WorldWideScience

Sample records for chandra x-ray spectra

  1. The X-ray Spectra of Black Hole X-ray Novae in Quiescence as Measured by Chandra

    CERN Document Server

    Kong, A K H; García, M R; Murray, S S; Barret, D

    2002-01-01

    We present Chandra observations of black hole X-ray novae V404 Cyg, A0620-00, GRO J1655-40 and XTE J1550-564 in quiescence. Their quiescent spectra can be well fitted by a power-law model with slope $\\alpha \\sim 2$. While a coronal (Raymond-Smith) model is also a statistically acceptable representation of the spectra, the best fit temperatures of these models is $\\sim 5$ times higher than that seen in active stellar coronae. These four spectra of quiescent X-ray novae are all consistent with that expected for accretion via an advection-dominated accretion flow (ADAF) and inconsistent with that expected from a stellar corona. This evidence for continued accretion in quiescence further strengthens the case for the existence of event horizons in black holes. Both A0620-00 and GRO J1655-40 were fainter than in previous observations, while V404 Cyg was more luminous and varied by a factor of 2 in a few ksec. A reanalysis of the X-ray data for XTE J1550-564 shows that (like V404 Cyg and A0620-00) its luminosity exc...

  2. PROBING WOLF–RAYET WINDS: CHANDRA/HETG X-RAY SPECTRA OF WR 6

    Energy Technology Data Exchange (ETDEWEB)

    Huenemoerder, David P.; Schulz, N. S. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA 02139 (United States); Gayley, K. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Hamann, W.-R.; Oskinova, L.; Shenar, T. [Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam (Germany); Ignace, R. [Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614 (United States); Nichols, J. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 34, Cambridge, MA 02138 (United States); Pollock, A. M. T., E-mail: dph@space.mit.edu, E-mail: ken.gayley@gmail.com, E-mail: wrh@astro.physik.uni-potsdam.de, E-mail: lida@astro.physik.uni-potsdam.de, E-mail: shtomer@astro.physik.uni-potsdam.de, E-mail: ignace@mail.etsu.edu, E-mail: jnichols@cfa.harvard.edu [European Space Agency, ESAC, Apartado 78, E-28691 Villanueva de la Cañada (Spain)

    2015-12-10

    With a deep Chandra/HETGS exposure of WR 6, we have resolved emission lines whose profiles show that the X-rays originate from a uniformly expanding spherical wind of high X-ray-continuum optical depth. The presence of strong helium-like forbidden lines places the source of X-ray emission at tens to hundreds of stellar radii from the photosphere. Variability was present in X-rays and simultaneous optical photometry, but neither were correlated with the known period of the system or with each other. An enhanced abundance of sodium revealed nuclear-processed material, a quantity related to the evolutionary state of the star. The characterization of the extent and nature of the hot plasma in WR 6 will help to pave the way to a more fundamental theoretical understanding of the winds and evolution of massive stars.

  3. A search for iron emission lines in the Chandra X-ray spectra of neutron star low-mass X-ray binaries

    CERN Document Server

    Cackett, E M; Homan, J; Van der Klis, M; Lewin, W H G; Méndez, M; Raymond, J; Steeghs, D; Wijnands, R

    2008-01-01

    While iron emission lines are well studied in black hole systems, both in X-ray binaries and Active Galactic Nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad asymmetric iron line profiles in 4 neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in 6 neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at 2 separate epochs, allowing for both a high resolution spectrum, as well as broadband spectral coverage. Out of the six objects in the survey, we only find significant iron lines in two of the objects, GX 17+2 and GX 349+2. However, we cannot rule out that there are weak, broad lines present in the other sources. The equivalent width of the line in GX 17+2 is consistent between the 2 epochs, while in GX 349+2 the line equivalent width increases by a factor of ~3 betwe...

  4. Beyond Chandra - the X-ray Surveyor

    CERN Document Server

    Weisskopf, Martin C; Tananbaum, Harvey; Vikhlinin, Alexey

    2015-01-01

    Over the past 16 years, NASA's Chandra X-ray Observatory has provided an unparalleled means for exploring the universe with its half-arcsecond angular resolution. Chandra studies have deepened our understanding of galaxy clusters, active galactic nuclei, galaxies, supernova remnants, planets, and solar system objects addressing almost all areas of current interest in astronomy and astrophysics. As we look beyond Chandra, it is clear that comparable or even better angular resolution with greatly increased photon throughput is essential to address even more demanding science questions, such as the formation and subsequent growth of black hole seeds at very high redshift; the emergence of the first galaxy groups; and details of feedback over a large range of scales from galaxies to galaxy clusters. Recently, NASA Marshall Space Flight Center, together with the Smithsonian Astrophysical Observatory, has initiated a concept study for such a mission named the X-ray Surveyor. This study starts with a baseline payloa...

  5. Highlights and Discoveries from the Chandra X-ray Observatory

    CERN Document Server

    Tananbaum, H; Tucker, W; Wilkes, B; Edmonds, P

    2014-01-01

    Within 40 years of the detection of the first extrasolar X-ray source in 1962,NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond X-ray images with 100-200 eV energy resolution for energies in the range 0.08X-ray sources to high precision, detecting extremely faint sources, and obtaining high resolution spectra of selected cosmic phenomena. The extended Chandra mission provides a long observing baseline with stable and well-calibrated instruments, enabling temporal studies over time-scales from milliseconds to years. In this report we present a selection of highlights that illustrate how observations using Chandra, sometimes alone, but often in conjunction with other telescopes, have deepened, and in some instances revolutionized, our understanding ...

  6. X-raying Galaxies: A Chandra Legacy

    CERN Document Server

    Wang, Q Daniel

    2010-01-01

    This presentation reviews Chandra's major contribution to the understanding of nearby galaxies. After a brief summary on significant advances in characterizing various types of discrete X-ray sources, the presentation focuses on the global hot gas in and around galaxies, especially normal ones like our own. The hot gas is a product of stellar and AGN feedback -- the least understood part in theories of galaxy formation and evolution. Chandra observations have led to the first characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our Galaxy. The gas is concentrated around the Galactic bulge and disk on scales of a few kpc. The column density of chemically-enriched hot gas on larger scales is at least an order magnitude smaller, indicating that it may not account for the bulk of the missing baryon matter predicted for the Galactic halo according to the standard cosmology. Similar results have also been obtained for other nearby galaxies. The X-ray emission from hot gas is well...

  7. Chandra X-ray Observatory Optical Axis and Aimpoint

    Science.gov (United States)

    Zhao, Ping

    2016-01-01

    Chandra X-ray Observatory revolutionized the X-ray astronomy as being the first, and so far the only, X-ray telescope achieving sub-arcsecond resolution. Chandra comprises of three principal elements: the High Resolution Mirror Assembly (HRMA), Pointing Control and Aspect Determination (PCAD) system, and the Science Instrument Module (SIM). To achieve and retain the unprecedented imaging quality, it is critical that these three principal elements stay rigid and stable for the entire life time of the Chandra operation. Tracking the Chandra optical axis and aimpoint with respect to detector positions is the most relevant measurement for understanding telescope stability. The study shows that both the optical axis and the aimpoint has been drifting since Chandra launch. I will discuss the telescope focal-point, optical axis, aimpoint, their positiondrifts during the mission, the impact to Chandra operations, and the permanent default aimpoint, to be implemented in Chandra cycle 18.

  8. Stellar X-ray sources in the Chandra COSMOS survey

    CERN Document Server

    Wright, Nicholas J; Civano, Francesca

    2010-01-01

    We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160ks) and wide (0.9 deg2) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distances ranging from 30pc to ~12kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L_X-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more...

  9. Chandra X-Ray Sources in the LALA Cetus Field

    Science.gov (United States)

    Wang, J. X.; Zheng, Z. Y.; Malhotra, S.; Finkelstein, S. L.; Rhoads, J. E.; Norman, C. A.; Heckman, T. M.

    2007-11-01

    The 174 ks Chandra Advanced CCD Imaging Spectrometer exposure of the Large Area Lyman Alpha Survey (LALA) Cetus field is the second of the two deep Chandra images on LALA fields. In this paper we present the Chandra X-ray sources detected in the Cetus field, along with an analysis of X-ray source counts, stacked X-ray spectrum, and optical identifications. A total of 188 X-ray sources were detected: 174 in the 0.5-7.0 keV band, 154 in the 0.5-2.0 keV band, and 113 in the 2.0-7.0 keV band. The X-ray source counts were derived and compared with LALA field (172 ks exposure). Interestingly, we find consistent hard-band X-ray source density, but (36+/-12)% higher soft-band X-ray source density in Cetus field. The weighted stacked spectrum of the detected X-ray sources can be fitted by a power law with photon index Γ=1.55. Based on the weighted stacked spectrum, we find that the resolved fraction of the X-ray background drops from (72+/-1)% at 0.5-1.0 keV to (63+/-4)% at 6.0-8.0 keV. The unresolved spectrum can be fitted by a power law over the range 0.5-7 keV, with a photon index Γ=1.22. We also present optical counterparts for 154 of the X-ray sources, down to a limiting magnitude of r'=25.9 (Vega), using a deep r'-band image obtained with the MMT. Optical Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.

  10. Highlights and discoveries from the Chandra X-ray Observatory.

    Science.gov (United States)

    Tananbaum, H; Weisskopf, M C; Tucker, W; Wilkes, B; Edmonds, P

    2014-06-01

    Within 40 years of the detection of the first extra-solar x-ray source in 1962, NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond x-ray images with 100-200 eV energy resolution for energies in the range 0.08 black holes; the growth of supermassive black holes and their role in the regulation of star formation and growth of galaxies; impacts of collisions, mergers, and feedback on growth and evolution of groups and clusters of galaxies; and properties of dark matter and dark energy.

  11. Chandra Multiwavelength Project X-ray Point Source Catalog

    CERN Document Server

    Kim, M; Wilkes, B J; Green, P J; Kim, E; Anderson, C S; Barkhouse, W A; Evans, N R; Ivezic, Z; Karovska, M; Kashyap, V L; Lee, M G; Maksym, P; Mossman, A E; Silverman, J D; Tananbaum, H D; Kim, Minsun; Kim, Dong-Woo; Wilkes, Belinda J.; Green, Paul J.; Kim, Eunhyeuk; Anderson, Craig S.; Barkhouse, Wayne A.; Evans, Nancy R.; Ivezic, Zeljko; Karovska, Margarita; Kashyap, Vinay L.; Lee, Myung Gyoon; Maksym, Peter; Mossman, Amy E.; Silverman, John D.; Tananbaum, Harvey D.

    2006-01-01

    We present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalog with ~6,800 X-ray sources detected in 149 Chandra observations covering \\~10 deg^2. The full ChaMP catalog sample is seven times larger than the initial published ChaMP catalog. The exposure time of the fields in our sample ranges from 0.9 to 124 ksec, corresponding to a deepest X-ray flux limit of f_{0.5-8.0} = 9 x 10^{-16} erg/cm2/sec. The ChaMP X-ray data have been uniformly reduced and analyzed with ChaMP-specific pipelines, and then carefully validated by visual inspection. The ChaMP catalog includes X-ray photometric data in 8 different energy bands as well as X-ray spectral hardness ratios and colors. To best utilize the ChaMP catalog, we also present the source reliability, detection probability and positional uncertainty. To quantitatively assess those parameters, we performed extensive simulations. In particular, we present a set of empirical equations: the flux limit as a function of effective exposure time, and the p...

  12. Automated classification of Chandra X-ray sources

    Science.gov (United States)

    Brehm, Derek; Kargaltsev, O.; Rangelov, B.; Volkov, I.; Pavlov, G. G.

    2014-01-01

    With the advent of the latest generation X-ray telescopes there has been a major influx of data associated with the detection of hundreds of thousands X-ray sources. As one can rarely tell a source type from its X-ray properties alone, the full potential of the X-ray catalogs can only be unlocked by correlating multiwavelength (MW) properties via cross-identification with other surveys. However, one would spend an enormous amount of time classifying these objects by their physical nature if the classification was to be done on a source-by-source basis by humans. Therefore, we are using a supervised learning algorithm to classify sources detected by the Chandra X-ray Observatory. The classifications are based on a training dataset which currently includes about 7,000 X-ray sources of known nature (main sequence stars, Wolf-Rayet stars, young stars, active galactic nuclei, low mass X-ray binaries, high mass x-ray binaries, and neutron stars). For each source, the training dataset includes up to 24 multiwavelength properties. The efficiency and accuracy of the classification is verified by dividing the training dataset in two and performing cross-validation. The results are also inspected by plotting source properties in 2D slices of the parameter space. As an application of our automated procedure we classified unidentified sources in the supernova remnant (SNR) G352.7-0.1, in the field of HESS J1809-193, and in part of the Chandra Source Catalog 1.0. We present the results of the verification tests and the classification results. This research was partially supported by NASA/SAO grant AR3-14017X.

  13. Highlights and discoveries from the Chandra X-ray Observatory

    Science.gov (United States)

    Tananbaum, H.; Weisskopf, M. C.; Tucker, W.; Wilkes, B.; Edmonds, P.

    2014-06-01

    Within 40 years of the detection of the first extra-solar x-ray source in 1962, NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond x-ray images with 100-200 eV energy resolution for energies in the range 0.08 cosmic phenomena. The extended Chandra mission provides a long observing baseline with stable and well-calibrated instruments, enabling temporal studies over timescales from milliseconds to years. In this report we present a selection of highlights that illustrate how observations using Chandra, sometimes alone, but often in conjunction with other telescopes, have deepened, and in some instances revolutionized, our understanding of topics as diverse as protoplanetary nebulae; massive stars; supernova explosions; pulsar wind nebulae; the superfluid interior of neutron stars; accretion flows around black holes; the growth of supermassive black holes and their role in the regulation of star formation and growth of galaxies; impacts of collisions, mergers, and feedback on growth and evolution of groups and clusters of galaxies; and properties of dark matter and dark energy.

  14. Deep Chandra Survey of the Small Magellanic Cloud. II. Timing Analysis of X-Ray Pulsars

    Science.gov (United States)

    Hong, JaeSub; Antoniou, Vallia; Zezas, Andreas; Haberl, Frank; Sasaki, Manami; Drake, Jeremy J.; Plucinsky, Paul P.; Laycock, Silas

    2017-09-01

    We report the timing analysis results of X-ray pulsars from a recent deep Chandra survey of the Small Magellanic Cloud (SMC). We analyzed a total exposure of 1.4 Ms from 31 observations over a 1.2 deg2 region in the SMC under a Chandra X-ray Visionary Program. Using the Lomb–Scargle and epoch-folding techniques, we detected periodic modulations from 20 pulsars and a new candidate pulsar. The survey also covered 11 other pulsars with no clear sign of periodic modulation. The 0.5–8 keV X-ray luminosity (L X ) of the pulsars ranges from 1034 to 1037 erg s‑1 at 60 kpc. All of the Chandra sources with L X ≳ 4 × 1035 erg s‑1 exhibit X-ray pulsations. The X-ray spectra of the SMC pulsars (and high-mass X-ray binaries) are in general harder than those of the SMC field population. All but SXP 8.02 can be fitted by an absorbed power-law model with a photon index of Γ ≲ 1.5. The X-ray spectrum of the known magnetar SXP 8.02 is better fitted with a two-temperature blackbody model. Newly measured pulsation periods of SXP 51.0, SXP 214, and SXP 701, are significantly different from the previous XMM-Newton and RXTE measurements. This survey provides a rich data set for energy-dependent pulse profile modeling. Six pulsars show an almost eclipse-like dip in the pulse profile. Phase-resolved spectral analysis reveals diverse spectral variations during pulsation cycles: e.g., for an absorbed power-law model, some exhibit an (anti)-correlation between absorption and X-ray flux, while others show more intrinsic spectral variation (i.e., changes in photon indices).

  15. Invisible Giant: Chandra's Limits on X-rays from Betelgeuse

    CERN Document Server

    Posson-Brown, J; Pease, D O; Drake, J J; Posson-Brown, Jennifer; Kashyap, Vinay L.; Pease, Deron O.; Drake, Jeremy J.

    2006-01-01

    We have analyzed Chandra calibration observations of Betelgeuse ($\\alpha$ Ori, M2 Iab, $m_{V} = 0.58$, 131 pc) obtained at the aimpoint locations of the HRC-I (8 ks), HRC-S (8 ks), and ACIS-I (5 ks). Betelgeuse is undetected in all the individual observations as well as cumulatively. We derive $3\\sigma$ upper limits to its X-ray count rates and compute the corresponding X-ray flux upper limits for isothermal coronal plasma over a range of temperatures, $T=0.3-10$~MK. We place a flux limit at the telescope of $\\fx\\approx4\\times10^{-15}$~ergs~s$^{-1}$ cm$^{-2}$ at T=1~MK. The upper limit is lowered by a factor of $\\approx3$ at higher temperatures, roughly an order of magnitude lower than that obtained previously. Assuming that the entire stellar surface is active, these fluxes correspond to a surface flux limit that ranges from 30-7000~ergs~s$^{-1}$ cm$^{-2}$ at T=1~MK, to $\\approx 1$~ergs~s$^{-1}$ cm$^{-2}$ at higher temperatures, five orders of magnitude lower than the quiet Sun X-ray surface flux. We discuss...

  16. X-ray Mass Profiles from Chandra Galaxy Atlas

    Science.gov (United States)

    Paggi, Alessandro; Kim, Dong-Woo; Anderson, Craig; Burke, Douglas J.; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer L.; McCollough, Michael L.; Morgan, Douglas; Mossman, Amy; O'Sullivan, Ewan; Trinchieri, Ginevra

    2016-04-01

    We present preliminary results of a Chandra/XMM-Newton joint analysis on a sample of three Early Type Galaxies (ETGs, namely NGC4649, NGC4636 and NGC5846). X-ray observations of the hot ISM is used to measure the total enclosed mass assuming hydrostatic equilibrium, and compasion with mass distributions obtained through optical kinematics data of globular clusters and planetary nebulae yields informations about disturbances in the ISM distribution due to nuclear activity, merging history, etc. Our analysis makes use of the Chandra Galaxy Atlas (CGA) data products - exploiting the unmatched spatial resolution of the ACIS detectors to reveal fine ISM features and disturbances in the inner galactic regions - and XMM-Newton data - relying on the large field of view of EPIC detector to extend the mass profiles to larger radii. We then measured the mass profiles in various pie sectors to separate different gas features (e.g., discontinuity and extended tail) and compared them with GCs/PNe based mass profiles. The X-ray mass profiles of NGC4649 show a generally relaxed morphology and, in agreement with previous analysis, the comparison with the optical mass profiles shows a significant deviations on parsec scale likely due to non-thermal pressure linked to nuclear activity. In significantly disturbed cases (NGC4648 and NGC5846) where we found discontinuities and extended tails, we found that the mass profiles are over-estimated toward the compressed discontinuity and under-estimated toward the extended tails, similar to inflow and outflow cases. These preliminary results are promising toward an extended analysis of the whole CGA sample in order to study the distribution of gas temperature and metal abundances in the ISM, and to investigate scaling relations between ETG global quantities like ISM temperature, luminosity and total mass.

  17. Chandra X-Ray Observatory Image of Crab Nebula

    Science.gov (United States)

    1999-01-01

    After barely 2 months in space, the Chandra X-Ray Observatory (CXO) took this sturning image of the Crab Nebula, the spectacular remains of a stellar explosion, revealing something never seen before, a brilliant ring around the nebula's heart. The image shows the central pulsar surrounded by tilted rings of high-energy particles that appear to have been flung outward over a distance of more than a light-year from the pulsar. Perpendicular to the rings, jet-like structures produced by high-energy particles blast away from the pulsar. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous x-ray images have shown the outer parts of the jet and hinted at the ring structure. With CXO's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with CXO's Advanced Charge-Coupled Device (CCD) Imaging Spectrometer (ACIS) and High Energy Transmission Grating. The Crab Nebula, easily the most intensively studied object beyond our solar system, has been observed using virtually every astronomical instrument that could see that part of the sky

  18. The Chandra X-ray Observatory is prepped for solar panel deployment

    Science.gov (United States)

    1999-01-01

    In the Vertical Processing Facility, a TRW technician checks the attachment of the solar panel array (out of sight to the right) to the Chandra X-ray Observatory, at left. Formerly called the Advanced X-ray Astrophysics Facility, Chandra comprises three major elements: the spacecraft, the science instrument module (SIM), and the world's most powerful X-ray telescope. Chandra will allow scientists from around the world to see previously invisible black holes and high-temperature gas clouds, giving the observatory the potential to rewrite the books on the structure and evolution of our universe. Chandra is scheduled for launch July 9 aboard Space Shuttle Columbia, on mission STS-93.

  19. Chandra X-ray Observations of 12 Millisecond Pulsars in the Globular Cluster M28

    CERN Document Server

    Bogdanov, Slavko; Servillat, Mathieu; Heinke, Craig O; Grindlay, Jonathan E; Stairs, Ingrid H; Ransom, Scott M; Freire, Paulo C C; Bégin, Steve; Becker, Werner

    2011-01-01

    We present a Chandra X-ray Observatory investigation of the millisecond pulsars (MSPs) in the globular cluster M28 (NGC 6626). In what is one of the deepest X-ray observations of a globular cluster, we firmly detect seven and possibly detect two of the twelve known M28 pulsars. With the exception of PSRs B1821-24 and J1824-2452H, the detected pulsars have relatively soft spectra, with X-ray luminosities 10^30-31 ergs s^-1 (0.3-8 keV),similar to most "recycled" pulsars in 47 Tucanae and the field of the Galaxy, implying thermal emission from the pulsar magnetic polar caps. We present the most detailed X-ray spectrum to date of the energetic PSR B1821-24. It is well described by a purely non-thermal spectrum with spectral photon index 1.23 and luminosity 1.4x10^33Theta(D/5.5 kpc)^2 ergs s^-1 (0.3-8 keV), where Theta is the fraction of the sky covered by the X-ray emission beam(s). We find no evidence for the previously reported line emission feature around 3.3 keV, most likely as a consequence of improvements i...

  20. Chandra Observations of the Faintest Low-Mass X-ray Binaries

    CERN Document Server

    Wilson, C A; Kouveliotou, C; Jonker, P G; Van der Klis, M; Lewin, W H G; Belloni, T; Méndez, M; Wilson, Colleen. A.; Patel, Sandeep K.; Kouveliotou, Chryssa; Jonker, Peter G.; Klis, Michiel van der; Lewin, Walter H.G; Belloni, Tomaso; Mendez, Mariano

    2003-01-01

    There exists a group of persistently faint galactic X-ray sources that, based on their location in the galaxy, high L_x/L_opt, association with X-ray bursts, and absence of low frequency X-ray pulsations, are thought to be low-mass X-ray binaries (LMXBs). We present results from Chandra observations for eight of these systems: 4U 1708-408, 2S 1711-339, KS 1739-304, SLX 1735-269, GRS 1736-297, SLX 1746-331, 1E 1746.7-3224, and 4U 1812-12. Locations for all sources, excluding GRS 1736-297, SLX 1746-331, and KS 1739-304 (which were not detected) were improved to 0.6" error circles (90% confidence). Our observations support earlier findings of transient behavior of GRS 1736-297, KS 1739-304, SLX 1746-331, and 2S 1711-339 (which we detect in one of two observations). Energy spectra for 4U 1708-408, 2S 1711-339, SLX 1735-269, 1E 1746.7-3224, and 4U 1812-12 are hard, with power law indices typically 1.4-2.1, which are consistent with typical faint LMXB spectra.

  1. THE CHANDRA X-RAY SURVEY OF PLANETARY NEBULAE (CHANPLANS): PROBING BINARITY, MAGNETIC FIELDS, AND WIND COLLISIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kastner, J. H.; Montez, R. Jr.; Rapson, V. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA (United States); Frew, D. J.; De Marco, O.; Parker, Q. A. [Department of Physics and Astronomy and Macquarie Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney, NSW 2109 (Australia); Miszalski, B. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Sahai, R. [Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, Pasadena, CA 91109 (United States); Blackman, E.; Frank, A. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Chu, Y.-H. [Department of Astronomy, University of Illinois, Champagne-Urbana, IL (United States); Guerrero, M. A. [Instituto de Astrofisica de Astronomia, Glorieta de la Astronomia s/n, Granada 18008 (Spain); Lopez, J. A. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Apdo. Postal 22860, Ensenada, B. C. (Mexico); Zijlstra, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Behar, E. [Department of Physics, Technion (Israel); Bujarrabal, V. [Observatorio Astronomico Nacional, Apartado 112, E-28803, Alcala de Henares (Spain); Corradi, R. L. M. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Nordhaus, J. [Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); Sandin, C., E-mail: jhk@cis.rit.edu, E-mail: soker@physics.technion.ac.il, E-mail: eva.villaver@uam.es [Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); and others

    2012-08-15

    We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate of {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100 kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication

  2. An X-ray view of 82 LINERs with Chandra and XMM-Newton data

    CERN Document Server

    Gonzalez-Martin, O; Márquez, I; Guainazzi, M; Jimenez-Bailon, E

    2009-01-01

    We present the results of an homogeneous X-ray analysis for 82 nearby LINERs selected from the catalogue of Carrillo et al. (1999). All sources have available Chandra (68 sources) and/or XMM-Newton (55 sources) observations. This is the largest sample of LINERs with X-ray spectral data (60 out of the 82 objects) and significantly improves our previous analysis based on Chandra data for 51 LINERs (Gonzalez-Martin et al. 2006). It increases both the sample size and adds XMM-Newton data. New models permit the inclusion of double absorbers in the spectral fits. Nuclear X-ray morphology is inferred from the compactness of detected nuclear sources in the hard band (4.5-8.0 keV). Sixty per cent of the sample shows a compact nuclear source and are classified as AGN candidates. The spectral analysis indicates that best fits involve a composite model: absorbed primary continuum and (2) soft spectrum below 2 keV described by an absorbed scatterer and/or a thermal component. The resulting median spectra parameters and th...

  3. CHANDRA ACIS Survey of X-Ray Point Sources: The Source Catalog

    Science.gov (United States)

    Wang, Song; Liu, Jifeng; Qiu, Yanli; Bai, Yu; Yang, Huiqin; Guo, Jincheng; Zhang, Peng

    2016-06-01

    The Chandra archival data is a valuable resource for various studies on different X-ray astronomy topics. In this paper, we utilize this wealth of information and present a uniformly processed data set, which can be used to address a wide range of scientific questions. The data analysis procedures are applied to 10,029 Advanced CCD Imaging Spectrometer observations, which produces 363,530 source detections belonging to 217,828 distinct X-ray sources. This number is twice the size of the Chandra Source Catalog (Version 1.1). The catalogs in this paper provide abundant estimates of the detected X-ray source properties, including source positions, counts, colors, fluxes, luminosities, variability statistics, etc. Cross-correlation of these objects with galaxies shows that 17,828 sources are located within the D 25 isophotes of 1110 galaxies, and 7504 sources are located between the D 25 and 2D 25 isophotes of 910 galaxies. Contamination analysis with the log N-log S relation indicates that 51.3% of objects within 2D 25 isophotes are truly relevant to galaxies, and the “net” source fraction increases to 58.9%, 67.3%, and 69.1% for sources with luminosities above 1037, 1038, and 1039 erg s-1, respectively. Among the possible scientific uses of this catalog, we discuss the possibility of studying intra-observation variability, inter-observation variability, and supersoft sources (SSSs). About 17,092 detected sources above 10 counts are classified as variable in individual observation with the Kolmogorov-Smirnov (K-S) criterion (P K-S < 0.01). There are 99,647 sources observed more than once and 11,843 sources observed 10 times or more, offering us a wealth of data with which to explore the long-term variability. There are 1638 individual objects (˜2350 detections) classified as SSSs. As a quite interesting subclass, detailed studies on X-ray spectra and optical spectroscopic follow-up are needed to categorize these SSSs and pinpoint their properties. In addition

  4. X-ray Flares of EV Lac: Statistics, Spectra, Diagnostics

    CERN Document Server

    Huenemoerder, David P; Testa, Paola; Drake, Jeremy J; Osten, Rachel A; Reale, Fabio

    2010-01-01

    We study the spectral and temporal behavior of X-ray flares from the active M-dwarf EV Lac in 200 ks of exposure with the Chandra/HETGS. We derive flare parameters by fitting an empirical function which characterizes the amplitude, shape, and scale. The flares range from very short (<1 ks) to long (10 ks) duration events with a range of shapes and amplitudes for all durations. We extract spectra for composite flares to study their mean evolution and to compare flares of different lengths. Evolution of spectral features in the density-temperature plane shows probable sustained heating. The short flares are significantly hotter than the longer flares. We determined an upper limit to the Fe K fluorescent flux, the best fit value being close to what is expected for compact loops.

  5. Chandra observations of the peculiar X-ray transient IGR J16358-4726

    Energy Technology Data Exchange (ETDEWEB)

    Patel, S.K.; Kouveliotou, C.; Tennant, A.; Woods, P.M.; Finger, M.; King, A.; Ubertini, P.; Winkler, C.; Courvoisier, T.J.-L.; Klis, M. van der; Wachter, S

    2004-06-01

    The new transient IGR J16358-4726 was discovered on 2003 March 19 with INTEGRAL. We detected the source serendipitously during our 2003 March 24 observation of SGR 1627 - 41 with the CHANDRA X-ray Observatory at the 1.7 x 10{sup -10} ergs s{sup -1} cm{sup -2} flux level (2-10 keV) with a very high absorption column (N{sub H}=3.3x10{sup 23} cm{sup -2}) and a hard power law spectrum of photon index 0.5(1). We discovered a very strong flux modulation with a period of 5880(50) s and peak-to-peak pulse fraction of 70(6) % (2-10 keV), clearly visible in the x-ray data. The nature, however, of IGR 16357-4726 remains unresolved. Most likely, we are looking at a galactic binary neutron star system as evidenced by the detection of rest frame fluorescence line emission from neutral Fe K (6.4 keV) in the Chandra spectrum. If the detected modulation is a spin period, this transient is a new kind of object, belonging to a class of very hard transients recently revealed with the unique INTEGRAL capabilities. The only neutron star systems known with similar spin periods are low luminosity persistent wind-fed pulsars, which exhibit very soft X-ray spectra. If this is an orbital period, then the system could be a compact Low Mass X-ray Binary.

  6. N132D: Chandra and XMM-Newton X-ray Imaging and Spectral Analysis

    Science.gov (United States)

    Plucinsky, Paul; Foster, Adam; Gaetz, Terrance; Jerius, Diab; Patnaude, Daniel; Edgar, Richard; Smith, Randall; Blair, William

    2015-09-01

    We present the results of an analysis of the archival XMM-Newton EPIC data (203ks for pn and 556/574ks for MOS1/MOS2) and the Chandra X-ray Observatory ACIS data (89ks) of the brightest X-ray supernova remnant (SNR) in the Large Magellanic Cloud (LMC) N132D. N132D has been classified as an ``O-rich'' remnant based on the UV and optical spectra which show emission from C, O, Ne, Mg, and Si.These spectra of the central optical knots do notshow any emission from elements with Z higher than Si, yet the nulceosynthesis models predict significant quantities of these higher Z elements. Our spectral analysis of the deep XMM data clearly shows emission lines from S, Ar, Ca, and Fe, with indications of other possible features between Ca and Fe. We use a combination of the high resolution images from Chandra and the sensitive spectra from XMM to disentangle the emission from swept-up interstellar material and a possiblehot ejecta component. We interpret these results in the context of a 3,000 year old remnant from a massive progenitor that has exploded into a cavity created by the progenitor. We also present simulations of the Athena X-ray Integral Field Unit (X-IFU) spectrum of N132D. We use themodel spectrum developed by the International Astronomical Consortium for High Energy Calibration (IACHEC) based on the high-resolution data acquired by the Reflection Gratings Spectrometer (RGS) on XMM as the input spectrumfor the X-IFU simulations.

  7. The Making of the Chandra X-ray Observatory: the Project Scientist's Perspective

    CERN Document Server

    Weisskopf, Martin C

    2010-01-01

    We review the history of the development of the Chandra X-ray Observatory from our personal perspective. This review is necessarily biased and limited by space since it attempts to cover a time span approaching 5 decades.

