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Otto Zhou - One of the best experts on this subject based on the ideXlab platform.
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stationary head ct scanner using cnt x Ray Source arRays
Medical Imaging 2021: Physics of Medical Imaging, 2021Co-Authors: Derrek Spronk, Otto Zhou, Yueting Luo, C Inscoe, Yueh Z LeeAbstract:X-Ray Computed Tomography (CT) is an indispensable imaging modality in the diagnosis of traumatic brain injury and brain hemorrhage. While the technology and the associated system components have been refined over the last several decades, all modern CT systems still rely on the principle of rotating Sources and detectors. The rotating gantry adds a high degree of complexity to the overall system design, and could be eliminated in favor of a configuration of stationary x-Ray Sources and detectors. Such a change could potentially enable CT systems to be better suited for austere environments. Furthermore, the image acquisition speed would no longer be limited by the maximum rotating speed of the gantry. Unfortunately, due to the size and bulk of existing commercial x-Ray Sources, such a configuration is impossible to build with a sufficient number of focal spots. Recently, carbon nanotube (CNT) x-Ray Source arRays have been used in various stationary imaging configurations to generate diagnostic quality tomosynthesis images in the fields of mammography, dentistry, and orthopedics. In this study, we present a potential stationary head CT (s-HCT) design which combines projection data from 3 separate but parallel imaging planes for a complete CT fan-beam reconstruction. The proposed scanner consists of 3 CNT x-Ray Source arRays with a large number distributed focal spots each, and an Electronic Control System (ECS) for high speed control of the x-Ray exposure from each focal spot. The projection data was collected by an arRay of multi-row detectors. For this unique imaging configuration, a customized geometry calibration procedure was developed. A linear collimator was designed and constructed for the reduction of cone-angle scatter. Finally, volumetric CT slice data was acquired through z-axis translation of the imaging object.
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stationary head ct with linear cnt x Ray Source arRays image quality assessment through simulation
Medical Imaging 2021: Physics of Medical Imaging, 2021Co-Authors: Yueting Luo, Derrek Spronk, C Inscoe, Yueh Z Lee, Otto ZhouAbstract:Purpose: Carbon nanotube (CNT) based field-emission x-Ray Source arRays allow the development of robust stationary computed tomography (CT) imaging systems with no gantry movement. There are many technical considerations that constrain the optimal system design. The aim of this work is to assess the image quality of a proposed Stationary Head CT (sHCT) system through simulation. Methods: In our previous work, we defined a system design consisting of three parallel imaging planes. Each plane consists of a CNT x-Ray Source arRay with a large number of linearly distributed focal spots and three strip detector modules. Each imaging plane is rotated 120° with respect to the adjacent plane to provide maximum projection view coverage of the region of interest (ROI). An iterative reconstruction algorithm based on the ASTRA toolbox was developed for the specific sHCT system. The ACR 464 phantom and a set of clinical head CT data were used to assess the system design and image quality. Imaging performance was evaluated both quantitatively and qualitatively. Results: The simulation results suggest that the proposed sHCT design is feasible and high-fidelity CT images can be obtained. The reconstructed image of the ACR 464 phantom reproduces accurate CT numbers. The reconstructed CT images for the human head confirm the capability of this prototype for identifying low contrast pathologies. Conclusion: A three-plane sHCT system is evaluated in this work. The iterative reconstruction algorithm produces high image quality in terms of uniformity, signal-to-noise ratio, signal-to-contrast ratio and structural information. Further work on the optimization of the current sHCT system will focus on speed up of volumetric image data collection in system hardware and further improvement of the reconstruction image quality through regularization and incorporating of machine leaning techniques.
