97 results on '"Ronald F Elsner"'
Search Results
2. Optics for the imaging x-ray polarimetry explorer
- Author
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Brian D. Ramsey, Stephen D. Bongiorno, Jeffery J. Kolodziejczak, Kiranmayee Kilaru, Cheryl Alexander, Wayne H. Baumgartner, Shawn Breeding, Ronald F. Elsner, Shelley Le Roy, Jeff McCracken, Ikuyuki Mitsuishi, Stephen L. O’Dell, Steven D. Pavelitz, Jaganathan Ranganathan, Javier Sanchez, Chet O. Speegle, Nicholas Thomas, Bruce Weddendorf, and Martin C. Weisskopf
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Space and Planetary Science ,Control and Systems Engineering ,Mechanical Engineering ,Astronomy and Astrophysics ,Instrumentation ,Electronic, Optical and Magnetic Materials - Published
- 2022
3. Toward Large-Area Sub-Arcsecond X-Ray Telescopes II
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Stephen L ODell, Ryan Allured, Andrew O Ames, Michael P Biskach, David M Broadway, Ricardo J Bruni, David Burrows, Jian Cao, Brandon D Chalifoux, Kai-wing Chan, Yip-Wah Chung, Vincenzo Cotroneo, Ronald F Elsner, Jessica A Gaskin, Mikhail V Gubarev, Ralf K Heilmann, Edward Hertz, Thomas N Jackson, Kiranmayee Kilaru, Jeffery J Kolodziejczak, Ryan S McClelland, Brian D Ramsey, Paul B Reid, Raul E Riveros, Jacqueline M Roche, Suzanne E Romaine, Timo T Saha, Mark L Schattenburg, Daniel A Schwartz, Eric D Schwartz, Peter M Solly, Susan E Trolier-McKinstry, Mellville P Ulmer, Alexey Vikhlilin, Margeaux L Wallace, and William W Zhang
- Subjects
Astronomy ,Optics - Abstract
In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (approx. = 3 sq m) and fine angular resolution (approx. = 1"). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 sq m) of lightweight (approx. = 2 kg/sq m areal density) high-quality mirrors, at an acceptable cost (approx. = 1 M$/sq m of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates.
- Published
- 2016
- Full Text
- View/download PDF
4. Full-shell x-ray optics development at NASA Marshall Space Flight Center
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Stephen L. O'Dell, Kiranmayee Kilaru, Jessica A. Gaskin, Patrick Champey, Jacqueline M. Davis, Martin C. Weisskopf, Brian D. Ramsey, Ronald F. Elsner, David M. Broadway, Samantha A. Johnson, S. Bongiorno, Oliver J. Roberts, Wayne H. Baumgartner, Jeffrey Kolodziejczak, and Douglas A. Swartz
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Engineering ,Fabrication ,business.industry ,Mechanical Engineering ,Shell (computing) ,X-ray optics ,Polishing ,Astronomy and Astrophysics ,X-ray telescope ,Diamond turning ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Metrology ,010309 optics ,Development (topology) ,Space and Planetary Science ,Control and Systems Engineering ,0103 physical sciences ,Aerospace engineering ,business ,010303 astronomy & astrophysics ,Instrumentation - Abstract
NASA’s Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication- and coating-induced stresses and mounting-induced distortions.
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- 2020
5. The Imaging X-ray polarimetry explorer (IXPE): Technical overview III
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Paolo Soffitta, Primo Attina', Luca Baldini, Mattia Barbanera, Wayne H. Baumgartner, Ronaldo Bellazzini, Jeff Bladt, Stephen D. Bongiorno, Alessandro Brez, Simone Castellano, Rita Carpentiero, Marco Castronuovo, Luca Cavalli, Elisabetta Cavazzuti, Fabio D' Amico, Saverio Citraro, Enrico Costa, William D. Deininger, ELisa D' Alba, Ettore Del Monte, Kutis L. Diets, Niccolo' Di Lalla, Alessandro Di Marco, Guseppe Di Persio, Immacolata Donnarumma, Ronald F. Elsner, Sergio Fabiani, Riccardo Ferrazzoli, Larry Guy, William Kalinowski, Jeffery Kolodziejczak, Luca Latronico, Carlo Lefevre, Paolo Lorenzi, Leonardo Lucchesi, Simone Maldera, Alberto Manfreda, Elio Mangraviti, Herman L. Marshall, James Masciarelli, Giorgio Matt, Massimo Minuti, Fabio Muleri, Hikmat Nasimi, Barbara Negri, Alessio Nuti, Leonardo Orsini, Darren Osborne, Maura Pilia, Matteo Perri, Melissa Pesce-Rollins, Colin Peterson, Michele Pinchera, Simonetta Puccetti, Brian Ramsey, Ajay Ratheesh, Roger W. Romani, Paolo Sarra, Francesco Santoli, Andrea Sciortino, Carmelo Sgro', Brian T. Smith, Gloria Spandre, Allyn F. Tennant, Antonino Tobia, Alessio Trois, Marco Vimercati, Jeffrey Wedmnore, Martin C. Weisskopf, Fei Xie, Francesco Zanetti, Cheryl Alexander, D. Zachery Allen, Fabrizio Amici, L. Angelo Antonelli, Spencer Antoniak, Matteo Bachetti, Raffaella Bonino, Fabio Borotto, Shawn Breeding, Daniele Brienza, H. Kyle Bygott, Claudia Cardelli, Marco Ceccanti, Mauro Centrone, Yuri Evangelista, MacKenzie Ferrie, Brent Forsyth, Michele Foster, Eli Gurnee, Grant Hibbard, Sandra R. Johnson, Erik Kelly, Kiranmayee Kilaru, Fabio La Monaca, Shelley Le Roy, Pasqualino Loffredo, Guido Magazzu', Marco Marengo, Alessandra Marrocchesi, Francesco Massaro, Alfredo Morbidini, Jeffrey McCracken, Michael McEachen, Paolo Mereu, Scott Mitchell, Ikuyuki Mitsuishi, Federico Mosti, Michela Nigro, Chiara Oppedisano, Richard Pacheco, alessandro Paggi, Steven D. Pavelitz, Cristina Pentz, Raffaele Piazzolla, Brad Porter, Alessandro Profeti, Jaganathan Ranganathan, John Rankin, Noah Root, Alda Rubini, Stephanie Ruswick, Javier Sanchez, Emanuele Scalise, Sara Schindhelm, Chet O. Speegle, Toru Tamagawa, Marcello Tardiola, Amy L. Walden, Bruce Weddendorf, David Welch, Michael Head, Stuart Gray, Rondal Mize, Stephen L. O'Dell, Christopher Schroeder, Nicholas E. Thomas, Randy M. Bagget, David Dolan, Kevin Ferrant, Joseph Footdale, Benjamin Garelick, Samantha Johnson, and Timothy Seek
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Physics ,X-ray ,Optics ,business.industry ,X-ray, Polarimetry, Astrophysics, Optics, Gas Pixel Detector ,Polarimetry ,business ,Astrophysics ,Gas Pixel Detector - Published
- 2020
6. The independent pulsations of Jupiter’s northern and southern X-ray auroras
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I. J. Rae, G. R. Gladstone, Geraint H. Jones, Marissa F. Vogt, James Sinclair, Zhonghua Yao, G. A. Graham, G. Branduardi-Raymont, G. S. Orton, Ronald F. Elsner, R. Caro-Carretero, William Dunn, Ralph P. Kraft, Andrew J. Coates, Licia C Ray, Caitriona M. Jackman, and Peter G. Ford
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Physics ,Brightness ,Solar System ,010504 meteorology & atmospheric sciences ,Astrophysics::High Energy Astrophysical Phenomena ,Magnetosphere ,Astronomy and Astrophysics ,Hot spot (veterinary medicine) ,F500 ,Astrophysics ,01 natural sciences ,Astrobiology ,Jupiter ,Atmosphere ,Planet ,Physics::Space Physics ,0103 physical sciences ,Astrophysics::Earth and Planetary Astrophysics ,Emission spectrum ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
Auroral hot spots are observed across the Universe at different scales 1 and mark the coupling between a surrounding plasma environment and an atmosphere. Within our own Solar System, Jupiter possesses the only resolvable example of this large-scale energy transfer. Jupiter’s northern X-ray aurora is concentrated into a hot spot, which is located at the most poleward regions of the planet’s aurora and pulses either periodically 2,3 or irregularly 4,5 . X-ray emission line spectra demonstrate that Jupiter’s northern hot spot is produced by high charge-state oxygen, sulfur and/or carbon ions with an energy o f tens of MeV (refs 4–6 ) that are undergoing charge exchange. Observations instead failed to reveal a similar feature in the south 2,3,7,8 . Here, we report the existence of a persistent southern X-ray hot spot. Surprisingly, this large-scale southern auroral structure behaves independently of its northern counterpart. Using XMM-Newton and Chandra X-ray campaigns, performed in May–June 2016 and March 2007, we show that Jupiter’s northern and southern spots each exhibit different characteristics, such as different periodic pulsations and uncorrelated changes in brightness. These observations imply that highly energetic, non-conjugate magnetospheric processes sometimes drive the polar regions of Jupiter’s dayside magnetosphere. This is in contrast to current models of X-ray generation for Jupiter 9,10 . Understanding the behaviour and drivers of Jupiter’s pair of hot spots is critical to the use of X-rays as diagnostics of the wide range of rapidly rotating celestial bodies that exhibit these auroral phenomena. The authors discover that Jupiter's southern X-ray aurora is concentrated into a hot spot (until now only the north pole was known to have one), which behaves completely differently in brightness and timing pulsation from its northern counterpart.
