.0001). On average, cases started wearing shoes ten years later than controls. Among cases, age of first wearing shoes was positively correlated with age of onset of podoconiosis (r = 0.6, t = 12.5, p<0.0001). Among all study participants average duration of shoe wearing was less than 30 years. Between both cases and controls, people in 'high' and 'medium' endemicity kebeles were less likely than people in 'low' endemicity areas to 'ever' have owned shoes (OR = 0.5, 95% CI = 0.4-0.7). CONCLUSIONS Late use of shoes, usually after the onset of podoconiosis, and inequalities in education, income and marriage were found among cases, particularly among females. There were clustering of cases within households, thus interventions against podoconiosis will benefit from household-targeted case tracing. Most importantly, we identified a secular increase in shoe-wearing over recent years, which may give opportunities to promote shoe-wearing without increasing stigma among those at high risk of podoconiosis

    Reclassification of ICD-9 Codes into Meaningful Categories for Oncology Survivorship Research

    Get PDF
    Background. The International Classification of Disease, ninth revision (ICD-9) is designed to code disease into categories which are placed into administrative databases. These databases have been used for epidemiological studies. However, the categories used in the ICD9-codes are not always the most effective for evaluating specific diseases or their outcomes, such as the outcomes of cancer treatment. Therefore a re-classification of the ICD-9 codes into new categories specific to cancer outcomes is needed. Methods. An expert panel comprised of two physicians created broad categories that would be most useful to researchers investigating outcomes and morbidities associated with the treatment of cancer. A Senior Data Coordinator with expertise in ICD-9 coding, then joined this panel and each code was re-classified into the new categories. Results. Consensus was achieved for the categories to go from the 17 categories in ICD-9 to 39 categories. The ICD-9 Codes were placed into new categories, and subcategories were also created for more specific outcomes. The results of this re-classification is available in tabular form. Conclusions. ICD-9 codes were re-classified by group consensus into categories that are designed for oncology survivorship research. The novel re-classification system can be used by those involved in cancer survivorship research

    PAMTEĆI POVIJEST KARDIOVASKULARNE KIRURGIJE U RIJECI, HRVATSKA (Uloga "manjeg" centra)

    Get PDF
    The article describes the development of the Cardiovascular surgery in Rijeka Croatia. It explains the historical and social circumstances of the region as well as the most important facts of the history of the medicine and surgery in this city. The standpoint of the paper is that all centers contribute to the progress of medicine. Besides the leading world centers which determine the pace of the development of medicine, all others are also relevant participants. The continous and coordinated efforts of leading and "minor" centers are also decisive in the field of cardiovascular surgery. The activity of Cardiovascular Surgery of the Clinical Hospital Center in fujeka, although a "minor" center, regarding international proportions, has been very important for the entire medicine in the region

    Низкочастотная пьезотромбоэластография — экспресс-метод оценки функционального состояния системы гемостаза

    Get PDF
    Освещены вопросы определения референтных величин анализируемых показателей низкочастотной пьезотромбоэластографии у здоровых добровольцев, а также проведена оценка возможности использованияметода для контроля за дезагрегантной и антикоагулянтной терапией.The article deals with questions of definition of the reference values of the analyzed indicators of low-frequency haemoviscoelastography in healthy volunteers and assessed the possibility of using the method for the control of antiplatelet and anticoagulant therapy
    corecore