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evaluation of carbon nanotube x Ray Source arRay for stationary head computed tomography
Medical Physics, 2021Co-Authors: Derrek Spronk, Yueting Luo, C Inscoe, Yueh Z Lee, Otto ZhouAbstract:PURPOSE Stationary computed tomography (s-CT) conceptually offers several advantages over existing rotating gantry-based CT. Over the last 40 yr, s-CT has been investigated using different technological approaches. We are developing a s-CT system specifically for head/brain imaging using carbon nanotube (CNT)-based field emission x-Ray Source arRay technology. The noncircular geometry requires different assessment approaches as compared to circular geometries. The purpose of the present study is to investigate whether the CNT Source arRay meets the requirements for stationary head CT (s-HCT). METHODS Multiple prototype CNT x-Ray Source arRays were manufactured based on the system requirements obtained from simulation. Source characterization was performed using a benchtop setup consisting of an x-Ray Source arRay with 45 distributed focal spots, each operating at 120 kVp, and an electronic control system (ECS) for high speed control of the x-Ray output from individual focal spots. Due to the forward-angled geometry of the linear anode, the projected focal spot shape is expected to vary at wide angle views. A pinhole method was implemented to determine the effective focal spot size (FSS) in the imaging plane at a range of angular viewpoints with a flat panel detector. The output spectrum and half value layer (HVL) were also evaluated for a range of viewing angles to characterize the beam quality across the fan-beam. Dosimetry was performed on a simulated scan to evaluate total exposure. RESULTS The prototype CNT x-Ray Source arRay demonstrated adequate specifications for a s-HCT imaging machine. The Source arRay was operated at 120 kVp with long-term stability over a full year of regular laboratory use. Multiple cathode current measurements were used to confirm submicrosecond accuracy with regards to exposure time and subsequently dose control. All 45 focal spots were measured with an average value of 1.26 (±0.04) mm × 1.21 (±0.03) mm (equivalent to IEC 1,0). The x-Ray spectrum was found to be appropriately filtered based on Sources used in existing rotary CT systems. A stable and reliable output of 0.04 mAs per emitter and a resulting dose of 0.015 mGy per projection were observed over several months of rigorous phantom imaging. Dose per projection was regulated by the ECS and measured with ±0.5% tolerance. CONCLUSIONS The CNT x-Ray Source arRay was found to meet the requirements for the proposed stationary head CT scanner, with regard to FSS, beam quality, and dose precision. The remaining challenges are related to the overall system design of a nonrotating CT scanner with distributed Sources. The next phase of the project will incorporate multiple CNT Source arRays with multirow detectors in a proof-of-concept study and analysis of a fully functional s-HCT system.
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simulation and optimization of system configuration for the stationary head ct using cnt x Ray Source arRay reconstruction and quality evaluation
Medical Imaging 2020: Physics of Medical Imaging, 2020Co-Authors: Yueting Luo, Derrek Spronk, Y. Z. Lee, Otto ZhouAbstract:Purpose: The invention of carbon nanotube (CNT) x-Ray Source arRay has allowed development of many novel imaging systems including stationary tomosynthesis devices for breast, chest and dental imaging. This technology enables stationary computed tomography with potentially a fast data acquisition rate and a mechanically robust structure by eliminating the rotating gantry. It reduces the image blur caused by the mechanical motion. The purpose of this work is to explore possible system configurations of stationary head CT (s-HCT) using fixed-position linear CNT x-Ray Source arRays and detector arRays. Methods: Sinogram coverage is used for qualitative evaluation on the CT projection data collection efficiency for a given configuration. Accordingly, the configuration is optimized based on the coverage in sinogram space. To evaluate the system feasibility on imaging low-contrast brain tissues, a modified low-contrast Shepp-Logan phantom is implemented for quality assessment using quantitative metrics. Different Iterative Reconstruction methods are compared for both qualitative and quantitative assessment as well. Results: The sinogram coverage of s-HCT configurations changes significantly with different number of CNT Source arRays used, as well as the layout of the geometry. Preliminary results suggest that a s-HCT configuration with three planes gives a nearly completed sinogram coverage which provides enough information to reconstruct image with good quality. Different reconstruction techniques are used for such configuration with a low-contrast head phantom. High-quality images are reconstructed for the proposed configuration. Conclusion: An optimized s-HCT system configuration can be built with few linear CNT x-Ray Source arRays. Given such configuration, Iterative Reconstruction algorithms in conjunction with Total-Variation Regularization provides highquality images even for low-contrast objects.