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- 2017
7. Two decades of Chandra high-resolution camera operations: lessons learned and future prospects
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Ronald F. Elsner, Daniel J. Patnaude, Stephen S. Murray, Stephen L. O'Dell, Almus T. Kenter, Ralph P. Kraft, Grant R. Tremblay, Joseph I. Minow, Linda Neergaard Parker, Esra Bulbul, Thomas Gauron, Paul Nulsen, and Gerald K. Austin
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Computer science ,High resolution ,Remote sensing - Published
- 2018
8. Methods for reducing singly reflected rays on the Wolter-I focusing mirrors of the FOXSI rocket experiment
- Author
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Brian D. Ramsey, Ronald F. Elsner, Juan Camilo Buitrago-Casas, Noriyuki Narukage, Sophie Musset, Shin-nosuke Ishikawa, Lindsay Glesener, Sasha Courtade, P. S. Athiray, Paul Turin, Säm Krucker, Juliana Vievering, and Steven Christe
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Physics ,Paraboloid ,Photon ,business.product_category ,Sounding rocket ,Dynamic range ,business.industry ,Astronomy ,X-ray telescope ,01 natural sciences ,Semiconductor detector ,010309 optics ,Cardinal point ,Optics ,Rocket ,0103 physical sciences ,business ,010303 astronomy & astrophysics - Abstract
In high energy solar astrophysics, imaging hard X-rays by direct focusing offers higher dynamic range and greater sensitivity compared to past techniques that used indirect imaging. The Focusing Optics X-ray Solar Imager (FOXSI) is a sounding rocket payload that uses seven sets of nested Wolter-I figured mirrors together with seven high-sensitivity semiconductor detectors to observe the Sun in hard X-rays through direct focusing. The FOXSI rocket has successfully flown twice and is funded to fly a third time in summer 2018. The Wolter-I geometry consists of two consecutive mirrors, one paraboloid and one hyperboloid, that reflect photons at grazing angles. Correctly focused X-rays reflect once per mirror segment. For extended sources, like the Sun, off-axis photons at certain incident angles can reflect on only one mirror and still reach the focal plane, generating a background pattern of singly reflected rays (i.e., ghost rays) that can limit the sensitivity of the observation to faint, focused sources. Understanding and mitigating the impact of the singly reflected rays on the FOXSI optical modules will maximize the instruments’ sensitivity to background-limited sources. We present an analysis of the FOXSI singly reflected rays based on ray-tracing simulations and laboratory measurements, as well as the effectiveness of different physical strategies to reduce them.
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- 2017
9. Active full-shell grazing-incidence optics
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Jacqueline M. Roche, Ronald F. Elsner, Brian D. Ramsey, Stephen L. O'Dell, Jeffrey J. Kolodziejczak, Martin C. Weisskopf, and Mikhail V. Gubarev
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Physics ,business.industry ,Antenna aperture ,Physics::Optics ,X-ray optics ,X-ray telescope ,Active optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,010309 optics ,Optics ,0103 physical sciences ,Angular resolution ,Spatial frequency ,0210 nano-technology ,business ,Adaptive optics ,Image resolution - Abstract
MSFC has a long history of developing full-shell grazing-incidence x-ray optics for both narrow (pointed) and wide field (surveying) applications. The concept presented in this paper shows the potential to use active optics to switch between narrow and wide-field geometries, while maintaining large effective area and high angular resolution. In addition, active optics has the potential to reduce errors due to mounting and manufacturing lightweight optics. The design presented corrects low spatial frequency error and has significantly fewer actuators than other concepts presented thus far in the field of active x-ray optics. Using a finite element model, influence functions are calculated using active components on a full-shell grazing-incidence optic. Next, the ability of the active optic to effect a change of optical prescription and to correct for errors due to manufacturing and mounting is modeled.
- Published
- 2016
10. Toward large-area sub-arcsecond x-ray telescopes II
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Stephen L. O'Dell, Ryan Allured, Andrew O. Ames, Michael P. Biskach, David M. Broadway, Ricardo J. Bruni, David N. Burrows, Jian Cao, Brandon D. Chalifoux, Kai-Wing Chan, Yip-Wah Chung, Vincenzo Cotroneo, Ronald F. Elsner, Jessica A. Gaskin, Mikhail V. Gubarev, Ralf K. Heilmann, Edward Hertz, Thomas N. Jackson, Kiranmayee Kilaru, Jeffrey J. Kolodziejczak, Ryan S. McClelland, Brian D. Ramsey, Paul B. Reid, Raul E. Riveros, Jacqueline M. Roche, Suzanne E. Romaine, Timo T. Saha, Mark L. Schattenburg, Daniel A. Schwartz, Eric D. Schwartz, Peter M. Solly, Susan Trolier-McKinstry, Melville P. Ulmer, Alexey Vikhlinin, Margeaux L. Wallace, Xiaoli Wang, David L. Windt, Youwei Yao, Shi Ye, William W. Zhang, Heng Zuo, and USA
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ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION - Abstract
In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (≍ 3 m2) and fine angular resolution (≍ 12). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (≍ 600 m2) of lightweight (≍ 2 kg/m2 areal density) high-quality mirrors, at an acceptable cost (≍ 1 M$/m2 of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates....
- Published
- 2016
11. AChandraSearch for Coronal X‐Rays from the Cool White Dwarf GD 356
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Ronald F. Elsner, Virginia Trimble, Chryssa Kouveliotou, Stephen L. O'Dell, Martin C. Weisskopf, Vyacheslav E. Zavlin, and Kinwah Wu
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Physics ,Electron density ,Space and Planetary Science ,Observatory ,Astrophysics (astro-ph) ,ROSAT ,FOS: Physical sciences ,White dwarf ,Astronomy and Astrophysics ,Cyclotron radiation ,Astrophysics ,Luminosity - Abstract
We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356 (GJ 1205), G 99-47 (GR 290 = V1201 Ori), GD 90, G 195-19 (EG250 = GJ 339.1), and WD 2316+123 and archival Chandra data for LHS 1038 (GJ 1004) and GD 358 (V777 Her). Our Chandra observation detected no X rays from GD 356, setting the most restrictive upper limit to the X-ray luminosity from any cool white dwarf -- L_{X} < 6.0 x 10^{25} ergs/s, at 99.7% confidence, for a 1-keV thermal-bremsstrahlung spectrum. The corresponding limit to the electron density is n_{0} < 4.4 x 10^{11} cm^{-3}. Our re-analysis of the archival data confirmed the non-detections reported by the original investigators. We discuss the implications of our and prior observations on models for coronal emission from white dwarfs. For magnetic white dwarfs, we emphasize the more stringent constraints imposed by cyclotron radiation. In addition, we describe (in an appendix) a statistical methodology for detecting a source and for constraining the strength of a source, which applies even when the number of source or background events is small., 27 pages, 4 figures, submitted to the Astrophysical Journal
- Published
- 2007
12. X-ray optics at NASA Marshall Space Flight Center
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Stephen L. O'Dell, Jeffery J. Kolodziejczak, Carolyn Atkins, Jessica A. Gaskin, Kiranmayee Kilaru, Allyn F. Tennant, Brian D. Ramsey, V. E. Zavlin, Ronald F. Elsner, David M. Broadway, Martin C. Weisskopf, Jacqueline M. Roche, Douglas A. Swartz, and Mikhail V. Gubarev
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Engineering ,business.product_category ,Fabrication ,business.industry ,X-ray optics ,Mature technology ,X-ray telescope ,law.invention ,Telescope ,Optics ,Rocket ,law ,Satellite ,Angular resolution ,business - Abstract
NASA's Marshall Space Flight Center (MSFC) engages in research, development, design, fabrication, coating, assembly, and testing of grazing-incidence optics (primarily) for x-ray telescope systems. Over the past two decades, MSFC has refined processes for electroformed-nickel replication of grazing-incidence optics, in order to produce high-strength, thin-walled, full-cylinder x-ray mirrors. In recent years, MSFC has used this technology to fabricate numerous x-ray mirror assemblies for several flight (balloon, rocket, and satellite) programs. Additionally, MSFC has demonstrated the suitability of this technology for ground-based laboratory applications-namely, x-ray microscopes and cold-neutron microscopes and concentrators. This mature technology enables the production, at moderately low cost, of reasonably lightweight x-ray telescopes with good (15-30 arcsecond) angular resolution. However, achieving arcsecond imaging for a lightweight x-ray telescope likely requires development of other technologies. Accordingly, MSFC is conducting a multi-faceted research program toward enabling cost-effective production of lightweight high-resolution x-ray mirror assemblies. Relevant research topics currently under investigation include differential deposition for post-fabrication figure correction, in-situ monitoring and control of coating stress, and direct fabrication of thin-walled full-cylinder grazing-incidence mirrors.
- Published
- 2015
13. SuperHERO: Design of a new hard-X-ray focusing telescope
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Brian D. Ramsey, Paul Seller, Steven Christe, Allyn F. Tennant, Ronald F. Elsner, Matthew D. Wilson, Albert Y. Shih, Kiranmayee Kilaru, Colleen A. Wilson-Hodge, David Stuchlik, Jessica A. Gaskin, Bruce Weddendorf, and Douglas A. Swartz
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Physics ,High energy ,X-ray astronomy ,business.industry ,Detector ,X-ray detector ,X-ray optics ,Astronomy ,X-ray telescope ,law.invention ,Telescope ,Optics ,law ,Angular resolution ,business - Abstract
SuperHERO is a hard x-ray (20–75 keV) balloon-borne telescope, currently in its proposal phase, that will utilize high angular-resolution grazing-incidence optics, coupled to novel CdTe multi-pixel, fine-pitch (250 µm) detectors. The high-resolution electroformed-nickel, grazing-incidence optics were developed at MSFC, and the detectors were developed at the Rutherford Appleton Laboratory in the UK, and are being readied for flight at GSFC. SuperHERO will use two active pointing systems; one for carrying out astronomical observations and another for solar observations during the same flight. The telescope will reside on a light-weight, carbon-composite structure that will integrate the Wallops Arc Second Pointer into its frame, for arcsecond or better pointing. This configuration will allow for Long Duration Balloon flights that can last up to 4 weeks. This next generation design, which is based on the High Energy Replicated Optics (HERO) and HERO to Explore the Sun (HEROES) payloads, will be discussed, with emphasis on the core telescope components.