  8. The Chandra Deep Field-North Survey and the Cosmic X-ray Background

    CERN Document Server

    Brandt, W N; Bauer, F E; Hornschemeier, A E

    2002-01-01

    Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multiwavelength (optical, infrared, submillimeter, and radio) properties. Special attention is paid to the HDF-N X-ray sources, luminous infrared starburst galaxies, optically faint X-ray sources, and high-to-extreme redshift AGN. We also describe how stacking analyses have been used to probe the average X-ray emission properties of normal and starburst galaxies at cosmologically interesting distances. Finally, we discuss plans to extend the survey and argue that a 5-10 Ms Chandra survey would lay key groundwork for future missions such as XEUS and Generation-X.

  9. X-ray spectral variability of seven LINER nuclei with XMM-Newton and Chandra data

    CERN Document Server

    Hernández-García, L; Márquez, I; Masegosa, J

    2013-01-01

    One of the most important features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on time scales from hours to years. Among the AGN family and according to theoretical studies, Low-Ionization Nuclear Emission Line Region (LINER) nuclei would be variable objects on long time scales. Our purpose is to investigate spectral X-ray variability in LINERs and to understand the nature of these kinds of objects, as well as their accretion mechanism. Chandra and XMM-Newton public archives were used to compile X-ray spectra of seven LINER nuclei at different epochs with time scales of years. To search for variability we fit all the spectra from the same object with a set of models, in order to identify the parameters responsible for the variability pattern. We also analyzed the light curves in order to search for short time scale (from hours to days) variability. Whenever possible, UV variability was also studied. We found spectral...

  10. Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines

    CERN Document Server

    Henley, D B; Pittard, J M; Stevens, I R; Hamaguchi, K; Gull, T R

    2008-01-01

    We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star Eta Carinae, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of Eta Car with the fast, low-density wind of an otherwise hidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companion's wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si XIII and S XV triplets is near or above the low-density limit in all observations, suggestin...

  11. Measuring redshift through X-ray spectroscopy of galaxy clusters: results from Chandra data and future prospects

    CERN Document Server

    Yu, Heng; Borgani, Stefano; Rosati, Piero; Zhu, Zong-Hong

    2011-01-01

    The ubiquitous presence of the Fe line complex in the X-ray spectra of galaxy clusters offers the possibility of measuring their redshift without resorting to spectroscopic follow-up observations. In this paper we assess the accuracy with which the redshift of galaxy clusters can be recovered from X-ray spectral analysis of Chandra archival data. This study indicates a strategy to build large surveys of clusters whose identification and redshift measurement are both based on X-ray data alone. We apply a blind search for K--shell and L--shell Fe line complex in X-ray cluster spectra using Chandra archival observations of galaxy clusters. The presence of the Fe line in the ICM spectra can be detected by simply analyzing the C-statistics variation $\\Delta C_{stat}$ as a function of the redshift parameter. We repeat the measurement under different conditions, and compare the X-ray derived redshift $z_X$ with the one obtained through optical spectroscopy $z_o$. We explore also how a number of priors on metallicity...

  12. Chandra Discovers the X-ray Signature of a Powerful Wind from a Galactic Microquasar

    Science.gov (United States)

    2000-11-01

    CCD Imaging Spectrometer (ACIS) was used as a camera to record the X-ray spectral data, which computers processed and plotted onto a graph, revealing the P Cygni signature. Specific elements, such as silicon or iron, emit specific X-ray wavelengths, revealing their presence in the emitting material to astronomers. Before the observation with Chandra, astronomers knew the force of gravity in an X-ray binary system strips material off the surface of the normal star and then pulls this material toward the surface of the super-dense neutron star, forming a relatively flat spiraling cloud of gas called an accretion disk. The detailed Chandra data revealed, in addition, that the radiation and rotational forces in the Circinus X-1 disk are blasting some of the inward-spiraling gas back out into space in a powerful wind, which creates the P Cygni lines in the object's spectrum. P Cygni profiles carry much diagnostic information that is hard to obtain in other ways--such as how fast the wind is moving, how much material it contains, how dense it is, and its chemical composition. "The wind coming out of Circinus X-1 is composed of gas that contains highly ionized atoms of silicon, neon, iron, magnesium, and sulfur, and its peak observed velocity is about 4.5 million miles per hour--so fast it would cross the entire radius of the Earth in about three seconds," Brandt reports. The astronomers used Doppler techniques that detect positive velocities from material moving away from Earth, with signals shifted toward the red end of the spectrum, and negative velocities from material that is coming toward Earth, with signals shifted toward the blue end of the spectrum. "We learned these two stars clearly interact dramatically with each other while this wind is blowing outward at high velocity, which appears to be causing certain properties of the wind to change over time," Schulz says. The researchers produced a time-lapse movie of one of their spectra, which is available on the World

  13. Finding Supernova Ia Progenitors with the Chandra X-ray Observatory

    DEFF Research Database (Denmark)

    Nielsen, Mikkel T. B.; Nelemans, Gijs; Voss, Rasmus

    2011-01-01

    We examine pre-supernova Chandra images to find X-ray luminosities of type Ia supernova progenitors. At present, we have one possible direct detection and upper limits for the X-ray luminosities of a number of other supernova progenitors. The method has also yielded a possible detection of a X...

  14. A Chandra X-Ray observation of the binary millisecond pulsar PSR J1023+0038

    NARCIS (Netherlands)

    Bogdanov, S.; Archibald, A.M.; Hessels, J.W.T.; Kaspi, V.M.; Lorimer, D.; McLaughlin, M.A.; Ransom, S.M.; Stairs, I.H.

    2011-01-01

    We present a Chandra X-Ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5σ) large-amplitude (factor of two to three) orbital variability over the

  15. Fine-structure of nonthermal X-rays in the Chandra image of SNR RX J1713.7-3946

    CERN Document Server

    Uchiyama, Y; Takahashi, T

    2003-01-01

    We present morphological and spectroscopic studies of the northwest rim of the supernova remnant RX J1713.7-3946 based on observations by the Chandra X-ray observatory. We found a complex network of nonthermal (synchrotron) X-ray filaments, as well as a 'void' type structure -- a dim region of a circular shape -- in the northwest rim. It is remarkable that despite distinct brightness variations, the X-ray spectra everywhere in this region can be well fitted with a power-law model with photon index around 2.3. We briefly discuss some implications of these results and argue that the resolved X-ray features in the northwest rim may challenge the perceptions of standard (diffusive shock-acceleration) models concerning the production, propagation and radiation of relativistic particles in supernova remnants.

  16. Recovery of the Historical SN1957D in X-rays with Chandra

    CERN Document Server

    Long, Knox S; Godfrey, L E H; Kuntz, K D; Plucinsky, Paul P; Soria, Roberto; Stockdale, Christopher J; Whitmore, Bradley C; Winkler, P Frank

    2012-01-01

    SN1957D, located in one of the spiral arms of M83, is one of the small number of extragalactic supernovae that has remained detectable at radio and optical wavelengths during the decades after its explosion. Here we report the first detection of SN1957D in X-rays, as part of a 729 ks observation of M83 with \\chandra. The X-ray luminosity (0.3 - 8 keV) is 1.7 (+2.4,-0.3) 10**37 ergs/s. The spectrum is hard and highly self-absorbed compared to most sources in M83 and to other young supernova remnants, suggesting that the system is dominated at X-ray wavelengths by an energetic pulsar and its pulsar wind nebula. The high column density may be due to absorption within the SN ejecta. HST WFC3 images resolve the supernova remnant from the surrounding emission and the local star field. Photometry of stars around SN1957D, using WFC3 images, indicates an age of less than 10**7 years and a main sequence turnoff mass more than 17 solar masses. New spectra obtained with Gemini-South show that the optical spectrum continu...

  17. NASA's High Energy Vision: Chandra and the X-Ray Universe

    Science.gov (United States)

    Mais, D. E.; Stencel, R. E.; Richards, D.

    2004-05-01

    The Chandra X-Ray Observatory is the most sophisticated X-ray observatory launched by NASA. Chandra is designed to observe X-rays from high-energy regions of the universe, such as the remnants of supernovae explosions, col- liding galaxies, black holes, pulsars, neutron stars, quasars, and X-ray bi- nary stars. The spectacular results from the first five years of Chandra ob- servations are changing and redefining theories with each observation. Every exciting new image shows glimpses of such exotic phenomena as super-massive black holes, surprising black hole activity in old galaxies, rivers of grav- ity that define the cosmic landscape, unexpected x-ray activity in proto- stars and failed stars, puzzling distributions of elements in supernovae remnants, the sound waves from a super-massive black hole, and the even the tantalizing possibility of an entirely new form of matter - the strange quark star. On September 14, 2000, triggered by alerts from amateur astron- omers worldwide, Chandra observed the outburst of the brightest northern dwarf nova SS Cygni. The cooperation of hundreds of amateur variable star astronomers and the Chandra X-Ray scientists and spacecraft specialists pro- vided proof that the collaboration of amateur and professional astronomers is a powerful tool to study cosmic phenomena.

  18. Chandra's Cosmos: Dark Matter, Black Holes, and Other Wonders Revealed by NASA's Premier X-ray Observatory

    Science.gov (United States)

    Tucker, Wallace H.

    2017-03-01

    On July 23, 1999, the Chandra X-Ray Observatory, the most powerful X-ray telescope ever built, was launched aboard the space shuttle Columbia. Since then, Chandra has given us a view of the universe that is largely hidden from telescopes sensitive only to visible light. In Chandra's Cosmos, the Smithsonian Astrophysical Observatory's Chandra science spokesperson Wallace H. Tucker uses a series of short, connected stories to describe the telescope's exploration of the hot, high-energy face of the universe. The book is organized in three parts: "The Big," covering the cosmic web, dark energy, dark matter, and massive clusters of galaxies; "The Bad," exploring neutron stars, stellar black holes, and supermassive black holes; and "The Beautiful," discussing stars, exoplanets, and life. Chandra has imaged the spectacular, glowing remains of exploded stars and taken spectra showing the dispersal of their elements. Chandra has observed the region around the supermassive black hole in the center of our Milky Way and traced the separation of dark matter from normal matter in the collision of galaxies, contributing to both dark matter and dark energy studies. Tucker explores the implications of these observations in an entertaining, informative narrative aimed at space buffs and general readers alike.

  19. Chandra Resolves Cosmic X-ray Glow and Finds Mysterious New Sources

    Science.gov (United States)

    2000-01-01

    While taking a giant leap towards solving one of the greatest mysteries of X-ray astronomy, NASA's Chandra X-ray Observatory also may have revealed the most distant objects ever seen in the universe and discovered two puzzling new types of cosmic objects. Not bad for being on the job only five months. Chandra has resolved most of the X-ray background, a pervasive glow of X-rays throughout the universe, first discovered in the early days of space exploration. Before now, scientists have not been able to discern the background's origin, because no X-ray telescope until Chandra has had both the angular resolution and sensitivity to resolve it. "This is a major discovery," said Dr. Alan Bunner, Director of NASA's Structure andEvolution of the universe science theme. "Since it was first observed thirty-seven years ago, understanding the source of the X-ray background has been aHoly Grail of X-ray astronomy. Now, it is within reach." The results of the observation will be discussed today at the 195th national meeting of the American Astronomical Society in Atlanta, Georgia. An article describing this work has been submitted to the journal Nature by Dr. Richard Mushotzky, of NASA Goddard Space Flight Center, Greenbelt, Md., Drs. Lennox Cowie and Amy Barger at the University of Hawaii, Honolulu, and Dr. Keith Arnaud of the University of Maryland, College Park. "We are all very excited by this finding," said Mushotzky. "The resolution of most of the hard X-ray background during the first few months of the Chandra mission is a tribute to the power of this observatory and bodes extremely well for its scientific future," Scientists have known about the X-ray glow, called the X-ray background, since the dawn of X-ray astronomy in the early 1960s. They have been unable to discern its origin, however, for no X-ray telescope until Chandra has had both the angular resolution and sensitivity to resolve it. The German-led ROSAT mission, now completed, resolved much of the lower

  20. The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project

    CERN Document Server

    Preibisch, T; Favata, F; Feigelson, E D; Flaccomio, E; Getman, K; Micela, G; Sciortino, S; Stassun, K G; Stelzer, B; Zinnecker, H; Preibisch, Thomas; Kim, Yong -Cheol; Favata, Fabio; Feigelson, Eric D.; Flaccomio, Ettore; Getman, Konstantin; Micela, Giusi; Sciortino, Salvatore; Stassun, Keivan; Stelzer, Beate; Zinnecker, Hans

    2005-01-01

    We use the data of the Chandra Orion Ultradeep Project (COUP) to study the nearly 600 X-ray sources that can be reliably identified with optically well characterized T Tauri stars (TTS) in the Orion Nebula Cluster. We detect X-ray emission from more than 97% of the optically visible late-type (spectral types F to M) cluster stars. This proofs that there is no ``X-ray quiet'' population of late-type stars with suppressed magnetic activity. All TTS with known rotation periods lie in the saturated or super-saturated regime of the relation between activity and Rossby numbers seen for main-sequence (MS) stars, but the TTS show a much larger scatter in X-ray activity than seen for the MS stars. Strong near-linear relations between X-ray luminosities, bolometric luminosities and mass are present. We also find that the fractional X-ray luminosity rises slowly with mass over the 0.1 - 2 M_sun range. The plasma temperatures determined from the X-ray spectra of the TTS are much hotter than in MS stars, but seem to follo...

  1. Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines

    Science.gov (United States)

    Henley, D. B.; Corcoran, M. F.; Pittard, J. M.; Stevens, I. R.; Hamaguchi, K.; Gull, T. R.

    2008-01-01

    We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star eta Car, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of eta Car with the fast, low-density wind of an otherwise hidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companion's wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si XIII and S XV triplets is near or above the low-density limit in all observations, suggesting that the line-forming region is > 1.6 stellar radii from the companion star, and that the emitting plasma may be in a non-equilibrium state. We show that simple geometrical models cannot simultaneously fit both the observed centroid variations and changes in line width as a function of phase. We show that the observed profiles can be fitted with synthetic profiles with a reasonable model of the emissivity along the wind-wind collision boundary. We use this analysis to help constrain the line formation region as a function of orbital phase, and the orbital geometry. Subject headings: X-rays: stars -stars: early-type-stars: individual (q Car)

  2. Unifying X-ray winds in radio galaxies with Chandra HETG

    Science.gov (United States)

    Tombesi, Francesco

    2013-09-01

    X-ray winds are routinely observed in the spectra of Seyfert galaxies. They can be classified as warm absorbers (WAs), with v~100-1,000km/s, and ultra-fast outflows (UFOs), with v>10,000km/s. In stark contrast, the lack of sensitive enough observations allowed the detection of WAs or UFOs only in very few radio galaxies. Therefore, we propose to observe a small sample of three radio galaxies with the Chandra HETG - 3C111 for 150ks, 3C390.3 for 150ks and 3C120 for 200ks - to detect and study in detail their WAs. We will quantify the importance of mechanical feedback from winds in radio galaxies and compare them to the radio jet power. We will also test whether WAs and UFOs can be unified in a single, multi-phase and multi-scale outflow, as recently reported for Seyferts.

  3. The O VII X-Ray Forest toward Markarian 421: Consistency between XMM-Newton and Chandra

    Science.gov (United States)

    Kaastra, J. S.; Werner, N.; Herder, J. W. A. den; Paerels, F. B. S.; de Plaa, J.; Rasmussen, A. P.; de Vries, C. P.

    2006-11-01

    Recently, the first detections of highly ionized gas associated with two warm-hot intergalactic medium (WHIM) filaments have been reported. The evidence is based on X-ray absorption lines due to O VII and other ions observed by Chandra toward the bright blazar Mrk 421. We investigate the robustness of this detection by a reanalysis of the original Chandra LETGS spectra, the analysis of a large set of XMM-Newton RGS spectra of Mrk 421, and additional Chandra observations. We address the reliability of individual spectral features belonging to the absorption components, and assess the significance of the detection of these components. We also use Monte Carlo simulations of spectra. We confirm the apparent strength of several features in the Chandra spectra, but demonstrate that they are statistically not significant. This decreased significance is due to the number of redshift trials that are made and that are not taken into account in the original discovery paper. Therefore, these features must be attributed to statistical fluctuations. This is confirmed by the RGS spectra, which have a higher signal-to-noise ratio than the Chandra spectra, but do not show features at the same wavelengths. Finally, we show that the possible association with a Lyα absorption system also lacks sufficient statistical evidence. We conclude that there is insufficient observational proof for the existence of the two proposed WHIM filaments toward Mrk 421, the brightest X-ray blazar in the sky. Therefore, the highly ionized component of the WHIM still remains to be discovered.

  4. Chandra x-ray results on v426 ophiuchi

    Directory of Open Access Journals (Sweden)

    Lee Homer

    2004-01-01

    Full Text Available De las observaciones de 45 ks de Chandra de V426 Oph hemos obtenido espectros de rayos X de alta resoluci on con relaci on se~nal-a-ruido moderada, y una curva de luz no interrumpida de buena calidad. Los espectros se adaptan razonablemente a un modelo de ujo de enfriamiento, similar a EX Hya y U Gem. Nuestro an alisis de las curvas de luz de Chandra y las adicionales de rayos X/ optico revela una modulaci on persistente a 4.2 hr desde 1988 hasta 2003, probablemente el per odo de giro de la enana blanca, indicando una naturaleza polar intermedia para V426 Oph.

  5. X-rays beware: the deepest Chandra catalogue of point sources in M31

    Science.gov (United States)

    Vulic, N.; Gallagher, S. C.; Barmby, P.

    2016-10-01

    This study represents the most sensitive Chandra X-ray point source catalogue of M31. Using 133 publicly available Chandra ACIS-I/S observations totalling ˜1 Ms, we detected 795 X-ray sources in the bulge, north-east, and south-west fields of M31, covering an area of ≈0.6 deg2, to a limiting unabsorbed 0.5-8.0 keV luminosity of ˜1034 erg s-1. In the inner bulge, where exposure is approximately constant, X-ray fluxes represent average values because they were determined from many observations over a long period of time. Similarly, our catalogue is more complete in the bulge fields since monitoring allowed more transient sources to be detected. The catalogue was cross-correlated with a previous XMM-Newton catalogue of M31's D25 isophote consisting of 1948 X-ray sources, with only 979 within the field of view of our survey. We found 387 (49 per cent) of our Chandra sources (352 or 44 per cent unique sources) matched to within 5 arcsec of 352 XMM-Newton sources. Combining this result with matching done to previous Chandra X-ray sources we detected 259. new sources in our catalogue. We created X-ray luminosity functions (XLFs) in the soft (0.5-2.0 keV) and hard (2.0-8.0 keV) bands that are the most sensitive for any large galaxy based on our detection limits. Completeness-corrected XLFs show a break around ≈1.3 × 1037 erg s-1, consistent with previous work. As in past surveys, we find that the bulge XLFs are flatter than the disc, indicating a lack of bright high-mass X-ray binaries in the disc and an aging population of low-mass X-ray binaries in the bulge.

  6. The Chandra X-Ray Observatory Radiation Environmental Model Update

    Science.gov (United States)

    Blackwell, William C.; Minow, Joseph I.; ODell, Stephen L.; Cameron, Robert A.; Virani, Shanil N.

    2003-01-01

    CRMFLX (Chandra Radiation Model of ion FLUX) is a radiation environment risk mitigation tool for use as a decision aid in planning the operation times for Chandra's Advanced CCD Imaging Spectrometer (ACIS) detector. The accurate prediction of the proton flux environment with energies of 100 - 200 keV is needed in order to protect the ACIS detector against proton degradation. Unfortunately, protons of this energy are abundant in the region of space where Chandra must operate. In addition, on-board particle detectors do not measure proton flux levels of the required energy range. CRMFLX is an engineering environment model developed to predict the proton flux in the solar wind, magnetosheath, and magnetosphere phenomenological regions of geospace. This paper describes the upgrades to the ion flux databases for the magnetosphere, magnetosheath, and solar wind regions. These data files were created by using Geotail and Polar spacecraft flux measurements only when the Advanced Composition Explorer (ACE) spacecraft's 0.14 MeV particle flux was below a threshold value. This new database allows for CRMFLX output to be correlated with both the geomagnetic activity level, as represented by the Kp index, as well as with solar proton events. Also, reported in this paper are results of analysis leading to a change in Chandra operations that successfully mitigates the false trigger rate for autonomous radiation events caused by relativistic electron flux contamination of proton channels.

  7. CHANDRA/ACIS-I STUDY OF THE X-RAY PROPERTIES OF THE NGC 6611 AND M16 STELLAR POPULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Guarcello, M. G.; Drake, J. J. [Smithsonian Astrophysical Observatory, MS-67, 60 Garden Street, Cambridge, MA 02138 (United States); Caramazza, M.; Micela, G.; Sciortino, S.; Prisinzano, L. [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo (Italy)

    2012-07-10

    Mechanisms regulating the origin of X-rays in young stellar objects and the correlation with their evolutionary stage are under debate. Studies of the X-ray properties in young clusters allow us to understand these mechanisms. One ideal target for this analysis is the Eagle Nebula (M16), with its central cluster NGC 6611. At 1750 pc from the Sun, it harbors 93 OB stars, together with a population of low-mass stars from embedded protostars to disk-less Class III objects, with age {<=}3 Myr. We study an archival 78 ks Chandra/ACIS-I observation of NGC 6611 and two new 80 ks observations of the outer region of M16, one centered on the Column V and the other on a region of the molecular cloud with ongoing star formation. We detect 1755 point sources with 1183 candidate cluster members (219 disk-bearing and 964 disk-less). We study the global X-ray properties of M16 and compare them with those of the Orion Nebula Cluster. We also compare the level of X-ray emission of Class II and Class III stars and analyze the X-ray spectral properties of OB stars. Our study supports the lower level of X-ray activity for the disk-bearing stars with respect to the disk-less members. The X-ray luminosity function (XLF) of M16 is similar to that of Orion, supporting the universality of the XLF in young clusters. Eighty-five percent of the O stars of NGC 6611 have been detected in X-rays. With only one possible exception, they show soft spectra with no hard components, indicating that mechanisms for the production of hard X-ray emission in O stars are not operating in NGC 6611.

  8. High Spatial Resolution X-Ray Spectroscopy of Cas A with Chandra

    Institute of Scientific and Technical Information of China (English)

    Xue-Juan Yang; Fang-Jun Lu; Li Chen

    2008-01-01

    We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10″× 10″ each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. From the results of the spectral analysis we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances of Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obvious jet structures, while Fe does not follow the jet but seems to be distributed perpendicular to it. The abundances of Si, S and Ca show tight correlations between one another over a range of about two dex. This suggests that they are ejecta from explosive Oburning and incomplete Si-buming. Meanwhile, the Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when the latter is lower than 3 times the solar value, and is negatively correlated when higher. We suggest that such a two phase correlation is due to the different ways in which Fe was synthesized.

  9. X-ray Sources with Periodic Variability in a Deep Chandra Image of the Galactic Center

    CERN Document Server

    Muno, M P; Bautz, M W; Brandt, W N; Garmire, G P; Ricker, G R

    2003-01-01

    We report the discovery of eight X-ray sources with periodic variability in 487 ks of observations of the Galactic center with Chandra. The sources are identified from a sample of 285 objects detected with 100-4200 net counts. Their periods range from 300 s to 4.5 h with amplitudes between 40% and 70% rms. They have luminosities of (1 - 5) \\times 10^{32} erg/sec (2--8 keV at 8 kpc). The spectra of seven of the eight sources are consistent with Gamma = 0 power laws absorbed by gas and dust with a column density equal to or higher than that toward the Galactic Center (6 times 10^{22} cm^{-2}). Four of these sources also exhibit emission lines near 6.7 keV from He-like Fe, with equivalent widths of 600-1000 eV. These properties are consistent with both magnetically accreting cataclysmic variables and wind-accreting neutron stars in high-mass X-ray binaries. The eighth source has an absorbing column of 5 \\times 10^{21} cm^{-2} that places it in the foreground. Its spectrum is consistent with either a Gamma = 1.4 ...

  10. The Norma Arm Region Chandra Survey: X-ray Populations in the Spiral Arms

    CERN Document Server

    Fornasini, Francesca M; Bodaghee, Arash; Krivonos, Roman A; An, Hongjun; Rahoui, Farid; Gotthelf, Eric V; Bauer, Franz E; Stern, Daniel

    2014-01-01

    We present a catalog of 1415 X-ray sources identified in the Norma arm region Chandra survey (NARCS), which covers a 2 deg x 0.8 deg region in the direction of the Norma spiral arm to a depth of $\\approx$20 ks. Of these sources, 1130 are point-like sources detected with $\\geq3\\sigma$ confidence in at least one of three energy bands (0.5-10, 0.5-2, and 2-10 keV), five have extended emission, and the remainder are detected at low significance. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. We analyze stacked spectra of X-ray sources within each group, in conjunction with their fluxes, variability, and infrared counterparts, to identify the dominant populations in our survey. We find that $\\sim$50% of our sources are foreground sources located within 1-2 kpc, which is consistent with expectations from previous surveys. Approximately 20% of sources are likely located in the proximity of the Scutum-Crux an...

  11. The Chandra Local Volume Survey: The X-ray Point Source Catalog of NGC 300

    CERN Document Server

    Binder, Breanna; Eracleous, Michael; Gaetz, Terrance J; Plucinsky, Paul P; Skillman, Evan D; Dalcanton, Julianne J; Anderson, Scott F; Weisz, Daniel R; Kong, Albert K H

    2012-01-01

    We present the source catalog of a new Chandra ACIS-I observation of NGC 300 obtained as part of the Chandra Local Volume Survey. Our 63 ks exposure covers ~88% of the D25 isophote (R~6.3 kpc) and yields a catalog of 95 X-ray point sources detected at high significance to a limiting unabsorbed 0.35-8 keV luminosity of ~10^36 erg s^-1. Sources were cross-correlated with a previous XMM-Newton catalog, and we find 75 "X-ray transient candidate" sources that were detected by one observatory, but not the other. We derive an X-ray scale length of 1.7+/-0.2 kpc and a recent star formation rate of 0.12 Msun yr^-1, in excellent agreement with optical observations. Deep, multi-color imaging from the Hubble Space Telescope, covering ~32% of our Chandra field, was used to search for optical counterparts to the X-ray sources, and we have developed a new source classification scheme to determine which sources are likely X-ray binaries, supernova remnants, and background AGN candidates. Finally, we present the X-ray luminos...

  12. Chandra X-ray Observations of the Young Stellar Cluster NGC 6193 in the Ara OB1 Association

    CERN Document Server

    Skinner, S L; Palla, F; Barbosa, C L D R

    2005-01-01

    A 90 ks Chandra HETG observation of the young stellar cluster NGC 6193 in the southern Ara OB1 association detected 43 X-ray sources in a 2' x 2' core region centered on the young O stars HD 150135 (O6.5V) and HD 150136 (O3+O6V). The cluster is dominated by exceptionally bright X-ray emission from the two O stars, which are separated by only 10 arcsecs. The X-ray luminosity of HD 150136 is log Lx = 33.39 (ergs/s), making it one of the most luminous O-star X-ray sources known. All of the fainter X-ray sources in the core region have near-IR counterparts, but JHK photometry provides little evidence for near-IR excesses. These core sources have typical mean photon energies of 2 keV and about one-third are variable. It is likely that some are young low-mass stars in the cluster, but cluster membership remains to be determined. Grating spectra show that the X-ray properties of HD 150135 and HD 150136 are similar, but not identical. Both have moderately broadened unshifted emission lines and their emission is domin...

  13. Historical Remembrances of the Chandra X-ray Observatory: How Partnerships Created Success

    Science.gov (United States)

    Burke, Robert

    2009-09-01

    As the astronomy community plans for new ventures in space, we're forced to find creative solutions to operate within the ever increasing fiscal constraints of the current economic environment. The Chandra X-ray Observatory program offers an example of how missions can be successfully developed within manageable budget constraints. The ten year anniversary offers us the chance to look back at the Chandra team's special partnership between scientists, managers, and industry that led to our success.Chandra experienced many of the challenges common to major observatories: state-of-the-art technical requirements, budget-induced slips, and restructurings. Yet the Chandra team achieved excellent performance for dramatically lower cost. In fact, Chandra completed its prime mission for billions of dollars less than originally planned. In 1992, NASA MSFC and Northrop Grumman (then TRW) together led a major restructure that saved approximately 3.4B in program cost, while we improved the imaging capability and observing efficiency of Chandra. This was accomplished by a combination of team-work, systems engineering, advanced technology insertion, and effective approaches for program implementation, combined with a high performance culture that aligned goals and focused on mission success. Northrop Grumman is proud of our role in supporting the NASA Marshall Space Flight Center and our academic partners in advancing the frontiers of x-ray astronomy and scientific discovery with Chandra. As Chandra continues its extended mission, the observatory continues to provide superb scientific performance.

  14. THE CHANDRA LOCAL VOLUME SURVEY: THE X-RAY POINT-SOURCE CATALOG OF NGC 300

    Energy Technology Data Exchange (ETDEWEB)

    Binder, B.; Williams, B. F.; Dalcanton, J. J.; Anderson, S. F.; Weisz, D. R. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Eracleous, M. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Gaetz, T. J.; Plucinsky, P. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street Cambridge, MA 02138 (United States); Skillman, E. D. [Astronomy Department, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Kong, A. K. H. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2012-10-10

    We present the source catalog of a new Chandra ACIS-I observation of NGC 300 obtained as part of the Chandra Local Volume Survey. Our 63 ks exposure covers {approx}88% of the D{sub 25} isophote (R Almost-Equal-To 6.3 kpc) and yields a catalog of 95 X-ray point sources detected at high significance to a limiting unabsorbed 0.35-8 keV luminosity of {approx}10{sup 36} erg s{sup -1}. Sources were cross-correlated with a previous XMM-Newton catalog, and we find 75 'X-ray transient candidate' sources that were detected by one observatory, but not the other. We derive an X-ray scale length of 1.7 {+-} 0.2 kpc and a recent star formation rate of 0.12 M{sub Sun} yr{sup -1} in excellent agreement with optical observations. Deep, multi-color imaging from the Hubble Space Telescope, covering {approx}32% of our Chandra field, was used to search for optical counterparts to the X-ray sources, and we have developed a new source classification scheme to determine which sources are likely X-ray binaries, supernova remnants, and background active galactic nucleus candidates. Finally, we present the X-ray luminosity functions (XLFs) at different X-ray energies, and we find the total NGC 300 X-ray point-source population to be consistent with other late-type galaxies hosting young stellar populations ({approx}< 50 Myr). We find that XLF of sources associated with older stellar populations has a steeper slope than the XLF of X-ray sources coinciding with young stellar populations, consistent with theoretical predictions.

  15. Modeling Contamination Migration on the Chandra X-Ray Observatory - III

    Science.gov (United States)

    O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexy A.; Tennant, Allyn F.; Dahmer, Matthew T.

    2015-01-01

    During its first 16 years of operation, the cold (about -60 C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity, in part to evaluate potential bake-out scenarios intended to reduce the level of contamination. Keywords: X-ray astronomy, CCDs, contamination, modeling and simulation, spacecraft operations

  16. The Norma arm region Chandra survey catalog: X-ray populations in the spiral arms

    Energy Technology Data Exchange (ETDEWEB)

    Fornasini, Francesca M. [Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720 (United States); Tomsick, John A.; Bodaghee, Arash; Krivonos, Roman A. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 (United States); An, Hongjun [Department of Physics, McGill University, Rutherford Physics Building, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Rahoui, Farid [European Southern Observatory, Karl Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany); Gotthelf, Eric V. [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Bauer, Franz E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile); Stern, Daniel, E-mail: f.fornasini@berkeley.edu [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 169-506, Pasadena, CA 91109 (United States)

    2014-12-01

    We present a catalog of 1415 X-ray sources identified in the Norma Arm Region Chandra Survey (NARCS), which covers a 2° × 0.°8 region in the direction of the Norma spiral arm to a depth of ≈20 ks. Of these sources, 1130 are point-like sources detected with ≥3σ confidence in at least one of three energy bands (0.5-10, 0.5-2, and 2-10 keV), five have extended emission, and the remainder are detected at low significance. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. We analyze stacked spectra of X-ray sources within each group, in conjunction with their fluxes, variability, and infrared counterparts, to identify the dominant populations in our survey. We find that ∼50% of our sources are foreground sources located within 1-2 kpc, which is consistent with expectations from previous surveys. Approximately 20% of sources are likely located in the proximity of the Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity of the far Norma arm or beyond. We argue that a mixture of magnetic and nonmagnetic cataclysmic variables dominates the Scutum-Crux and near Norma arms, while intermediate polars and high-mass stars (isolated or in binaries) dominate the far Norma arm. We also present the cumulative number count distribution for sources in our survey that are detected in the hard energy band. A population of very hard sources in the vicinity of the far Norma arm and active galactic nuclei dominate the hard X-ray emission down to f{sub X} ≈ 10{sup –14} erg cm{sup –2} s{sup –1}, but the distribution curve flattens at fainter fluxes. We find good agreement between the observed distribution and predictions based on other surveys.