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feasibility of a stationary head ct scanner using a cnt x Ray Source arRay
Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 2020Co-Authors: Derrek Spronk, Y. Z. Lee, Yueting Luo, C Inscoe, Alex J Billingsley, Otto ZhouAbstract:Purpose: Today’s state-of-the-art CT systems rely on a rotating gantry to acquire projections spanning up to 360 degrees around the head and/or body. By replacing the rotating Source and detector with a stationary arRay of x-Ray Sources and line detectors, a head CT scanner could be potentially constructed with a small footprint and fast scanning speed. The purpose of this project is to design and construct a stationary head CT (s-HCT) scanner capable of diagnosis of stroke and head trauma patients in limited reSource areas such as forward operating bases. Here we present preliminary imaging results which demonstrate the feasibility of such a system using carbon nanotube (CNT) x-Ray Source arRays. Methods: The feasibility study was performed using a benchtop setup consisting of an x-Ray Source arRay with 45 distributed focal spots, each operating at 120kVp, and an Electronic Control System (ECS) for high speed control of the x-Ray output from individual focal spots. The projection data was collected by an arRay of detectors configured specifically for head imaging. The basic performance of the CNT x-Ray Source arRay was characterized. By rotating the object in discrete angular steps, a potential s-HCT configuration was emulated. The collected projection images were reconstructed using an iterative reconstruction algorithm developed specifically for this configuration. Evaluation of the image quality was completed by comparing this image of the ACR CT phantom obtained with the s-HCT to that obtained by a clinical CT scanner. Results: The CNT x-Ray Source arRay was found to have a consistent focal spot size of 1.3×1.1 mm2 for all beams (IEC 1.0). At 120 kVp the HVL was measured to be 5.8 mm Al. Axial images have been acquired with slice thickness 2.5 mm to evaluate the imaging performance of the s-HCT system. Contrast-noise-ratio was measured for the acrylic (120 HU) and water (0 HU) materials in the ACR CT 464 phantom Module 01. A value of 5.2 is reported for the benchtop setup with an entrance dose of 2.9 mGy, compared to the clinical measurement of 30.5 found at 74.5 mGy. These images demonstrate that the s-HCT system based on CNT x-Ray Source arRays is feasible. Conclusion: Customized CNT x-Ray Sources were developed specifically for head CT imaging. The feasibility of using this Source arRay to construct a s-HCT scanner has been demonstrated by emulating a potential CT configuration. It is shown that diagnostic quality CT images can be obtained using the proposed system geometry. These preliminary images provide confidence that a s-HCT system can be constructed for clinical evaluation.
Jun Chen - One of the best experts on this subject based on the ideXlab platform.
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fully vacuum sealed addressable nanowire cold cathode flat panel x Ray Source
Applied Physics Letters, 2021Co-Authors: Xiuqing Cao, Shao Zhi Deng, Juncong She, Guofu Zhang, Yangyang Zhao, Jun ChenAbstract:Addressable flat-panel x-Ray Source has important applications in next-generation low-dose x-Ray imaging technology. In this study, a fully vacuum-sealed addressable flat-panel x-Ray Source has been fabricated using a ZnO nanowire cold cathode. The x-Ray Source was formed by assembling gated ZnO nanowire field emitters and a molybdenum thin film transmission anode target. Pulsed and addressable x-Ray emission was achieved by applying voltages to the extraction gate. Radiation dose rates of 235 nGy/s were achieved when the device was operated at 21 kV anode voltage and 140 V gate voltage. Projection x-Ray images of objects were obtained by the flat-panel x-Ray Source. Our results demonstrated the feasibility of a fully addressable cold cathode flat-panel x-Ray Source.