- Published
- 2015
14. High-time-resolution Measurements of the Polarization of the Crab Pulsar at 1.38 GHz
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B. W. Stappers, Ronald F. Elsner, Alice K. Harding, Agnieszka Slowikowska, Stephen L. O'Dell, Martin C. Weisskopf, Alexander J. van der Horst, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Crab Pulsar ,Linear polarization ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Approx ,Position angle ,Polarization (waves) ,Astrophysics - Astrophysics of Galaxies ,Quadratic variation ,Radio telescope ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Atomic physics ,Astrophysics - High Energy Astrophysical Phenomena ,Circular polarization - Abstract
Using the Westerbork Synthesis Radio Telescope (WSRT), we obtained high-time-resolution measurements of the full (linear and circular) polarization of the Crab pulsar. Taken at a resolution of 1/8192 of the 34-ms pulse period (i.e., $4.1~\mu{\rm s}$), the 1.38-GHz linear-polarization measurements are in general agreement with previous lower-time-resolution 1.4-GHz measurements of linear polarization in the main pulse (MP), in the interpulse (IP), and in the low-frequency component (LFC). We find the MP and IP to be linearly polarized at about $24\%$ and $21\%$, with no discernible difference in polarization position angle. However, and contrary to theoretical expectations and measurements in the visible, we find no evidence for significant variation (sweep) in polarization position angle over the MP, the IP, or the LFC. Although, the main pulse exhibits a small but statistically significant quadratic variation in the degree of linear polarization. We discuss the implications which appear to be in contradiction to theoretical expectations. In addition, we detect weak circular polarization in the main pulse and interpulse, and strong ($\approx 20\%$) circular polarization in the low-frequency component, which also exhibits very strong ($\approx 98\%$) linear polarization at a position angle about $40\degree$ from that of the MP or IP. The pulse-mean polarization properties are consistent with the LFC being a low-altitude component and the MP and IP being high-altitude caustic components. Nevertheless, current models for the MP and IP emission do not readily account for the observed absence of pronounced polarization changes across the pulse. Finally, we measure IP and LFC pulse phases relative to the MP that are consistent with recent measurements, which have shown that the phases of these pulse components are evolving with time., Comment: 28 pages, 10 figures, accepted by the Astrophysical Journal
- Published
- 2015
15. A Search for the X‐Ray Counterpart of the Unidentified γ‐Ray Source 3EG J2020+4017 (2CG078+2)
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Allyn F. Tennant, Ronald F. Elsner, David L. Kaplan, Alberto Carramiñana, Douglas A. Swartz, L. Carrasco, Stephen L. O'Dell, Gottfried Kanbach, Martin C. Weisskopf, and Werner Becker
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Physics ,Active galactic nucleus ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Gamma ray ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Optical spectra ,Stars ,Pulsar ,Space and Planetary Science ,Sky ,Observatory ,Supernova remnant ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report observations with the Chandra X-ray Observatory of a field in the gamma$-Cygni supernova remnant (SNR78.2+2.1) centered on the cataloged location of the unidentified, bright gamma-ray source 3EG J2020+4017. In this search for an X-ray counterpart to the gamma-ray source, we detected 30 X-ray sources. Of these, we found 17 strong-candidate counterparts in optical (visible through near-infrared) cataloged and an additional 3 through our optical observations. Based upon colors and (for several objects) optical spectra, nearly all the optically identified objects appear to be reddened main-sequence stars. None of the X-ray sources with an optical counterpart is a plausible X-ray counterpart to 3EG J2020+4017 --if that gamma-ray source is a spin-powered pulsar. Many of the 10 X-ray sources lacking optical counterparts are likely (extragalactic) active galactic nuclei, based upon the sky density of such sources. Although one of the 10 optically unidentified X-ray sources could be the gamma-ray source, there is no auxiliary evidence supporting such an identification.
- Published
- 2006
16. The Herbig Ae Star HD 163296 in X‐Rays
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Ronald F. Elsner, Jeremy J. Drake, Bruce E. Woodgate, Kajal K. Ghosh, Randy A. Kimble, Edward J. Wassell, Carol A. Grady, and Douglas A. Swartz
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Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Spectral component ,Accretion (astrophysics) ,Magnetic field ,Luminosity ,Dipole ,Stars ,T Tauri star ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Angular resolution ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Chandra X-ray imaging spectroscopy of the nearby Herbig Ae star HD 163296 at 100 AU angular resolution is reported. A point-like, soft (kT~0.5 keV), emission-line source is detected at the location of the star with an X-ray luminosity of 4.0e29 erg/s. In addition, faint emission along the direction of a previously-detected Ly-alpha-emitting jet and Herbig-Haro outflow may be present. The relatively low luminosity, lack of a hard spectral component, and absence of strong X-ray variability in HD 163296 can be explained as originating from optically-thin shock-heated gas accreting onto the stellar surface along magnetic field lines. This would require a (dipole) magnetic field strength at the surface of HD 163296 of at least ~100 G and perhaps as high as several kG. HD 163296 joins the T Tauri star TW Hya in being the only examples known to date of pre-main-sequence stars whose quiescent X-ray emission appears to be completely dominated by accretion., Comment: 7 pages, to be published in ApJ, 20 June 2005
- Published
- 2005
17. The Discovery of Oxygen Kα X-Ray Emission from the Rings of Saturn
- Author
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G. Randall Gladstone, J. Hunter Waite, Thomas E. Cravens, Ronald F. Elsner, Anil Bhardwaj, and Peter G. Ford
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Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Rings of Saturn ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Photon energy ,Space and Planetary Science ,Observatory ,Planet ,Saturn ,Astrophysics::Earth and Planetary Astrophysics ,Ionosphere ,Advanced CCD Imaging Spectrometer ,Astrophysics::Galaxy Astrophysics ,Line (formation) - Abstract
Using the Advanced CCD Imaging Spectrometer (ACIS), the Chandra X-ray Observatory (CXO) observed the Saturnian system for one rotation of the planet (approx.37 ks) on 20 January, 2004, and again on 26-27 January, 2004. In this letter we report the detection of X-ray emission from the rings of Saturn. The X-ray spectrum from the rings is dominated by emission in a narrow (approx.130 eV wide) energy band centered on the atomic oxygen Ka fluorescence line at 0.53 keV. The X-ray power emitted from the rings in the 0.49-0.62 keV band is about one-third of that emitted from Saturn disk in the photon energy range 0.24-2.0 keV. Our analysis also finds a clear detection of X-ray emission from the rings in the 0.49-0.62 keV band in an earlier (14-15 April, 2003) Chandra ACIS observation of Saturn. Fluorescent scattering of solar X-rays from oxygen atoms in the H20 icy ring material is the likely source mechanism for ring X-rays, consistent with the scenario of solar photo-production of a tenuous ring oxygen atmosphere and ionosphere recently discovered by Cassini.
- Published
- 2005
18. A Multiwavelength Search for a Counterpart of the Brightest Unidentified Gamma‐Ray Source 3EG J2020+4017 (2CG 078+2)
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Olaf Reimer, Allyn F. Tennant, Duncan R. Lorimer, Stephen L. O'Dell, Martin C. Weisskopf, Fernando Camilo, Ronald F. Elsner, Gottfried Kanbach, Zaven Arzoumanian, Douglas A. Swartz, and Werner Becker
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Physics ,Line-of-sight ,Pulsar ,Space and Planetary Science ,Observatory ,Infrared ,ROSAT ,Gamma ray ,Green Bank Telescope ,Flux ,Astronomy and Astrophysics ,Astrophysics - Abstract
In search of the counterpart to the brightest unidentified gamma-ray source 3EG J2020+4017 we report on new X-ray and radio observations of the gamma-Cygni field with the Chandra X-ray Observatory and with the Green Bank Telescope. We also report on reanalysis of archival ROSAT data. With Chandra it became possible for the first time to measure the position of the putative gamma-ray counterpart RX J2020.2+4026 with sub-arcsec accuracy and to deduce its X-ray spectral characteristics. These observations demonstrate that RX J2020.2+4026 is associated with a K field star and therefore is unlikely to be the counterpart of the bright gamma-ray source 2CG078+2 in the SNR G78.2+2.1 as had been previously suggested. The Chandra observation detected 37 additional X-ray sources which were correlated with catalogs of optical and infrared data. Subsequent GBT radio observations covered the complete 99% EGRET likelihood contour of 3EG J2020+4017 with a sensitivity limit of L_820 ~ 0.1 mJy kpc^2 which is lower than most of the recent deep radio search limits. If there is a pulsar operating in 3EG J2020+4017 this sensitivity limit suggests that the pulsar either does not produce significant amounts of radio emission or that its geometry is such that the radio beam does not intersect with the line of sight. Finally, reanalysis of archival ROSAT data leads to a flux upper limit of f_x = 160 (d/1.5 kpc)^-1 ms, P_dot >= 5 x 10^-13 (d/1.5 kpc)^-1 s s^-1 and B_perp >= 9 x 10^12 (d/1.5 kpc)^-1 G.