  17. A Chandra X-ray Study of Cygnus A. 2; The Nucleus

    Science.gov (United States)

    Young, Andrew J.; Wilson, Andrew; Terashima, Yuichi; Arnaud, Keith A.; Smith, David A.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report Chandra Advanced CCD Imaging Spectrometer and quasi-simultaneous Rossi X-Ray Timing Explorer (RXTE) observations of the nearby, powerful radio galaxy Cygnus A, with the present paper focusing on the properties of the active nucleus. In the Chandra observation, the hard (less than a few keV) X-ray emission is spatially unresolved with a size is approximately 1" (1.5 kpc, H(sub 0) = 50 km/s/Mpc) and coincides with the radio and near-infrared nuclei. In contrast, the soft (less than 2 keV) emission exhibits a bipolar nebulosity that aligns with the optical bipolar continuum and emission-line structures and approximately with the radio jet. In particular, the soft X-ray emission corresponds very well with the [O III] (lambda)5007 and H(alpha) + [N II] lambda(lambda)6548, 6583 nebulosity imaged with Hubble Space Telescope. At the location of the nucleus, there is only weak soft X-ray emission, an effect that may be intrinsic or result from a dust lane that crosses the nucleus perpendicular to the source axis. The spectra of the various X-ray components have been obtained by simultaneous fits to the six detectors. The compact nucleus is detected to 100 keV and is well described by a heavily absorbed power-law spectrum with Gamma(sub h) = 1.52(sup + 0.12, sub -0.12) (similar to other 0.12 narrow-line radio galaxies) and equivalent hydrogen column N(sub H)(nuc) = 2.0(sup +0.1, sub -0.1) x 10(exp 23)/sq cm. This 0.2 column is compatible with the dust obscuration to the near-infrared source for a normal gas-to-dust ratio. The soft (less than 2 keV) emission from the nucleus may be described by a power-law spectrum with the same index (i.e., Gamma(sub l) = Gamma(sub h), although direct fits suggest a slightly larger value for Gamma(sub l). Narrow emission lines from highly ionized neon and silicon, as well as a "neutral" Fe K(alpha) line, are detected in the nucleus and its vicinity (r approximately less than 2 kpc). The equivalent width (EW) of the Fe K(alpha) line

  18. The Chandra Local Volume Survey: The X-ray Point Source Population of NGC 404

    CERN Document Server

    Binder, B; Eracleous, M; Gaetz, T J; Kong, A K H; Skillman, E D; Weisz, D R

    2012-01-01

    We present a comprehensive X-ray point source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new, 97 ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123 ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6x10^35 erg s^-1 in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping HST observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background AGN. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% comple...

  19. Near-infrared counterparts of Chandra X-ray sources toward the Galactic Center

    CERN Document Server

    DeWitt, Curtis; Eikenberry, Stephen S; Blum, Robert; Olsen, Knut; Sellgren, Kris; Sarajedini, Ata

    2010-01-01

    The Chandra X-ray Observatory has now discovered nearly 10,000 X-ray point sources in the 2 x 0.8 degree region around the Galactic Center (Muno 2009). The sources are likely to be a population of accreting binaries in the Galactic Center, but little else is known of their nature. We obtained JHKs imaging of the 17'x 17' region around Sgr A*, an area containing 4339 of these X-ray sources, with the ISPI camera on the CTIO 4-m telescope. We cross-correlate the Chandra and ISPI catalogs to find potential IR counterparts to the X-ray sources. The extreme IR source crowding in the field means that it is not possible to establish the authenticity of the matches with astrometry and photometry alone. We find 2137 IR/X-ray astrometrically matched sources: statistically we estimate that our catalog contains 289 +/- 13 true matches to soft X-ray sources and 154 +/- 39 matches to hard X-ray sources. However, the fraction of true counterparts to candidate counterparts for hard sources is just 11 %, compared to 60 % for s...

  20. Infrared Counterparts to Chandra X-Ray Sources in the Antennae

    CERN Document Server

    Clark, D M; Brandl, B R; Wilson, J C; Carson, J C; Henderson, C P; Hayward, T L; Barry, D J; Ptak, A F; Colbert, E J M

    2006-01-01

    We use deep J and Ks images of the Antennae (NGC 4038/9) obtained with WIRC on the Palomar 200-inch telescope, together with the Chandra X-ray source list of Zezas et al. (2002a), to search for IR counterparts to X-ray point sources. We establish an X-ray/IR astrometric frame tie with 0.5" rms residuals over a \\~4.3' field. We find 13 ``strong'' IR counterparts brighter than Ks = 17.8 mag and < 1.0" from X-ray sources, and an additional 6 ``possible'' IR counterparts between 1.0" and 1.5" from X-ray sources. The surface density of IR sources near the X-ray sources suggests only ~2 of the ``strong'' counterparts and ~3 of the ``possible'' counterparts are chance superpositions of unrelated objects. Comparing both strong and possible IR counterparts to our photometric study of ~220 Antennae, IR clusters, we find the IR counterparts to X-ray sources are \\~1.2 mag more luminous in Ks than average non-X-ray clusters. We also note that the X-ray/IR matches are concentrated in the spiral arms and ``overlap'' regi...

  1. A Comprehensive Archival Chandra Search for X-ray Emission from Ultracompact Dwarf Galaxies

    CERN Document Server

    Pandya, Viraj; Greene, Jenny E

    2016-01-01

    We present the first comprehensive archival study of the X-ray properties of ultracompact dwarf (UCD) galaxies, with the goal of identifying weakly-accreting central black holes in UCDs. Our study spans 578 UCDs distributed across thirteen different host systems, including clusters, groups, fossil groups, and isolated galaxies. Of the 336 spectroscopically-confirmed UCDs with usable archival Chandra imaging observations, 21 are X-ray-detected. Imposing a completeness limit of $L_X>2\\times10^{38}$ erg s$^{-1}$, the global X-ray detection fraction for the UCD population is $\\sim3\\%$. Of the 21 X-ray-detected UCDs, seven show evidence of long-term X-ray time variability on the order of months to years. X-ray-detected UCDs tend to be more compact than non-X-ray-detected UCDs, and we find tentative evidence that the X-ray detection fraction increases with surface luminosity density and global stellar velocity dispersion. The X-ray emission of UCDs is fully consistent with arising from a population of low-mass X-ra...

  2. Chandra ACIS Survey of X-ray Point Sources in Nearby Galaxies. II. X-ray Luminosity Functions and Ultraluminous X-ray Sources

    CERN Document Server

    Wang, Song; Liu, Jifeng; Bregman, Joel N

    2016-01-01

    Based on the recently completed {\\it Chandra}/ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library for 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm with good statistics that the XLF slope flattens from lenticular ($\\alpha\\sim1.50\\pm0.07$) to elliptical ($\\sim1.21\\pm0.02$), to spirals ($\\sim0.80\\pm0.02$), to peculiars ($\\sim0.55\\pm0.30$), and to irregulars ($\\sim0.26\\pm0.10$). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosi...

  3. THE CHANDRA LOCAL VOLUME SURVEY: THE X-RAY POINT-SOURCE POPULATION OF NGC 404

    Energy Technology Data Exchange (ETDEWEB)

    Binder, B.; Williams, B. F.; Weisz, D. R. [University of Washington, Department of Astronomy, Box 351580, Seattle, WA 98195 (United States); Eracleous, M. [Department of Astronomy and Astrophysics and Center for Gravitational Wave Physics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Gaetz, T. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street Cambridge, MA 02138 (United States); Kong, A. K. H. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Skillman, E. D. [University of Minnesota, Astronomy Department, 116 Church St. SE, Minneapolis, MN 55455 (United States)

    2013-02-15

    We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97 ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of {approx}123 ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of {approx}6 Multiplication-Sign 10{sup 35} erg s{sup -1} in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% completeness limit of 10{sup 35} erg s{sup -1} and 10{sup 36} erg s{sup -1}, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10{sup 37} erg s{sup -1}) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation {approx}0.5 Gyr ago.

  4. The Chandra ACIS Timing Survey Project: glimpsing a sample of faint X-ray pulsators

    CERN Document Server

    Israel, Gian Luca; Castillo, Guillermo Andres Rodriguez; Sidoli, Lara

    2016-01-01

    We report on the discovery of 41 new pulsating sources in the data of the Chandra Advanced CCD Imaging Spectrometer, which is sensitive to X-ray photons in the 0.3-10 keV band. The archival data of the first 15 years of Chandra observations were retrieved and analysed by means of fast Fourier transforms, employing a peak-detection algorithm able to screen candidate signals in an automatic fashion. We carried out the search for new X-ray pulsators in light curves with more than 50 photons, for a total of about 190,000 lightcurves out of about 430,000 extracted. With these numbers, the ChAndra Timing Survey at Brera And Roma astronomical observatories (CATS@BAR) - as we called the project - represents the largest ever systematic search for coherent signals in the classic X-ray band. More than 50 per cent of the signals were confirmed by further Chandra (for those sources with two or more pointings), XMM-Newton or ROSAT data. The period distribution of the new X-ray pulsators above about 2,000s resembles that of...

  5. Chandra X-ray Detection of the Enigmatic Field Star BP Psc

    CERN Document Server

    Kastner, Joel H; Rodriguez, David; Grosso, Nicolas; Zuckerman, B; Perrin, Marshall D; Forveille, Thierry; Graham, James R

    2010-01-01

    BP Psc is a remarkable emission-line field star that is orbited by a dusty disk and drives a parsec-scale system of jets. We report the detection by the Chandra X-ray Observatory of a weak X-ray point source coincident with the centroids of optical/IR and submillimeter continuum emission at BP Psc. As the star's photosphere is obscured throughout the visible and near-infrared, the Chandra X-ray source likely represents the first detection of BP Psc itself. The X-rays most likely originate with magnetic activity at BP Psc and hence can be attributed either to a stellar corona or to star-disk interactions. The log of the ratio of X-ray to bolometric luminosity (log(L_X/L_{bol}) lies in the range -5.8 to -4.2. This is smaller than log(L_X/L_{bol}) ratios typical of low-mass, pre-main sequence stars, but is well within the log(L_X/L_{bol}) range observed for rapidly-rotating (FK Com-type) G giant stars. Hence, the Chandra results favor an exotic model wherein the disk/jet system of BP Psc is the result of its ver...

  6. Modeling Contamination Migration on the Chandra X-ray Observatory II

    Science.gov (United States)

    O'Dell, Steve; Swartz, Doug; Tice, Neil; Plucinsky, Paul; Grant, Catherine; Marshall, Herman; Vikhlinin, Alexey

    2013-01-01

    During its first 14 years of operation, the cold (about -60degC) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition may have changed, perhaps partially related to changes in the operating temperature of the ACIS housing. This evolution of the accumulation of the molecular contamination has motivated further analysis of contamination migration on the Chandra X-ray Observatory, particularly within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon monitored temperature data, and an accordingly refined model of the molecular transport.

  7. Observations of the Crab Nebula with the Chandra X-Ray Observatory

    Science.gov (United States)

    Weisskopf, Martin C.

    2012-01-01

    The Crab Nebula and its pulsar has been the subject of a number of detailed observations with the Chandra X-ray Observatory. The superb angular resolution of Chandra s high-resolution telescope has made possible numerous remarkable results. Here we describe a number of specific studies of the Crab that I and my colleagues have undertaken. We discuss the geometry of the system, which indicates that the "inner X-ray ring", typically identified with the termination shock of the pulsar s particle wind, is most likely not in the equatorial plane of the pulsar. Other topics are the northern wisps and their evolution with time; the characterization of features in the jet to the southeast; pulse-phase spectroscopy and possible correlations with the features at other wavelengths, particularly the optical polarization; and a search for correlations of the X-ray flux with the recently-discovered gamma -ray flares.

  8. An Overview of the Performance of the Chandra X-Ray Observatory

    CERN Document Server

    Weisskopf, M C; Bautz, M; Cameron, R A; Dewey, D; Drake, J J; Grant, C E; Marshall, H L; Murray, S S

    2003-01-01

    The Chandra X-ray Observatory is the X-ray component of NASA's Great Observatory Program which includes the recently launched Spitzer Infrared Telescope, the Hubble Space Telescope (HST) for observations in the visible, and the Compton Gamma-Ray Observatory (CGRO) which, after providing years of useful data has reentered the atmosphere. All these facilities provide, or provided, scientific data to the international astronomical community in response to peer-reviewed proposals for their use. The Chandra X-ray Observatory was the result of the efforts of many academic, commercial, and government organizations primarily in the United States but also in Europe. NASA's Marshall Space Flight Center (MSFC) manages the Project and provides Project Science; Northrop Grumman Space Technology (NGST -- formerly TRW) served as prime contractor responsible for providing the spacecraft, the telescope, and assembling and testing the Observatory; and the Smithsonian Astrophysical Observatory (SAO) provides technical support a...

  9. The Chandra X-ray Observatory is prepped for solar panel deployment copy form; photos beginning with

    Science.gov (United States)

    1999-01-01

    TRW workers in the Vertical Processing Facility check equipment after deployment of the solar panel array above them, attached to the Chandra X-ray Observatory. Formerly called the Advanced X-ray Astrophysics Facility, Chandra comprises three major elements: the spacecraft, the science instrument module (SIM), and the world's most powerful X-ray telescope. Chandra will allow scientists from around the world to see previously invisible black holes and high-temperature gas clouds, giving the observatory the potential to rewrite the books on the structure and evolution of our universe. Chandra is scheduled for launch July 9 aboard Space Shuttle Columbia, on mission STS-93.

  10. The O VII X-ray forest toward Markarian 421: Consistency between XMM-Newton and Chandra

    CERN Document Server

    Kaastra, J S; Den Herder, J W A; Paerels, F B S; De Plaa, J; Rasmussen, A P; De Vries, C P

    2006-01-01

    Recently the first detections of highly ionised gas associated with two Warm-Hot Intergalactic Medium (WHIM) filaments have been reported. The evidence is based on X-ray absorption lines due to O VII and other ions observed by Chandra towards the bright blazar Mrk 421. We investigate the robustness of this detection by a re-analysis of the original Chandra LETGS spectra, the analysis of a large set of XMM-Newton RGS spectra of Mrk 421, and additional Chandra observations. We address the reliability of individual spectral features belonging to the absorption components, and assess the significance of the detection of these components. We also use Monte Carlo simulations of spectra. We confirm the apparent strength of several features in the Chandra spectra, but demonstrate that they are statistically not significant. This decreased significance is due to the number of redshift trials that are made and that are not taken into account in the original discovery paper. Therefore these features must be attributed t...

  11. The End of Days -- Chandra Catches X-ray Glow From Supernova

    Science.gov (United States)

    1999-12-01

    Through a combination of serendipity and skill, scientists have used NASA's Chandra X-ray Observatory to capture a rare glimpse of X-radiation from the early phases of a supernova, one of the most violent events in nature. Although more than a thousand supernovas have been observed by optical astronomers, the early X-ray glow from the explosions has been detected in less than a dozen cases. The Chandra observations were made under the direction of a team of scientists from the Massachusetts Institute of Technology (MIT) in Cambridge, led by Walter Lewin and his graduate student, Derek Fox. When combined with simultaneous observations by radio and optical telescopes, the X-ray observations tell about the thickness of the shell that was blown off, its density, its speed, and how much material was shed by the star before it exploded. Chandra observed an X-ray glow from SN1999em with the total power of 50,000 suns. Ten days later it observed the supernova for another nine hours, and found that the X rays had faded to half their previous intensity. The optical luminosity, which had the brightness of 200 million suns, had faded somewhat less. No radio emission was detected at any time. With this information, the MIT group and their colleagues are already piecing together a picture of the catastrophic explosion. Observations by optical astronomers showed that SN1999em was a Type II supernova produced by the collapse of the core of a star ten or more times as massive as the Sun. The intense heat generated in the collapse produces a cataclysmic rebound that sends high speed debris flying outward at speeds in excess of 20 million miles per hour. The debris crashes into matter shed by the former star before the explosion. This awesome collision generates shock waves that heat expanding debris to three million degrees. The X-ray glow from this hot gas was detected by Chandra and gives astrophysicists a better understanding of the dynamics of the explosion, as well as the

  12. The Restless Universe - Understanding X-Ray Astronomy in the Age of Chandra and Newton

    Science.gov (United States)

    Schlegel, Eric M.

    2002-10-01

    Carl Sagan once noted that there is only one generation that gets to see things for the first time. We are in the midst of such a time right now, standing on the threshold of discovery in the young and remarkable field of X-ray astronomy. In The Restless Universe , astronomer Eric Schlegel offers readers an informative survey of this cutting-edge science. Two major space observatories launched in the last few years--NASA's Chandra and the European Newton --are now orbiting the Earth, sending back a gold mine of data on the X-ray universe. Schlegel, who has worked on the Chandra project for seven years, describes the building and launching of this space-based X-ray observatory. But the book goes far beyond the story of Chandra . What Schlegel provides here is the background a nonscientist would need to grasp the present and follow the future of X-ray astronomy. He looks at the relatively brief history of the field, the hardware used to detect X-rays, the satellites--past, present, and future--that have been or will be flown to collect the data, the way astronomers interpret this data, and, perhaps most important, the insights we have already learned as well as speculations about what we may soon discover. And throughout the book, Schlegel conveys the excitement of looking at the universe from the perspective brought by these new observatories and the sharper view they deliver. Drawing on observations obtained from Chandra, Newton , and previous X-ray observatories, The Restless Universe gives a first look at an exciting field which significantly enriches our understanding of the universe.

  13. Chandra Image Gives First Look at Mars Emitted X-Rays

    Science.gov (United States)

    2001-01-01

    Giving scientists their first look, Chandra observed x-rays produced by fluorescent radiation from oxygen atoms of the Sun in the sparse upper atmosphere of Mars, about 120 kilometers (75 miles) above its surface. The x-ray power detected from the Martian atmosphere is very small, amounting to only 4 megawatts, comparable to the x-ray power of about ten thousand medical x-ray machines. At the time of the Chandra observation, a huge dust storm developed on Mars that covered about one hemisphere, later to cover the entire planet. This hemisphere rotated out of view over the 9-hour observation, but no change was observed in the x-ray intensity indicating that the dust storm did not affect the upper atmosphere. Scientists also observed a halo of x-rays extending out to 7,000 kilometers above the surface of Mars believed to be produced by collisions of ions racing away from the Sun (the solar wind).

  14. NASA's Chandra Finds That Saturn Reflects X-rays From Sun

    Science.gov (United States)

    2005-05-01

    When it comes to mysterious X-rays from Saturn, the ringed planet may act as a mirror, reflecting explosive activity from the sun, according to scientists using NASA's Chandra X-ray Observatory. The findings stem from the first observation of an X-ray flare reflected from Saturn's low-latitudes - the region that correlates to Earth's equator and tropics. Led by Dr. Anil Bhardwaj, a planetary scientist at NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., the study revealed that Saturn acts as a diffuse mirror for solar X-rays. Counting photons - particles that carry electromagnetic energy including X-rays - was critical to this discovery. For every few thousand X-ray photons Saturn receives from the sun, it reflects a single X-ray photon back. Previous studies revealed that Jupiter, with a diameter 11 times that of Earth, behaves in a similar fashion. Saturn is about 9.5 times as big as Earth, but is twice as far from Earth as Jupiter. "The bigger the planet and nearer to the Sun, the more solar photons it will intercept - resulting in more reflected X-rays," said Bhardwaj. "These results imply we could use giant planets like Jupiter and Saturn as remote-sensing tools. By reflecting solar activity back to us, they could help us monitor X-ray flaring on portions of the sun facing away from Earth's space satellites." Massive solar explosions called flares often accompany coronal mass ejections, which emit solar material and magnetic field. When directed toward the Earth, these ejections can wreak havoc on communication systems from cell phones to satellites. Even as the research appears to have solved one mystery - the source of Saturn's X-rays, it fueled longstanding questions about magnetic fields. Earth's magnetic field is the reason compasses work, since the field acts like a huge bar magnet, causing the magnetic north pole of a compass to point to the magnetic south pole of the Earth. In addition, migratory birds seem to sense the magnetic field

  15. X-ray Sources in the Hubble Deep Field Detected by Chandra

    CERN Document Server

    Hornschemeier, A E; Garmire, G P; Schneider, D P; Broos, P S; Townsley, L K; Bautz, M W; Burrows, D N; Chartas, G; Feigelson, E D; Griffiths, R; Lumb, D H; Nousek, J A; Sargent, W L W

    2000-01-01

    We present first results from an X-ray study of the Hubble Deep Field North (HDF-N) and its environs obtained using 166 ks of data collected by the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. This is the deepest X-ray observation ever reported, and in the HDF-N itself we detect six X-ray sources down to a 0.5--8 keV flux limit of 4E-16 erg cm^-2 s^-1. Comparing these sources with objects seen in multiwavelength HDF-N studies shows positional coincidences with the extremely red object NICMOS J123651.74 +621221.4, an active galactic nucleus (AGN), three elliptical galaxies, and one nearby spiral galaxy. The X-ray emission from the ellipticals is consistent with that expected from a hot interstellar medium, and the spiral galaxy emission may arise from a `super-Eddington' X-ray binary or ultraluminous supernova remnant. Four of the X-ray sources have been detected at radio wavelengths. We also place X-ray upper limits on AGN candidates found in the HDF-N, and we present the t...

  16. Chandra and XMM-Newton X-ray Observations of the Hyperactive T Tauri Star RY Tau

    CERN Document Server

    Skinner, Stephen L; Guedel, Manuel

    2016-01-01

    We present results of pointed X-ray observations of the accreting jet-driving T Tauri star RY Tau using Chandra and XMM-Newton. We obtained high-resolution grating spectra and excellent-quality CCD spectra and light curves with the objective of identifying the physical mechanisms underlying RY Tau's bright X-ray emission. Grating spectra reveal numerous emission lines spanning a broad range of temperature superimposed on a hot continuum. The X-ray emission measure distribution is dominated by very hot plasma at T_hot ~ 50 MK but higher temperatures were present during flares. A weaker cool plasma component is also present as revealed by low-temperature lines such as O VIII. X-ray light curves show complex variability consisting of short-duration (~hours) superhot flares accompanied by fluorescent Fe emission at 6.4 keV superimposed on a slowly-varying (~one day) component that may be tied to stellar rotation. The hot flaring component is undoubtedly of magnetic (e.g. coronal) origin. Soft and hard-band light ...

  17. Chandra measurements of non-thermal X-ray emission from massive, merging, radio-halo clusters

    CERN Document Server

    Million, E T

    2008-01-01

    We report the discovery of spatially-extended, non-thermal or hot, quasi-thermal emission components in Chandra X-ray spectra for five of a sample of seven massive, merging galaxy clusters with powerful radio halos: Abell 665, 2163, 2255, 2319, and 1E0657-56. The emission components can be fitted by power-law models with mean photon indices in the range 1.4 20 keV. A control sample of regular, dynamically relaxed clusters without radio halos but with comparable thermal temperatures and luminosities shows no evidence for similar components in their Chandra spectra. Detailed X-ray spectral mapping reveals the complex thermodynamic states of the radio halo clusters. We report the discovery of a clear, large-scale shock front in Abell 2219. Our deepest observations, of the Bullet Cluster 1E0657-56, demonstrate a spatial correlation between the strongest power law X-ray emission, highest thermal pressure, and brightest 1.34GHz radio halo emission in this cluster. The integrated flux and mean spectral index of the...

  18. Compton spectra of atoms at high x-ray intensity

    Science.gov (United States)

    Son, Sang-Kil; Geffert, Otfried; Santra, Robin

    2017-03-01

    Compton scattering is the nonresonant inelastic scattering of an x-ray photon by an electron and has been used to probe the electron momentum distribution in gas-phase and condensed-matter samples. In the low x-ray intensity regime, Compton scattering from atoms dominantly comes from bound electrons in neutral atoms, neglecting contributions from bound electrons in ions and free (ionized) electrons. In contrast, in the high x-ray intensity regime, the sample experiences severe ionization via x-ray multiphoton multiple ionization dynamics. Thus, it becomes necessary to take into account all the contributions to the Compton scattering signal when atoms are exposed to high-intensity x-ray pulses provided by x-ray free-electron lasers (XFELs). In this paper, we investigate the Compton spectra of atoms at high x-ray intensity, using an extension of the integrated x-ray atomic physics toolkit, xatom. As the x-ray fluence increases, there is a significant contribution from ionized electrons to the Compton spectra, which gives rise to strong deviations from the Compton spectra of neutral atoms. The present study provides not only understanding of the fundamental XFEL-matter interaction but also crucial information for single-particle imaging experiments, where Compton scattering is no longer negligible. , which features invited work from the best early-career researchers working within the scope of J. Phys. B. This project is part of the Journal of Physics series’ 50th anniversary celebrations in 2017. Sang-Kil Son was selected by the Editorial Board of J. Phys. B as an Emerging Leader.

  19. Chandra Studies of Unidentified X-ray Sources in the Galactic Bulge

    Science.gov (United States)

    Mori, Hideyuki

    2013-09-01

    We propose to study a complete X-ray sample in the luminosity range of > 10^34 erg s^-1 in the Galactic bulge, including 5 unidentified sources detected in the ROSAT All Sky Survey. Our goal is to obtain a clear picture about X-ray populations in the bulge, by utilizing the excellent Chandra position accuracy leading to unique optical identification together with the X-ray spectral properties. This is a new step toward understanding the formation history of the bulge. Furthermore, because the luminosity range we observe corresponds to a ``missing link'' region ever studied for a neutron star or blackhole X-ray binary, our results are also unique to test accretion disk theories at intermediate mass accretion rates.

  20. High-resolution x-ray photoemission spectra of silver

    DEFF Research Database (Denmark)

    Barrie, A.; Christensen, N. E.

    1976-01-01

    An electron spectrometer fitted with an x-ray monochromator for Al Kα1,2 radiation (1486.6 eV) has been used to record high-resolution x-ray photoelectron spectra for the 4d valence band as well as the 3d spin doublet in silver. The core-level spectrum has a line shape that can be described...

  1. X-ray absorption spectra of plasmas

    Institute of Scientific and Technical Information of China (English)

    PENG; Yonglun彭永伦; HAN; Xiaoying韩小英; LI; Jiaming李家明; DING; Yaonan丁耀南; YANG; Jiamin杨家敏; ZHENG; Zhijian郑志坚

    2002-01-01

    In this paper we present a theoretical method to calculate the absorption spectra of hot dense plasmas. Based on our fully relativistic treatment incorporated with the quantum defect theory to handle the huge number of transition arrays from many configurations with high principal quantum number, we can calculate the absorption spectra for any element or multi-element plasmas with little computational efforts. We calculate the absorption spectra of C10H1605 plasmas, which are in good agreement with the experimental spectra. We can then provide diagnostic analysis for plasmas in relevant inertial confinement fusion (lCF) experiments; namely not only to determine plasmas' temperatures and densities, but also to provide the population densities of various ionic stages. Our theoretical method verified by "benchmark experiments" will be a basic tool to provide "precise" opacity data for the ICF research.``

  2. Modeling of the EUV and X-Ray Emission Spectra Induced by the Solar Winds Ions in the Heliosphere

    Science.gov (United States)

    Kharchenko, Vasili

    2005-01-01

    We have carried out investigation of the EUV and X-ray emission spectra induced in interaction between the Solar Wind (SW) and interstellar neutral gas. The spectra of most important SW ions have been computed for the charge-exchange mechanism of X-ray emission using new accurate spectroscopic data from recent laboratory measurements and theoretical calculations. Total spectra have been constructed as a sum of spectra induced in the charge-exchange collisions by individual O(exp q+), C(exp q+), N(exp q+), Ne(exp q+), Mg (exp q+) and Fe(exp q+) ions. Calculations have been performed for X-ray emission from the heliospheric hydrogen and helium gas. X-ray maps of the heliosphere have been computed. The power density of X-ray sources in the heliospheric ecliptic plane is shown for the H gas and for the He gas. Distances from the Sun (0,0) are given in AU. The helium cone is clear seen in the X-ray map of the charge-exchange emission induced by the solar wind. X-ray emission spectra detected by the Chandra X-ray telescope from the "dark" side of Moon has been identified as a X-ray background emission induced by the solar wind from the geocorona. Spectra and intensities of this charge-exchange X-rays have been compared with the heliospheric component of the X-ray background. Observations and modeling of the SW spectra induced from the geocorona indicate a strong presence of emission lines of highly charged oxygen ions. Anisotropy in distribution of heliospheric X-rays has been predicted and calculated for the regions of the fast and slow solar winds.

  3. The 172 ks Chandra Exposure of the LALA Bootes Field: X-Ray Source Catalog

    Science.gov (United States)

    Wang, J. X.; Malhotra, S.; Rhoads, J. E.; Brown, M. J. I.; Dey, A.; Heckman, T. M.; Jannuzi, B. T.; Norman, C. A.; Tiede, G. P.; Tozzi, P.

    2004-01-01

    We present an analysis of a deep, 172 ks Chandra observation of the Large Area Lyman Alpha survey (LALA) Bootes field, obtained with the Advanced CCD Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This is one of the deepest Chandra images of the extragalactic sky; only the 2 Ms Chandra Deep Field North (CDF-N) and 1 Ms Chandra Deep Field South (CDF-S) are substantially deeper. In this paper we present the X-ray source catalog obtained from this image, along with an analysis of source counts and optical identifications. The X-ray image is composed of two individual observations obtained in 2002 and reaches 0.5-2.0 and 2.0-10.0 keV flux limits of 1.5×10-16 and 1.0×10-15 ergs cm-2 s-1, respectively, for point sources near the aim point. A total of 168 X-ray sources were detected: 160 in the 0.5-7.0 keV band, 132 in the 0.5-2.0 keV band, and 111 in the 2.0-7.0 keV band. The X-ray source counts were derived and compared with those from other Chandra deep surveys; the hard X-ray source density of the LALA Bootes field is 33% higher than that of CDF-S at the flux level of 2.0×10-15 ergs cm-2 s-1, confirming the field-to-field variances of the hard-band source counts reported by previous studies. The deep exposure resolves >~72% of the 2.0-10.0 keV X-ray background. Our primary optical data are R-band imaging from the NOAO Deep Wide-Field Survey (NDWFS), with a limiting magnitude of R=25.7 (Vega, 3 σ, and 4" diameter aperture). We have found optical counterparts for 152 of the 168 Chandra sources (90%); 144 of these are detected in the R-band image, and eight have optical counterparts in other bands (either BW, V, I, or z'). Among the R-band nondetected sources, not more than 11 of them can possibly be at z>5, based on the hardness ratios of their X-ray emission and nondetections in bluer bands (BW, V). The majority (~76%) of the X-ray sources are found to have log(fX/fR) within 0.0+/-1 these are believed to be AGNs. Most of the X-ray

  4. An X-ray Tour of Massive Star-forming Regions with Chandra

    CERN Document Server

    Townsley, L K

    2006-01-01

    The Chandra X-ray Observatory is providing fascinating new views of massive star-forming regions, revealing all stages in the life cycles of massive stars and their effects on their surroundings. I present a Chandra tour of some of the most famous of these regions: M17, NGC 3576, W3, Tr14 in Carina, and 30 Doradus. Chandra highlights the physical processes that characterize the lives of these clusters, from the ionizing sources of ultracompact HII regions (W3) to superbubbles so large that they shape our views of galaxies (30 Dor). X-ray observations usually reveal hundreds of pre-main sequence (lower-mass) stars accompanying the OB stars that power these great HII region complexes, although in one case (W3 North) this population is mysteriously absent. The most massive stars themselves are often anomalously hard X-ray emitters; this may be a new indicator of close binarity. These complexes are sometimes suffused by soft diffuse X-rays (M17, NGC 3576), signatures of multi-million-degree plasmas created by fas...