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diagonal 4 in zno nanowire cold cathode flat panel x Ray Source preparation and projection imaging properties
IEEE Transactions on Nuclear Science, 2021Co-Authors: Libin Wang, Shao Zhi Deng, Xiuqing Cao, J X Huang, Jun ChenAbstract:Uniform large-area flat-panel X-Ray Sources have potential applications in projection imaging. Achieving such a Source has remained a challenge. A diagonal 4-in cold cathode flat-panel X-Ray Source device has been fabricated using ZnO nanowire field emitter arRays. A large-area uniform X-Ray emission was produced, and projection imaging with a resolution of more than 5.0 lp/mm was realized. Its projection imaging resolution and its dependence on geometric imaging parameter settings were studied along with the imaging performance of the device. Simulations using the fast Ray-tracing algorithm were performed, yielding results consistent with those from experiments. Optimal parameter settings for high-resolution projection imaging using the flat-panel X-Ray Source are presented. This study has significance in the application of this cold cathode flat-panel X-Ray Source in X-Ray imaging.
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fabrication of zno nanowire cold cathode flat panel x Ray Source module for adaptive x Ray imaging
International Vacuum Nanoelectronics Conference, 2020Co-Authors: Shuai Wang, Shao Zhi Deng, Guofu Zhang, Daokun Chen, Libin Wang, Xinpeng Bai, Jun ChenAbstract:Flat panel X-Ray Source enables the possibility of adaptive X-Ray imaging which could achieve close range imaging. In this study, a flat panel X-Ray Source module based on ZnO nanowire field emitter arRays was fabricated. High resolution projection imaging using the module was achieved, which demonstrated the feasibility of adaptive X-Ray imaging using nanowire FEA flat panel X-Ray Source.
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An 8-inch diagonal ZnO nanowire cold cathode panel for flat-panel X-Ray Source
2018 31st International Vacuum Nanoelectronics Conference (IVNC), 2018Co-Authors: Daokun Chen, Shao Zhi Deng, Juncong She, Keshuang Zheng, Guofu Zhang, Zhipeng Zhang, Jun ChenAbstract:An 8-inch diagonal ZnO nanowire cold cathode panel was fabricated. The morphologies and field emission properties of the ZnO nanowire arRay grown on the panel was characterized. The results demonstrated that the ZnO nanowires have a relatively uniform distribution and good emission properties with an emission current of 14.5 mA, showing promising application for diode-structure flat-panel X-Ray Source.
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transmission type flat panel x Ray Source using zno nanowire field emitters
Applied Physics Letters, 2015Co-Authors: Daokun Chen, Shao Zhi Deng, Juncong She, Zhipeng Zhang, Xiaomeng Song, Jun ChenAbstract:A transmission type flat-panel X-Ray Source in diode structure was fabricated. Large-scale patterned ZnO nanowires grown on a glass substrate by thermal oxidation were utilized as field emitters, and tungsten thin film coated on silica glass was used as the transmission anode. Uniform distribution of X-Ray generation was achieved, which benefited from the uniform electron emission from ZnO nanowires. Self-ballasting effect induced by the intrinsic resistance of ZnO nanowire and decreasing of screening effect caused by patterned emitters account for the uniform emission. Characteristic X-Ray peaks of W-L lines and bremsstrahlung X-Rays have been observed under anode voltages at a range of 18–20 kV, the latter of which were the dominant X-Ray signals. High-resolution X-Ray images with spatial resolution less than 25 μm were obtained by the flat-panel X-Ray Source. The high resolution was attributed to the small divergence angle of the emitted X-Rays from the transmission X-Ray Source.
J P Halpern - One of the best experts on this subject based on the ideXlab platform.
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discovery of an energetic 38 5 ms pulsar powering the gamma Ray Source igr j18490 0000 hess j1849 000
The Astrophysical Journal, 2011Co-Authors: E V Gotthelf, J P Halpern, R Terrier, F MattanaAbstract:We report the discovery of a 38.5 ms X-Ray pulsar in observations of the soft γ-Ray Source IGR J18490–0000 with the Rossi X-Ray Timing Explorer (RXTE). PSR J1849–0001 is spinning down rapidly with period derivative 1.42 × 10–14 s s–1, yielding a spin-down luminosity 9.8 × 1036 erg s–1, characteristic age 42.9 kyr, and surface dipole magnetic field strength Bs = 7.5 × 1011 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-Ray Source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point Source is well fitted by an absorbed power-law model with photon index ΓPSR = 1.1 ± 0.2, N H = (4.3 ± 0.6) × 1022 cm–2, and F PSR(2-10 keV) = (3.8 ± 0.3) × 10–12 erg cm–2 s–1, while the spectral parameters of the extended emission are roughly ΓPWN ≈ 2.1 and F PWN(2-10 keV) ≈ 9 × 10–13 erg cm–2 s–1. IGR J18490–0000 is also coincident with the compact TeV Source HESS J1849–000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849–000 is 0.13% of the pulsar's spin-down energy, while the ratio F(0.35-10 TeV)/F PWN(2-10 keV) ≈ 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849–0001 in a stage of transition from a synchrotron X-Ray Source to an inverse Compton γ-Ray Source.