- Published
- 2004
19. Chandra X-Ray Observatory observations of the globular cluster M28 and its millisecond pulsar PSR B1821–24
- Author
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Douglas A. Swartz, Jonathan E. Grindlay, Ronald F. Elsner, Vincenzo Testa, Allyn F. Tennant, Roberto Mignani, George G. Pavlov, Don Backer, Werner Becker, L. Pulone, and Martin C. Weisskopf
- Subjects
Physics ,Nuclear and High Energy Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Radius ,Corona ,Atomic and Molecular Physics, and Optics ,Neutron star ,Pulsar ,Millisecond pulsar ,Observatory ,Globular cluster ,Emission spectrum ,Astrophysics::Galaxy Astrophysics - Abstract
We discuss the results of the first Chandra X-Ray Observatory observations of the globular cluster M28 (NGC 6626). We detect 46 X-ray sources of which 12 lie within one core radius of the center. We measure the radial distribution of the X-ray sources and fit it to a King profile finding a core radius of r c , x ≈11″. We measure for the first time the unconfused phase-averaged X-ray spectrum of the 3.05-ms pulsar B1821–24 and find it is best described by a power law with photon index Γ≃1.2. We find marginal evidence of an emission line centered at 3.3 keV in the pulsar spectrum, which could be interpreted as cyclotron emission from a corona above the pulsar's polar cap if the magnetic field is strongly different from a centered dipole. We present a spectral analyses of the brightest unidentified source and suggest that it is a transiently accreting neutron star in a low-mass X-ray binary, in quiescence. In addition to the resolved sources, we detect fainter, unresolved X-ray emission from the central core.
- Published
- 2004
20. ChandraPhase‐resolved X‐Ray Spectroscopy of the Crab Pulsar
- Author
-
Martin C. Weisskopf, Stephen L. O’Dell, Frits Paerels, Ronald F. Elsner, Werner Becker, Allyn F. Tennant, and Douglas A. Swartz
- Subjects
Physics ,Spectral index ,Crab Pulsar ,Astrophysics::High Energy Astrophysical Phenomena ,Extinction (astronomy) ,Astronomy and Astrophysics ,Astrophysics ,Neutron star ,Crab Nebula ,Pulsar ,Space and Planetary Science ,Observatory ,Spectroscopy ,Astrophysics::Galaxy Astrophysics - Abstract
We present the first phase-resolved study of the X-ray spectral properties of the Crab Pulsar that covers all pulse phases. The superb angular resolution of the Chandra X-ray Observatory enables distinguishing the pulsar from the surrounding nebulosity, even at pulse minimum. Analysis of the pulse-averaged spectrum measures interstellar X-ray extinction due primarily to photoelectric absorption and secondarily to scattering by dust grains in the direction of the Crab Nebula. We confirm previous findings that the line-of-sight to the Crab is underabundant in oxygen, although more-so than recently measured. Using the abundances and cross sections from Wilms, Allen & McCray (2000) we find [O/H] = (3.33 +/-0.25) x 10**-4. Analysis of the spectrum as a function of pulse phase measures the low-energy X-ray spectral index even at pulse minimum -- albeit with large statistical uncertainty -- and we find marginal evidence for variations of the spectral index. The data are also used to set a new (3-sigma) upper limit to the temperature of the neutron star of log T(infinity) < 6.30.
- Published
- 2004
21. The Imaging X-ray Polarimetry Explorer (IXPE)
- Author
-
Martin C. Weisskopf, Ronald F. Elsner, Roger W. Romani, Giorgio Matt, Enrico Costa, Herman L. Marshall, Fabio Muleri, Ronaldo Bellazzini, Brian D. Ramsey, Jeffrey Kolodziejczak, Victoria M. Kaspi, Paolo Soffitta, Allyn F. Tennant, and Stephen L. O'Dell
- Subjects
Physics ,X-ray astronomy ,COSMIC cancer database ,010308 nuclear & particles physics ,Linear polarization ,High-energy astronomy ,Astrophysics::High Energy Astrophysical Phenomena ,X-ray imaging ,Polarimetry ,Astrophysics::Instrumentation and Methods for Astrophysics ,General Physics and Astronomy ,Astronomy ,X-ray telescope ,Optical polarization ,Astrophysics ,Physics and Astronomy(all) ,01 natural sciences ,lcsh:QC1-999 ,Neutron star ,0103 physical sciences ,X-ray polarimetry ,010303 astronomy & astrophysics ,lcsh:Physics - Abstract
The Imaging X-ray Polarimetry Explorer (IXPE) is an exciting international collaboration for a scientific mission that dramatically brings together the unique talents of the partners to expand observation space by simultaneously adding polarization measurements to the array of source properties currently measured (energy, time, and location). IXPE uniquely brings to the table polarimetric imaging. IXPE will thus open new dimensions for understanding how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions-such as neutron stars and black holes. Polarization singularly probes physical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. Hence, IXPE complements all other investigations in high-energy astrophysics by adding important and relatively unexplored information to the parameter space for studying cosmic X-ray sources and processes, as well as for using extreme astrophysical environments as laboratories for fundamental physics.
- Published
- 2016
22. First Images from HERO, a Hard X‐Ray Focusing Telescope
- Author
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Jeffery J. Kolodziejczak, Brian D. Ramsey, Martin C. Weisskopf, Jeff Apple, Ronald F. Elsner, Darell Engelhaupt, C. M. Benson, Cheryl D. Alexander, Kurtis L. Dietz, Douglas A. Swartz, Kajal K. Ghosh, Chet O. Speegle, and Stephen L. O'Dell
- Subjects
Physics ,business.industry ,Payload ,Astronomy ,Astronomy and Astrophysics ,Galaxy ,law.invention ,Telescope ,Optics ,Space and Planetary Science ,law ,HERO ,Sensitivity (control systems) ,business - Abstract
We are developing a balloon-borne hard-x-ray telescope that utilizes grazing incidence optics. Termed HERO, for High-Energy Replicated Optics, the instrument will provide unprecented sensitivity in the hard-x-ray region and will achieve milliCrab-level sensitivity in a typical 3-hour balloon-flight observation and 50 microCrab sensitivity on ultra-long-duration flights. A recent proof-of-concept flight, featuring a small number of mirror shells captured the first focused hard-x-ray images of galactic x-ray sources. Full details of the payload, its expected future performance and its recent measurements are provided.
- Published
- 2002
23. Active figure control effects on mounting strategy for x-ray optics
- Author
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Martin C. Weisskopf, Stephen L. O'Dell, Brian D. Ramsey, Mikhail V. Gubarev, Carolyn Atkins, Jacqueline M. Roche, Ronald F. Elsner, and Jeffery J. Kolodziejczak
- Subjects
Physics ,Optics ,Mathematical model ,business.industry ,Distortion (optics) ,Acoustics ,Control (management) ,X-ray optics ,Active optics ,Shell theory ,X-ray telescope ,Kinematics ,business - Abstract
As part of ongoing development efforts at MSFC, we have begun to investigate mounting strategies for highly nested xray optics in both full-shell and segmented configurations. The analytical infrastructure for this effort also lends itself to investigation of active strategies. We expect that a consequence of active figure control on relatively thin substrates is that errors are propagated to the edges, where they might affect the effective precision of the mounting points. Based upon modeling, we describe parametrically, the conditions under which active mounts are preferred over fixed ones, and the effect of active figure corrections on the required number, locations, and kinematic characteristics of mounting points.
- Published
- 2014
24. Toward large-area sub-arcsecond x-ray telescopes
- Author
-
Carolyn Atkins, Martin C. Weisskopf, William W. Zhang, Ralf K. Heilmann, Mark L. Schattenburg, Charles F. Lillie, Stuart McMuldroch, Michael E. Graham, Rudeger H. T. Wilke, Raul E. Riveros, Brian D. Ramsey, Jacqueline M. Roche, Ronald F. Elsner, Kiranmayee Kilaru, Kai Wing Chan, Jeffery J. Kolodziejczak, Paul B. Reid, David N. Burrows, Alexey Vikhlinin, Stephen L. O'Dell, Semyon Vaynman, Xiaoli Wang, Jian Cao, Ryan Allured, Timo T. Saha, Thomas L. Aldcroft, Mikhail V. Gubarev, Brandon D. Chalifoux, Daniel A. Schwartz, Susan Trolier-McKinstry, Melville P. Ulmer, Raegan L. Johnson-Wilke, and Vincenzo Cotroneo
- Subjects
Physics ,Optics ,Aperture ,business.industry ,Astrophysics::Instrumentation and Methods for Astrophysics ,X-ray optics ,Square (unit) ,Active optics ,Angular resolution ,X-ray telescope ,Area density ,Approx ,business - Abstract
The future of x-ray astronomy depends upon development of x-ray telescopes with larger aperture areas (approx. = 3 square meters) and fine angular resolution (approx. = 1 inch). Combined with the special requirements of nested grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging. Achieving this goal will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 square meters) of lightweight (approx. = 1 kilogram/square meter areal density) high-quality mirrors at an acceptable cost (approx. = 1 million dollars/square meter of mirror surface area). This paper reviews relevant technological and programmatic issues, as well as possible approaches for addressing these issues-including active (in-space adjustable) alignment and figure correction.
- Published
- 2014
25. SuperHERO: the next generation hard x-ray HEROES telescope
- Author
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Allyn F. Tennant, Ronald F. Elsner, Brian D. Ramsey, Albert Y. Shih, Paul Seller, Jessica A. Gaskin, Kiranmayee Kilaru, Matthew Wilson, Bruce Weddendorf, Colleen A. Wilson-Hodge, David Stuchlik, Douglas A. Swartz, and Steven Christe
- Subjects
Telescope ,Physics ,X-ray astronomy ,Heliophysics ,law ,Payload ,Launched ,Astronomy ,X-ray optics ,X-ray telescope ,Solar physics ,law.invention - Abstract
SuperHERO is a new high-sensitivity Long Duration Balloon (LDB)-capable, hard-x-ray (20-75 keV) telescope for making novel astrophysics and heliophysics observations. The proposed SuperHERO payload will be developed jointly by the Astrophysics Office at NASA Marshall Space Flight Center, the Solar Physics Laboratory and Wallops Flight Facility at NASA Goddard Space Flight Center. SuperHERO is a follow-on payload to the High Energy Replicated Optics to Explore the Sun (HEROES) balloon-borne telescope that recently launched from Fort Sumner, NM in September of 2013. The HEROES core instrument is a hard x-ray telescope consisting of x-ray 109 optics configured into 8 modules. Each module is aligned to a matching gas-filled detector at a focal length of 6 m. SuperHERO will make significant improvements to the HEROES payload, including: new solid-state multi-pixel CdTe detectors, additional optics, the Wallops Arc-Second Pointer, alignment monitoring systems and lighter gondola.