  5. X-Rays Beware: The Deepest Chandra Catalogue of Point Sources in M31

    CERN Document Server

    Vulic, N; Barmby, P

    2016-01-01

    This study represents the most sensitive Chandra X-ray point source catalogue of M31. Using 133 publicly available Chandra ACIS-I/S observations totalling ~1 Ms, we detected 795 X-ray sources in the bulge, northeast, and southwest fields of M31, covering an area of approximately 0.6 deg$^{2}$, to a limiting unabsorbed 0.5-8.0 keV luminosity of $10^{34}$ erg/s. In the inner bulge, where exposure is approximately constant, X-ray fluxes represent average values because they were determined from many observations over a long period of time. Similarly, our catalogue is more complete in the bulge fields since monitoring allowed more transient sources to be detected. The catalogue was cross-correlated with a previous XMM-Newton catalogue of M31's $D_{25}$ isophote consisting of 1948 X-ray sources, with only 979 within the field of view of our survey. We found 387 (49%) of our Chandra sources (352 or 44% unique sources) matched to within 5 arcsec of 352 XMM-Newton sources. Combining this result with matching done to ...

  6. The STS-93 crew takes part in payload familiarization of the Chandra X-ray Observatory

    Science.gov (United States)

    1999-01-01

    A TRW technician joins STS-93 Commander Eileen Collins (center) and Pilot Jeffrey S. Ashby (right) as they observe the Chandra X- ray Observatory on its work stand inside the Vertical Processing Facility. Other members of the STS-93 crew who are at KSC for payload familiarization are Mission Specialists Catherine G. Coleman and Michel Tognini of France, who represents the Centre National d'Etudes Spatiales (CNES). Collins is the first woman to serve as a shuttle mission commander. She was the first woman pilot of a Space Shuttle, on mission STS-63, and also served as pilot on mission STS-84. The fifth member of the crew is Mission Specialist Steven A. Hawley. Chandra is scheduled for launch July 9 aboard Space Shuttle Columbia, on mission STS-93 . Formerly called the Advanced X-ray Astrophysics Facility, Chandra comprises three major elements: the spacecraft, the science instrument module (SIM), and the world's most powerful X-ray telescope. Chandra will allow scientists from around the world to see previously invisible black holes and high-temperature gas clouds, giving the observatory the potential to rewrite the books on the structure and evolution of our universe.

  7. X-ray observations of dust obscured galaxies in the Chandra Deep Field South

    CERN Document Server

    Corral, A; Comastri, A; Ranalli, P; Akylas, A; Salvato, M; Lanzuisi, G; Vignali, C; Koutoulidis, L

    2016-01-01

    We present the properties of X-ray detected dust obscured galaxies (DOGs) in the Chandra Deep Field South. In recent years, it has been proposed that a significant percentage of the elusive Compton-thick (CT) active galactic nuclei (AGN) could be hidden among DOGs. In a previous work, we presented the properties of X-ray detected DOGs by making use of the deepest X-ray observations available at that time, the 2Ms observations of the Chandra deep fields. In that work, we only found a moderate percentage ($<$ 50%) of CT AGN among the DOGs sample, but we were limited by poor photon statistics. In this paper, we use not only a deeper 6 Ms Chandra survey of the Chandra Deep Field South (CDF-S), but combine these data with the 3 Ms XMM-Newton survey of the CDF-S. We also take advantage of the great coverage of the CDF-S region from the UV to the far-IR to fit the spectral energy distributions (SEDs) of our sources. Out of the 14 AGN composing our sample, 9 are highly absorbed (but only 3 could be CT AGN), wherea...

  8. CHANDRA DETECTION OF X-RAY EMISSION FROM ULTRACOMPACT DWARF GALAXIES AND EXTENDED STAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Meicun; Li, Zhiyuan, E-mail: lizy@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210046 (China)

    2016-03-10

    We have conducted a systematic study of X-ray emission from ultracompact dwarf (UCD) galaxies and extended star clusters (ESCs), based on archival Chandra observations. Among a sample of 511 UCDs and ESCs complied from the literature, 17 X-ray counterparts with 0.5–8 keV luminosities above ∼5 × 10{sup 36} erg s{sup −1} are identified, which are distributed in eight early-type host galaxies. To facilitate comparison, we also identify X-ray counterparts of 360 globular clusters (GCs) distributed in four of the eight galaxies. The X-ray properties of the UCDs and ESCs are found to be broadly similar to those of the GCs. The incidence rate of X-ray-detected UCDs and ESCs, 3.3% ± 0.8%, while lower than that of the X-ray-detected GCs (7.0% ± 0.4%), is substantially higher than expected from the field populations of external galaxies. A stacking analysis of the individually undetected UCDs/ESCs further reveals significant X-ray signals, which corresponds to an equivalent 0.5–8 keV luminosity of ∼4 × 10{sup 35} erg s{sup −1} per source. Taken together, these provide strong evidence that the X-ray emission from UCDs and ESCs is dominated by low-mass X-ray binaries having formed from stellar dynamical interactions, consistent with the stellar populations in these dense systems being predominantly old. For the most massive UCDs, there remains the possibility that a putative central massive black hole gives rise to the observed X-ray emission.

  9. The Chandra planetary nebula survey (CHANPLANS). II. X-ray emission from compact planetary nebulae

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, M.; Kastner, J. H. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Montez, R. Jr. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA (United States); Frew, D. J.; De Marco, O.; Parker, Q. A. [Department of Physics and Astronomy and Macquarie Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney, NSW 2109 (Australia); Jones, D. [Departamento de Física, Universidad de Atacama, Copayapu 485, Copiapó (Chile); Miszalski, B. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Sahai, R. [Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States); Blackman, E.; Frank, A. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Chu, Y.-H. [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Guerrero, M. A. [Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, E-18008 (Spain); Lopez, J. A. [Instituto de Astronomía, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Apdo. Postal 22860, Ensenada, B. C. (Mexico); Zijlstra, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Bujarrabal, V. [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Corradi, R. L. M. [Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain); Nordhaus, J. [NSF Astronomy and Astrophysics Fellow, Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); and others

    2014-10-20

    We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (CHANPLANS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ∼1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. CHANPLANS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. CHANPLANS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R {sub neb} ≲ 0.4 pc), young PNe that lie within ∼1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall CHANPLANS diffuse X-ray detection rate to ∼27% and the point source detection rate to ∼36%. It has become clearer that diffuse X-ray emission is associated with young (≲ 5 × 10{sup 3} yr), and likewise compact (R {sub neb} ≲ 0.15 pc), PNe with closed structures and high central electron densities (n{sub e} ≳ 1000 cm{sup –3}), and is rarely associated with PNe that show H{sub 2} emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, two of the five new diffuse X-ray detections (NGC 1501 and NGC 6369) host [WR]-type central stars, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.

  10. The Chandra ACIS Timing Survey Project: glimpsing a sample of faint X-ray pulsators

    Science.gov (United States)

    Israel, G. L.; Esposito, P.; Rodríguez Castillo, G. A.; Sidoli, L.

    2016-11-01

    We report on the discovery of 41 new pulsating sources in the data of the Chandra Advanced CCD Imaging Spectrometer, which is sensitive to X-ray photons in the 0.3-10 keV band. The archival data of the first 15 yr of Chandra observations were retrieved and analysed by means of fast Fourier transforms, employing a peak-detection algorithm able to screen candidate signals in an automatic fashion. We carried out the search for new X-ray pulsators in light curves with more than 50 photons, for a total of about 190 000 light curves out of about 430 000 extracted. With these numbers, the ChAndra Timing Survey at Brera And Roma astronomical observatories (CATS @ BAR) - as we called the project - represents the largest ever systematic search for coherent signals in the classic X-ray band. More than 50 per cent of the signals were confirmed by further Chandra (for those sources with two or more pointings), XMM-Newton or ROSAT data. The period distribution of the new X-ray pulsators above ˜2000 s resembles that of cataclysmic variables, while there is a paucity of sources with shorter period and low fluxes. Since there is not an obvious bias against these detections, a possible interpretation is in terms of a magnetic gating mechanism in accreting neutron stars. Finally, we note that CATS @ BAR is a living project and the detection algorithm will continue to be routinely applied to the new Chandra data as they become public. Based on the results obtained so far, we expect to discover about three new pulsators every year.

  11. Modeling Contamination Migration on the Chandra X-ray Observatory - II

    Science.gov (United States)

    O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexey A.; Tennant, Allyn F.

    2013-01-01

    During its first 14 years of operation, the cold (about -60C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon temperature data, and a refined model of the molecular transport.

  12. Chandra and XMM Monitoring of the Black Hole X-ray Binary IC 10 X-1

    OpenAIRE

    Laycock, Silas G. T.; Cappallo, Rigel C.; Moro, Matthew J.

    2014-01-01

    The massive black hole + Wolf-Rayet binary IC10 X-1 was observed in a series of 10 Chandra and 2 XMM-Newton observations spanning 2003-2012, showing consistent variability around 7 x10^37 erg/s, with a spectral hardening event in 2009. We phase-connected the entire light-curve by folding the photon arrival times on a series of trial periods spanning the known orbital period and its uncertainty, refining the X-ray period to P = 1.45175(1)d. The duration of minimum-flux in the X-ray eclipse is ...

  13. Probing Large-scale Coherence between Spitzer IR and Chandra X-Ray Source-subtracted Cosmic Backgrounds

    Science.gov (United States)

    Cappelluti, N.; Arendt, R.; Kashlinsky, A.; Li, Y.; Hasinger, G.; Helgason, K.; Urry, M.; Natarajan, P.; Finoguenov, A.

    2017-09-01

    We present new measurements of the large-scale clustering component of the cross-power spectra of the source-subtracted Spitzer-IRAC cosmic infrared background and Chandra-ACIS cosmic X-ray background surface brightness fluctuations Our investigation uses data from the Chandra Deep Field South, Hubble Deep Field North, Extended Groth Strip/AEGIS field, and UDS/SXDF surveys, comprising 1160 Spitzer hours and ∼12 Ms of Chandra data collected over a total area of 0.3 deg2. We report the first (>5σ) detection of a cross-power signal on large angular scales >20″ between [0.5–2] keV and the 3.6 and 4.5 μm bands, at ∼5σ and 6.3σ significance, respectively. The correlation with harder X-ray bands is marginally significant. Comparing the new observations with existing models for the contribution of the known unmasked source population at z < 7, we find an excess of about an order of magnitude at 5σ confidence. We discuss possible interpretations for the origin of this excess in terms of the contribution from accreting early black holes (BHs), including both direct collapse BHs and primordial BHs, as well as from scattering in the interstellar medium and intra-halo light.

  14. Soft X-ray Spectroscopy of NGC 1068 with XMM-Newton RGS and Chandra LETGS

    CERN Document Server

    Kinkhabwala, A; Behar, E; Kahn, S M; Paerels, F B S; Brinkman, A C; Kaastra, J S; Van der Meer, R L J; Gu, M F; Liedahl, D A

    2002-01-01

    We present high-resolution soft-X-ray spectra of the prototypical Seyfert 2 galaxy, NGC 1068, taken with XMM-Newton RGS and Chandra LETGS. Its rich emission-line spectrum is dominated by recombination in a warm plasma (bright, narrow radiative recombination continua provide the ``smoking gun''), which is photoionized by the inferred nuclear power-law continuum. Radiative decay following photoexcitation of resonant transitions is also significant. A self-consistent model of an irradiated cone of gas is capable of reproducing the hydrogenic/heliumlike ionic line series in detail. The radial ionic column densities we infer are consistent with absorption measurements (the ``warm absorber'') in Seyfert 1 galaxies. This strongly suggests that the emission spectrum we observe from NGC 1068 emanates from its ``warm absorber.'' The observed extent of the ionization-cone/''warm absorber'' in NGC 1068 of 500 pc implies that a large fraction of the gas associated with generic ``warm absorbers'' may typically exist on the...

  15. First Images From Chandra X-Ray Observatory to be Released

    Science.gov (United States)

    1999-08-01

    The first images from the world's most powerful X-ray telescope, NASA's Chandra X-ray Observatory, will be unveiled at a media briefing at 1 p.m. EDT, Thursday, Aug. 26. The briefing will be held in the James E. Webb Auditorium at NASA Headquarters, 300 E St. SW, Washington, DC. The images include the spectacular remnants of a supernova and other astronomical objects. Panelists will be: - Dr. Edward Weiler, Associate Administrator for Space Science, NASA Headquarters, Washington, DC; - Dr. Harvey Tananbaum, Director of the Smithsonian Astrophysical Observatory's Chandra X-ray Center, Cambridge, MA; - Dr. Martin Weisskopf, NASA's Chandra Project Scientist, NASA's Marshall Space Flight Center, Huntsville, AL; and - Dr. Robert Kirshner, astrophysicist, Harvard University, Cambridge, MA. The event will be carried live on NASA Television with question-and-answer capability for reporters covering the briefing from participating NASA centers and from the Chandra Operations Control Center in Cambridge. NASA Television is available on transponder 9C, satellite GE-2 at 85 degrees West longitude, vertical polarization, frequency 3880 MHz, audio of 6.8 MHz. Chandra has been undergoing activation and checkout since it was placed into orbit during Space Shuttle mission STS-93 in July. Chandra will examine exploding stars, black holes, colliding galaxies and other high-energy cosmic phenomena to help scientists gain a better understanding of the structure and evolution of the universe. Chandra images and additional information will be available following the briefing on the Internet at: http://chandra.nasa.gov and http://chandra.harvard.edu NASA press releases and other information are available automatically by sending an Internet electronic mail message to domo@hq.nasa.gov. In the body of the message (not the subject line) users should type the words "subscribe press-release" (no quotes). The system will reply with a confirmation via E-mail of each subscription. A second

  16. Shelter from the Storm: Protecting the Chandra X-ray Observatory from Radiation

    Science.gov (United States)

    Cameron, Robert A.; Morris, David C.; Virani, Shanil N.; Wolk, Scott J.; Blackwell, William C.; Minow, Joseph I.; O'dell, Stephen L.

    NASA's Chandra X-ray Observatory was launched in July 1999, and the first images were recorded by the ACIS x-ray detector in August 1999. Shortly after first light, degradation of the energy resolution and charge transfer efficiency in the ACIS CCD detectors was observed, and this was quickly attributed to cumulative particle radiation damage in the CCD's, in particular from 100 keV to 200 keV protons. Since the onset of this radiation damage to ACIS, several improvements have been made to autonomous Chandra operation and ground-based operations and mission planning, to limit the effects of radiation while preserving optimum observing efficiency for the Observatory. These changes include implementing an automatic science instrument radiation protection system on Chandra, implementing a real-time radiation monitoring and alert system by the Science Operations Team, and improving the radiation prediction models used in mission planning for the Observatory. These satellite- and ground-based systems provide protection for Chandra from passages through the Earth's trapped radiation belts and outer magnetosphere and from flares and coronal mass ejections from the Sun. We describe the design and performance of the automatic on-board radiation protection system on Chandra, and the ground-based software systems and data products for real-time radiation monitoring. We also describe the development and characterize the performance of the Chandra Radiation Model (CRM), which provides predictions of the solar wind and magnetospheric proton fluxes along Chandra's orbit, indexed by the geomagnetic activity index, Kp. We compare the observed and predicted damage rates to ACIS based on net mission proton fluence, and outline planned enhancements to the CRM.

  17. A Deep Chandra X-ray Limit on the Putative IMBH in Omega Centauri

    CERN Document Server

    Haggard, Daryl; Heinke, Craig O; van der Marel, Roeland; Cohn, Haldan N; Lugger, Phyllis M; Anderson, Jay

    2013-01-01

    We report a sensitive X-ray search for the proposed intermediate mass black hole (IMBH) in the massive Galactic cluster, Omega Centauri (NGC 5139). Combining Chandra X-ray Observatory data from Cycles 1 and 13, we obtain a deep (~291 ks) exposure of the central regions of the cluster. We find no evidence for an X-ray point source near any of the cluster's proposed dynamical centers, and place an upper limit on the X-ray flux from a central source of f_X(0.5-7.0 keV) <= 5.0x10^-16 erg cm^-2 s^-1, after correcting for absorption. This corresponds to an unabsorbed X-ray luminosity of L_X(0.5-7.0 keV) <= 1.6x10^30 erg s^-1, for a cluster distance of 5.2 kpc, Galactic column density N_H = 1.2x10^21 cm^-2, and powerlaw spectrum with Gamma = 2.3. If a ~10^4 M_sun IMBH resides in the cluster's core, as suggested by some stellar dynamical studies, its Eddington luminosity would be L_Edd ~10^42 erg s^-1. The new X-ray limit would then establish an Eddington ratio of L_X/L_Edd <~ 10^-12, a factor of ~10 lower t...

  18. Groups of Galaxies in AEGIS: The 200 ksec Chandra Extended X-ray Source catalogue

    CERN Document Server

    Jeltema, Tesla E; Laird, Elise S; Willmer, Christopher N A; Coil, Alison L; Cooper, Michael C; Davis, Marc; Nandra, Kirpal; Newman, Jeffrey A

    2009-01-01

    We present the discovery of seven X-ray emitting groups of galaxies selected as extended X-ray sources in the 200 ksec Chandra coverage of the All-wavelength Extended Groth Strip International Survey (AEGIS). In addition, we report on AGN activity associated to these systems. Using the DEEP2 Galaxy Redshift Survey coverage, we identify optical counterparts and determine velocity dispersions. In particular, we find three massive high-redshift groups at z>0.7, one of which is at z=1.13, the first X-ray detections of spectroscopically selected DEEP2 groups. We also present a first look at the the L_X-T, L_X-sigma, and sigma-T scaling relations for high-redshift massive groups. We find that the properties of these X-ray selected systems agree well with the scaling relations of similar systems at low redshift, although there are X-ray undetected groups in the DEEP2 catalogue with similar velocity dispersions. The other three X-ray groups with identified redshifts are associated with lower mass groups at z~0.07 and...

  19. The Chandra view of NGC1800 and the X-ray scaling properties of dwarf starbursts

    CERN Document Server

    Rasmussen, J; Ponman, T J

    2004-01-01

    The superb spatial resolution of Chandra is utilized to study the X-ray morphology of the dwarf starburst galaxy NGC1800 embedded in a small group of galaxies. Diffuse galactic emission is detected, extending several kpc above the galactic plane, with an overall morphology similar to the galactic winds seen in nearby X-ray bright starburst galaxies. This makes NGC1800 the most distant dwarf starburst with a clear detection of diffuse X-ray emission. The diffuse X-ray luminosity of 1.3+/-0.3 *10^38 erg/s accounts for at least 60 per cent of the total soft X-ray output of the galaxy. A hot gas temperature of kT=0.25 keV and metallicity Z~0.05Z_Sun are derived, the latter in consistency with results from optical spectroscopy of the interstellar medium. Our failure to detect any hot gas associated with the embedding galaxy group translates into an upper limit to the group X-ray luminosity of L_X<10^41 erg/s. There is no convincing evidence that the outflowing wind of NGC1800 is currently interacting with any i...

  20. Deep X-ray and UV Surveys of Galaxies with Chandra, XMM-Newton, and GALEX

    Science.gov (United States)

    Hornschemeier, Ann

    2006-01-01

    Only with the deepest Chandra surveys has X-ray emission from normal and star forming galaxies (as opposed to AGN, which dominate the X-ray sky) been accessible at cosmologically interesting distances. The X-ray emission from accreting binaries provide a critical glimpse into the binary phase of stellar evolution and studies of the hot gas reservoir constrain past star formation. UV studies provide important, sensitive diagnostics of the young star forming populations and provide the most mature means for studying galaxies at 2 luminosity function of galaxies and important constraints on star formation scaling relations such as the X-ray-Star Formation Rate correlation and the X-ray/Stellar Mass correlation. We will discuss what we learn from these deep observations of Coma, including the recently established suppression of the X-ray emission from galaxies in the Coma outskirts that is likely associated with lower levels of past star formation and/or the results of tidal gas stripping.

  1. High-Resolution X-ray Spectroscopy of SNR 1987A: Chandra LETG and HETG Observations in 2007

    CERN Document Server

    Zhekov, Svetozar A; Dewey, Daniel; Canizares, Claude R; Borkowski, Kazimierz J; Burrows, David N; Park, Sangwook

    2008-01-01

    We present an extended analysis of the deep Chandra LETG and HETG observations of the supernova remnant 1987A (SNR 1987A) carried out in 2007. The global fits to the grating spectra show that the temperature of the X-ray emitting plasma in the slower shocks in this system has remained stable for the last three years, while that in the faster shocks has decreased. This temperature evolution is confirmed by the first light curves of strong X-ray emission lines and their ratios. On the other hand, bulk gas velocities inferred from the X-ray line profiles are too low to account for the post-shock plasma temperatures inferred from spectral fits. This suggests that the X-ray emission comes from gas that has been shocked twice, first by the blast wave and again by shocks reflected from the inner ring of SNR 1987A. A new model that takes these considerations into account gives support to this physical picture.

  2. Finding Rare AGN: X-ray Number Counts of Chandra Sources in Stripe 82

    CERN Document Server

    LaMassa, Stephanie M; Glikman, Eilat; Cappelluti, Nico; Civano, Francesca; Comastri, Andrea; Treister, Ezequiel; Arifin,; Boehringer, Hans; Cardamone, Carie; Chon, Gayoung; Kephart, Miranda; Murray, Stephen S; Richards, Gordon; Ross, Nic; Rozner, Joshua S; Schawinski, Kevin

    2012-01-01

    We present the first results of a wide area X-ray survey within the Sloan Digital Sky Survey (SDSS) Stripe 82, a 300 deg$^2$ region of the sky with a substantial investment in multi-wavelength coverage. We analyzed archival {\\it Chandra} observations that cover 7.5 deg$^2$ within Stripe 82 ("Stripe 82 ACX"), reaching 4.5$\\sigma$ flux limits of 7.9$\\times10^{-16}$, 3.4$\\times10^{-15}$ and 1.8$\\times10^{-15}$ erg s$^{-1}$ cm$^{-2}$ in the soft (0.5-2 keV), hard (2-7 keV) and full (0.5-7 keV) bands, to find 774, 239 and 1118 X-ray sources, respectively. Three hundred twenty-one sources are detected only in the full band and 9 sources are detected solely in the soft band. Utilizing data products from the {\\it Chandra} Source Catalog, we construct independent Log$N$-Log$S$ relationships, detailing the number density of X-ray sources as a function of flux, which show general agreement with previous {\\it Chandra} surveys. We compare the luminosity distribution of Stripe 82 ACX with the smaller, deeper CDF-S + E-CDFS...

  3. The Chandra Cygnus OB2 Legacy Survey: Design and X-ray Point Source Catalog

    CERN Document Server

    Wright, Nicholas J; Guarcello, Mario G; Aldcroft, Tom L; Kashyap, Vinay L; Damiani, Francesco; DePasquale, Joe; Fruscione, Antonella

    2014-01-01

    The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated 65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer onboard the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg^2 of the Cyg OB2 association with an effective exposure of 120ks and an outer 0.35 deg^2 area with an exposure of 60ks. Here we describe the survey design and observations, the data reduction and source detection, and present a catalog of 8,000 X-ray point sources. The survey design employs a grid of 36 heavily (~50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg^2. The full X-ray catalog is described here and is made available online.

  4. Chandra Smells a RRAT: X-ray Detection of a Rotating Radio Transient

    CERN Document Server

    Gaensler, B M; Reynolds, S; Borkowski, K; Rea, N; Possenti, A; Israel, G; Burgay, M; Camilo, F; Chatterjee, S; Krämer, M; Lyne, A; Stairs, I

    2006-01-01

    "Rotating RAdio Transients" (RRATs) are a newly discovered astronomical phenomenon, characterised by occasional brief radio bursts, with average intervals between bursts ranging from minutes to hours. The burst spacings allow identification of periodicities, which fall in the range 0.4 to 7 seconds. The RRATs thus seem to be rotating neutron stars, albeit with properties very different from the rest of the population. We here present the serendipitous detection with the Chandra X-ray Observatory of a bright point-like X-ray source coincident with one of the RRATs. We discuss the temporal and spectral properties of this X-ray emission, consider counterparts in other wavebands, and interpret these results in the context of possible explanations for the RRAT population.

  5. The outer regions of galaxy clusters: Chandra constraints on the X-ray surface brightness

    CERN Document Server

    Ettori, S

    2008-01-01

    (Abridged version) We study the properties of the X-ray surface brightness profiles in a sample of galaxy clusters that are observed with Chandra and have emission detectable with a signal-to-noise ratio larger than 2 at a radius beyond R500 ~ 0.7 R200. Our study aims at measuring the slopes of the X-ray surface brightness and of the gas density profiles in the outskirts of massive clusters. These constraints are then compared to similar results obtained from observations and numerical simulations of the temperature and dark matter density profiles with the intention to present a consistent picture of the outer regions of galaxy clusters. We extract the surface brightness profiles S_b(r) from X-ray exposures obtained with Chandra of 52 X-ray luminous galaxy clusters at z>0.3. We estimate R200 both using a beta-model to reproduce the surface brightness profile and scaling relations from the literature, showing that the two methods converge to comparable values. We evaluate then the radius, R_S2N, at which the ...

  6. The Chandra COSMOS Survey: III. Optical and Infrared Identification of X-ray Point Sources

    CERN Document Server

    Civano, F; Brusa, M; Comastri, A; Salvato, M; Zamorani, G; Aldcroft, T; Bongiorno, A; Capak, P; Cappelluti, N; Cisternas, M; Fiore, F; Fruscione, A; Hao, H; Kartaltepe, J; Koekemoer, A; Gilli, R; Impey, C D; Lanzuisi, G; Lusso, E; Mainieri, V; Miyaji, T; Lilly, S; Masters, D; Puccetti, S; Schawinski, K; Scoville, N Z; Silverman, J; Trump, J; Urry, M; Vignali, C; Wright, N J

    2012-01-01

    The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg^2 of the COSMOS field down to limiting depths of 1.9 10^-16 erg cm^-2 s-1 in the 0.5-2 keV band, 7.3 10^-16 erg cm^-2 s^-1 in the 2-10 keV band, and 5.7 10^-16 erg cm^-2 s-1 in the 0.5-10 keV band. In this paper we report the i, K and 3.6micron identifications of the 1761 X-ray point sources. We use the likelihood ratio technique to derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only 2 sources are truly empty fields. Making use of the large number of X-ray sources, we update the "classic locus" of AGN and define a new locus containing 90% of the AGN in the survey with full band luminosi...

  7. High-Resolution Chandra X-ray Imaging and Spectroscopy of the Sigma Orionis Cluster

    CERN Document Server

    Skinner, S L; Cohen, D H; Gagné, M; Owocki, S P; Townsend, R D

    2008-01-01

    We present results of a 90 ksec Chandra X-ray observation of the young sigma Orionis cluster (age ~3 Myr) obtained with the High Energy Transmission Grating Spectrometer. We use the high resolution grating spectrum and moderate resolution CCD spectrum of the massive central star sigma Ori AB (O9.5V + B0.5V) to test wind shock theories of X-ray emission and also analyze the high spatial resolution zero-order ACIS-S image of the central cluster region. Chandra detected 42 X-ray sources on the primary CCD (ACIS-S3). All but five have near-IR or optical counterparts and about one-fourth are variable. Notable high-mass stellar detections are sigma Ori AB, the magnetic B star sigma Ori E, and the B5V binary HD 37525. Most of the other detections have properties consistent with lower mass K or M-type stars. We present the first X-ray spectrum of the unusual infrared source IRS1 located 3.3 arc-sec north of sigma Ori AB, which is likely an embedded T Tauri star whose disk/envelope is being photoevaporated by sigma Or...

  8. Managing radiation degradation of CCDs on the Chandra X-ray Observatory II

    Science.gov (United States)

    O'Dell, Stephen L.; Aldcroft, Thomas L.; Bissell, Bradley A.; Blackwell, William C.; Cameron, Robert A.; Chappell, Jon II.; DePasquale, Joseph M.; Gage, Kenneth R.; Grant, Catherine E.; Harbison, Christine F.

    2005-01-01

    The CCDs on the Chandra X-ray Observatory are vulnerable to radiation damage from low-energy protons scattered off the telescope's mirrors onto the focal plane. Following unexpected damage incurred early in the mission, the Chandra Team developed, implemented, and maintains a radiation-protection program. This program - involving scheduled radiation safing during radiation-belt passes, intervention based upon real-time space-weather conditions and radiation-environment modeling, and on-board radiation monitoring with autonomous radiation safing - has successfully managed the radiation damage to the CCDs. Since implementing the program, the charge-transfer inefficiency (CTI) has increased at an average annual rate of only 2.9x10^-6 (2.3%) for the front- illuminated CCDs and 0.95x10^-6 (6.5%) for the back-illuminated CCDs. This paper describes the current status of Chandra radiation-management program.

  9. Analyzing the Spectra of Accreting X-Ray Pulsars

    Science.gov (United States)

    Wolff, Michael

    This proposal seeks funding for the analysis of accretion-powered X-ray pulsar spectra from NASA/ HEASARC archived X-ray data. Spectral modeling of accreting X-ray pulsars can tell us a great deal about the physical conditions in and near high mass X-ray binary systems. Such systems have accretion flows where plasma is initially channeled from an accretion disk by the strong neutron star magnetic field, eventually falling onto the magnetic polar cap of the neutron star compact object. Many of these accreting X-ray pulsars have X-ray spectra that consist of broad power-law continua with superposed cyclotron resonant scattering features indicating magnetic field strengths above 10^12 G. The energies of these cyclotron line features have recently been shown to vary with X-ray luminosity in a number of sources such as Her X-1 and V 0332+53, a phenomenon not well understood. Another recent development is the relatively new analytic model for the spectral continuum formation in accretion-powered pulsar systems developed by Becker & Wolff. In their formalism the accretion flows are assumed to go through radiation- dominated radiative shocks and settle onto the neutron star surface. The radiation field consists of strongly Comptonized bremsstrahlung emission from the entire plasma, Comptonized cyclotron emission from the de-excitations of Landau-excited electrons in the neutron star magnetic field, and Comptonized black-body emission from a thermal mound near the neutron star surface. We seek to develop the data analysis tools to apply this model framework to the X-ray data from a wide set of sources to make progress characterizing the basic accretion properties (e.g., magnetic field strength, plasma temperatures, polar cap size, accretion rate per unit area, dominance of bulk vs. thermal Comptonization) as well as understanding the variations of the cyclotron line energies with X-ray luminosity. The three major goals of our proposed work are as follows: In the first year

  10. Photoionized Lines in the X-ray Spectra of SMC X-1

    CERN Document Server

    Vrtilek, S D; Boroson, B S; McCray, R

    2005-01-01

    We present a detailed spectral analysis of Chandra/ACIS-S CC mode observations of the massive X-ray binary system SMC X-1. The system was observed during both the high and low X-ray states of the roughly 60-day superorbital period. The continuum spectra during both states are well represented by a power law with photon index $\\alpha$=0.9 and a blackbody of kT = 0.15keV. The high state spectra are dominated by the continuum and independent of orbital phase whereas the low state spectra show a strong orbital dependence as well as line emission from O, Ne, Mg, Fe, and Si. This is consistent with the states attributed to disk precession: during the high state X-ray emission is dominated by the compact source which is abrubtly eclipsed and during the low state the compact object is hidden by the disk and a larger, less luminous scattering region is responsible for the X-ray emission. A prominent Ne IX feature places a stringent limit (Log $\\xi$ = 2.0-2.5) on the ionization parameter which constrains the wind dynam...