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discovery of an energetic 38 5 ms pulsar powering the gamma Ray Source igr j18490 0000 hess j1849 000
arXiv: High Energy Astrophysical Phenomena, 2010Co-Authors: E V Gotthelf, J P Halpern, R Terrier, F MattanaAbstract:We report the discovery of a 38.5 ms X-Ray pulsar in observations of the soft gamma-Ray Source IGR J18490-0000 with the Rossi X-Ray Timing Explorer (RXTE). PSR J1849-0001 is spinning down rapidly with period derivative 1.42E-14 s/s, yielding a spin-down luminosity 9.8E36 erg/s, characteristic age 42.9 kyr, and surface dipole magnetic field strength 7.5E11 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-Ray Source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point Source is well fitted by an absorbed power-law model with photon index Gamma(PSR) = 1.1 +/- 0.2, N_H = (4.3+/-0.6)E22 cm^-2, and F(PSR;2-10keV) = (3.8+/-0.3)E-12 erg/s/cm^2, while the spectral parameters of the extended emission are Gamma(PWN) = 2.1 and F(PWN;2-10 keV) = 9E-13 erg/s/cm^2. IGR J18490-0000 is also coincident with the compact TeV Source HESS J1849-000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849-000 is 0.13% of the pulsar's spin down energy, while the ratio F(0.35-10 TeV)/F(PWN; 2-10 keV) of approx. 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849-0001 in a stage of transition from a synchrotron X-Ray Source to an inverse Compton gamma-Ray Source.
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a neutron star identification for the high energy gamma Ray Source 3eg j1835 5918 detected in the rosat all sky survey
The Astrophysical Journal, 2001Co-Authors: N Mirabal, J P HalpernAbstract:In the error box of 3EG J1835+5918, the brightest as-yet unidentified EGRET Source at intermediate Galactic latitude, we find a weak, ultrasoft X-Ray Source at energies E 25.2. The corresponding lower limit on fX/fV is 300, which signifies that the X-Ray Source is probably a thermally emitting neutron star. Considering our previous complete multiwavelength survey of the 3EG J1835+5918 region, which failed to find any other notable candidate for identification with 3EG J1835+5918, we propose that this X-Ray Source, RX J1836.2+5925, is a rotation-powered γ-Ray pulsar that is either older or more distant than the prototype Geminga. We see marginal evidence for variability between two ROSAT HRI observations. If real, this would indicate that the X-Ray emission has an external origin, perhaps due to intermittent heating of the polar caps by a variable particle accelerator. RX J1836.2+5925 could even be an old, recycled pulsar, which may nevertheless have a high γ-Ray efficiency.
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discovery of soft x Ray pulsations from the gamma Ray Source geminga
Nature, 1992Co-Authors: J P Halpern, S S HoltAbstract:THE nature of the γ-Ray Source 'Geminga' (2CG195 + 04) is a problem of considerable importance in high-energy astrophysics. First discovered in 1972 by the SAS-2 satellite1, Geminga emits virtually all its power at energies above 50 MeV, and at energies above 100 MeV is the second brightest Source in the γ-Ray sky survey made by the Cos-B satellite2. It eluded identification at all other wavelengths until the Einstein Observatory found an unusual soft X-Ray Source, 1E0630 + 178, in its error box3. This Source also has a claimed twenty-fifth magnitude optical counterpart4–6. This distinctive set of properties is reminiscent of the Vela pulsar, except for the absence of radio emission7 or a synchroton nebula3. We have made a more sensitive soft X-Ray observation of the Geminga field using Rosat, and have detected coherent pulsations from 1E0630+178 at a period of 0.237s. This result confirms suggestions3–6,8,9 that Geminga is, like Vela, a γ-Ray pulsar. We speculate that Geminga is somewhat the older of the two. With this discovery we consider the mystery of Geminga largely solved.