- Published
- 2014
26. Mounting for fabrication, metrology, and assembly of full-shell grazing-incidence optics
- Author
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Jeffery J. Kolodziejczak, Ronald F. Elsner, Stephen L. O'Dell, Jacqueline M. Roche, Brian D. Ramsey, Mikhail V. Gubarev, Martin C. Weisskopf, and W. S. Smith
- Subjects
Materials science ,Optics ,Fabrication ,business.industry ,Shell (structure) ,X-ray telescope ,business ,Finite element method ,Metrology ,Incidence (geometry) - Abstract
Future x-ray telescopes will likely require lightweight mirrors to attain the large collecting areas needed to accomplish the science objectives. Understanding and demonstrating processes now is critical to achieving sub-arcsecond performance in the future. Consequently, designs not only of the mirrors but of fixtures for supporting them during fabrication, metrology, handling, assembly, and testing must be adequately modeled and verified. To this end, MSFC is using finite-element modeling to study the effects of mounting on full-shell grazing-incidence mirrors, during all processes leading to flight mirror assemblies. Here we report initial results of this study.
- Published
- 2014
27. Discovery of X-Ray Emission from the Crab Pulsar at Pulse Minimum
- Author
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Jeffery J. Kolodziejczak, Stephen L. O'Dell, Frits Paerels, Ronald F. Elsner, Allyn F. Tennant, Werner Becker, Stephen S. Murray, Martin C. Weisskopf, Douglas A. Swartz, Michael Juda, and Noriaki Shibazaki
- Subjects
Physics ,X-ray astronomy ,Crab Pulsar ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Pulse (physics) ,Neutron star ,Crab Nebula ,Pulsar ,Space and Planetary Science ,Observatory ,Emission spectrum - Abstract
The Chandra X-ray Observatory observed the Crab Nebula and Pulsar using the Low-Energy Transmission Grating (LETG) with the High-Resolution Camera (HRC). Time-resolved zeroth-order images reveal that the pulsar emits x rays at all pulse phases. Analysis of the flux at minimum -- most likely nonthermal in origin -- places an upper limit (T(sub infinity) < 2.1 MK) on the surface temperature of the underlying neutron star. In addition, analysis of the pulse profile appears to confirm the absolute timing of the Observatory to within about 0.2 ms.
- Published
- 2001
28. Development of a high energy X-ray polarimeter for small satellites
- Author
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Robert A. Austin, Brian D. Ramsey, S. Gunji, Martin C. Weisskopf, and Ronald F. Elsner
- Subjects
Physics ,Nuclear and High Energy Physics ,X-ray astronomy ,Physics::Instrumentation and Detectors ,business.industry ,Thomson scattering ,Astrophysics::High Energy Astrophysical Phenomena ,Detector ,Proportional counter ,chemistry.chemical_element ,Polarimeter ,Polarization (waves) ,Particle detector ,Optics ,Nuclear Energy and Engineering ,chemistry ,Electrical and Electronic Engineering ,Beryllium ,business - Abstract
We are developing a Thomson-scattering-type polarimeter sensitive in the energy range from 10 keV to 20 keV for a small satellite. The polarimeter consists of three beryllium disks as scatterers and a cylindrical position-sensitive proportional counter as a detector of the scattered X-rays. Its performance has been investigated through computer simulations. From these, it was concluded that the polarimeter can obtain a modulation factor of 34%, a detection efficiency of /spl sim/10%, and a minimum detectable polarization of about 3.0% for Her X-1 in 2 keV bands and a 2/spl times/10/sup 5/ sec observation.
- Published
- 1997
29. Opto-mechanical analyses for performance optimization of lightweight grazing-incidence mirrors
- Author
-
Jacqueline M. Roche, Ronald F. Elsner, Jeffery J. Kolodziejczak, Brian D. Ramsey, Martin C. Weisskopf, Mikhail V. Gubarev, and Stephen L. O'Dell
- Subjects
Fabrication ,Optics ,Computer science ,business.industry ,Distortion ,Mechanical engineering ,X-ray telescope ,Substrate (printing) ,Sensitivity (control systems) ,Material properties ,business ,Incidence (geometry) ,Parametric statistics - Abstract
New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve subarcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Lightweight mirrors are typically flimsy and are, therefore, susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Here we report initial results of this study.
- Published
- 2013
30. Measuring x-ray polarization in the presence of systematic effects: known background
- Author
-
Ronald F. Elsner, Stephen L. O'Dell, and Martin C. Weisskopf
- Subjects
Physics ,X-ray astronomy ,Photon ,Linear polarization ,Polarimetry ,FOS: Physical sciences ,Probability density function ,Polarization (waves) ,Position angle ,High Energy Physics - Experiment ,Computational physics ,High Energy Physics - Experiment (hep-ex) ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Background radiation - Abstract
The prospects for accomplishing x-ray polarization measurements of astronomical sources have grown in recent years, after a hiatus of more than 37 years. Unfortunately, accompanying this long hiatus has been some confusion over the statistical uncertainties associated with x-ray polarization measurements of these sources. We have initiated a program to perform the detailed calculations that will offer insights into the uncertainties associated with x-ray polarization measurements. Here we describe a mathematical formalism for determining the 1- and 2-parameter errors in the magnitude and position angle of x-ray (linear) polarization in the presence of a (polarized or unpolarized) background. We further review relevant statistics-including clearly distinguishing between the Minimum Detectable Polarization (MDP) and the accuracy of a polarization measurement., 12 pages, 4 figures, for SPIE conference proceedings
- Published
- 2012
31. Unraveling the Geometry of the Crab Nebula's 'Inner Ring'
- Author
-
Ronald F. Elsner, Allyn F. Tennant, Jeffery J. Kolodziejczak, Martin C. Weisskopf, and Stephen L. O'Dell
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Aspect ratio ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Geometry ,Ring (chemistry) ,Position angle ,Pulsar wind nebula ,Relativistic particle ,Crab Nebula ,Pulsar ,Space and Planetary Science ,Astrophysics - High Energy Astrophysical Phenomena ,Heliosphere ,Astrophysics::Galaxy Astrophysics - Abstract
Chandra images of the Crab Nebula resolve the detailed structure of its "inner ring", possibly a termination shock where pulsar-accelerated relativistic particles begin to emit X radiation. Analysis of these images finds that the center of the ellipse-presumably a circular ring in projection-lies about 0.9" (10 light-days at 2 kpc) from the pulsar's image, at a position angle of about 300{\deg} (East of North). This analysis also measures properties of the ellipse: The position angle of the semi-major axis is about 210{\deg} (East of North); the aspect ratio, 0.49. In a simple-albeit, not unique-de-projection of the observed geometry, a circular ring is centered on the axis of symmetry of the pulsar wind nebula. This ring is not equatorial but rather lies near +4.5{\deg} latitude in pulsar-centered coordinates. Alternative geometries are briefly discussed., Comment: 12 pages, f figures, submitted to the Astrophysical Journal
- Published
- 2011
32. Mathematical formalism for designing wide-field x-ray telescopes: mirror nodal positions and detector tilts
- Author
-
Martin C. Weisskopf, Ronald F. Elsner, Stephen L. O'Dell, and Brian D. Ramsey
- Subjects
Physics ,business.industry ,Detector ,X-ray optics ,Field of view ,X-ray telescope ,law.invention ,Optical axis ,Telescope ,Optics ,law ,Figure of merit ,business ,Image resolution - Abstract
We provide a mathematical formalism for optimizing the mirror nodal positions along the optical axis and the tilt of a commonly employed detector configuration at the focus of a x-ray telescope consisting of nested mirror shells with known mirror surface prescriptions. We adopt the spatial resolution averaged over the field-of-view as the figure of merit M. A more complete description appears in our paper in these proceedings.