  11. Chandra Reveals The X-Ray Glint In The Cat's Eye

    Science.gov (United States)

    2001-01-01

    SAN DIEGO -- Scientists have discovered a glowing bubble of hot gas and an unexpected X-ray bright central star within the planetary nebula known as the Cat's Eye using NASA's Chandra X-ray Observatory. The new results, presented today at the American Astronomical Society meeting, provide insight into the ways that stars like our Sun end their lives. Scientists believe they are witnessing the expulsion of material from a star that is in the last stages of its existence as a normal star. Material shed by the star is flying away at a speed of about 4 million miles per hour, and the star itself is expected to collapse to become a white dwarf star in a few million years. The X-ray data from the Cat's Eye Nebula, also known as NGC 6543, clearly show a bright central star surrounded by a cloud of multimillion-degree gas. By comparing the Chandra data with those from the Hubble Space Telescope, researchers are able to see where the hotter, X-ray emitting gas appears in relation to the cooler material seen in optical wavelengths by Hubble. "Despite the complex optical appearance of the nebula, the X-ray emission illustrates unambiguously that the hot gas in the central bubble is driving the expansion of the optical nebula," said You-Hua Chu of the University of Illinois and lead author of the paper submitted to the Astrophysical Journal. "The Chandra data will help us to better understand how stars similar to our Sun produce planetary nebulas and evolve into white dwarfs as they grow old." With Chandra, astronomers measured the temperature of the central bubble of X-ray emitting material, and this presents a new puzzle. Though still incredibly energetic and hot enough to emit X-rays, this hot gas is cooler than scientists would have expected from the stellar wind that has come to stagnation from the initial high speed of 4 million miles per hour. At first, the researchers thought that the cooler, outer shell might have mixed with the energetic material closer to the

  12. The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra

    CERN Document Server

    Neilsen, J; Nowak, M A; Dexter, J; Witzel, G; Barrière, N; Li, Y; Baganoff, F K; Degenaar, N; Fragile, P C; Gammie, C; Goldwurm, A; Grosso, N; Haggard, D

    2014-01-01

    We present a statistical analysis of the X-ray flux distribution of Sgr A* from the Chandra X-ray Observatory's 3 Ms Sgr A* X-ray Visionary Project (XVP) in 2012. Our analysis indicates that the observed X-ray flux distribution can be decomposed into a steady quiescent component, represented by a Poisson process with rate $Q=(5.24\\pm0.08)\\times10^{-3}$ cts s$^{-1},$ and a variable component, represented by a power law process ($dN/dF\\propto F^{-\\xi},$ $\\xi=1.92_{-0.02}^{+0.03}$). This slope matches our recently-reported distribution of flare luminosities. The variability may also be described by a log-normal process with a median unabsorbed 2-8 keV flux of $1.8^{+0.9}_{-0.6}\\times10^{-14}$ erg s$^{-1}$ cm$^{-2}$ and a shape parameter $\\sigma=2.4\\pm0.2,$ but the power law provides a superior description of the data. In this decomposition of the flux distribution, all of the intrinsic X-ray variability of Sgr A* (spanning at least three orders of magnitude in flux) can be attributed to flaring activity, likely ...

  13. Chandra Observation of the X-Ray Source Population of NGC 6946

    CERN Document Server

    Holt, S S; Hwang, U; Petre, R

    2003-01-01

    We present the results of a study of discrete X-ray sources in NGC 6946 using a deep Chandra ACIS observation. Based on the slope of the log N-log S distribution and the general correlation of sources with the spiral arms, we infer that the overall discrete source sample in NGC 6946 is dominated by high mass X-ray binaries, in contrast to the source distributions in M31 and the Milky Way. This is consistent with the higher star formation rate in NGC 6946 than in those galaxies. We find that the strong X-ray sources in the region of the galactic center do not correlate in detail with images of the region in the near-IR, although one of them may be coincident with the galactic center. The non-central ultra-luminous X-ray source in NGC 6946, previously identified with a supernova remnant, has an X-ray spectrum and luminosity that is inconsistent with either a traditional pulsar wind nebula or a blast wave remnant.

  14. Symbiotic Stars in X-rays. II. Faint Sources Detected with XMM-Newton and Chandra

    Science.gov (United States)

    Nunez, N. E.; Luna, G. J. M.; Pillitteri, I.; Mukai, K.

    2014-01-01

    We report the detection from four symbiotic stars that were not known to be X-ray sources. These four object show a ß-type X-ray spectrum, that is, their spectra can be modeled with an absorbed optically thin thermal emission with temperatures of a few million degrees. Photometric series obtained with the Optical Monitor on board XMM-Newton from V2416 Sgr and NSV 25735 support the proposed scenario where the X-ray emission is produced in a shock-heated region inside the symbiotic nebulae.

  15. Unfolding X-ray spectra using a flat panel detector.

    Science.gov (United States)

    Gallardo, Sergio; Juste, Belén; Pozuelo, Fausto; Ródenas, José; Querol, Andrea; Verdú, Gumersindo

    2013-01-01

    It is difficult to measure the energy spectrum of X-ray tubes due to the pile up effect produced by the high fluence of photons. Using attenuating materials, appropriate detector devices and the Monte Carlo method, primary X-ray spectrum of these devices can be estimated. In this work, a flat panel detector with a PMMA wedge has been used to obtain a dose curve corresponding to certain working conditions of a radiodiagnostic X-ray tube. The relation between the dose curve recorded by the flat panel and the primary X-ray spectrum is defined by a response function. Normally this function can be approximated by a matrix, which can be obtained by means of the Monte Carlo method. Knowing the measured dose curve and the response matrix, the primary X-ray spectrum can be unfolded. However, there are some problems that strongly affect the applicability of this method: i.e. technical features of the flat panel and inherent characteristics of the involved radiation physics (ill-posed problem). Both aspects are analyzed in this work, concluding that the proposed method can be applied with an acceptable accuracy for spectra without characteristic lines, for instance, tungsten anode in the 50-70 kVp range.

  16. Chandra reveals a black-hole X-ray binary within the ultraluminous supernova remnant MF 16

    CERN Document Server

    Roberts, T P

    2003-01-01

    We present evidence, based on Chandra ACIS-S observations of the nearby spiral galaxy NGC 6946, that the extraodinary X-ray luminosity of the MF 16 supernova remnant actually arises in a black-hole X-ray binary. This conclusion is drawn from the point-like nature of the X-ray source, its X-ray spectrum closely resembling the spectrum of other ultraluminous X-ray sources thought to be black-hole X-ray binary systems, and the detection of rapid hard X-ray variability from the source. We briefly discuss the nature of the hard X-ray variability, and the origin of the extreme radio and optical luminosity of MF 16 in light of this identification.

  17. Chandra ACIS Survey of X-ray Point Sources: The Source Catalog

    CERN Document Server

    Wang, Song; Qiu, Yanli; Bai, Yu; Yang, Huiqin; Guo, Jincheng; Zhang, Peng

    2016-01-01

    The $Chandra$ archival data is a valuable resource for various studies on different topics of X-ray astronomy. In this paper, we utilize this wealth and present a uniformly processed data set, which can be used to address a wide range of scientific questions. The data analysis procedures are applied to 10,029 ACIS observations, which produces 363,530 source detections, belonging to 217,828 distinct X-ray sources. This number is twice the size of the $Chandra$ Source Catalog (Version 1.1). The catalogs in this paper provide abundant estimates of the detected X-ray source properties, including source positions, counts, colors, fluxes, luminosities, variability statistics, etc. Cross-correlation of these objects with galaxies shows 17,828 sources are located within the $D_{25}$ isophotes of 1110 galaxies, and 7504 sources are located between the $D_{25}$ and 2$D_{25}$ isophotes of 910 galaxies. Contamination analysis with the log$N$--log$S$ relation indicates that 51.3\\% of objects within 2$D_{25}$ isophotes are...

  18. The Chandra X-Ray Observatory's Radiation Environment and the AP-8/AE-8 Model

    CERN Document Server

    Virani, S N; Plucinsky, P P; Butt, Y M; Virani, Shanil N.; Mueller-Mellin, Reinhold; Plucinsky, Paul P.; Butt, Yousaf M.

    2000-01-01

    The Chandra X-ray Observatory (CXO) was launched on July 23, 1999 and reached its final orbit on August 7, 1999. The CXO is in a highly elliptical orbit, approximately 140,000 km x 10,000 km, and has a period of approximately 63.5 hours (~ 2.65 days). It transits the Earth's Van Allen belts once per orbit during which no science observations can be performed due to the high radiation environment. The Chandra X-ray Observatory Center (CXC) currently uses the National Space Science Data Center's ``near Earth'' AP-8/AE-8 radiation belt model to predict the start and end times of passage through the radiation belts. However, our scheduling software uses only a simple dipole model of the Earth's magnetic field. The resulting B, L magnetic coordinates, do not always give sufficiently accurate predictions of the start and end times of transit of the Van Allen belts. We show this by comparing to the data from Chandra's on-board radiation monitor, the EPHIN (Electron, Proton, Helium Instrument particle detector) instr...

  19. Chandra and Swift X-ray Observations of the X-ray Pulsar SMC X-2 During the Outburst of 2015

    CERN Document Server

    Li, K L; Lin, L C C; Kong, Albert K H

    2016-01-01

    We report the Chandra/HRC-S and Swift/XRT observations for the 2015 outburst of the high-mass X-ray binary (HMXB) pulsar in the Small Magellanic Cloud, SMC X-2. While previous studies suggested that either an O star or a Be star in the field is the high-mass companion of SMC X-2, our Chandra/HRC-S image unambiguously confirms the O-type star as the true optical counterpart. Using the Swift/XRT observations, we extracted accurate orbital parameters of the pulsar binary through a time of arrivals (TOAs) analysis. In addition, there were two X-ray dips near the inferior conjunction, which are possibly caused by eclipses or an ionized high-density shadow wind near the companion's surface. Finally, we propose that an outflow driven by the radiation pressure from day ~10 played an important role in the X-ray/optical evolution of the outburst.

  20. The X-Ray Environment During the Epoch of Terrestrial Planet Formation: Chandra Observations of h Persei

    CERN Document Server

    Currie, Thayne; Spitzbart, Brad; Irwin, Jonathan; Wolk, Scott J; Hernandez, Jesus; Kenyon, Scott J; Pasachoff, Jay

    2008-01-01

    We describe Chandra/ACIS-I observations of the massive ~ 13--14 Myr-old cluster, h Persei, part of the famous Double Cluster (h and chi Persei) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~ 165 X-ray bright stars with V 1.5 Msun) fall out of X-ray saturation by ~ 10--15 Myr. Changes in stellar structure for > 1.5 Msun stars likely play an important role in this decline of X-ray emission.

  1. Relativistic Effects on Reflection X-ray Spectra of AGN

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Khee-Gan; /University Coll. London; Fuerst, Steven V.; /KIPAC, Menlo Park; Brandwardi-Raymond, Graziella; Wu, Kinwah; Crowley, Oliver; /University Coll. London

    2007-01-05

    We have calculated the reflection component of the X-ray spectra of active galactic nuclei (AGN) and shown that they can be significantly modified by the relativistic motion of the accretion flow and various gravitational effects of the central black hole. The absorption edges in the reflection spectra suffer severe energy shifts and smearing. The degree of distortion depends on the system parameters, and the dependence is stronger for some parameters such as the inner radius of the accretion disk and the disk viewing inclination angles. The relativistic effects are significant and are observable. Improper treatment of the reflection component of the X-ray continuum in spectral fittings will give rise to spurious line-like features, which will mimic the fluorescent emission lines and mask the relativistic signatures of the lines.

  2. Chandra Phase-Resolved X-ray Spectroscopy of the Crab Pulsar II

    CERN Document Server

    Weisskopf, Martin C; Yakovlev, Dmitry G; Harding, Alice; Zavlin, Vyacheslav E; O'Dell, Stephen L; Elsner, Ronald F; Becker, Werner

    2011-01-01

    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 $\\tau_{\\rm scat} = 0.147 \\pm 0.043$. Analysis of the spectrum as a function of pulse phase also measures the X-ray spectral index even at...

  3. Chandra Observations of the X-ray Point Source Population in NGC 4636

    CERN Document Server

    Posson-Brown, J; Forman, W; Donnelly, R H; Jones, C; Posson-Brown, Jennifer; Raychaudhury, Somak; Forman, William; Jones, Christine

    2006-01-01

    We present an analysis of the X-ray point source population in the nearby Virgo elliptical galaxy NGC 4636 from four Chandra X-ray observations. These ACIS observations, totaling ~210 ks, were taken over a three year period. Using a wavelet decomposition detection algorithm, we detect 336 individual point sources. For our analysis, we use a subset of the 245 detections with >10 cts (a limiting luminosity of approximately 1E37 erg/s in the 0.5-2 keV band, outside the 1.5' bright galaxy core). Of these sources, ~120 are likely members of the galaxy. We examine, for the first time, variability over a period of years for X-ray point sources in an elliptical galaxy. We present a luminosity function for the point sources in NGC 4636, fit by a power-law with gamma= -1.24 +/- 0.04, as well as a radial source density profile, hardness ratios for the sources, and lightcurves for bright sources which display short-term variability. We find an upper limit to the current X-ray luminosity of the historical supernova SN1939...

  4. The Chandra COSMOS-Legacy survey: Source X-ray spectral properties

    CERN Document Server

    Marchesi, S; Civano, F; Iwasawa, K; Suh, H; Comastri, A; Zamorani, G; Allevato, V; Griffiths, R; Miyaji, T; Ranalli, P; Salvato, M; Schawinski, K; Silverman, J; Treister, E; Urry, C M; Vignali, C

    2016-01-01

    We present the X-ray spectral analysis of the 1855 extragalactic sources in the Chandra COSMOS-Legacy survey catalog having more than 30 net counts in the 0.5-7 keV band. 38% of the sources are optically classified Type 1 active galactic nuclei (AGN), 60% are Type 2 AGN and 2% are passive, low-redshift galaxies. We study the distribution of AGN photon index and of the intrinsic absorption N(H,z) based on the sources optical classification: Type 1 have a slightly steeper mean photon index than Type 2 AGN, which on the other hand have average intrinsic absorption ~3 times higher than Type 1 AGN. We find that ~15% of Type 1 AGN have N(H,z)>1E22 cm^(-2), i.e., are obscured according to the X-ray spectral fitting; the vast majority of these sources have L(2-10keV)>$1E44 erg/s. The existence of these objects suggests that optical and X-ray obscuration can be caused by different phenomena, the X-ray obscuration being for example caused by dust-free material surrounding the inner part of the nuclei. ~18% of Type 2 AG...

  5. Chandra X-ray Observations of NGC 4258: Iron Absorption Lines from the Nucleus

    CERN Document Server

    Young, A J

    2004-01-01

    We report sub-arcsecond resolution X-ray imaging spectroscopy of the low luminosity active galactic nucleus of NGC 4258 and its immediate surroundings with the Chandra X-ray Observatory. NGC 4258 was observed four times, with the first two observations separated by one month, followed over a year later by two consecutive observations. The spectrum of the nucleus is well described by a heavily absorbed, hard X-ray power law of variable luminosity, plus a constant, thermal soft X-ray component. We do not detect an iron K alpha emission line with the upper limit to the equivalent width of a narrow, neutral iron line ranging between 94 and 887 eV (90% confidence) for the different observations. During the second observation on 2000-04-17, two narrow absorption features are seen with >99.5% confidence at ~6.4 keV and ~6.9 keV, which we identify as resonant absorption lines of Fe XVIII - Fe XIX K alpha and Fe XXVI K alpha, respectively. In addition, the 6.9 keV absorption line is probably variable on a timescale of...

  6. Simulating the sensitivity to stellar point sources of Chandra X-ray observations

    CERN Document Server

    Wright, Nicholas J; Guarcello, Mario G; Kashyap, Vinay L; Zezas, Andreas

    2015-01-01

    The Chandra Cygnus OB2 Legacy Survey is a wide and deep X-ray survey of the nearby and massive Cygnus OB2 association. The survey has detected ~8,000 X-ray sources, the majority of which are pre-main sequence X-ray emitting young stars in the association itself. To facilitate quantitative scientific studies of these sources as well as the underlying OB association it is important to understand the sensitivity of the observations and the level of completeness the observations have obtained. Here we describe the use of a hierarchical Monte Carlo simulation to achieve this goal by combining the empirical properties of the observations, analytic estimates of the source verification process, and an extensive set of source detection simulations. We find that our survey reaches a 90% completeness level for a pre-main-sequence population at the distance of Cyg OB2 at an X-ray luminosity of 4 x 10^30 ergs/s and a stellar mass of 1.3 Msun for a randomly distributed population. For a spatially clustered population such ...

  7. A Synoptic X-ray Study of M31 with the Chandra-HRC

    CERN Document Server

    Williams, B F; Kong, A K H; Primini, F A; King, A R; Murray, S S; Williams, Benjamin F.; Garcia, Michael R.; Kong, Albert K. H.; Primini, Frank A.; Murray, Stephen S.

    2003-01-01

    We have obtained 17 epochs of Chandra High Resolution Camera (HRC) snapshot images, each covering most of the M31 disk. The data cover a baseline of ~2.5 years and contain a mean effective exposure of 17 ks. We have measured the mean fluxes and long-term lightcurves for 173 objects detected in these data. The cumulative luminosity function of the disk sources is a power-law, while that of the bulge is more complex. Bright disk sources tend to lie in the southwestern half of the disk. At least 25% of the sources show significant variability. We cross-correlate all of our sources with published X-ray, optical and radio catalogs, as well as new optical data, finding counterpart candidates for 53 sources. In addition, 17 sources are likely X-ray transients. We analyze follow-up HST WFPC2 data of two X-ray transients, finding U band counterparts. In both cases, the counterparts are variable. In one case, the optical counterpart is transient with U = 22.3+/-0.1. The X-ray and optical properties of this object are c...

  8. Modeling Contamination Migration on the Chandra X-Ray Observatory - IV

    Science.gov (United States)

    O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil William; Plucinsky, Paul P.; Marshall, Herman L.; Bogdan, Akos; Grant, Catherine E.; Tennant, Allyn F.; Dahmer, Matthew

    2017-01-01

    During its first 18 years of operation, the cold (about -60degC) optical blocking filters of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination, which attenuates low-energy x rays. Over the past several years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity, in part to evaluate potential bake-out scenarios intended to reduce the level of contamination. This paper, the fourth on this topic, reports the results of recent contamination-migration simulations and their relevance to a decision whether to bake-out the ACIS instrument.

  9. Lessons from the development and operation of the Chandra x-ray observatory

    Science.gov (United States)

    Schwartz, Daniel A.

    2014-07-01

    Genuine teamwork was a key ingredient of the success of the Chandra x-ray observatory mission. Examples are the science center personnel working as part of the instrument principal investigators (IPI) teams during pre-launch development, the Smithsonian Astrophysical Observatory (SAO) supporting NASA/Marshall Space Flight Center (MSFC) by directly working with the prime contractor, TRW (now Northrop Grumman Aerospace Systems), and TRW acceptance of outside scientists performing the data reduction and analysis for qualification of the aspect camera. An end-to-end thread was defined early on, based on the MSFC/SAO operation of the Einstein observatory x-ray telescope, and covered the cycle from solicitation and peer review of observation proposals through scheduling to data processing and delivery. An open science working group chaired by MSFC included instrument principal investigators and interdisciplinary scientists spanning diverse astrophysical and instrumental expertise.

  10. The Chandra X-ray Survey of Planetary Nebulae (ChanPlaNS): Probing Binarity, Magnetic Fields, and Wind Collisions

    CERN Document Server

    Kastner, J H; Balick, B; Frew, D J; Miszalski, B; Sahai, R; Blackman, E; Chu, Y -H; De Marco, O; Frank, A; Guerrero, M A; Lopez, J A; Rapson, V; Zijlstra, A; Behar, E; Bujarrabal, V; Corradi, R L M; Nordhaus, J; Parker, Q; Sandin, C; Schönberner, D; Soker, N; Sokoloski, J L; Steffen, M; Ueta, T; Villaver, E

    2012-01-01

    We present an overview of the initial results from the Chandra Planetary Nebula Survey (ChanPlaNS), the first systematic (volume-limited) Chandra X-ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of ChanPlaNS targeted 21 mostly high-excitation PNe within ~1.5 kpc of Earth, yielding 3 detections of diffuse X-ray emission and 9 detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within ~1.5 kpc that have been observed to date, we find an overall X-ray detection rate of 68%. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks formed by energetic wind collisions is detected in ~30%; five objects display both diffuse and point-like emission components. The presence of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are...

  11. Using ACIS on the Chandra X-ray Observatory as a particle radiation monitor II

    CERN Document Server

    Grant, C E; Bautz, M W; O'Dell, S L

    2012-01-01

    The Advanced CCD Imaging Spectrometer is an instrument on the Chandra X-ray Observatory. CCDs are vulnerable to radiation damage, particularly by soft protons in the radiation belts and solar storms. The Chandra team has implemented procedures to protect ACIS during high-radiation events including autonomous protection triggered by an on-board radiation monitor. Elevated temperatures have reduced the effectiveness of the on-board monitor. The ACIS team has developed an algorithm which uses data from the CCDs themselves to detect periods of high radiation and a flight software patch to apply this algorithm is currently active on-board the instrument. In this paper, we explore the ACIS response to particle radiation through comparisons to a number of external measures of the radiation environment. We hope to better understand the efficiency of the algorithm as a function of the flux and spectrum of the particles and the time-profile of the radiation event.

  12. Real Time Space Weather Support for Chandra X-Ray Observatory Operations

    Science.gov (United States)

    O'Dell, Stephen L.; Minow, Joseph I.; Miller, J. Scott; Wolk, Scott J.; Aldcroft, Thomas L.; Spitzbart, Bradley D.; Swartz. Douglas A.

    2012-01-01

    NASA launched the Chandra X-ray Observatory in July 1999. Soon after first light in August 1999, however, degradation in the energy resolution and charge transfer efficiency of the Advanced CCD Imaging Spectrometer (ACIS) x-ray detectors was observed. The source of the degradation was quickly identified as radiation damage in the charge-transfer channel of the front-illuminated CCDs, by weakly penetrating ( soft , 100 500 keV) protons as Chandra passed through the Earth s radiation belts and ring currents. As soft protons were not considered a risk to spacecraft health before launch, the only on-board radiation monitoring system is the Electron, Proton, and Helium Instrument (EPHIN) which was included on Chandra with the primary purpose of monitoring energetic solar particle events. Further damage to the ACIS detector has been successfully mitigated through a combination of careful mission planning, autonomous on-board radiation protection, and manual intervention based upon real-time monitoring of the soft-proton environment. The AE-8 and AP-8 trapped radiation models and Chandra Radiation Models are used to schedule science operations in regions of low proton flux. EPHIN has been used as the primary autonomous in-situ radiation trigger; but, it is not sensitive to the soft protons that damage the front-illuminated CCDs. Monitoring of near-real-time space weather data sources provides critical information on the proton environment outside the Earth s magnetosphere due to solar proton events and other phenomena. The operations team uses data from the Geostationary Operational Environmental Satellites (GOES) to provide near-real-time monitoring of the proton environment; however, these data do not give a representative measure of the soft-proton (Space Weather Prediction Center. This presentation describes the radiation mitigation strategies to minimize the proton damage in the ACIS CCD detectors and the importance of real-time data sources that are used to protect

  13. The 3 Ms Chandra Campaign on Sgr A*: A Census of X-ray Flaring Activity from the Galactic Center

    CERN Document Server

    Neilsen, J; Gammie, C; Dexter, J; Markoff, S; Haggard, D; Nayakshin, S; Wang, Q D; Grosso, N; Porquet, D; Tomsick, J A; Degenaar, N; Fragile, P C; Houck, J C; Wijnands, R; Miller, J M; Baganoff, F K

    2013-01-01

    Over the last decade, X-ray observations of Sgr A* have revealed a black hole in a deep sleep, punctuated roughly once per day by brief flares. The extreme X-ray faintness of this supermassive black hole has been a long-standing puzzle in black hole accretion. To study the accretion processes in the Galactic Center, Chandra (in concert with numerous ground- and space-based observatories) undertook a 3 Ms campaign on Sgr A* in 2012. With its excellent observing cadence, sensitivity, and spectral resolution, this Chandra X-ray Visionary Project (XVP) provides an unprecedented opportunity to study the behavior of the closest supermassive black hole. We present a progress report from our ongoing study of X-ray flares, including the brightest flare ever seen from Sgr A*. Focusing on the statistics of the flares and the quiescent emission, we discuss the physical implications of X-ray variability in the Galactic Center.

  14. The Chandra Survey of Extragalactic Sources in the 3CR Catalog: X-ray Emission from Nuclei, Jets, and Hotspots in the Chandra Archival Observations

    CERN Document Server

    Massaro, F; Liuzzo, E; Orienti, M; Paladino, R; Paggi, A; Tremblay, G R; Wilkes, B J; Kuraszkiewicz, J; Baum, S A; O'Dea, C P

    2016-01-01

    As part of our program to build a complete radio and X-ray database of all the 3CR extragalactic radio sources, we present an analysis of 93 sources for which Chandra archival data are available. Most of these sources have been already published. Here we provide a uniform re-analysis and present nuclear X-ray fluxes and X-ray emission associated with radio jet knots and hotspots using both publicly available radio images and new radio images that have been constructed from data available in the VLA archive. For about 1/3 of the sources in the selected sample a comparison between the Chandra and the radio observations was not reported in the literature: we find X-ray detections of 2 new radio jet knots and 17 hotspots. We also report the X-ray detection of extended emission from the intergalactic medium of 15 galaxy clusters, two of which were most likely unknown previously.

  15. THE CHANDRA SURVEY OF EXTRAGALACTIC SOURCES IN THE 3CR CATALOG: X-RAY EMISSION FROM NUCLEI, JETS, AND HOTSPOTS IN THE CHANDRA ARCHIVAL OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Harris, D. E.; Paggi, A.; Wilkes, B. J.; Kuraszkiewicz, J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Liuzzo, E.; Orienti, M.; Paladino, R. [Istituto di Radioastronomia, INAF, via Gobetti 101, I-40129, Bologna (Italy); Tremblay, G. R. [Yale Center for Astronomy and Astrophysics, Physics Department, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States); Baum, S. A.; O’Dea, C. P. [University of Manitoba, Dept of Physics and Astronomy, Winnipeg, MB R3T 2N2 (Canada)

    2015-09-15

    As part of our program to build a complete radio and X-ray database of all Third Cambridge catalog extragalactic radio sources, we present an analysis of 93 sources for which Chandra archival data are available. Most of these sources have already been published. Here we provide a uniform re-analysis and present nuclear X-ray fluxes and X-ray emission associated with radio jet knots and hotspots using both publicly available radio images and new radio images that have been constructed from data available in the Very Large Array archive. For about 1/3 of the sources in the selected sample, a comparison between the Chandra and radio observations was not reported in the literature: we find X-ray detections of 2 new radio jet knots and 17 hotspots. We also report the X-ray detection of extended emission from the intergalactic medium for 15 galaxy clusters.

  16. Chandra Discovers X-Ray Ring Around Cosmic Powerhouse in Crab Nebula

    Science.gov (United States)

    1999-09-01

    After barely two months in space, NASA's Chandra X-ray Observatory has taken a stunning image of the Crab Nebula, the spectacular remains of a stellar explosion, and has revealed something never seen before: a brilliant ring around the nebula's heart. Combined with observations from the Hubble Space Telescope, the image provides important clues to the puzzle of how the cosmic "generator," a pulsing neutron star, energizes the nebula, which still glows brightly almost 1,000 years after the explosion. "The inner ring is unique," said Professor Jeff Hester of Arizona State University, Tempe, AZ. "It has never been seen before, and it should tell us a lot about how the energy from the pulsar gets into the nebula. It's like finding the transmission lines between the power plant and the light bulb." Professor Mal Ruderman of Columbia University, New York, NY, agreed. "The X-rays Chandra sees are the best tracer of where the energy is. With images such as these, we can directly diagnose what is going on." What is going on, according to Dr. Martin Weisskopf, Chandra Project Scientist from NASA's Marshall Space Flight Center, Huntsville, AL, is awesome. "The Crab pulsar is accelerating particles up to the speed of light and flinging them out into interstellar space at an incredible rate." The image shows tilted rings or waves of high-energy particles that appear to have been flung outward over the distance of a light year from the central star, and high-energy jets of particles blasting away from the neutron star in a direction perpendicular to the spiral. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous X-ray images have shown the outer parts of the jet and hinted at the ring structure. With Chandra's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with Chandra's Advanced CCD Imaging Spectrometer and High Energy Transmission

  17. A CHANDRA OBSERVATION OF THE BURSTING MILLISECOND X-RAY PULSAR IGR J17511-3057

    Energy Technology Data Exchange (ETDEWEB)

    Paizis, A. [Istituto Nazionale di Astrofisica, INAF-IASF, Via Bassini 15, 20133 Milano (Italy); Nowak, M. A. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States); Rodriguez, J.; Chaty, S. [Astrophysique, Instrumentation et Modelisation (AIM, UMR-E 9005 CEA/DSM-CNRS-Universite Paris Diderot) Irfu/Service d' Astrophysique, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Wilms, J. [Dr. Karl Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Universitaet Erlangen-Nuernberg, Sternwartstr. 7, 96049 Bamberg (Germany); Del Santo, M.; Ubertini, P., E-mail: ada@iasf-milano.inaf.it, E-mail: mnowak@space.mit.edu [IAPS, INAF, Via Fosso del Cavaliere 100, 00133 Rome (Italy)

    2012-08-10

    IGR J17511-3057 is a low-mass X-ray binary hosting a neutron star and is one of the few accreting millisecond X-ray pulsars with X-ray bursts. We report on a 20 ks Chandra grating observation of IGR J17511-3057, performed on 2009 September 22. We determine the most accurate X-ray position of IGR J17511-3057, {alpha}{sub J2000} = 17{sup h}51{sup m}08.{sup s}66, {delta}{sub J2000} = -30 Degree-Sign 57'41.''0 (90% uncertainty of 0.''6). During the observation, a {approx}54 s long type-I X-ray burst is detected. The persistent (non-burst) emission has an absorbed 0.5-8 keV luminosity of 1.7 Multiplication-Sign 10{sup 36} erg s{sup -1} (at 6.9 kpc) and can be well described by a thermal Comptonization model of soft, {approx}0.6 keV, seed photons upscattered by a hot corona. The type-I X-ray burst spectrum, with average luminosity over the 54 s duration L{sub 0.5-8{sub keV}} = 1.6 Multiplication-Sign 10{sup 37} erg s{sup -1}, can be well described by a blackbody with kT{sub bb} {approx} 1.6 keV and R{sub bb} {approx} 5 km. While an evolution in temperature of the blackbody can be appreciated throughout the burst (average peak kT{sub bb} = 2.5{sup +0.8}{sub -0.4} keV to tail kT{sub bb} = 1.3{sup +0.2}{sub -0.1} keV), the relative emitting surface shows no evolution. The overall persistent and type-I burst properties observed during the Chandra observation are consistent with what was previously reported during the 2009 outburst of IGR J17511-3057.

  18. Chemical Speciation via X-ray Emission Spectra

    Science.gov (United States)

    Ankudinov, A. L.; Rehr, J. J.; Elam, W. T.; Sieber, J. R.

    2002-03-01

    We have extended our calculations of lineshapes in x-ray emission and x-ray fluorescence (XRF) spectroscopy to investigate the dependence on formal oxidation state. We used the self-consistent x-ray spectroscopy code FEFF8.1 [1], which is based on a real-space Green's function formalism, to calculate the phosphorus K-M_2,3 line and the Cr K and L emission lines for a range of simple oxides. These lines exhibit changes depending on oxidation state. Convolution with an algorithm describing the response function of the spectrometer is necessary to compare to experimental measurements. The calculated spectra are compared to measured spectra and to other relevant calculations, e.g., Fujikawa and Kawai [2]. The comparisons thus far indicate that calculations and measurements together can yield a quantitative analysis of compounds. [1] A. L. Ankudinov and J. J. Rehr, Phys. Rev. B 62, 2437 (2000). [2] T. Fujikawa and J. Kawai, J. Phys. Soc. Japan 68, 4032 (1999).