F Mattana - One of the best experts on this subject based on the ideXlab platform.
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discovery of an energetic 38 5 ms pulsar powering the gamma Ray Source igr j18490 0000 hess j1849 000
The Astrophysical Journal, 2011Co-Authors: E V Gotthelf, J P Halpern, R Terrier, F MattanaAbstract:We report the discovery of a 38.5 ms X-Ray pulsar in observations of the soft γ-Ray Source IGR J18490–0000 with the Rossi X-Ray Timing Explorer (RXTE). PSR J1849–0001 is spinning down rapidly with period derivative 1.42 × 10–14 s s–1, yielding a spin-down luminosity 9.8 × 1036 erg s–1, characteristic age 42.9 kyr, and surface dipole magnetic field strength Bs = 7.5 × 1011 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-Ray Source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point Source is well fitted by an absorbed power-law model with photon index ΓPSR = 1.1 ± 0.2, N H = (4.3 ± 0.6) × 1022 cm–2, and F PSR(2-10 keV) = (3.8 ± 0.3) × 10–12 erg cm–2 s–1, while the spectral parameters of the extended emission are roughly ΓPWN ≈ 2.1 and F PWN(2-10 keV) ≈ 9 × 10–13 erg cm–2 s–1. IGR J18490–0000 is also coincident with the compact TeV Source HESS J1849–000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849–000 is 0.13% of the pulsar's spin-down energy, while the ratio F(0.35-10 TeV)/F PWN(2-10 keV) ≈ 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849–0001 in a stage of transition from a synchrotron X-Ray Source to an inverse Compton γ-Ray Source.
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discovery of an energetic 38 5 ms pulsar powering the gamma Ray Source igr j18490 0000 hess j1849 000
arXiv: High Energy Astrophysical Phenomena, 2010Co-Authors: E V Gotthelf, J P Halpern, R Terrier, F MattanaAbstract:We report the discovery of a 38.5 ms X-Ray pulsar in observations of the soft gamma-Ray Source IGR J18490-0000 with the Rossi X-Ray Timing Explorer (RXTE). PSR J1849-0001 is spinning down rapidly with period derivative 1.42E-14 s/s, yielding a spin-down luminosity 9.8E36 erg/s, characteristic age 42.9 kyr, and surface dipole magnetic field strength 7.5E11 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-Ray Source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point Source is well fitted by an absorbed power-law model with photon index Gamma(PSR) = 1.1 +/- 0.2, N_H = (4.3+/-0.6)E22 cm^-2, and F(PSR;2-10keV) = (3.8+/-0.3)E-12 erg/s/cm^2, while the spectral parameters of the extended emission are Gamma(PWN) = 2.1 and F(PWN;2-10 keV) = 9E-13 erg/s/cm^2. IGR J18490-0000 is also coincident with the compact TeV Source HESS J1849-000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849-000 is 0.13% of the pulsar's spin down energy, while the ratio F(0.35-10 TeV)/F(PWN; 2-10 keV) of approx. 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849-0001 in a stage of transition from a synchrotron X-Ray Source to an inverse Compton gamma-Ray Source.
E V Gotthelf - One of the best experts on this subject based on the ideXlab platform.