- Published
- 2011
33. Chandra Phase-Resolved X-ray Spectroscopy of the Crab Pulsar II
- Author
-
Ronald F. Elsner, Werner Becker, Alice K. Harding, Vyacheslav E. Zavlin, Martin C. Weisskopf, Dmitry G. Yakovlev, Stephen L. O'Dell, and Allyn F. Tennant
- Subjects
Physics ,Spectral index ,Crab Pulsar ,Astrophysics::High Energy Astrophysical Phenomena ,Extinction (astronomy) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Optical polarization ,Astrophysics ,Position angle ,Astrophysics - Astrophysics of Galaxies ,Neutron star ,Crab Nebula ,Pulsar ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Astrophysics::Galaxy Astrophysics - Abstract
We present a new study of the X-ray spectral properties of the Crab Pulsar. The superb angular resolution of the Chandra X-ray Observatory enables distinguishing the pulsar from the surrounding nebulosity. Analysis of the spectrum as a function of pulse phase allows the least-biased measure of interstellar X-ray extinction due primarily to photoelectric absorption and secondarily to scattering by dust grains in the direction of the Crab Nebula. We modify previous findings that the line-of-sight to the Crab is under-abundant in oxygen and provide measurements with improved accuracy and less bias. Using the abundances and cross sections from Wilms, Allen & McCray (2000) we find [O/H] = $(5.28 \pm 0.28)\times10^{-4}$ ($4.9 \times10^{-4}$ is solar abundance). We also measure for the first time the impact of scattering of flux out of the image by interstellar grains. We find $��_{\rm scat} = 0.147 \pm 0.043$. Analysis of the spectrum as a function of pulse phase also measures the X-ray spectral index even at pulse minimum --- albeit with increasing statistical uncertainty. The spectral variations are, by and large, consistent with a sinusoidal variation. The only significant variation from the sinusoid occurs over the same phase range as some rather abrupt behavior in the optical polarization magnitude and position angle. We compare these spectral variations to those observed in Gamma-rays and conclude that our measurements are both a challenge and a guide to future modeling and will thus eventually help us understand pair cascade processes in pulsar magnetospheres. The data were also used to set new, and less biased, upper limits to the surface temperature of the neutron star for different models of the neutron star atmosphere., 32 pages, 6 figures submitted to the Astrophysical journal
- Published
- 2011
34. The Identification of the X-ray Counterpart to PSR J2021+4026
- Author
-
M. Ziegler, Pablo M. Saz Parkinson, Ronald F. Elsner, Andrea Belfiore, M. Dormody, Stephen L. O'Dell, Paul S. Ray, Matthew Kerr, Alice K. Harding, Andrea De Luca, Alberto Carramiñana, Roger W. Romani, Gottfried Kanbach, Werner Becker, D. J. Thompson, Allyn F. Tennant, Massimiliano Razzano, Martin C. Weisskopf, and Douglas A. Swartz
- Subjects
Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,biology ,Astrophysics::High Energy Astrophysical Phenomena ,Flux ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,biology.organism_classification ,Acis ,Neutron star ,Pulsar ,Space and Planetary Science ,Observatory ,Coincident ,Satellite ,Astrophysics - High Energy Astrophysical Phenomena ,Fermi Gamma-ray Space Telescope - Abstract
We report the probable identification of the X-ray counterpart to the gamma-ray pulsar PSR J2021+4026 using imaging with the Chandra X-ray Observatory ACIS and timing analysis with the Fermi satellite. Given the statistical and systematic errors, the positions determined by both satellites are coincident. The X-ray source position is R.A. 20h21m30.733s, Decl. +40 deg 26 min 46.04sec (J2000) with an estimated uncertainty of 1.3 arsec combined statistical and systematic error. Moreover, both the X-ray to gamma-ray and the X-ray to optical flux ratios are sensible assuming a neutron star origin for the X-ray flux. The X-ray source has no cataloged infrared-to-visible counterpart and, through new observations, we set upper limits to its optical emission of i' >23.0 mag and r' > 25.2mag. The source exhibits an X-ray spectrum with most likely both a powerlaw and a thermal component. We also report on the X-ray and visible light properties of the 43 other sources detected in our Chandra observation., Accepted for publication in the Astrophysical Journal
- Published
- 2011
- Full Text
- View/download PDF
35. On understanding the figures of merit for detection and measurement of x-ray polarization
- Author
-
Ronald F. Elsner, Martin C. Weisskopf, and Stephen L. O'Dell
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,X-ray astronomy ,medicine ,FOS: Physical sciences ,Astronomy ,Figure of merit ,medicine.symptom ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Polarization (waves) ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Confusion - Abstract
The prospects for accomplishing X-ray polarization measurements appear to have grown in recent years after a more than 35-year hiatus. Unfortunately, this long hiatus has brought with it some confusion over the statistical uncertainties associated with polarization measurements of astronomical sources. The heart of this confusion stems from a misunderstanding (or potential misunderstanding) of a standard figure of merit-the minimum detectable polarization (MDP)-that one of us introduced many years ago. We review the relevant statistics, and quantify the differences between the MDP and the uncertainty of an actual polarization measurement. We discuss the implications for future missions., 5 pages, 2 figures, to be presented at SPIE conference 7732 (paper 13), corrected typos
- Published
- 2010
36. Effects of contamination upon the performance of x-ray telescopes
- Author
-
T. Oosterbroek, Ronald F. Elsner, and Stephen L. O'Dell
- Subjects
Telescope ,Point spread function ,Physics ,Contamination control ,law ,Observatory ,Calibration ,X-ray telescope ,Sensitivity (control systems) ,Contamination ,law.invention ,Remote sensing - Abstract
Particulate and molecular contamination can each impact the performance of x-ray telescope systems. Furthermore, any changes in the level of contamination between on-ground calibration and in-space operation can compromise the validity of the calibration. Thus, it is important to understand the sensitivity of telescope performance, especially the net effective area and the wings of the point spread function to contamination. Here, we quantify this sensitivity and discuss the flow-down of science requirements to contamination-control requirements. As an example, we apply this methodology to the International X-ray Observatory (IXO), currently under joint study by ESA, JAXA, and NASA.
- Published
- 2010
37. High-resolution x-ray telescopes
- Author
-
Brian D. Ramsey, Paul B. Reid, Paul Gorenstein, Diab Jerius, Ronald F. Elsner, Stephen L. O'Dell, Timo T. Saha, Susan Trolier-McKinstry, Terrance J. Gaetz, Roger Brissenden, Jeffery J. Kolodziejczak, Martin Elvis, William N. Davis, Stephen S. Murray, Mikhail V. Gubarev, Rudeger H. T. Wilke, Scott J. Wolk, William W. Zhang, Michael Juda, Daniel A. Schwartz, Mark D. Freeman, William A. Podgorski, Martin C. Weisskopf, and Robert Petre
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Dark matter ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy ,FOS: Physical sciences ,X-ray telescope ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Neutron star ,Observatory ,Dark energy ,Astrophysics::Solar and Stellar Astrophysics ,Angular resolution ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics - Abstract
High-energy astrophysics is a relatively young scientific field, made possible by space-borne telescopes. During the half-century history of x-ray astronomy, the sensitivity of focusing x-ray telescopes-through finer angular resolution and increased effective area-has improved by a factor of a 100 million. This technological advance has enabled numerous exciting discoveries and increasingly detailed study of the high-energy universe-including accreting (stellar-mass and super-massive) black holes, accreting and isolated neutron stars, pulsar-wind nebulae, shocked plasma in supernova remnants, and hot thermal plasma in clusters of galaxies. As the largest structures in the universe, galaxy clusters constitute a unique laboratory for measuring the gravitational effects of dark matter and of dark energy. Here, we review the history of high-resolution x-ray telescopes and highlight some of the scientific results enabled by these telescopes. Next, we describe the planned next-generation x-ray-astronomy facility-the International X-ray Observatory (IXO). We conclude with an overview of a concept for the next next-generation facility-Generation X. The scientific objectives of such a mission will require very large areas (about 10000 m2) of highly-nested lightweight grazing-incidence mirrors with exceptional (about 0.1-arcsecond) angular resolution. Achieving this angular resolution with lightweight mirrors will likely require on-orbit adjustment of alignment and figure., Comment: 19 pages, 11 figures, SPIE Conference 7803 "Adaptive X-ray Optics", part of SPIE Optics+Photonics 2010, San Diego CA, 2010 August 2-5
- Published
- 2010
- Full Text
- View/download PDF
38. X-rays from solar system objects
- Author
-
Anil Bhardwaj, Steven L. Snowden, J. Hunter Waite, Thomas E. Cravens, Ina Robertson, Vasili Kharchenko, Nikolai Østgaard, G. Randall Gladstone, Konrad Dennerl, Carey M. Lisse, Bradford J. Wargelin, Peter Beiersdorfer, Ronald F. Elsner, and Graziella Branduardi-Raymont
- Subjects
Solar System ,Astrophysics::High Energy Astrophysical Phenomena ,Orbital resonance ,FOS: Physical sciences ,Astrobiology ,Jupiter ,symbols.namesake ,Physics - Space Physics ,Planet ,Saturn ,Solar and Stellar Astrophysics (astro-ph.SR) ,Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Astronomy ,Astronomy and Astrophysics ,Space Physics (physics.space-ph) ,Galilean moons ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Physics::Space Physics ,symbols ,Natural satellite ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,Magnetosphere of Jupiter ,Astrophysics - Earth and Planetary Astrophysics - Abstract
During the last few years our knowledge about the X-ray emission from bodies within the solar system has significantly improved. Several new solar system objects are now known to shine in X-rays at energies below 2 keV. Apart from the Sun, the known X-ray emitters now include planets (Venus, Earth, Mars, Jupiter, and Saturn), planetary satellites (Moon, Io, Europa, and Ganymede), all active comets, the Io plasma torus (IPT), the rings of Saturn, the coronae (exospheres) of Earth and Mars, and the heliosphere. The advent of higher-resolution X-ray spectroscopy with the Chandra and XMM-Newton X-ray observatories has been of great benefit in advancing the field of planetary X-ray astronomy. Progress in modeling X-ray emission, laboratory studies of X-ray production, and theoretical calculations of cross-sections, have all contributed to our understanding of processes that produce X-rays from the solar system bodies. At Jupiter and Earth, both auroral and non-auroral disk X-ray emissions have been observed. X-rays have been detected from Saturn's disk, but no convincing evidence of an X-ray aurora has been observed. The first soft (0.1–2 keV) X-ray observation of Earth's aurora by Chandra shows that it is highly variable. The non-auroral X-ray emissions from Jupiter, Saturn, and Earth, those from the disk of Mars, Venus, and Moon, and from the rings of Saturn, are mainly produced by scattering of solar X-rays. The spectral characteristics of X-ray emission from comets, the heliosphere, the geocorona, and the Martian halo are quite similar, but they appear to be quite different from those of Jovian auroral X-rays. X-rays from the Galilean satellites and the IPT are mostly driven by impact of Jovian magnetospheric particles. This paper reviews studies of the soft X-ray emission from the solar system bodies, excluding the Sun. Processes of production of solar system X-rays are discussed and an overview is provided of the main source mechanisms of X-ray production at each object. A brief account on recent development in the area of laboratory studies of X-ray production is also provided.