  19. Emission lines between 1 and 2 keV in Cometary X-ray Spectra

    CERN Document Server

    Ewing, Ian; Bodewits, Dennis; Dennerl, Konrad; Lisse, Carey M; Wolk, Scott J

    2012-01-01

    We present the detection of new cometary X-ray emission lines in the 1.0 to 2.0 keV range using a sample of comets observed with the Chandra X-ray observatory and ACIS spectrometer. We have selected 5 comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are: C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model (Bodewits et al. 2007). Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV that we identify as being created by solar wind charge exchange lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to ...

  20. Measuring x-ray spectra of flash radiographic sources

    Science.gov (United States)

    Gehring, Amanda E.; Espy, Michelle A.; Haines, Todd J.; Mendez, Jacob; Moir, David C.; Sedillo, Robert; Shurter, Roger P.; Volegov, Petr; Webb, Timothy J.

    2015-08-01

    A Compton spectrometer has been re-commissioned for measurements of flash radiographic sources. The determination of the energy spectrum of these sources is difficult due to the high count rates and short nature of the pulses (~50 ns). The spectrometer is a 300 kg neodymium-iron magnet which measures spectra in the <1 MeV to 20 MeV energy range. Incoming x-rays are collimated into a narrow beam incident on a converter foil. The ejected Compton electrons are collimated so that the forward-directed electrons enter the magnetic field region of the spectrometer. The position of the electrons at the magnet's focal plane is a function of their momentum, allowing the x-ray spectrum to be reconstructed. Recent measurements of flash sources are presented.

  1. A Chandra/ACIS Study of 30 Doradus II. X-ray Point Sources in the Massive Star Cluster R136 and Beyond

    CERN Document Server

    Townsley, L K; Feigelson, E D; Garmire, G P; Getman, K V

    2006-01-01

    We have studied the X-ray point source population of the 30 Doradus star-forming complex in the Large Magellanic Cloud using high-spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory. Here we describe the X-ray sources in a 17' x 17' field centered on R136, the massive star cluster at the center of the main 30 Dor nebula. We detect 20 of the 32 Wolf-Rayet stars in the ACIS field. R136 is resolved at the subarcsecond level into almost 100 X-ray sources, including many typical O3--O5 stars as well as a few bright X-ray sources previously reported. Over two orders of magnitude of scatter in L_X is seen among R136 O stars, suggesting that X-ray emission in the most massive stars depends critically on the details of wind properties and binarity of each system, rather than reflecting the widely-reported characteristic value L_X/L_bol ~ 10^{-7}. Such a canonical ratio may exist for single massive stars in R136, ...

  2. The peculiar optical-UV X-ray spectra of the X-ray weak quasar PG 0043+039

    CERN Document Server

    Kollatschny, W; Zetzl, M; Santos-Lleó, M; Rodríguez-Pascual, P M; Ballo, L; Talavera, A

    2016-01-01

    The object PG 0043+039 has been identified as a broad absorption line (BAL) quasar based on its UV spectra. However, this optical luminous quasar has not been detected before in deep X-ray observations, making it the most extreme X-ray weak quasar known today. This study aims to detect PG 0043+039 in a deep X-ray exposure. The question is what causes the extreme X-ray weakness of PG 0043+039? Does PG 0043+039 show other spectral or continuum peculiarities? We took simultaneous deep X-ray spectra with XMM-Newton, far-ultraviolet (FUV) spectra with the Hubble Space Telescope (HST) and optical spectra of PG 0043+039 with the Hobby-Eberly Telescope (HET) and Southern African Large Telescope (SALT) in July, 2013. We have detected PG 0043+039 in our X-ray exposure taken in 2013. We presented our first results in a separate paper (Kollatschny et al. 2015). PG 0043+039 shows an extreme {\\alpha}_ox gradient ({\\alpha}_ox =-2.37). Furthermore, we were able to verify an X-ray flux of this source in a reanalysis of the X-...

  3. X-ray spectroscopy of the ADC source X1822-371 with Chandra and XMM-Newton

    CERN Document Server

    Iaria, R; D'Aì, A; Burderi, L; Mineo, T; Riggio, A; Papitto, A; Robba, N R

    2012-01-01

    The eclipsing low-mass X-ray binary X1822-371 is the prototype of the accretion disc corona (ADC) sources. We analyse two Chandra observations and one XMM-Newton observation to study the discrete features and their variation as a function of the orbital phase, deriving constraints on the temperature, density, and location of the plasma responsible for emission lines. The HETGS and XMM/Epic-pn observed X1822-371 for 140 and 50 ks, respectively. We extracted an averaged spectrum and five spectra from five selected orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.75-0.95, and, finally, 0.95-1.04; the orbital phase zero corresponds to the eclipse time. All spectra cover the energy band between 0.35 and 12 keV. We confirm the presence of local neutral matter that partially covers the X-ray emitting region; the equivalent hydrogen column is $5 \\times 10^{22}$ cm$ ^{-2}$ and the covered fraction is about 60-65%. We identify emission lines from highly ionised elements, and a prominent fluorescence ...

  4. The X-ray spectrum of delta Orionis observed by LETGS aboard Chandra

    CERN Document Server

    Raassen, A J J

    2013-01-01

    We analyze the high-resolution X-ray spectrum of the supergiant O-star delta Orionis (O9.5II) with line ratios of He-like ions and a thermal plasma model, and we examine its variability. The O-supergiant delta Ori was observed in the wavelength range 5-175 Angstrom by the X-ray detector HRC-S in combination with the grating LETG aboard Chandra. We studied the He-like ions in combination with the UV-radiation field to determine local plasma temperatures and to establish the distance of the X-ray emitting ions to the stellar surface. We measured individual lines by means of Gaussian profiles, folded through the response matrix, to obtain wavelengths, line fluxes, half widths at half maximum (HWHM) and line shifts to characterize the plasma. We consider multitemperature models in collisional ionization equilibrium (CIE) to determine temperatures, emission measures, and abundances. Analysis of the He-like triplets extended to N VI and C V implies ionization stratification with the hottest plasma to be found withi...

  5. Chandra Observations of the Gamma-ray Binary LSI+61303: Extended X-ray Structure?

    CERN Document Server

    Paredes, J M; Bosch-Ramon, V; West, J R; Butt, Y M; Torres, D F; Martí, J

    2007-01-01

    We present a 50 ks observation of the gamma-ray binary LSI+61303 carried out with the ACIS-I array aboard the Chandra X-ray Observatory. This is the highest resolution X-ray observation of the source conducted so far. Possible evidence of an extended structure at a distance between 5 and 12 arcsec towards the North of LSI+61303 have been found at a significance level of 3.2 sigma. The asymmetry of the extended emission excludes an interpretation in the context of a dust-scattered halo, suggesting an intrinsic nature. On the other hand, while the obtained source flux, of F_{0.3-10 keV}=7.1^{+1.8}_{-1.4} x 10^{-12} ergs/cm^2/s, and hydrogen column density, N_{H}=0.70+/-0.06 x 10^{22} cm^{-2}, are compatible with previous results, the photon index Gamma=1.25+/-0.09 is the hardest ever found. In light of these new results, we briefly discuss the physics behind the X-ray emission, the location of the emitter, and the possible origin of the extended emission ~0.1 pc away from LSI+61303.

  6. Too Young to Shine? Chandra analysis of X-ray emission in nearby primordial galaxies

    Science.gov (United States)

    Basu-Zych, Antara; Henry, Alaina L.; Yukita, Mihoko; Fragos, Tassos; Hornschemeier, Ann E.; Lehmer, Bret; Ptak, Andrew; Zezas, Andreas

    2017-01-01

    The 2—10 keV X-ray emission in star-forming galaxies traces the population of high mass X-ray binaries (HMXBs) and is a function of both the star formation rate (SFR) and metallicity, according to several studies. Theoretical studies predict that stars retain more mass over their lifetimes due to weaker stellar winds in lower metallicity environments, and therefore, produce more luminous and numerous HMXBs. We present Chandra analysis for a local sample of primordial galaxies, Hα emitters (HAEs). Our selection is based on large Hα equivalent widths (EW(Hα)>500Å, suggestive of bursts of star formation within 6 Myr), SFR >1 M⊙/yr and low metallicities (Z extreme youth (young stellar age) of the galaxies, where HMXBs may not have fully formed. Our investigation of HMXB formation as a function of stellar age, metallicity and SFR offers important refinements to the X-ray emission from the first galaxies and on predictions of black hole binaries, which are precursors of gravitational wave sources.

  7. X-Ray Spectroscopy of diffuse Galactic Interstellar Matter with Chandra

    Science.gov (United States)

    Schulz, Norbert S.; Paerels, Frits

    One of the expectations with the advent of the High Energy Transmission Grating (HETG) spectrometer onboard the Chandra X-ray Observatory was to measure precise photoelectric edges of major cosmic elements such as O, Ne, Mg, Si, S, Ar, Ca, and Fe. Early studies revealed complex absorption structures around the O K, Fe L, and Ne K edges which were identified with absorption from the various phases of the interstellar medium and which could place limits on ionization fractions in these phases. The dust content in interstellar matter as well as, for example, the fraction of how much oxygen is locked into dust are issues of importance and here resolved X-ray edges can determine significant limits. I will review predictions made by cross-sections and depletion factors and compare with current observations specifically with respect to silicon absorption in the interstellar medium. Dust grain models and in conjunction with laboratory measurements are now used to improve current interstellar X-ray absorption models.

  8. X-Ray Localization of the Intermediate-Mass Black Hole in the Globular Cluster G1 with Chandra

    CERN Document Server

    Kong, A K H; Di Stefano, R; Barmby, P; Lewin, W H G; Primini, F A

    2009-01-01

    We report the most accurate X-ray position of the giant globular cluster G1 in M31 by using the Chandra X-ray Observatory, Hubble Space Telescope (HST), and Canada-France-Hawaii Telescope (CFHT). G1 is clearly detected with Chandra and by cross-registering with HST and CFHT images, we derive a 1sigma error radius of 0.15", significantly smaller than the previous measurement by XMM-Newton. We conclude that the X-ray emission of G1 comes from within the core radius of the cluster. There are two possibilities for the origin of the X-ray emission: it could be due to either accretion of a central intermediate-mass black hole, or ordinary low-mass X-ray binaries. Based on the ratio of X-ray to the Eddington luminosity, an intermediate-mass black hole accreting from the cluster gas seems unlikely and we suggest that the X-rays are due to accretion from a companion. We also find that the X-ray emission may be offset from the radio emission. Future high-resolution and high-sensitivity radio imaging observations will r...

  9. Chandra Phase-Resolved X-ray Spectroscopy of the Crab Pulsar II

    Science.gov (United States)

    Weisskopf, Martin C.; Tennant, Allyn F.; Yakovlev, Dimitry G.; Harding, Alice; Zavlin, Vyacheslav E.; Elsner, Ronald F.; Becker, Werner

    2012-01-01

    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+\\-0.28) x 10(exp -4) (4.9 x 10(exp -4) is solar abundance). \\rVe also measure for the first time the impact of scattering of flux out of the image by interstellar grains. \\rYe find T(sub scat) = 0.147+/-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.

  10. Chandra and XMM monitoring of the black hole X-ray binary IC 10 X-1

    Science.gov (United States)

    Laycock, Silas G. T.; Cappallo, Rigel C.; Moro, Matthew J.

    2015-01-01

    The massive black hole (BH)+Wolf-Rayet (WR) binary IC 10 X-1 was observed in a series of 10 Chandra and two XMM-Newton observations spanning 2003-2012, showing consistent variability around 7 × 1037 erg s-1, with a spectral hardening event in 2009. We phase connected the entire light curve by folding the photon arrival times on a series of trial periods spanning the known orbital period and its uncertainty, refining the X-ray period to P = 1.45175(1) d. The duration of minimum flux in the X-ray eclipse is ˜5 h which together with the optical radial velocity (RV) curve for the companion yields a radius for the eclipsing body of 8-10 R⊙ for the allowed range of masses. The orbital separation (a1 + a2) = 18.5-22 R⊙ then provides a limiting inclination i > 63° for total eclipses to occur. The eclipses are asymmetric (egress duration ˜0.9 h) and show energy dependence, suggestive of an accretion disc hotspot and corona. The eclipse is much (˜5×) wider than the 1.5-2 R⊙ WR star, pointing to absorption/scattering in the dense wind of the WR star. The same is true of the close analog NGC 300 X-1. RV measurements of the He II [λλ4686] line from the literature show a phase shift with respect to the X-ray ephemeris such that the velocity does not pass through zero at mid-eclipse. The X-ray eclipse leads inferior conjunction of the RV curve by ˜90°, so either the BH is being eclipsed by a trailing shock/plume, or the He II line does not directly trace the motion of the WR star and instead originates in a shadowed partially ionized region of the stellar wind.

  11. A DEEP CHANDRA X-RAY LIMIT ON THE PUTATIVE IMBH IN OMEGA CENTAURI

    Energy Technology Data Exchange (ETDEWEB)

    Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Physics and Astronomy Department, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Cool, Adrienne M. [Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Ave., San Francisco, CA 94132 (United States); Heinke, Craig O. [Department of Physics, University of Alberta, Room 238 CEB, Edmonton, AB T6G 2G7 (Canada); Van der Marel, Roeland; Anderson, Jay [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Cohn, Haldan N.; Lugger, Phyllis M., E-mail: dhaggard@northwestern.edu, E-mail: cool@sfsu.edu [Department of Astronomy, Indiana University, 727 E. Third St., Bloomington, IN 47405 (United States)

    2013-08-20

    We report a sensitive X-ray search for the proposed intermediate-mass black hole (IMBH) in the massive Galactic cluster, {omega} Centauri (NGC 5139). Combining Chandra X-ray Observatory data from Cycles 1 and 13, we obtain a deep ({approx}291 ks) exposure of the central regions of the cluster. We find no evidence for an X-ray point source near any of the cluster's proposed dynamical centers, and place an upper limit on the X-ray flux from a central source of f{sub X}(0.5-7.0 keV) {<=}5.0 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1}, after correcting for absorption. This corresponds to an unabsorbed X-ray luminosity of L{sub X}(0.5-7.0 keV) {<=}1.6 Multiplication-Sign 10{sup 30} erg s{sup -1}, for a cluster distance of 5.2 kpc, Galactic column density N{sub H} = 1.2 Multiplication-Sign 10{sup 21} cm{sup -2}, and power-law spectrum with {Gamma} = 2.3. If a {approx}10{sup 4} M{sub sun} IMBH resides in the cluster's core, as suggested by some stellar dynamical studies, its Eddington luminosity would be L{sub Edd} {approx}10{sup 42} erg s{sup -1}. The new X-ray limit would then establish an Eddington ratio of L{sub X}/L{sub Edd} {approx}< 10{sup -12}, a factor of {approx}10 lower than even the quiescent state of our Galaxy's notoriously inefficient supermassive black hole Sgr A*, and imply accretion efficiencies as low as {eta} {approx}< 10{sup -6}-10{sup -8}. This study leaves open three possibilities: either {omega} Cen does not harbor an IMBH or, if an IMBH does exist, it must experience very little or very inefficient accretion.

  12. Chandra X-Ray Observations of the Redshift 1.53 Radio-loud Quasar 3C 270.1.

    NARCIS (Netherlands)

    Wilkes, Belinda J.; Lal, Dharam V.; Worrall, D. M.; Birkinshaw, Mark; Haas, Martin; Willner, S. P.; Antonucci, Robert; Ashby, M. L. N.; Avara, Mark; Barthel, Peter; Chini, Rolf; Fazio, G. G.; Hardcastle, Martin; Lawrence, Charles; Leipski, Christian; Ogle, Patrick; Schulz, Bernhard

    Chandra X-ray observations of the high redshift (z = 1.532) radio-loud quasar 3C 270.1 in 2008 February show the nucleus to have a power-law spectrum, Γ = 1.66 ± 0.08, typical of a radio-loud quasar, and a marginally detected Fe Kα emission line. The data also reveal extended X-ray emission, about

  13. Chandra X-Ray Observations of the Redshift 1.53 Radio-loud Quasar 3C 270.1.

    NARCIS (Netherlands)

    Wilkes, Belinda J.; Lal, Dharam V.; Worrall, D. M.; Birkinshaw, Mark; Haas, Martin; Willner, S. P.; Antonucci, Robert; Ashby, M. L. N.; Avara, Mark; Barthel, Peter; Chini, Rolf; Fazio, G. G.; Hardcastle, Martin; Lawrence, Charles; Leipski, Christian; Ogle, Patrick; Schulz, Bernhard

    2012-01-01

    Chandra X-ray observations of the high redshift (z = 1.532) radio-loud quasar 3C 270.1 in 2008 February show the nucleus to have a power-law spectrum, Γ = 1.66 ± 0.08, typical of a radio-loud quasar, and a marginally detected Fe Kα emission line. The data also reveal extended X-ray emission, about

  14. Chandra-SDSS Normal and Star-Forming Galaxies I: X-ray Source Properties of Galaxies Detected by Chandra in SDSS DR2

    CERN Document Server

    Hornschemeier, A E; Ptak, A F; Tremonti, C A; Colbert, E J M

    2004-01-01

    We have cross-correlated X-ray catalogs derived from archival Chandra ACIS observations with a Sloan Digital Sky Survey (SDSS) Data Release 2 (DR2) galaxy catalog to form a sample of 42 serendipitously X-ray detected galaxies over the redshift interval 0.03 < z < 0.25. This pilot study will help fill in the "redshift gap" between local X-ray-studied samples of normal galaxies and those in the deepest X-ray surveys. Our chief purpose is to compare optical spectroscopic diagnostics of activity (both star-formation and accretion) with X-ray properties of galaxies. Our work supports a normalization value of the X-ray-star-formation-rate (X-ray-SFR) correlation consistent with the lower values published in the literature. The difference is in the allocation of X-ray emission to high-mass X-ray binaries relative to other components such as hot gas, low-mass X-ray binaries, and/or AGN. We are able to quantify a few pitfalls in the use of lower-resolution, lower signal-to-noise optical spectroscopy to identify ...

  15. Deep Chandra X-ray Imaging of a Nearby Radio Galaxy 4C+29.30: X-ray/Radio Connection

    CERN Document Server

    Siemiginowska, Aneta; Cheung, Chi C; Aldcroft, Thomas L; Bechtold, Jill; Burke, D J; Evans, Daniel; Holt, Joanna; Jamrozy, Marek; Migliori, Giulia; .,

    2012-01-01

    We report results from our deep Chandra X-ray observations of a nearby radio galaxy, 4C+29.30 (z=0.0647). The Chandra image resolves structures on sub-arcsec to arcsec scales, revealing complex X-ray morphology and detecting the main radio features: the nucleus, a jet, hotspots, and lobes. The nucleus is absorbed (N(H)=3.95 (+0.27/-0.33)x10^23 atoms/cm^2) with an unabsorbed luminosity of L(2-10 keV) ~ (5.08 +/-0.52) 10^43 erg/s characteristic of Type 2 AGN. Regions of soft (<2 keV) X-ray emission that trace the hot interstellar medium (ISM) are correlated with radio structures along the main radio axis indicating a strong relation between the two. The X-ray emission beyond the radio source correlates with the morphology of optical line-emitting regions. We measured the ISM temperature in several regions across the galaxy to be kT ~ 0.5 with slightly higher temperatures (of a few keV) in the center and in the vicinity of the radio hotspots. Assuming these regions were heated by weak shocks driven by the exp...

  16. The Chandra Planetary Nebula Survey (ChanPlaNS). II. X-ray Emission from Compact Planetary Nebulae

    CERN Document Server

    Freeman, M; Montez, R; Balick, B; Frew, D J; Jones, D; Miszalski, B; Sahai, R; Blackman, E; Chu, Y -H; De Marco, O; Frank, A; Guerrero, M A; Lopez, J A; Zijlstra, A; Bujarrabal, V; Corradi, R L M; Nordhaus, J; Parker, Q A; Sandin, C; Schönberner, D; Soker, N; Sokoloski, J L; Steffen, M; Toalá, J A; Ueta, T; Villaver, E

    2014-01-01

    We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (ChanPlaNS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ~1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. ChanPlaNS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. ChanPlaNS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R_neb ~1000 cm^-3), and rarely associated with PNe that show H_2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, of the five new diffuse X-ray detections, two host [WR]-type CSPNe, NGC 1501 and NGC 6369, supporting the hypothes...

  17. A Chandra X-ray study of the young star cluster NGC 6231: low-mass population and initial mass function

    CERN Document Server

    Damiani, F; Sciortino, S

    2016-01-01

    NGC6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data, where we detect 1613 point X-ray sources. Our main aim is to clarify global properties of NGC6231 down to low masses through a detailed membership assessment, and to study the cluster stars' spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and initial mass function. We use X-ray data, complemented by optical/IR data, to establish cluster membership. The spatial distribution of different stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. We perform spectral modeling of group-stacked X-ray source spectra. We find a large cluster population down to ~0.3 Msun (complete to ~1 Msun), with minimal non-member contamination, with a definite age spread (1-8 ...

  18. Chandra Survey of Nearby Highly-Inclined Disk Galaxies I: X-ray Measurements of Galactic Coronae

    CERN Document Server

    Li, Jiang-Tao

    2012-01-01

    We present a systematical analysis of the Chandra observations of 53 nearby highly-inclined (i>60 degree) disk galaxies to study the coronae around them. This sample covers a broad range of galaxy properties: e.g., about three orders of magnitude in the SFR and more than two orders of magnitude in the stellar mass. The Chandra observations of the diffuse soft X-ray emission from 20 of these galaxies are presented for the first time. The data are reduced in a uniform manner, including the excision/subtraction of both resolved and unresolved stellar contributions. Various coronal properties, such as the scale height and luminosity, are characterized for all the sample galaxies. For galaxies with high enough counting statistics, we also examine the thermal and chemical states of the coronal gas. We note on galaxies with distinct multi-wavelength characteristics which may affect the coronal properties. The uniformly processed images, spectra, and brightness profiles, as well as the inferred hot gas parameters, fo...

  19. X-ray Sources in the Magellanic Clouds: analysis of 15 Years of XMM-Newton and Chandra Observations

    Science.gov (United States)

    Yang, J.; Laycock, S.; Christodoulou, D.; Drake, J.; Fingerman, S.; Hong, J.; Zezas, A.; Antoniou, V.; Coe, M.; Ho, W.

    2016-06-01

    Using ˜160 XMM-Newton, ˜180 Chandra, and all weekly RXTE observations, we have generated a comprehensive library of the known pulsars in the Small and Large Magellanic Clouds (SMC, LMC). We classify various pulsar properties in the range of log L_{X}=32-38 erg s^{-1} and incorporate related parameters in theoretical models. With the high time-resolution data of the EPIC and Chandra cameras and the latest calibration files and software, our 15 year pipeline generates a suite of useful products for each pulsar detection: event lists, high time-resolution light curves, periodograms, spectra, and complete histories of the dot{P}, the pulse fraction, etc., in the broad, soft (0.2-2 keV), and hard (2-12 keV) energy bands. After combining the observations from these telescopes, we found that 15 pulsars are clearly spinning up and another 15 pulsars are distinctly spinning down. We also used the faintest and brightest sources to map out the propeller line and the Eddington line, respectively. We compared the observed pulse profiles to geometric models of X-ray emission in order to constrain the physical parameters of the pulsars. We are preparing a public release of this library so that it can be used by other groups as well.

  20. Impacts of Chandra X-ray Observatory Public Communications and Engagement

    Science.gov (United States)

    Arcand, Kimberly K.; Watzke, Megan; Lestition, Kathleen; Edmonds, Peter

    2015-01-01

    The Chandra X-ray Observatory Center runs a multifaceted Public Communications & Engagement program encompassing press relations, public engagement, and education. Our goals include reaching a large and diverse audience of national and international scope, establishing direct connections and working relationships with the scientists whose research forms the basis for all products, creating peer-reviewed materials and activities that evolve from an integrated pipeline design and encourage users toward deeper engagement, and developing materials that target underserved audiences such as women, Spanish speakers, and the sight and hearing impaired. This talk will highlight some of the key features of our program, from the high quality curated digital presence to the cycle of research and evaluation that informs our practice at all points of the program creation. We will also discuss the main impacts of the program, from the tens of millions of participants reached through the establishment and sustainability of a network of science 'volunpeers.'

  1. A Narrow Band Chandra X-ray Analysis of SNR 3C 391

    Institute of Scientific and Technical Information of China (English)

    Yang Su; Yang Chen

    2005-01-01

    We present narrow-band and equivalent width (EW) images of the thermal composite supernova remnant (SNR) 3C 391 in the X-ray emission lines of Mg, Si and S using the Chandra ACIS Observational data. The EW images re veal the spatial distribution of the emission of the metal species Mg, Si and S in the remnant. They have a clumpy structure similar to that seen in the broadband diffuse emission, suggesting that they are largely of interstellar origin. We find an interesting finger-like feature protruding outside the southwestern radio border of the remnant, somewhat similar to the jet-like Si structure found in the famous SNR Cas A. This feature may possibly be the debris of the jet of ejecta from an asymmetrical supernova explosion of a massive progenitor star.

  2. Annealing bounds to prevent further Charge Transfer Inefficiency increase of the Chandra X-ray CCDs

    Energy Technology Data Exchange (ETDEWEB)

    Monmeyran, Corentin, E-mail: comonmey@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Patel, Neil S., E-mail: neilp@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Bautz, Mark W., E-mail: mwb@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Grant, Catherine E., E-mail: cgrant@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Prigozhin, Gregory Y., E-mail: gyp@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Agarwal, Anuradha, E-mail: anu@mit.edu [Microphotonics Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Kimerling, Lionel C., E-mail: lckim@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Microphotonics Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2016-12-15

    After the front-illuminated CCDs on board the X-ray telescope Chandra were damaged by radiation after launch, it was decided to anneal them in an effort to remove the defects introduced by the irradiation. The annealing led to an unexpected increase of the Charge Transfer Inefficiency (CTI). The performance degradation is attributed to point defect interactions in the devices. Specifically, the annealing at 30 °C activated the diffusion of the main interstitial defect in the device, the carbon interstitial, which led to its association with a substitutional impurity, ultimately resulting in a stable and electrically active defect state. Because the formation reaction of this carbon interstitial and substitutional impurity associate is diffusion limited, we recommend a higher upper bound for the annealing temperature and duration of any future CCD anneals, that of −50 °C for one day or −60 °C for a week, to prevent further CTI increase.

  3. Annealing bounds to prevent further Charge Transfer Inefficiency increase of the Chandra X-ray CCDs

    Science.gov (United States)

    Monmeyran, Corentin; Patel, Neil S.; Bautz, Mark W.; Grant, Catherine E.; Prigozhin, Gregory Y.; Agarwal, Anuradha; Kimerling, Lionel C.

    2016-12-01

    After the front-illuminated CCDs on board the X-ray telescope Chandra were damaged by radiation after launch, it was decided to anneal them in an effort to remove the defects introduced by the irradiation. The annealing led to an unexpected increase of the Charge Transfer Inefficiency (CTI). The performance degradation is attributed to point defect interactions in the devices. Specifically, the annealing at 30 °C activated the diffusion of the main interstitial defect in the device, the carbon interstitial, which led to its association with a substitutional impurity, ultimately resulting in a stable and electrically active defect state. Because the formation reaction of this carbon interstitial and substitutional impurity associate is diffusion limited, we recommend a higher upper bound for the annealing temperature and duration of any future CCD anneals, that of -50 °C for one day or -60 °C for a week, to prevent further CTI increase.

  4. Chandra X-ray Spectroscopy of Kes75, its Young Pulsar, and its Synchrotron Nebula

    CERN Document Server

    Collins, B F; Helfand, D J

    2001-01-01

    We have observed the young Galactic supernova remnant Kes 75 with the Chandra X-ray Observatory. This object is one of an increasing number of examples of a shell-type remnant with a central extended radio core harboring a pulsar. Here we present a preliminary spatially resolved spectroscopic analysis of the Kes~75 system. We find that the spectrum of the pulsar is significantly harder than that of the wind nebula, and both of these components can be isolated from the diffuse thermal emission that seems to follow the same distribution as the extended radio shell. When we characterize the thermal emission with a model of an under-ionized plasma and non-solar elemental abundances, we require a significant diffuse high energy component, which we model as a power-law with a photon index similar to that of the synchrotron nebula.

  5. Deep Chandra Observations of the Compact Starburst Galaxy Henize 2-10: X-rays from the Massive Black Hole

    CERN Document Server

    Reines, Amy; Miller, Jon; Sivakoff, Gregory; Greene, Jenny; Hickox, Ryan; Johnson, Kelsey

    2016-01-01

    We present follow-up X-ray observations of the candidate massive black hole (BH) in the nucleus of the low-mass, compact starburst galaxy Henize 2-10. Using new high-resolution observations from the Chandra X-ray Observatory totaling 200 ks in duration, as well as archival Chandra observations from 2001, we demonstrate the presence of a previously unidentified X-ray point source that is spatially coincident with the known nuclear radio source in Henize 2-10 (i.e., the massive BH). We show that the hard X-ray emission previously identified in the 2001 observation is dominated by a source that is distinct from the nucleus, with the properties expected for a high-mass X-ray binary. The X-ray luminosity of the nuclear source suggests the massive BH is radiating significantly below its Eddington limit (~10^-6 L_Edd), and the soft spectrum resembles other weakly accreting massive BHs including Sagittarius A*. Analysis of the X-ray light curve of the nucleus reveals the tentative detection of a ~9-hour periodicity, ...

  6. Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions

    CERN Document Server

    Bhardwaj, A; Elsner, R F; Ford, P G; Gladstone, G R; Bhardwaj, Anil; Cravens, Thomas E.; Elsner, Ronald F.; Ford, Peter G.

    2005-01-01

    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.

  7. Chandra Observations of a 1.9 kpc Separation Double X-ray Source in a Candidate Dual AGN Galaxy at z=0.16

    CERN Document Server

    Comerford, Julia M; Gerke, Brian F; Madejski, Greg M

    2011-01-01

    We report Chandra observations of a double X-ray source in the z=0.1569 galaxy SDSS J171544.05+600835.7. The galaxy was initially identified as a dual AGN candidate based on the double-peaked [O III] emission lines, with a line-of-sight velocity separation of 350 km/s, in its Sloan Digital Sky Survey spectrum. We used the Kast Spectrograph at Lick Observatory to obtain two longslit spectra of the galaxy at two different position angles, which reveal that the two AGN emission components have not only a velocity offset, but also a projected spatial offset of 1.9 kpc/h70 on the sky. Chandra/ACIS observations of two X-ray sources with the same spatial offset and orientation as the optical emission suggest the galaxy most likely contains Compton-thick dual AGN, although the observations could also be explained by AGN jets. Deeper X-ray observations that reveal Fe K lines, if present, would distinguish between the two scenarios. The observations of a double X-ray source in SDSS J171544.05+600835.7 are a proof of co...

  8. The jet and counterjet of 3C 270 (NGC 4261) viewed in the X-ray with Chandra

    CERN Document Server

    Worrall, D M; O'Sullivan, E; Zezas, A; Wolter, A; Trinchieri, G; Fabbiano, G

    2010-01-01

    The radio source 3C 270, hosted by NGC 4261, is the brightest known example of counterjet X-ray emission from a low-power radio galaxy. We report on the X-ray emission of the jet and counterjet from 130 ks of Chandra data. We argue that the X-ray emission is synchrotron radiation and that the internal properties of the jet and counterjet are remarkably similar. We find a smooth connection in X-ray hardness and X-ray to radio ratio between the jet and one of the X-ray components within the core spectrum. We observe wedge-like depressions in diffuse X-ray surface brightness surrounding the jets, and interpret them as regions where an aged population of electrons provides pressure to balance the interstellar medium of NGC 4261. About 20% of the mass of the interstellar medium has been displaced by the radio source. Treating 3C 270 as a twin-jet system, we find an interesting agreement between the ratio of jet-to-counterjet length in X-rays and that expected if X-rays are observed over the distance that an outflo...