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nustar detection of a hard x Ray Source in the supernova remnant molecular cloud interaction site of ic 443
arXiv: High Energy Astrophysical Phenomena, 2018Co-Authors: Shuo Zhang, E V Gotthelf, Xiaping Tang, Xiao Zhang, Lei Sun, Zhiyu Zhang, Allen Cheng, Dheeraj R Pasham, F K Baganoff, K PerezAbstract:We report on a broadband study of a complex X-Ray Source (1SAX J0618.0+2227) associated with the interaction site of the supernova remnant (SNR) IC 443 and ambient molecular cloud (MC) using NuSTAR, XMM_Newton, and Chandra observations. Its X-Ray spectrum is composed of both thermal and non-thermal components. The thermal component can be equally well represented by either a thin plasma model with kT=0.19 keV or a blackbody model with kT=0.11 keV. The non-thermal component can be fit with either a power-law with Gamma~1.7 or a cutoff power-law with Gamma~1.5 and a cutoff energy at E_cut~18 keV. Using the newly obtained NuSTAR dataset, we test three possible scenarios for isolated X-Ray Sources in the SNR-MC interaction site: 1) pulsar wind nebula (PWN); 2) SNR ejecta fragment; 3) shocked molecular clump. We conclude that this Source is most likely composed of a SNR ejecta (or a PWN) and surrounding shocked molecular clumps. The nature of this hard X-Ray Source in the SNR-MC interaction site of IC 443 may shed light on unidentified X-Ray Sources with hard X-Ray spectra in rich environments for star forming regions, such as the Galactic center.
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discovery of an energetic 38 5 ms pulsar powering the gamma Ray Source igr j18490 0000 hess j1849 000
The Astrophysical Journal, 2011Co-Authors: E V Gotthelf, J P Halpern, R Terrier, F MattanaAbstract:We report the discovery of a 38.5 ms X-Ray pulsar in observations of the soft γ-Ray Source IGR J18490–0000 with the Rossi X-Ray Timing Explorer (RXTE). PSR J1849–0001 is spinning down rapidly with period derivative 1.42 × 10–14 s s–1, yielding a spin-down luminosity 9.8 × 1036 erg s–1, characteristic age 42.9 kyr, and surface dipole magnetic field strength Bs = 7.5 × 1011 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-Ray Source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point Source is well fitted by an absorbed power-law model with photon index ΓPSR = 1.1 ± 0.2, N H = (4.3 ± 0.6) × 1022 cm–2, and F PSR(2-10 keV) = (3.8 ± 0.3) × 10–12 erg cm–2 s–1, while the spectral parameters of the extended emission are roughly ΓPWN ≈ 2.1 and F PWN(2-10 keV) ≈ 9 × 10–13 erg cm–2 s–1. IGR J18490–0000 is also coincident with the compact TeV Source HESS J1849–000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849–000 is 0.13% of the pulsar's spin-down energy, while the ratio F(0.35-10 TeV)/F PWN(2-10 keV) ≈ 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849–0001 in a stage of transition from a synchrotron X-Ray Source to an inverse Compton γ-Ray Source.
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discovery of an energetic 38 5 ms pulsar powering the gamma Ray Source igr j18490 0000 hess j1849 000
arXiv: High Energy Astrophysical Phenomena, 2010Co-Authors: E V Gotthelf, J P Halpern, R Terrier, F MattanaAbstract:We report the discovery of a 38.5 ms X-Ray pulsar in observations of the soft gamma-Ray Source IGR J18490-0000 with the Rossi X-Ray Timing Explorer (RXTE). PSR J1849-0001 is spinning down rapidly with period derivative 1.42E-14 s/s, yielding a spin-down luminosity 9.8E36 erg/s, characteristic age 42.9 kyr, and surface dipole magnetic field strength 7.5E11 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-Ray Source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point Source is well fitted by an absorbed power-law model with photon index Gamma(PSR) = 1.1 +/- 0.2, N_H = (4.3+/-0.6)E22 cm^-2, and F(PSR;2-10keV) = (3.8+/-0.3)E-12 erg/s/cm^2, while the spectral parameters of the extended emission are Gamma(PWN) = 2.1 and F(PWN;2-10 keV) = 9E-13 erg/s/cm^2. IGR J18490-0000 is also coincident with the compact TeV Source HESS J1849-000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849-000 is 0.13% of the pulsar's spin down energy, while the ratio F(0.35-10 TeV)/F(PWN; 2-10 keV) of approx. 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849-0001 in a stage of transition from a synchrotron X-Ray Source to an inverse Compton gamma-Ray Source.