- Published
- 2010
- Full Text
- View/download PDF
39. X-rays from Saturn: A study with XMM-Newton and Chandra over the years 2002-05
- Author
-
Ronald F. Elsner, Anil Bhardwaj, Pedro Rodríguez, and Graziella Branduardi-Raymont
- Subjects
Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Uranus ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Atmosphere ,Jupiter ,Space and Planetary Science ,Planet ,Neptune ,Saturn ,Physics::Space Physics ,Emission spectrum ,Astrophysics::Earth and Planetary Astrophysics ,Line (formation) ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We present the results of the two most recent (2005) XMM-Newton observations of Saturn together with the re-analysis of an earlier (2002) observation from the XMM-Newton archive and of three Chandra observations in 2003 and 2004. While the XMM-Newton telescope resolution does not enable us to resolve spatially the contributions of the planet's disk and rings to the X-ray flux, we can estimate their strengths and their evolution over the years from spectral analysis, and compare them with those observed with Chandra. The spectrum of the X-ray emission is well fitted by an optically thin coronal model with an average temperature of 0.5 keV. The addition of a fluorescent oxygen emission line at ~0.53 keV improves the fits significantly. In accordance with earlier reports, we interpret the coronal component as emission from the planetary disk, produced by the scattering of solar X-rays in Saturn's upper atmosphere, and the line as originating from the Saturnian rings. The strength of the disk X-ray emission is seen to decrease over the period 2002 - 2005, following the decay of solar activity towards the current minimum in the solar cycle. By comparing the relative fluxes of the disk X-ray emission and the oxygen line, we suggest that the line strength does not vary over the years in the same fashion as the disk flux. We consider possible alternatives for the origin of the line. The connection between solar activity and the strength of Saturn's disk X-ray emission is investigated and compared with that of Jupiter. We also discuss the apparent lack of X-ray aurorae on Saturn and conclude that they are likely to lie below the sensitivity threshold of current Earth-bound observatories. A similar comparison for Uranus and Neptune leads to the same disappointing conclusion., 10 pages, 5 figures; to be published in 'Astronomy and Astrophysics'
- Published
- 2009
40. Development of a silicon drift detector array: an x-ray fluorescence spectrometer for remote surface mapping
- Author
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Georgiana Kramer, Ronald F. Elsner, Brian D. Ramsey, Pavel Rehak, Jessica A. Gaskin, D. Peter Siddons, Jeffrey W. Keister, Gabriella Carini, Zheng Li, Wei Chen, and Gianluigi De Geronimo
- Subjects
Kaguya ,Physics ,Silicon drift detector ,Spectrometer ,Silicon ,business.industry ,Fluorescence spectrometry ,chemistry.chemical_element ,X-ray fluorescence ,Radiation ,Jupiter ,Optics ,chemistry ,business - Abstract
Over the past three years NASA Marshall Space Flight Center has been collaborating with Brookhaven National Laboratory to develop a modular Silicon Drift Detector (SDD) X-Ray Spectrometer (XRS) intended for fine surface mapping of the light elements of the moon. The value of fluorescence spectrometry for surface element mapping is underlined by the fact that the technique has recently been employed by three lunar orbiter missions; Kaguya, Chandrayaan-1, and Chang e. The SDD-XRS instrument we have been developing can operate at a low energy threshold (i.e. is capable of detecting Carbon), comparable energy resolution to Kaguya (
- Published
- 2009
41. On the design of wide-field x-ray telescopes
- Author
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Brian D. Ramsey, Martin C. Weisskopf, Ronald F. Elsner, and Stephen L. O'Dell
- Subjects
Physics ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,X-ray optics ,Field of view ,X-ray telescope ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Radius ,law.invention ,Ray tracing (physics) ,Telescope ,Optics ,Cardinal point ,law ,business ,Image resolution - Abstract
X-ray telescopes having a relatively wide field-of-view and spatial resolution vs. polar off-axis angle curves much flatter than the parabolic dependence characteristic of Wolter I designs are of great interest for surveys of the X-ray sky and potentially for study of the Sun s X-ray emission. We discuss the various considerations affecting the design of such telescopes, including the possible use of polynomial mirror surface prescriptions, a method of optimizing the polynomial coefficients, scaling laws for mirror segment length vs. intersection radius, the loss of on-axis spatial resolution, and the positioning of focal plane detectors.
- Published
- 2009
42. X-RAY EMISSION FROM PLANETS AND COMETS: RELATIONSHIP WITH SOLAR X-RAYS AND SOLAR WIND
- Author
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Thomas E. Cravens, S. M. Petrinec, Anil Bhardwaj, Ronald F. Elsner, Bradford J. Wargelin, Peter Beiersdorfer, Graziella Branduardi-Raymont, G. Randall Gladstone, Steven L. Snowden, Nikolai Østgaard, Konrad Dennerl, J. Hunter Waite, Ina Robertson, Vasili Kharchenko, and Carey M. Lisse
- Subjects
Physics ,Solar System ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy ,Stellar-wind bubble ,Space weather ,Corona ,Solar cycle ,Interplanetary dust cloud ,Physics::Space Physics ,Coronal mass ejection ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Magnetosphere of Jupiter - Abstract
Scattering of solar X-ray radiation mainly produces the non-auroral X-ray emissions from Jupiter, Saturn, and Earth, those from the disk of Mars, Venus, and Moon, and from the rings of Saturn. Recently X-ray flares are observed from the low-latitude disk of giant planets Jupiter and Saturn in the energy range of 0.2-2 keV. These flares are found to occur in tandem with the occurrence of solar X-ray flare, when light travel time delay is accounted, suggesting that X-rays from these planets can be used to study flaring on the hemisphere of the Sun invisible to near-Earth space weather satellites. Also by proper modeling of the observed planetary X-rays the solar soft X-ray flux can be derived. X-ray flares are also observed recently from Mars in direct response to solar flares. The X-ray emission from comets, the heliosphere, the geocorona, and the Martian and Venusian halo are all largely driven by charge exchange collision between highly ionized minor heavy ions in the solar wind and gaseous neutral species in the bodies' atmosphere or exosphere - a process known as solar wind charge exchange (SWCX). In particular, the cometary X-ray spectrum can be used to derive abundances of high-charge state ions of O, C, Ne as well as the speed of the solar wind. Thus cometary X-rays can provide a diagnostic of the solar wind properties even at far off distances from the Earth. This paper provides a brief overview of X-rays from some of the solar system bodies and their connection with solar X-rays and solar wind, and how planetary and cometary X-rays can be used to study the solar X-ray radiation and solar wind properties.
- Published
- 2009
43. X-Ray Polarimetry and Its Potential Use for Understanding Neutron Stars
- Author
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George G. Pavlov, Ronald F. Elsner, Brain D. Ramsey, Stephen L. O'Dell, Martin C. Weisskopf, and Victoria M. Kaspi
- Subjects
Physics ,Photoelectric absorption ,Neutron star ,Crab Nebula ,Polarimetry ,X-ray ,Astronomy ,Astrophysics - Published
- 2009
44. Spectral morphology of the X-ray emission from Jupiter's aurorae
- Author
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G. R. Gladstone, Marina Galand, J. H. Waite, Peter G. Ford, Denis Grodent, Thomas E. Cravens, Ronald F. Elsner, and Graziella Branduardi-Raymont
- Subjects
Atmospheric Science ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,Soil Science ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Electron ,Aquatic Science ,Oceanography ,Spectral line ,Ion ,Jupiter ,Atmosphere ,Geochemistry and Petrology ,Planet ,Earth and Planetary Sciences (miscellaneous) ,education ,Earth-Surface Processes ,Water Science and Technology ,Physics ,education.field_of_study ,Ecology ,Bremsstrahlung ,Paleontology ,Astronomy ,Forestry ,Geophysics ,Space and Planetary Science ,Physics::Space Physics ,Astrophysics::Earth and Planetary Astrophysics - Abstract
Simultaneous Chandra X-ray and Hubble Space Telescope FUV observations of Jupiter's aurorae carried out in February 2003 have been re-examined to investigate the spatial morphology of the X-ray events in different energy bands. The data clearly show that in the Northern auroral region (in the main auroral oval and the polar cap) events with energy > 2 keV are located at the periphery of those with energy 2 keV events (similar to 45 MW emitted power) with the electron bremsstrahlung component recently revealed by XMM-Newton in the spectra of Jupiter's aurorae, and the 2 keV X-ray and FUV (340 GW) powers measured during the observations shows that they are broadly consistent with the predicted emissions from a population of energetic electrons precipitating in the planet's atmosphere, thus supporting our interpretation.
- Published
- 2008
45. Low- to middle-latitude X-ray emission from Jupiter
- Author
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Anil Bhardwaj, J. Hunter Waite, Thomas E. Cravens, Ronald F. Elsner, G. Randall Gladstone, Peter G. Ford, and Graziella Branduardi-Raymont
- Subjects
Atmospheric Science ,Astrophysics::High Energy Astrophysical Phenomena ,Soil Science ,Flux ,Astrophysics ,Aquatic Science ,Oceanography ,Atmosphere ,Jupiter ,symbols.namesake ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Emission spectrum ,Advanced CCD Imaging Spectrometer ,Spectroscopy ,Earth-Surface Processes ,Water Science and Technology ,Physics ,Ecology ,Gamma ray ,Paleontology ,Astronomy ,Forestry ,Geophysics ,Space and Planetary Science ,Van Allen radiation belt ,symbols ,Astrophysics::Earth and Planetary Astrophysics - Abstract
The Chandra X-ray Observatory (CXO) observed Jupiter during the period 24-26 February 2003 for approx. 40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each -8.5 hours long, were separated by an HRC-I exposure of approx. 20 hours. The low- to middle-latitude nonauroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to middle-latitude X-ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X-ray spectra from regions corresponding to 3-5 gauss and 5-7 gauss surface fields show significant differences in the energy band 1.26-1.38 keV, perhaps partly due to line emission occurring in the 3-5 gauss region but not the 5-7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC-I data, at a time when solar activity was high. The low- to middle-latitude disk X-ray count rate observed by the HRC-I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to middle-latitude X-ray emission does not show any oscillations similar to the approx. 45 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2.0 keV low- to middle-latitude X-ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X-ray emission on a timescale of a day. The 0.3-2.0 keV X-ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the dependence of count rate on surface magnetic-field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.