  9. The statistical uncertainties on X-ray flux and spectral parameters from Chandra ACIS-I observations of faint sources: Application to the Cygnus OB2 Association

    CERN Document Server

    Albacete-Colombo, J F; Drake, J J; Wright, N J; Guarcello, M; Kashyap, V

    2016-01-01

    We investigate the uncertainties of fitted X-ray model parameters and fluxes for relatively faint Chandra ACIS-I source spectra. Monte-Carlo (MC) simulations are employed to construct a large set of 150,000 fake X-ray spectra in the low photon count statistics regime (from 20 to 350 net counts) using the XSPEC spectral model fitting package. The simulations employed both absorbed thermal (APEC) and non-thermal (power-law) models, in concert with the Chandra ACIS-I instrument response and interstellar absorption. Simulated X-ray spectra were fit assuming a wide set of different input parameters and C-statistic minimization criteria to avoid numerical artifacts in the accepted solutions. Results provide an error estimate for each parameter (absorption, NH, plasma temperature, kT, or power-law slope, Gamma, and flux, and for different background contamination levels. The distributions of these errors are studied as a function of the 1 sigma quantiles and we show how these correlate with different model parameter...

  10. Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the Globular Cluster 47 Tucanae

    CERN Document Server

    Bogdanov, S; Heinke, C O; Camilo, F; Freire, P C C; Becker, W; Bogdanov, Slavko; Grindlay, Jonathan E.; Heinke, Craig O.; Camilo, Fernando; Freire, Paulo C. C.; Becker, Werner

    2006-01-01

    We present spectral and long-timescale variability analyses of \\textit{Chandra} ACIS-S observations of the 19 millisecond pulsars (MSPs) with precisely known positions in the globular cluster 47 Tucanae. The X-ray emission of the majority of these MSPs is well described by a thermal (blackbody or neutron star hydrogen atmosphere) spectrum with a temperature $T_{\\rm eff}\\sim(1-3)\\times10^6$ K, emission radius $R_{\\rm eff}\\sim0.1-3$ km, and luminosity $L_{X}\\sim10^{30-31}$ ergs s$^{-1}$. For several MSPs, there is indication that a second thermal component is required, similar to what is seen in some nearby field MSPs. The radio-eclipsing binary MSPs 47 Tuc J, O, and W show a significant non-thermal component, with photon index $\\Gamma\\sim 1-1.5$, which may originate in an shock formed due to interaction between the relativistic pulsar wind and matter from the stellar companion. We re-examine the X-ray--spindown luminosity relation ($L_{X}-\\dot{E}$) and find that due to the large uncertainties in both parameter...

  11. HST/ACS Imaging of Omega Centauri: Optical Counterparts of Chandra X-Ray Sources

    CERN Document Server

    Cool, Adrienne M; Arias, Tersi; Brochmann, Michelle; Dorfman, Jason; Gafford, April; White, Vivian; Anderson, Jay

    2012-01-01

    We present results of a search for optical counterparts of X-ray sources in and toward the globular cluster Omega Centauri (NGC 5139) using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The ACS data consist of a mosaic of Wide Field Channel (WFC) images obtained using F625W, F435W, and F658N filters; with 9 pointings we cover the central ~10'x10' of the cluster and encompass 109 known Chandra sources. We find promising optical counterparts for 59 of the sources, ~40 of which are likely to be associated with the cluster. These include 27 candidate cataclysmic variables (CVs), 24 of which are reported here for the first time. Fourteen of the CV candidates are very faint, with absolute magnitudes in the range M_625 = 10.4 - 12.6, making them comparable in brightness to field CVs near the period minimum discovered in the SDSS (Gansicke et al. 2009). Additional optical counterparts include three BY Dra candidates, a possible blue straggler, and a previously-reported quiescent low-mass X-ray ...

  12. A Systematic Chandra study of Sgr A$^{\\star}$: I. X-ray flare detection

    CERN Document Server

    Yuan, Qiang

    2016-01-01

    Daily X-ray flaring represents an enigmatic phenomenon of Sgr A$^{\\star}$ --- the supermassive black hole at the center of our Galaxy. We report initial results from a systematic X-ray study of this phenomenon, based on extensive {\\it Chandra} observations obtained from 1999 to 2012, totaling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pile-up effect in the modeling of the flare lightcurves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of $6\\%-14\\%$, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flar...

  13. Chandra and XMM Monitoring of the Black Hole X-ray Binary IC 10 X-1

    CERN Document Server

    Laycock, Silas G T; Moro, Matthew J

    2014-01-01

    The massive black hole + Wolf-Rayet binary IC10 X-1 was observed in a series of 10 Chandra and 2 XMM-Newton observations spanning 2003-2012, showing consistent variability around 7 x10^37 erg/s, with a spectral hardening event in 2009. We phase-connected the entire light-curve by folding the photon arrival times on a series of trial periods spanning the known orbital period and its uncertainty, refining the X-ray period to P = 1.45175(1)d. The duration of minimum-flux in the X-ray eclipse is 5 hr which together with the optical radial velocity curve for the companion yields a radius for the eclipsing body of 8-10 Rsun for the allowed range of masses. The orbital separation of 18.5-22 Rsun then provides a limiting inclination i>63 degrees for total eclipses to occur. The eclipses are asymmetric (egress duration 0.9 hr) and show energy dependence, suggestive of an accretion-disk hotspot and corona. The eclipse is much (5X) wider than the 1.5-2 Rsun WR star, pointing to absorption/scattering in the dense wind of...

  14. A Chandra Archival Survey of the X-ray Source Populations of Nearby Galaxies

    Science.gov (United States)

    Kilgard, Roy E.; Wright, Simon; Fonseca, Gloria; Santini, Anthony; Fritze, Hannah

    2017-08-01

    We present results of a volume-limited Chandra archival survey of the X-ray point sources populations of nearby galaxies. We define our sample to include all observations of at least 5 ks of any galaxy within 15 Mpc. The complete sample is in excess of 15000 individual point sources, approximately half of which are contained with the D25 ellipses of galaxies. We present spectral and temporal analyses of this sample, from which we can cleanly define the parameter spaces in color, variability, and luminosity occupied by different classes of sources (e.g., LMXBs vs. HMXBs). For all sources, we perform detailed spatial modeling, spectral fitting, multiband X-ray photometry, and multimodal timing analyses. We further discuss source classes as a function of host galaxy morphology, star formation rate, stellar mass distribution, optical extent, interaction history, and metallicity. Finally, we discuss incompleteness in the sample, and what observations can be conducted in the following years to fill the gap.

  15. X-ray-binary spectra in the lamp post model

    CERN Document Server

    Vincent, F H; Zdziarski, A A; Madej, J

    2016-01-01

    [Abridged] Context. The high-energy radiation from black-hole binaries may be due to the reprocessing of a lamp located on the black hole axis, emitting X-rays. The observed spectrum is made of 3 components: the direct spectrum; the thermal bump; and the reflected spectrum made of the Compton hump and the iron-line complex. Aims. We aim at computing accurately the complete reprocessed spectrum (thermal bump + reflected) of black-hole binaries over the entire X-ray band. We also determine the strength of the direct component. Our choice of parameters is adapted to a source showing an important thermal component. Methods. We compute in full GR the illumination of a thin disk by a lamp along the rotation axis. We use the ATM21 radiative transfer code to compute the spectrum emitted along the disk. We ray trace this local spectrum to determine the reprocessed spectrum as observed at infinity. We discuss the dependence of the local and ray-traced spectra on the emission angle and spin. Results. We show the importa...

  16. A bright thermonuclear X-ray burst simultaneously observed with Chandra and RXTE

    CERN Document Server

    Zand, J J M in t; Marshall, H L; Ballantyne, D R; Jonker, P G; Paerels, F B S; Palmer, D M; Patruno, A; Weinberg, N N

    2013-01-01

    The prototypical accretion-powered millisecond pulsar SAX J1808.4-3658 was observed simultaneously with Chandra-LETGS and RXTE-PCA near the peak of a transient outburst in November 2011. A single thermonuclear (type-I) burst was detected, the brightest yet observed by Chandra from any source, and the second-brightest observed by RXTE. We found no evidence for discrete spectral features during the burst; absorption edges have been predicted to be present in such bursts, but may require a greater degree of photospheric expansion than the rather moderate expansion seen in this event (a factor of a few). These observations provide a unique data set to study an X-ray burst over a broad bandpass and at high spectral resolution (lambda/delta-lambda=200-400). We find a significant excess of photons at high and low energies compared to the standard black body spectrum. This excess is well described by a 20-fold increase of the persistent flux during the burst. We speculate that this results from burst photons being sc...

  17. Shuttle and Transfer Orbit Thermal Analysis and Testing of the Chandra X-Ray Observatory CCD Imaging Spectrometer Radiator Shades

    Science.gov (United States)

    Sharp, John R.

    2001-01-01

    Contents include the following: (1) Introduction: Chandra X-ray observatory. Advanced CCD imaging spectrometer. (2) LEO and transfer orbit analyses: Geometric modeling in TSS w/specularity. Low earth orbital heating calculations. (3) Thermal testing and LMAC. (4) Problem solving. (5) VDA overcoat analyses. (6) VDA overcoat testing and MSFC. (7) Post-MSFC test evaluation.

  18. Measurements of Variability of Low Mass X-ray Binary Candidates in the Early-Type Galaxy NGC 4697 from Multi-Epoch Chandra X-ray Observations

    CERN Document Server

    Sivakoff, Gregory R; Juett, Adrienne M; Sarazin, Craig L; Irwin, Jimmy A

    2008-01-01

    Multi-epoch Chandra X-ray observations of nearby massive early-type galaxies open up the study of an important regime of low-mass X-ray binary (LMXB) behavior -- long term variability. In a companion paper, we report on the detection of 158 X-ray sources down to a detection/completeness limit of 0.6/1.4 x 10^{37} ergs/s using five Chandra observations of NGC 4697, one of the nearest (11.3 Mpc), optically luminous (M_B < -20), elliptical (E6) galaxy. In this paper, we report on the variability of LMXB candidates measured on timescales from seconds to years. At timescales of seconds to hours, we detect five sources with significant variability. Approximately 7% of sources show variability between any two observations, and 16+/-4% of sources do not have a constant luminosity over all five observations. Among variable sources, we identify eleven transient candidates, with which we estimate that if all LMXBs in NGC 4697 are long-term transients then they are on for ~ 100 yr and have a 7% duty cycle. These numbe...

  19. The puzzling detection of x-rays from Pluto by Chandra

    Science.gov (United States)

    Lisse, C. M.; McNutt, R. L.; Wolk, S. J.; Bagenal, F.; Stern, S. A.; Gladstone, G. R.; Cravens, T. E.; Hill, M. E.; Kollmann, P.; Weaver, H. A.; Strobel, D. F.; Elliott, H. A.; McComas, D. J.; Binzel, R. P.; Snios, B. T.; Bhardwaj, A.; Chutjian, A.; Young, L. A.; Olkin, C. B.; Ennico, K. A.

    2017-05-01

    Using Chandra ACIS-S, we have obtained low-resolution imaging X-ray spectrophotometry of the Pluto system in support of the New Horizons flyby on 14 July 2015. Observations were obtained in a trial ;seed; campaign conducted in one visit on 24 Feb 2014, and a follow-up campaign conducted soon after the New Horizons flyby that consisted of 3 visits spanning 26 Jul to 03 Aug 2015. In a total of 174 ksec of on-target time, in the 0.31 to 0.60 keV passband, we measured 8 total photons in a co-moving 11 × 11 pixel2 box (the 90% flux aperture determined by observations of fixed background sources in the field) measuring ∼121,000 × 121,000 km2 (or ∼100 × 100 RPluto) at Pluto. No photons were detected from 0.60 to 1.0 keV in this box during the same exposures. Allowing for background, we find a net signal of 6.8 counts and a statistical noise level of 1.2 counts, for a detection of Pluto in this passband at > 99.95% confidence. The Pluto photons do not have the spectral shape of the background, are coincident with a 90% flux aperture co-moving with Pluto, and are not confused with any background source, so we consider them as sourced from the Pluto system. The mean 0.31 - 0.60 keV X-ray power from Pluto is 200 +200/-100 MW, in the middle range of X-ray power levels seen for other known Solar System emission sources: auroral precipitation, solar X-ray scattering, and charge exchange (CXE) between solar wind (SW) ions and atmospheric neutrals. We eliminate auroral effects as a source, as Pluto has no known magnetic field and the New Horizons Alice UV spectrometer detected no airglow from Pluto during the flyby. Nano-scale atmospheric haze particles could lead to enhanced resonant scattering of solar X-rays from Pluto, but the energy signature of the detected photons does not match the solar spectrum and estimates of Pluto's scattered X-ray emission are 2 to 3 orders of magnitude below the 3.9 ± 0.7 × 10-5cps found in our observations. Charge-exchange-driven emission

  20. Chandra Reveals Twin X-ray Jets in the Powerful FR-II Radio Galaxy 3C353

    Energy Technology Data Exchange (ETDEWEB)

    Kataoka, J.; Stawarz, L.; Harris, D.E.; Siemiginowska, A.; Ostrowski, M.; Swain, M.R.; Hardcastle, M.J.; Goodger, J.L.; Iwasawa, K.; Edwards, P.G.

    2008-06-13

    We report X-ray imaging of the powerful FR II radio galaxy 3C 353 using the Chandra X-ray Observatory. 3C 353's two 4-inch wide and 2-feet long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution provided by the VLA and Chandra instruments. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C 353, including the nucleus, the jet and the counterjet, the terminal jet regions (hotspots), and one radio lobe. We show that the detection of the X-ray emission associated with the radio knots and counterknots, which is most likely non-thermal in origin, puts several crucial constraints on the X-ray emission mechanisms in powerful large-scale jets of quasars and FR II sources. In particular, we show that this detection is inconsistent with the inverse-Compton model proposed in the literature, and instead implies a synchrotron origin of the X-ray jet photons. We also find that the width of the X-ray counterjet is possibly narrower than that measured in radio bands, that the radio-to-X-ray flux ratio decreases systematically downstream along the jets, and that there are substantial (kpc-scale) offsets between the positions of the X-ray and radio intensity maxima within each knot, whose magnitudes increase away from the nucleus. We discuss all these findings in the wider context of the physics of extragalactic jets, proposing some particular though not definitive solutions or interpretations for each problem. In general, we find that the synchrotron X-ray emission of extragalactic large-scale jets is not only shaped by the global hydrodynamical configuration of the outflows, but is also likely to be very sensitive to the microscopic parameters of the jet plasma. A complete, self-consistent model for the X-ray emission of extragalactic jets still remains elusive.

  1. HST/ACS IMAGING OF OMEGA CENTAURI: OPTICAL COUNTERPARTS OF CHANDRA X-RAY SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Cool, Adrienne M.; Arias, Tersi; Brochmann, Michelle; Dorfman, Jason; Gafford, April; White, Vivian [Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 (United States); Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Physics and Astronomy Department, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Anderson, Jay, E-mail: cool@sfsu.edu, E-mail: dhaggard@northwestern.edu [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

    2013-02-15

    We present results of a search for optical counterparts of X-ray sources in and toward the globular cluster Omega Centauri (NGC 5139) using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The ACS data consist of a mosaic of Wide Field Channel images obtained using F625W, F435W, and F658N filters; with nine pointings we cover the central {approx}10' Multiplication-Sign 10' of the cluster and encompass 109 known Chandra sources. We find promising optical counterparts for 59 of the sources, {approx}40 of which are likely to be associated with the cluster. These include 27 candidate cataclysmic variables (CVs), 24 of which are reported here for the first time. Fourteen of the CV candidates are very faint, with absolute magnitudes in the range M {sub 625} =10.4-12.6, making them comparable in brightness to field CVs near the period minimum discovered in the Sloan Digital Sky Survey. Additional optical counterparts include three BY Dra candidates, a possible blue straggler, and a previously reported quiescent low-mass X-ray binary. We also identify 3 foreground stars and 11 probable active galactic nuclei. Finally, we report the discovery of a group of seven stars whose X-ray properties are suggestive of magnetically active binaries, and whose optical counterparts lie on or very near the metal-rich anomalous giant and subgiant branches in {omega} Cen. If the apparent association between these seven stars and the RGB/SGB-a stars is real, then the frequency of X-ray sources in this metal-rich population is enhanced by a factor of at least five relative to the other giant and subgiant populations in the cluster. If these stars are not members of the metal-rich population, then they bring the total number of red stragglers (also known as sub-subgiants) that have been identified in {omega} to Cen 20, the largest number yet known in any globular cluster.

  2. Chandra Phase-resolved X-Ray Spectroscopy of the Crab Pulsar

    Science.gov (United States)

    Weisskopf, Martin C.; Tennant, Allyn F.; Yakovlev, Dmitry G.; Harding, Alice; Zavlin, Vyacheslav E.; O'Dell, Stephen L.; Elsner, Ronald F.; Becker, Werner

    2011-12-01

    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 underabundant in oxygen and provide measurements with improved accuracy and less bias. Using the abundances and cross sections from Wilms et al. we find [O/H] = (5.28 ± 0.28) × 10-4 (4.9 × 10-4 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 τscat = 0.147 ± 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 also 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 are 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. We discuss how such data are best connected to theoretical models of neutron star cooling and neutron star interiors. The data restrict the neutrino emission rate in the pulsar core and the amount of light elements in the heat-blanketing envelope. The observations allow the pulsar

  3. Extended X-ray Monitoring of Gravitational Lenses with Chandra and Joint Constraints on X-ray Emission Regions

    CERN Document Server

    Guerras, Eduardo; Steele, Shaun; Liu, Ang; Kochanek, Christopher S; Chartas, George; Morgan, Christopher W; Chen, Bin

    2016-01-01

    We present an X-ray photometric analysis of six gravitationally lensed quasars spanning from 5 to 14 years, measuring the total (0.83-21.8 keV restframe), soft (0.83-3.6 keV), and hard (3.6-21.8 keV) band image flux ratios for each epoch. Using the ratios of the model-predicted macro-magnifications as baselines, we build differential microlensing curves and obtain joint likelihood functions for the average X-ray emission region sizes. Our analysis yields a Probability Distribution Function for the average half-light radius of the X-Ray emission region in the sample that peaks slightly above 1 gravitational radius, and yields nearly indistinguishable 68 % confidence (one-sided) upper limits of 17.8 (18.9) gravitational radii for the soft (hard) X-ray emitting region, assuming a mean stellar mass of 0.3 solar masses. We see hints of energy dependent microlensing between the soft and hard bands in two of the objects. In a separate analysis on the root-mean-square (RMS) of the microlensing variability, we find si...

  4. The X-Ray Line Feature At 3.5 Kev In Galaxy Cluster Spectra

    CERN Document Server

    Phillips, K J H; Sylwester, J

    2015-01-01

    Recent work by Bulbul et al. and Boyarsky et al. has suggested that a line feature at approx. 3.5 keV in the X-ray spectra of galaxy clusters and individual galaxies seen with XMM-Newton is due to the decay of sterile neutrinos, a dark matter candidate. This identification has been criticized by Jeltema and Profumo on the grounds that model spectra suggest that atomic transitions in helium-like potassium (K XVIII) and chlorine (Cl XVI) are more likely to be the emitters. Here it is pointed out that the K XVIII lines have been observed in numerous solar flare spectra at high spectral resolution with the RESIK crystal spectrometer and also appear in Chandra HETG spectra of the coronally active star sigma Gem. In addition, the solar flare spectra at least indicate a mean coronal potassium abundance which is a factor of between 9 and 11 higher than the solar photospheric abundance. This fact, together with the low statistical quality of the XMM-Newton spectra, completely accounts for the approx. 3.5 keV feature a...

  5. Contributions of the "Great" X-Ray Observatories (XMM-Newton and Chandra) to Astronomy and Astrophysics

    Science.gov (United States)

    Weisskopf, Martin

    2011-01-01

    NASA s Chandra X-ray Observatory and ESA s XMM-Newton made their first observations over a decade ago. The unprecedented and complementary capabilities of these observatories to detect, image, and measure the energy of cosmic X-rays, achieved less than 50 years after the first detection of an extra-solar X-ray source, represent an increase in sensitivity comparable in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. In this presentation we highlight some of the many discoveries made using these powerful X-ray observatories that have transformed 21st century astronomy. We briefly discuss future prospects for this truly exciting field.

  6. X-ray spectra of hot accretion flows

    CERN Document Server

    Niedzwiecki, Andrzej; Stepnik, Agnieszka

    2014-01-01

    We study radiative properties of hot accretion flows in a general relativistic model with an exact treatment of global Comptonization, developed in our recent works. We note a strong dependence of electron temperature on the strength of magnetic field and we clarify that the underlying mechanism involves the change of the flow structure, with more strongly magnetised flows approaching the slab geometry more closely. We find that the model with thermal synchrotron radiation being the main source of seed photons agrees with the spectral index vs Eddington ratio relation observed in black hole transients below 1 per cent of the Eddington luminosity, LEdd, and models with a weak direct heating of electrons (small delta) are more consistent with observations. Models with large delta predict slightly too soft spectra, furthermore, they strongly overpredict electron temperatures at ~0.01 LEdd. The low-luminosity spectra, at <0.001 LEdd, deviate from a power-law shape in the soft X-ray range and we note that the f...

  7. Contemporaneous Chandra HETG and Suzaku X-ray observations of NGC 4051

    Science.gov (United States)

    Lobban, A. P.; Reeves, J. N.; Miller, L.; Turner, T. J.; Braito, V.; Kraemer, S. B.; Crenshaw, D. M.

    2011-07-01

    We present the results of a deep 300 ks Chandra High Energy Transmission Grating (HETG) observation of the highly variable narrow-line Seyfert Type 1 galaxy NGC 4051. The HETG spectrum reveals 28 significant soft X-ray ionized lines in either emission or absorption; primarily originating from H-like and He-like K-shell transitions of O, Ne, Mg and Si (including higher order lines and strong forbidden emission lines from O VII and Ne IX) plus high-ionization L-shell transitions from Fe XVII to Fe XXII and lower ionization inner-shell lines (e.g. O VI). Modelling the data with XSTAR requires four distinct ionization zones for the gas, all outflowing with velocities log ξ= 4.1+0.2-0.1; vout˜-0.02c) which potentially may have a significant effect on the host galaxy environment via feedback. Finally, we also simultaneously model the broad-band 2008 XIS+HXD (Hard X-ray Detector) Suzaku data with archival Suzaku data from 2005 when the source was observed to have entered an extended period of low flux in an attempt to analyse the cause of the long-term spectral variability. We find that we can account for this by allowing for large variations in the normalization of the intrinsic power-law component which may be interpreted as being due to significant changes in the covering fraction of a Compton-thick partial-coverer obscuring the central continuum emission.

  8. NASA Chandra X-ray Observatory Selected as Editor's Choice in 2000 Discover Magazine Awards for Technological Innovation

    Science.gov (United States)

    2000-06-01

    The Chandra X-ray Observatory, NASA's newest and most powerful X-ray space telescope, has been selected as the winner of the Editor's Choice category of the 2000 Discover Magazine Awards for Technological Innovation. The team of government, industry, university and research institutions that designed, built and deployed Chandra for NASA's Marshall Space Flight Center, Huntsville, Ala, will be formally recognized June 24 at a gala awards celebration at Epcot at the Walt Disney World Resort in Orlando, Fl. Dr. Harvey Tananbaum, director of the Smithsonian Astrophysical Observatory's Chandra X-ray Science Center, Cambridge, Mass., which conducts the Chandra science mission for NASA, will receive the award on behalf of the team. "Chandra has opened a new window for astronomers into the universe of high-energy cosmic events such as pulsars, supernova remnants and black holes," said Tananbaum. "We're now able to create spectacularly detailed images of celestial phenomena whose mere existence we could only hypothesize before." Among Chandra's most significant discoveries to date, he lists the detection of a giant ring around the heart of the Crab Nebula, details of the shock wave created by an exploding star and resolution of the high-energy X-ray "glow" in the universe into millions of specific light sources. "The successful launch, deployment and on-orbit operations of NASA's Chandra X-ray Observatory is a testament to the solid partnership between TRW, NASA and the science community that has been enabling NASA's most important space science missions for the past 40 years," said Timothy W. Hannemann, executive vice president and general manager, TRW Space & Electronics Group. "The extraordinary images that Chandra is delivering daily speaks loudly not only to the quality of the science instruments on board, but also to the engineering talents and dedication to mission success exhibited by every member of NASA's Chandra mission team." Chandra, named in honor of Nobel

  9. Interstellar X-ray Absorption Spectroscopy of Oxygen, Neon, and Iron with the Chandra LETGS Spectrum of X0614+091

    CERN Document Server

    Paerels, F B S; Van der Meer, R L J; Kaastra, J S; Kuulkers, E; Den Boggende, A J F; Predehl, P; Drake, J J; Kahn, S M; Savin, D W; McLaughlin, B M; Paerels, Frits; Drake, Jeremy J.; Kahn, Steven M.; Savin, Daniel W.; Laughlin, Brendan M. Mc

    2000-01-01

    We find resolved interstellar O K, Ne K, and Fe L absorption spectra in the Chandra Low Energy Transmission Grating Spectrometer spectrum of the low mass X-ray binary X0614+091. We measure the column densities in O and Ne, and find direct spectroscopic constraints on the chemical state of the interstellar O. These measurements probably probe a low-density line of sight through the Galaxy and we discuss the results in the context of our knowledge of the properties of interstellar matter in regions between the spiral arms.

  10. Near-Infrared Properties of Faint X-rays Sources from NICMOS Imaging in the Chandra Deep Fields

    CERN Document Server

    Colbert, J W; Yan, L; Malkan, M A; McCarthy, P; Colbert, James W.; Teplitz, Harry; Yan, Lin; Malkan, Matthew; Carthy, Patrick Mc

    2004-01-01

    We measure the near-infrared properties of 42 X-ray detected sources from the Chandra Deep Fields North and South, the majority of which lie within the NICMOS Hubble Deep Field North and Ultra Deep Field. We detect all 42 Chandra sources with NICMOS, with 95% brighter than H = 24.5. We find that X-ray sources are most often in the brightest and most massive galaxies. Neither the X-ray fluxes nor hardness ratios of the sample show any correlation with near-infrared flux, color or morphology. This lack of correlation indicates there is little connection between the two emission mechanisms and is consistent with the near-infrared emission being dominated by starlight rather than a Seyfert non-stellar continuum. Near-infrared X-ray sources make up roughly half of all extremely red (J-H > 1.4) objects brighter than H > 24.5. These red X-ray sources have a range of hardness ratios similar to the rest of the sample, decreasing the likelihood of dust-obscured AGN activity as the sole explanation for their red color. ...

  11. Chandra & XMM-Newton Observations of NGC5253. Analysis of the X-ray Emission from a Dwarf Starburst Galaxy

    CERN Document Server

    Summers, L K; Strickland, D K; Heckman, T M; Summers, Lesley K.; Stevens, Ian R.; Strickland, David K.; Heckman, Timothy M.

    2004-01-01

    We present Chandra and XMM-Newton X-ray data of NGC5253, a local starbursting dwarf elliptical galaxy, in the early stages of a starburst episode. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission, in the form of what appear to be multiple superbubbles, and smaller bubbles probably associated with individual star clusters. Chandra detects 17 sources within the optical extent of NGC5253 down to a completeness level corresponding to a luminosity of 1.5E37 erg/s.The slope of the point source X-ray luminosity function is -0.54, similar to that of other nearby dwarf starburst galaxies. Several different types of source are detected within the galaxy, including X-ray binaries and the emission associated with star-clusters. Comparison of the diffuse X-ray emission with the observed Halpha emission shows similarities in their extent. The best spectral fit to the diffuse emission is obtained with an absorbed, two temperature model giving temperatures for the two gas com...

  12. X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view

    CERN Document Server

    Raiteri, C M; Kadler, M; Krichbaum, T P; Böttcher, M; Fuhrmann, L; Orio, M

    2006-01-01

    In this paper we analyse five observations of the BL Lac object AO 0235+16 performed with the Chandra and XMM-Newton satellites during the years 2000-2005. In the February 2002 observation the source is found in a bright state and presents a steep X-ray spectrum, while in all the other epochs it is faint and the spectrum is hard. The soft X-ray spectrum appears to be strongly absorbed, likely by the intervening system at z=0.524, which also absorbs the optical-UV radiation. We find that models that consider spectral curvature are superior to single power law ones in fitting the X-ray spectrum. In particular, we favour a double power law model, which agrees with the assumption of a superposition of two different components in the X-ray domain. Both in the Chandra and in one of the XMM-Newton observations, a tentative detection of the redshifted Fe Kalpha emission line may suggest its origin from the inner part of an accretion disc. Thermal emission from this accretion disc might explain the UV-soft-X-ray bump ...

  13. X-Ray/Ultraviolet Observing Campaign of the Markarian 279 Active Galactic Nucleus Outflow: a close look at the absorbing/emitting gas with Chandra-LETGS

    CERN Document Server

    Costantini, E; Arav, N; Kriss, G A; Steenbrugge, K C; Gabel, J R; Verbunt, F; Behar, E; Gaskell, C M; Korista, K T; Proga, D; Quijano, J K; Scott, J E; Klimek, E S; Hedrick, C H

    2006-01-01

    We present a Chandra-LETGS observation of the Seyfert 1 galaxy Mrk 279. This observation was carried out simultaneously with HST-STIS and FUSE, in the context of a multiwavelength study of this source. The Chandra pointings were spread over ten days for a total exposure time of ~360 ks. The spectrum of Mrk279 shows evidence of broad emission features, especially at the wavelength of the OVII triplet. We quantitatively explore the possibility that this emission is produced in the broad line region (BLR). We modeled the broad UV emission lines seen in the FUSE and HST-STIS spectra following the ``locally optimally emitting cloud" approach. We find that the X-ray lines luminosity derived from the best fit BLR model can match the X-ray features, suggesting that the gas producing the UV lines is sufficient to account also for the X-ray emission. The spectrum is absorbed by ionized gas whose total column density is ~5x10^{20} cm^{-2}. The absorption spectrum can be modeled by two distinct gas components (log xi ~ 0...

  14. X-ray measurements on wood - spectra measurements

    DEFF Research Database (Denmark)

    Jensen, Signe Kamp; Thygesen, Lisbeth Garbrecht; Gerward, Leif

    (free-scanning). In this way 100 points are measured for each wood sample. This produces information about moisture content and density of the samples as water and wood attenuations of the x-rays are different for the different energy levels contained in the x-rays. The "real" density and moisture...

  15. Contemporaneous Chandra HETG and Suzaku X-ray Observations of NGC 4051

    CERN Document Server

    Lobban, A P; Miller, L; Turner, T J; Braito, V; Kraemer, S B; Crenshaw, D M

    2011-01-01

    We present the results of a deep 300 ks Chandra HETG observation of the highly variable narrow-line Seyfert Type 1 galaxy NGC 4051. The HETG spectrum reveals 28 significant soft X-ray ionised lines in either emission or absorption; primarily originating from H-like and He-like K-shell transitions of O, Ne, Mg and Si (including higher order lines and strong forbidden emission lines from O VII and Ne IX) plus high ionisation L-shell transitions from Fe XVII to Fe XXII and lower ionisation inner-shell lines (e.g. O VI). Modelling the data with XSTAR requires four distinct ionisation zones for the gas, all outflowing with velocities < 1000 km/s. A selection of the strongest emission/absorption lines appear to be resolved with FWHM of ~600 km/s. We also present the results from a quasi-simultaneous 350 ks Suzaku observation of NGC 4051 where the XIS spectrum reveals strong evidence for blueshifted absorption lines at ~6.8 and ~7.1 keV, consistent with previous findings. Modelling with XSTAR suggests that this i...