- Published
- 2006
46. A study of Jupiter's aurorae with XMM-Newton
- Author
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Gavin Ramsay, Pedro Rodríguez, Anil Bhardwaj, Roberto Soria, Ronald F. Elsner, Graziella Branduardi-Raymont, J. H. Waite, G. R. Gladstone, and Thomas E. Cravens
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Bremsstrahlung ,FOS: Physical sciences ,Magnetosphere ,Astronomy and Astrophysics ,Astrophysics ,Spectral line ,Jupiter ,Solar wind ,Space and Planetary Science ,Planet ,Physics::Space Physics ,Emission spectrum ,Astrophysics::Earth and Planetary Astrophysics ,Line (formation) - Abstract
We present a detailed analysis of Jupiter's X-ray (0.2-10 keV) auroral emissions as observed by XMM-Newton in Nov. 2003 and compare it with that of an Apr. 2003 observation. We discover the existence of an electron bremsstrahlung component in the aurorae, which accounts for essentially all the X-ray flux above 2 keV: its presence had been predicted but never detected for lack of sensitivity of previous X-ray missions. This bremsstrahlung component varied significantly in strength and spectral shape over the 3.5 days covered by the Nov. 2003 observation, displaying substantial hardening of the spectrum with increasing flux. This variability may be linked to the strong solar activity taking place at the time, and may be induced by changes in the acceleration mechanisms inside Jupiter's magnetosphere. As in Apr. 2003, the auroral spectra below 2 keV are best fitted by a superposition of line emission most likely originating from ion charge exchange, with OVII playing the dominant role. We still cannot resolve conclusively the ion species responsible for the lowest energy lines (around 0.3 keV), so the question of the origin of the ions (magnetospheric or solar wind) is still open. It is conceivable that both scenarios play a role in what is certainly a very complex planetary structure. High resolution spectra of the whole planet obtained with the XMM-Newton RGS in the range 0.5-1 keV clearly separate emission lines (mostly of Fe) originating at low latitudes on Jupiter from the auroral lines due to O. These are shown to possess very broad wings which imply velocities of ~5000 km/s. Such speeds are consistent with the energies at which precipitating and charge exchanging O ions are expected to be accelerated in Jupiter's magnetosphere. Overall we find good agreement between our measurements and the predictions of recent models., 16 pages, 17 figures, to be published in 'Astronomy and Astrophysics'
- Published
- 2006
47. XMM-NEWTON OBSERVATIONS OF X-RAY EMISSION FROM JUPITER
- Author
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Pedro Rodríguez, Anil Bhardwaj, G. R. Gladstone, Gavin Ramsay, Roberto Soria, Graziella Branduardi-Raymont, Ronald F. Elsner, J. H. Waite, and Thomas E. Cravens
- Subjects
Physics ,Atmosphere ,Jupiter ,Planet ,Astrophysics::High Energy Astrophysical Phenomena ,Physics::Space Physics ,Bremsstrahlung ,Flux ,Astrophysics::Earth and Planetary Astrophysics ,Electron ,Astrophysics ,Emission spectrum ,Spectral line - Abstract
We present the results of two XMM-Newton observations of Jupiter carried out in 2003 for 100 and 250 ks (or 3 and 7 planet rotations) respectively. X-ray images from the EPIC CCD cameras show prominent emission from the auroral regions in the 0.2-2.0 keV band: the spectra are well modelled by a combination of emission lines, including most prominently those of highly ionised oxygen (OVIII and OVIII). In addition, and for the first time, XMM-Newton reveals the presence in both aurorae of a higher energy component (3-7 keV) which is well described by an electron bremsstrahlung spectrum. This component is found to be variable in flux and spectral shape during the Nov. 2003 observation, which corresponded to an extended period of intense solar activity. Emission from the equatorial regions of the Jupiter's disk is also observed, with a spectrum consistent with that of solar X-rays scattered in the planet's upper atmosphere. Jupiter's X-rays are spectrally resolved with the RGS which clearly separates the prominent OVII contribution of the aurorae from the OVIII, FeXVII and MgXI lines, originating in the low-latitude disk regions of the planet.
- Published
- 2006
48. The First Chandra Field
- Author
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Cédric Foellmi, Ronald F. Elsner, Robert A. Cameron, Poshak Gandhi, Sandeep K. Patel, Stephen L. O'Dell, Kinwah Wu, Thomas L. Aldcroft, Martin C. Weisskopf, Laboratoire d'Astrophysique de Grenoble (LAOG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Physics ,Active galactic nucleus ,010504 meteorology & atmospheric sciences ,Astrophysics (astro-ph) ,Balmer series ,FOS: Physical sciences ,Astronomy and Astrophysics ,Context (language use) ,Astrophysics ,01 natural sciences ,Redshift ,law.invention ,Telescope ,symbols.namesake ,13. Climate action ,Space and Planetary Science ,Observatory ,law ,0103 physical sciences ,Eddington luminosity ,symbols ,Advanced CCD Imaging Spectrometer ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
Before the official first-light images, the Chandra X-Ray Observatory obtained an X-ray image of the field to which its focal plane was first exposed. We describe this historic observation and report our study of the first Chandra field. Chandra's Advanced CCD Imaging Spectrometer (ACIS) detected 15 X-ray sources, the brightest being dubbed ``Leon X-1'' to honor the Chandra Telescope Scientist, Leon Van Speybroeck. Based upon our analysis of the X-ray data and spectroscopy at the European Southern Observatory (ESO; La Silla, Chile), we find that Leon X-1 is a Type-1 (unobscured) active galactic nucleus (AGN) at a redshift z=0.3207. Leon X-1 exhibits strong Fe II emission and a broad-line Balmer decrement that is unusually flat for an AGN. Within the context of the Eigenvector-1 correlation space, these properties suggest that Leon X-1 may be a massive (> 10**{9} solar mass) black hole, accreting at a rate approaching its Eddington limit., 39 pages, 9 figures, accepted for publication in ApJ
- Published
- 2005
49. Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions
- Author
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J. Hunter Waite, Peter G. Ford, G. Randall Gladstone, Ronald F. Elsner, Thomas E. Cravens, and Anil Bhardwaj
- Subjects
Physics ,Sunspot ,Epoch (astronomy) ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Flux ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Space weather ,law.invention ,Jupiter ,Space and Planetary Science ,law ,Planet ,Saturn ,Physics::Space Physics ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Flare - Abstract
Saturn was observed by Chandra ACIS-S on 20 and 26-27 January 2004 for one full Saturn rotation (10.7 hr) at each epoch. We report here the first observation of an X-ray flare from Saturn's non-auroral (low-latitude) disk, which is seen in direct response to an M6-class flare emanating from a sunspot that was clearly visible from both Saturn and Earth. Saturn's disk X-ray emissions are found to be variable on time scales of hours to weeks to months, and correlated with solar F10.7 cm flux. Unlike Jupiter, X-rays from Saturn's polar (auroral) region have characteristics similar to those from its disk. This report, combined with earlier studies, establishes that disk X-ray emissions of the giant planets Saturn and Jupiter are directly regulated by processes happening on the Sun. We suggest that these emissions could be monitored to study X-ray flaring from solar active regions when they are on the far side and not visible to Near-Earth space weather satellites., Total 12 pages including 4 figures
- Published
- 2005
50. Simultaneous Chandra X ray, Hubble Space Telescope ultraviolet, and Ulysses radio observations of Jupiter's aurora
- Author
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Tariq Majeed, Michael D. Desch, Ronald F. Elsner, Anil Bhardwaj, Peter G. Ford, Noé Lugaz, G. R. Gladstone, Robert J. MacDowall, Denis Grodent, Thomas E. Cravens, and J. H. Waite
- Subjects
Atmospheric Science ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,Soil Science ,X-ray telescope ,Astrophysics ,Aquatic Science ,Oceanography ,Spectral line ,Jovian ,Relativistic particle ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Emission spectrum ,Advanced CCD Imaging Spectrometer ,education ,Earth-Surface Processes ,Water Science and Technology ,Physics ,education.field_of_study ,Ecology ,Paleontology ,Astronomy ,Forestry ,Solar wind ,Geophysics ,Space and Planetary Science ,Physics::Space Physics - Abstract
Observations of Jupiter carried out by the Chandra Advanced CCD Imaging Spectrometer (ACIS-S) instrument over 24-26 February 2003 show that the auroral X-ray spectrum consists of line emission consistent with high-charge states of precipitating ions, and not a continuum as might be expected from bremsstrahlung. The part of the spectrum due to oxygen peaks around 650 eV, which indicates a high fraction of fully stripped oxygen in the precipitating ion flux. A combination of the OVIII emission lines at 653 eV and 774 eV, as well as the OVII emission lines at 561 eV and 666 eV, are evident in the measure auroral spectrum. There is also line emission at lower energies in the spectral region extending from 250 to 350 eV, which could be from sulfur and/or carbon. The Jovian auroral X-ray spectra are significantly different from the X-ray spectra of comets. The charge state distribution of the oxygen ions implied by the measured auroral X-ray spectra strongly suggests that independent of the source of the energetic ions, magnetospheric or solar wind, the ions have undergone additional acceleration. This spectral evidence for ion acceleration is also consistent with the relatively high intensities of the X rays compared with the available phase space density of the (unaccelerated) source populations of solar wind or magnetospheric ions at Jupiter, which are orders of magnitude too small to explain the observed emissions. The Chandra X-ray observations were executed simultaneously with observations at ultraviolet wavelengths by the Hubble Space Telescope and at radio wavelengths by the Ulysses spacecraft. These additional data sets suggest that the source of the X rays is magnetospheric in origin and that the precipitating particles are accelerated by strong field-aligned electric fields, which simultaneously create both the several-MeV energetic ion population and the relativistic electrons observed in situ by Ulysses that are correlated with approx.40 min quasi-periodic radio outbursts.
- Published
- 2005
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