  16. A Chandra X-ray observation of the globular cluster Terzan 1

    CERN Document Server

    Cackett, E M; Heinke, C O; Pooley, D; Lewin, W H G; Grindlay, J E; Edmonds, P D; Jonker, P G; Miller, J M

    2005-01-01

    We present a 19 ks Chandra ACIS-S observation of the globular cluster Terzan 1. Fourteen sources are detected within 1.4 arcmin of the cluster center with 2 of these sources predicted to be not associated with the cluster (background AGN or foreground objects). The neutron star X-ray transient, X1732-304, has previously been observed in outburst within this globular cluster with the outburst seen to last for at least 12 years. Here we find 4 sources that are consistent with the ROSAT position for this transient, but none of the sources are fully consistent with the position of a radio source detected with the VLA that is likely associated with the transient. The most likely candidate for the quiescent counterpart of the transient has a relatively soft spectrum and an unabsorbed 0.5-10 keV luminosity of 2.6E32 ergs/s, quite typical of other quiescent neutron stars. Assuming standard core cooling, from the quiescent flux of this source we predict long (>400 yr) quiescent episodes to allow the neutron star to co...

  17. Deep Chandra X-ray Observations of Low Mass X-ray Binary Candidates in the Early-Type Galaxy NGC 4697

    CERN Document Server

    Sivakoff, Gregory R; Juett, Adrienne M; Sarazin, Craig L; Irwin, Jimmy A

    2008-01-01

    Chandra X-ray observations routinely resolve tens to hundreds of low-mass X-ray binaries (LMXBs) per galaxy in nearby massive early-type galaxies. These studies have raised important issues regarding the behavior of this population of remnants of the once massive stars in early-type galaxies, namely the connection between LMXBs and globular clusters (GCs) and the nature of the LMXB luminosity function (LF). In this paper, we combine five epochs of Chandra observations and one central field Hubble Space Telescope Advance Camera for Surveys observation of NGC 4697, one of the nearest, optically luminous elliptical (E6) galaxies, to probe the GC-LMXB connection and LMXB-LF down to a detection/completeness limit of (0.6/1.4) x 10^{37} ergs/s. We detect 158 sources, present their luminosities and hardness ratios, and associate 34 LMXBs with GCs. We confirm that GCs with higher encounter rates (\\Gamma_h) and redder colors (higher metallicity Z) are more likely to contain GCs, and find that the expected number of LM...

  18. X-ray spectra of hot accretion flows

    Science.gov (United States)

    Niedźwiecki, Andrzej; Xie, Fu-Guo; Stȩpnik, Agnieszka

    2014-09-01

    We study radiative properties of hot accretion flows in a general relativistic model with an exact treatment of global Comptonization, developed in our recent works. We note a strong dependence of electron temperature on the strength of magnetic field and we clarify that the underlying mechanism involves the change of the flow structure, with more strongly magnetized flows approaching the slab geometry more closely. We find that the model with thermal synchrotron radiation being the main source of seed photons agrees with the spectral index versus Eddington ratio relation observed in black hole transients below 1 per cent of the Eddington luminosity, LEdd, and models with a weak direct heating of electrons (small δ) are more consistent with observations. Models with large δ predict slightly too soft spectra, furthermore, they strongly overpredict electron temperatures at ˜0.01LEdd. The low-luminosity spectra, at ≲ 0.001LEdd, deviate from a power-law shape in the soft X-ray range, and we note that the first-scattering bump often resembles a thermal like component, with the temperature of a few hundred eV, superimposed on a power-law spectrum. The model with thermal Comptonization of thermal synchrotron radiation does not agree with well-studied AGNs observed below ˜0.01LEdd, for which there is a substantial evidence for the lack of an inner cold disc. This indicates that the model of hot flows powering AGNs should be revised, possibly by taking into account an additional (but internal to the flow) source of seed photons.

  19. Chandra X-ray Observations of the 0.6 < z < 1.1 Red-Sequence Cluster Survey Sample

    CERN Document Server

    Hicks, Amalia K; Bautz, Mark; Cain, Benjamin; Gilbank, David; Gladders, M D; Hoekstra, Henk; Yee, Howard; Garmire, Gordon

    2007-01-01

    We present the results of Chandra observations of 13 optically-selected clusters with 0.63; though 3 were not observed long enough to support detailed analysis. Surface brightness profiles are fit to beta-models. Integrated spectra are extracted within R(2500), and Tx and Lx information is obtained. We derive gas and total masses within R(2500) and R(500). Cosmologically corrected scaling relations are investigated, and we find the RCS clusters to be consistent with self-similar scaling expectations. However discrepancies exist between the RCS sample and lower-z X-ray selected samples for relationships involving Lx, with the higher-z RCS clusters having lower Lx for a given Tx. In addition, we find that gas mass fractions within R(2500) for the high-z RCS sample are lower than expected by a factor of ~2. This suggests that the central entropy of these high-z objects has been elevated by processes such as pre-heating, mergers, and/or AGN outbursts, that their gas is still infalling, or that they contain compar...

  20. Evolution of temperature-dependent charge transfer inefficiency correction for ACIS on the Chandra X-ray Observatory

    Science.gov (United States)

    Grant, Catherine E.; Bautz, Marshall W.; Durham, R. Nick; Plucinsky, Paul P.

    2016-07-01

    As ACIS on the Chandra X-ray Observatory enters its seventeenth year of operation, it continues to perform well and produce spectacular scientific results. The response of ACIS has evolved over the lifetime of the observatory due to radiation damage and aging of the spacecraft. The ACIS instrument team developed a software tool which applies a correction to each X-ray event and mitigates charge transfer inefficiency (CTI) and spectral resolution degradation. The behavior of the charge traps that cause CTI are temperature dependent, however, and warmer temperatures reduce the effectiveness of the correction algorithm. As the radiator surfaces on Chandra age, ACIS cooling has become less efficient and temperatures can increase by a few degrees. A temperature-dependent component was added to the CTI correction algorithm in 2010. We present an evaluation of the effectiveness of this algorithm as the radiation damage and thermal environment continue to evolve and suggest updates to improve the calibration fidelity.

  1. X-ray properties of radio-selected star forming galaxies in the Chandra-COSMOS survey

    CERN Document Server

    Ranalli, P; Zamorani, G; Cappelluti, N; Civano, F; Georgantopoulos, I; Gilli, R; Schinnerer, E; Smolcic, V; Vignali, C

    2012-01-01

    X-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4 GHz in the VLA-COSMOS survey, classified by Smolcic et al. (2008) according to their optical colours and observed with Chandra. A similarly selected control sample of AGN is also used for comparison. We review some X-ray based classification criteria and check how they affect the sample composition. The efficiency of the classification scheme devised by Smolcic et al. (2008) is such that ~30% of composite/misclassified objects are expected because of the higher X-ray brightness of AGN with respect to galaxies. The latter fraction is actually 50% in the X-ray detected sources, while it is expected to be muc...

  2. Resonant soft X-ray fluorescence spectra of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Nordgren, J.; Glans, P.; Gunnelin, K.; Guo, J.; Skytt, P.; Saathe, C.; Wassdahl, N. [Uppsala Univ. (Sweden). Dept. of Phys.

    1997-08-01

    A review is presented of some recent advancements in resonant soft X-ray fluorescence spectroscopy applied to molecules. The concept of inelastic scattering is discussed for molecules with an element of symmetry, which introduces degeneracy or near-degeneracy of core excited states. The potential of the symmetry selection rules associated with resonant X-ray fluorescence is illustrated in studies of electronic structure as well as molecular dynamics. The use of polarized photons for exciting X-ray emission is discussed, and examples are presented where anisotropy of X-ray emission provides more detailed information. A brief section discusses the experimental considerations relevant for the spectroscopic technique. (orig.) With 013 figs., 28 refs.

  3. X-ray measurements on wood - spectra measurements

    DEFF Research Database (Denmark)

    Jensen, Signe Kamp; Thygesen, Lisbeth Garbrecht; Gerward, Leif

    The report concerns simultaneous non-destructive measurements of water content and density of wood. Theoretically, this should be possible using a x-ray equipment newly build at BKM, and this work is an attempt to use the equipment for assessing water content and density of wood samples under...... laboratory conditions. A number of wood samples with different densities are placed at different relative humidities from 0.5 to 97 %RH. When equilibrium is obtained the samples are measured with the x-ray equipment such that 10 points are measured in the sample followed by measurements outside the sample...... (free-scanning). In this way 100 points are measured for each wood sample. This produces information about moisture content and density of the samples as water and wood attenuations of the x-rays are different for the different energy levels contained in the x-rays. The "real" density and moisture...

  4. The Extended Chandra Deep Field-South Survey: Optical spectroscopy of faint X-ray sources with the VLT and Keck

    CERN Document Server

    Silverman, J D; Salvato, M; Hasinger, G; Bergeron, J; Capak, P; Szokoly, G; Finoguenov, A; Gilli, R; Rosati, P; Tozzi, P; Vignali, C; Alexander, D M; Brandt, W N; Lehmer, B D; Luo, B; Rafferty, D; Xue, Y Q; Balestra, I; Bauer, F E; Brusa, M; Comastri, A; Kartaltepe, J; Koekemoer, A M; Miyaji, T; Schneider, D P; Treister, E; Wisotski, L; Schramm, M

    2010-01-01

    We present the results of a program to acquire high-quality optical spectra of X-ray sources detected in the E-CDF-S and its central area. New spectroscopic redshifts are measured for 283 counterparts to Chandra sources with deep exposures (t~2-9 hr per pointing) using multi-slit facilities on both the VLT and Keck thus bringing the total number of spectroscopically-identified X-ray sources to over 500 in this survey field. We provide a comprehensive catalog of X-ray sources detected in the E-CDF-S including the optical and near-infrared counterparts, and redshifts (both spectroscopic and photometric) that incorporate published spectroscopic catalogs thus resulting in a final sample with a high fraction (80%) of X-ray sources having secure identifications. We demonstrate the remarkable coverage of the Lx-z plane now accessible from our data while emphasizing the detection of AGNs that contribute to the faint end of the luminosity function at 1.5

  5. Thermodynamic perturbations in the X-ray halo of 33 clusters of galaxies observed with Chandra ACIS

    CERN Document Server

    Hofmann, F; Nandra, K; Clerc, N; Gaspari, M

    2016-01-01

    In high-resolution X-ray observations of the hot plasma in clusters of galaxies significant structures caused by AGN feedback, mergers, and turbulence can be detected. Many clusters have been observed by Chandra in great depth and at high resolution. Using archival data taken with the Chandra ACIS instrument the aim was to study thermodynamic perturbations of the X-ray emitting plasma and to apply this to better understand the thermodynamic and dynamic state of the intra cluster medium (ICM). We analysed deep observations for a sample of 33 clusters with more than 100 ks of Chandra exposure each at distances between redshift 0.025 and 0.45. The combined exposure of the sample is 8 Ms. Fitting emission models to different regions of the extended X-ray emission we searched for perturbations in density, temperature, pressure, and entropy of the hot plasma. For individual clusters we mapped the thermodynamic properties of the ICM and measured their spread in circular concentric annuli. Comparing the spread of dif...

  6. Chandra observation of the fast X-ray transient IGR J17544-2619: evidence for a neutron star?

    CERN Document Server

    in 't Zand, J J M

    2005-01-01

    IGR J17544-2619 belongs to a distinct group of at least seven fast X-ray transients that cannot readily be associated with nearby flare stars or pre-main sequence stars and most probably are X-ray binaries with wind accretion. Sofar, the nature of the accretor has been determined in only one case (SAX J1819.3-2525/V4641 Sgr). We carried out a 20 ks Chandra ACIS-S observation of IGR J17544-2619 which shows the source in quiescence going into outburst. The Chandra position confirms the previous tentative identification of the optical counterpart, a blue O9Ib supergiant at 3 to 4 kpc (Pellizza, Chaty & Negueruela, in prep.). This is the first detection of a fast X-ray transient in quiescence. The quiescent spectrum is very soft. The photon index of 5.9+/-1.2 (90% confidence error margin) is much softer than 6 quiescent black hole candidates that were observed with Chandra ACIS-S (Kong et al. 2002; Tomsick et al. 2003). Assuming that a significant fraction of the quiescent photons comes from the accretor and ...

  7. The restless universe understanding X-ray astronomy in the age of Chandra and Newton

    CERN Document Server

    Schlegel, Eric M

    2002-01-01

    This title tells the story of the development and launch of a major space-based telescope, and explains the discoveries of the nature of the universe in the X-ray spectre. The author looks at the brief history of X-ray astronomy to explore what can and has been learnt by using X-ray.

  8. Markov Chain Monte Carlo Joint Analysis of Chandra X-Ray Imaging Spectroscopy and Sunyaev-Zel'dovich Effect Data

    Science.gov (United States)

    Bonamente, Massimillano; Joy, Marshall K.; Carlstrom, John E.; Reese, Erik D.; LaRoque, Samuel J.

    2004-01-01

    X-ray and Sunyaev-Zel'dovich effect data can be combined to determine the distance to galaxy clusters. High-resolution X-ray data are now available from Chandra, which provides both spatial and spectral information, and Sunyaev-Zel'dovich effect data were obtained from the BIMA and Owens Valley Radio Observatory (OVRO) arrays. We introduce a Markov Chain Monte Carlo procedure for the joint analysis of X-ray and Sunyaev- Zel'dovich effect data. The advantages of this method are the high computational efficiency and the ability to measure simultaneously the probability distribution of all parameters of interest, such as the spatial and spectral properties of the cluster gas and also for derivative quantities such as the distance to the cluster. We demonstrate this technique by applying it to the Chandra X-ray data and the OVRO radio data for the galaxy cluster A611. Comparisons with traditional likelihood ratio methods reveal the robustness of the method. This method will be used in follow-up paper to determine the distances to a large sample of galaxy cluster.

  9. X-rays from Saturn: A study with XMM-Newton and Chandra over the years 2002-05

    CERN Document Server

    Branduardi-Raymont, G; Elsner, R F; Rodriguez, P

    2009-01-01

    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 se...

  10. Copper L X-ray spectra measured by a high resolution ion-induced X-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryohei; Hamaguchi, Dai; Kageyama, Hiroyoshi [Kyoto Inst. of Tech. (Japan)] [and others

    1997-03-01

    High resolution L X-ray emission spectra of Cu have been measured by 0.75 MeV/u H, He, and F, 0.73 MeV/u Ar, 0.64 MeV/u Si, and 0.073 MeV/u Si ion impacts with a crystal spectrometer. The X-ray transition energies in the Cu target for L{iota}, L{eta}, L{alpha}{sub 1,2}, L{beta}{sub 1}, and L{beta}{sub 3,4} diagram lines induced by light ion impacts are determined, which are in good agreement with those given in the reference. The difference in L X-ray emission spectra produced by H, He, F, Si, and Ar ions are considered and the L{alpha}{sub 1,2} and L{beta}{sub 1} emission spectra are compared with the calculated ones based on the multiconfiguration Dirac-Fock method. (author)

  11. A Chandra X-ray study of the young star cluster NGC 6231: low-mass population and initial mass function

    Science.gov (United States)

    Damiani, F.; Micela, G.; Sciortino, S.

    2016-12-01

    Context. NGC 6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data, where we detect 1613 point X-ray sources. Aims: Our main aim is to clarify global properties of NGC 6231 down to low masses through a detailed membership assessment, and to study the cluster stars' spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and initial mass function. Methods: We use X-ray data, complemented by optical and IR data, to establish cluster membership. The spatial distribution of different stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. We perform spectral modelling of group-stacked X-ray source spectra. Results: We find a large cluster population down to 0.3 M⊙ (complete to 1 M⊙), with minimal non-member contamination, with a definite age spread (1-8 Myr) for the low-mass PMS stars. We argue that low-mass cluster stars also constitute the majority of the few hundreds unidentified X-ray sources. We find mass segregation for the most massive stars. The fraction of circumstellar-disk bearing members is found to be 5%. Photoevaporation of disks under the action of massive stars is suggested by the spatial distribution of the IR-excess stars. We also find strong Hα emission in 9% of cluster PMS stars. The dependence of X-ray properties on mass, stellar structure, and age agrees with extrapolations based on other young clusters. The cluster initial mass function, computed over 2 dex in mass, has a slope Γ -1.14. The total mass of cluster members above 1 M⊙ is 2.28 × 103M⊙, and the inferred total mass is 4.38 × 103M⊙. We also study the peculiar, hard X-ray spectrum of the Wolf-Rayet star WR 79. Full Tables B.1 and B.2 are only available at the CDS via anonymous ftp

  12. The MOJAVE Chandra Sample: A Correlation Study of Blazars and Radio Galaxies in X-ray and Radio Wavelengths

    Science.gov (United States)

    Hogan, Brandon Scott

    2011-05-01

    The Chandra X-ray observatory has increased the quality and number of detections the X-ray regime since its launch in 1999. It is an important tool for studying the jets which are associated with Active Galactic Nuclei (AGN) and their possible emission mechanisms. The MOJAVE Chandra Sample (MCS) is a sample of 27 AGN which have been selected from the radio flux-limited MOJAVE (Monitoring of Jets in AGN with VLBA Experiments) sample. The objects contained in the MOJAVE sample are traditionally associated with relativistically beamed jets that have small viewing angles. The MCS was created to study the correlation of X-ray and radio emission on kiloparsec scales. The complete sample is made up of all MOJAVE Fanaroff & Riley type II objects which have over 100 mJy of extended radio emission at 1.4 GHz and a radio structure of at least 3" in extent. Chandra observations have revealed X-ray and radio correlation in 21 of the 27 jets, bringing the detection rate to ˜78%. The selection criteria provides a quantitative method of discovering new X-ray jets associated with AGN from radio observations. The X-ray morphologies are usually well correlated with the radio emission, except for the sources which show extreme bending on the kiloparsec scale. The emission mechanism for these relativistically beamed quasars and radio galaxies can be interpreted as inverse Compton scattering off of the cosmic microwave background by the electrons in the jets (IC/CMB). The emission mechanism is reinforced by spectral energy distributions (SED) which model the emission mechanisms for sources with sufficient X-ray, optical, and radio data available. I have explored the effects of jet bending and jet deceleration in conjunction with the inverse Compton emission model and used different scenarios to derive best fit viewing angles and bulk Lorentz factors, which were calculated by using the superluminal speeds along with parameters that were derived from the IC/CMB model. The range of

  13. Chandra and XMM-Newton observations of the first quasars X-rays from the age of cosmic enlightenment

    CERN Document Server

    Vignali, C; Schneider, D P; Anderson, S F; Fan, X; Gunn, J E; Kaspi, S; Richards, G T; Strauss, M A; Strauss, Michael A.

    2003-01-01

    We report on Chandra and XMM-Newton observations of a sample of 13 quasars at z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present sample complements previous X-ray studies of z>4 quasars, in which the majority of the objects are optically more luminous and at lower redshifts. All but two of our quasars have been detected in the X-ray band, thus doubling the number of z>4.8 X-ray detected quasars. The two non-detections are likely to be due to a short exposure time and to the presence of intrinsic absorption. We confirm and extend to the highest redshifts the presence of a correlation between AB1450(1+z) magnitude and soft X-ray flux for z>4 quasars, and the presence of a steeper optical-to-X-ray spectral energy distribution (parameterized by aox) for high-luminosity, high-redshift quasars than for lower-luminosity, lower-redshift quasars. The second effect is likely due to the known anti-correlation between aox and rest-frame 2500 Angstrom luminosity, whose significance is confirmed v...

  14. Around 200 new X-ray binary IDs from 13 years of Chandra observations of the M31 center

    CERN Document Server

    Barnard, R; Primini, F; Li, Z; Baganoff, F; Murray, S S

    2013-01-01

    We have created 0.3--10 keV, 13 year, unabsorbed luminosity lightcurves for 528 X-ray sources in the central 20' of M31. We have 174 Chandra observations spaced at ~1 month intervals thanks to our transient monitoring program, deeper observations of the M31 nucleus, and some public data from other surveys. We created 0.5--4.5 keV structure functions (SFs) for each source, for comparison with the ensemble structure function of AGN. We find 220 X-ray sources with luminosities > ~1E+35 erg/s that have SFs with significantly more variability than the ensemble AGN SF, and are likely X-ray binaries (XBs). A further 30 X-ray sources were identified as XBs using other methods. We therefore have 250 probable XBs in total, including ~200 new identifications. This result represents great progress over the ~50 XBs and ~40 XB candidates previously identified out of the ~2000 X-ray sources within the D_25 region of M31; it also demonstrates the power of SF analysis for identifying XBs in external galaxies. We also identify...

  15. Chandra/ACIS-I study of the X-ray properties of the NGC 6611 and M16 stellar population

    CERN Document Server

    Guarcello, M G; Micela, G; Sciortino, S; Drake, J J; Prisinzano, L

    2012-01-01

    Mechanisms regulating the origin of X-rays in YSOs and the correlation with their evolutionary stage are under debate. Studies of the X-ray properties in young clusters allow to understand these mechanisms. One ideal target for this analysis is the Eagle Nebula (M16), with its central cluster NGC6611. At 1750 pc from the Sun, it harbors 93 OB stars, together with a population of low-mass stars from embedded protostars to disk-less Class III objects, with age <= 3Myrs. We study an archival 78 ksec Chandra/ACIS-I observation of NGC6611, and two new 80ksec observations of the outer region of M16, one centered on the Column V, and one on a region of the molecular cloud with ongoing star-formation. We detect 1755 point sources, with 1183 candidate cluster members (219 disk-bearing and 964 disk-less). We study the global X-ray properties of M16 and compare them with those of the Orion Nebula Cluster. We also compare the level of X-ray emission of Class II and Class III stars, and analyze the X-ray spectral prope...

  16. Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

    Science.gov (United States)

    Preibisch, T.; Flaischlen, S.; Gaczkowski, B.; Townsley, L.; Broos, P.

    2017-09-01

    Context. NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that has remained poorly explored until now. Aims: We characterize the stellar population of NGC 3293 in order to evaluate key parameters of the cluster population such as the age and the mass function, and to test claims of an abnormal IMF and a deficit of M ≤ 2.5 M⊙ stars. Methods: We performed a deep (70 ks) X-ray observation of NGC 3293 with Chandra and detected 1026 individual X-ray point sources. These X-ray data directly probe the low-mass (M ≤ 2 M⊙) stellar population by means of the strong X-ray emission of young low-mass stars. We identify counterparts for 74% of the X-ray sources in our deep near-infrared images. Results: Our data clearly show that NGC 3293 hosts a large population of ≈solar-mass stars, refuting claims of a lack of M ≤ 2.5 M⊙ stars. The analysis of the color magnitude diagram suggests an age of 8-10 Myr for the low-mass population of the cluster. There are at least 511 X-ray detected stars with color magnitude positions that are consistent with young stellar members within 7 arcmin of the cluster center. The number ratio of X-ray detected stars in the [1-2 ] M⊙ range versus the M ≥ 5 M⊙ stars (known from optical spectroscopy) is consistent with the expectation from a normal field initial mass function. Most of the early B-type stars and ≈20% of the later B-type stars are detected as X-ray sources. Conclusions: Our data shows that NGC 3293 is one of the most populous stellar clusters in the entire Carina Nebula Complex (very similar to Tr 16 and Tr 15; only Tr 14 is more populous). The cluster probably harbored several O-type stars, whose supernova explosions may have had an important impact on the early evolution of the Carina Nebula Complex. The Chandra data described in this paper have been obtained in the open time project with ObsID 16648 (PI: T. Preibisch) ivo://ADS/Sa.CXO#obs/16648.Tables 1-3 are only

  17. The Chandra Galactic Bulge Survey: optical catalogue and point-source counterparts to X-ray sources

    Science.gov (United States)

    Wevers, T.; Hodgkin, S. T.; Jonker, P. G.; Bassa, C.; Nelemans, G.; van Grunsven, T.; Gonzalez-Solares, E. A.; Torres, M. A. P.; Heinke, C.; Steeghs, D.; Maccarone, T. J.; Britt, C.; Hynes, R. I.; Johnson, C.; Wu, Jianfeng

    2016-06-01

    As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centred at Galactic latitude b = 1.5° above and below the Galactic Centre, spanning (l × b) = (6° × 1°). The catalogue consists of two or more epochs of observations for each line of sight in r', i' and H α filters. The catalogue is complete down to r' = 20.2 and i' = 19.2 mag; the mean 5σ depth is r' = 22.5 and i' = 21.1 mag. The mean root-mean-square residuals of the astrometric solutions is 0.04 arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and find candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ˜10 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4σ X-ray error circle. This analysis yields 1480 potential counterparts (˜90 per cent of the sample). 584 counterparts have saturated photometry (r' ≤ 17, i' ≤ 16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.

  18. CHANDRA X-RAY OBSERVATIONS OF THE REDSHIFT 1.53 RADIO-LOUD QUASAR 3C 270.1

    Energy Technology Data Exchange (ETDEWEB)

    Wilkes, Belinda J.; Lal, Dharam V.; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Worrall, D. M.; Birkinshaw, Mark [HH Wills Physics Laboratory, University of Bristol, Bristol (United Kingdom); Haas, Martin; Chini, Rolf [Astronomisches Institut, Ruhr-University, Bochum (Germany); Antonucci, Robert [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Avara, Mark [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Barthel, Peter [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Hardcastle, Martin [School of Physics and Astronomy, University of Hertfordshire, Hatfield (United Kingdom); Lawrence, Charles [JPL, Pasadena, CA 91109 (United States); Leipski, Christian [MPIA, Heidelberg (Germany); Ogle, Patrick [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Schulz, Bernhard [IPAC, Caltech, Pasadena, CA 91125 (United States)

    2012-01-20

    Chandra X-ray observations of the high redshift (z = 1.532) radio-loud quasar 3C 270.1 in 2008 February show the nucleus to have a power-law spectrum, {Gamma} = 1.66 {+-} 0.08, typical of a radio-loud quasar, and a marginally detected Fe K{alpha} emission line. The data also reveal extended X-ray emission, about half of which is associated with the radio emission from this source. The southern emission is co-spatial with the radio lobe and peaks at the position of the double radio hot spot. Modeling this hot spot, including Spitzer upper limits, rules out synchrotron emission from a single power-law population of electrons, favoring inverse Compton emission with a field of {approx}11 nT, roughly a third of the equipartition value. The northern emission is concentrated close to the location of a 40 Degree-Sign bend where the radio jet is presumed to encounter an external medium. It can be explained by inverse Compton emission involving cosmic microwave background photons with a field of {approx}3 nT, a factor of 7-10 below the equipartition value. The remaining, more diffuse X-ray emission is harder (HR = -0.09 {+-} 0.22). With only 22.8 {+-} 5.6 counts, the spectral form cannot be constrained. Assuming thermal emission with a temperature of 4 keV yields an estimate for the luminosity of 1.8 Multiplication-Sign 10{sup 44} erg s{sup -1}, consistent with the luminosity-temperature relation of lower-redshift clusters. However, deeper Chandra X-ray observations are required to delineate the spatial distribution and better constrain the spectrum of the diffuse emission to verify that we have detected X-ray emission from a high-redshift cluster.

  19. Measuring the shock-heating rate in the winds of O stars using X-ray line spectra

    CERN Document Server

    Cohen, David H; Gayley, Kenneth G; Owocki, Stanley P; Sundqvist, Jon O; Petit, Veronique; Leutenegger, Maurice A

    2014-01-01

    We present a new method for using measured X-ray emission line fluxes from O stars to determine the shock-heating rate due to instabilities in their radiation-driven winds. The high densities of these winds means that their embedded shocks quickly cool by local radiative emission, while cooling by expansion should be negligible. Ignoring for simplicity any non-radiative mixing or conductive cooling, the method presented here exploits the idea that the cooling post-shock plasma systematically passes through the temperature characteristic of distinct emission lines in the X-ray spectrum. In this way, the observed flux distribution among these X-ray lines can be used to construct the cumulative probability distribution of shock strengths that a typical wind parcel encounters as it advects through the wind. We apply this new method (Gayley 2014) to Chandra grating spectra from five O stars with X-ray emission indicative of embedded wind shocks in effectively single massive stars. Correcting for wind absorption of...

  20. Optical and infrared counterparts of the X-ray sources detected in the Chandra Cygnus OB2 Legacy Survey

    CERN Document Server

    Guarcello, M G; Wright, N J; Naylor, T; Flaccomio, E; Kashyap, V L; Garcia-Alvarez, D

    2015-01-01

    The young massive OB association Cygnus OB2, in the Cygnus X complex, is the closest (1400 pc) star forming region to the Sun hosting thousands of young low mass stars and up to 1000 OB stars, among which are some of the most massive stars known in our Galaxy. This region holds great importance for several fields of modern astrophysics, such as the study of the physical properties of massive and young low-mass stars and the feedback provided by massive stars on star and planet formation process. Cygnus OB2 has been recently observed with Chandra/ACIS-I as part of the 1.08Msec Chandra Cygnus OB2 Legacy Project. This survey detected 7924 X-ray sources in a square degree area centered on Cyg OB2. Since a proper classification and study of the observed X-ray sources also requires the analysis of their optical and infrared counterparts, we combined a large and deep set of optical and infrared catalogs available for this region with our new X-ray catalog. In this paper we describe the matching procedure and present...

  1. The Chandra Galactic Bulge Survey: optical catalogue and point-source counterparts to X-ray sources

    CERN Document Server

    Wevers, T; Jonker, P G; Bassa, C; Nelemans, G; van Grunsven, T; Gonzalez-Solares, E A; Torres, M A P; Heinke, C; Steeghs, D; Maccarone, T J; Britt, C; Hynes, R I; Johnson, C; Wu, Jianfeng

    2016-01-01

    As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b = 1.5 degrees above and below the Galactic Centre, spanning (l x b) = (6x1) degrees. The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{\\alpha} filters. It is complete down to r' = 20.2 and i' = 19.2 mag; the mean 5{\\sigma} depth is r' = 22.5 and i' = 21.1 mag. The mean root-mean-square residuals of the astrometric solutions is 0.04 arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and find candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~ 10 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all o...

  2. X-ray spectra induced in highly charged 40Arq+ interacting with Au surface

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    By use of optical spectrum technology, the spectra of X-ray induced by highly charged 40Arq+ ions interacting with Au surface have been studied. The results show that the argon Kα X-ray were emitted from the hollow atoms formed below the surface. There is a process of multi-electron exciting in neutralization of the Ar16+ion, with electronic configuration 1s2 in its ground state below the solid surface. The yield of the projectile Kα X-ray is related to its initial electronic configuration, and the yield of the target X-ray is related to the projectile kinetic energy.

  3. Multiwavelength Study of Chandra X-Ray Sources in the Antennae

    CERN Document Server

    Clark, D M; Brandl, B R; Wilson, J C; Carson, J C; Henderson, C P; Hayward, T L; Barry, D J; Ptak, A F; Colbert, E J M

    2010-01-01

    We use WIRC, IR images of the Antennae (NGC 4038/4039) together with the extensive catalogue of 120 X-ray point sources (Zezas et al. 2006) to search for counterpart candidates. Using our proven frame-tie technique, we find 38 X-ray sources with IR counterparts, almost doubling the number of IR counterparts to X-ray sources first identified in Clark et al. (2007). In our photometric analysis, we consider the 35 IR counterparts that are confirmed star clusters. We show that the clusters with X-ray sources tend to be brighter, K_s ~16 mag, with (J-K_s) = 1.1 mag. We then use archival HST images of the Antennae to search for optical counterparts to the X-ray point sources. We employ our previous IR-to-X-ray frame-tie as an intermediary to establish a precise optical-to-X-ray frame-tie with <0.6 arcsec rms positional uncertainty. Due to the high optical source density near the X-ray sources, we determine that we cannot reliably identify counterparts. Comparing the HST positions to the 35 identified IR star clu...

  4. THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Trichas, Markos; Green, Paul J.; Aldcroft, Tom; Kim, Dong-Woo; Mossman, Amy [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Silverman, John D. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan); Barkhouse, Wayne [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Cameron, Robert A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Constantin, Anca [Department of Physics and Astronomy, James Madison University, PHCH, Harrisonburg, VA 22807 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1 (Canada); Foltz, Craig [Division of Astronomical Sciences, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230 (United States); Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Jannuzi, Buell T. [NOAO, Kitt Peak National Observatory, Tucson, AZ 85726 (United States); Marshall, Herman L. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Perez, Laura M. [Department of Astronomy, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125 (United States); Romero-Colmenero, Encarni [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ruiz, Angel [Osservatorio Astronomico di Brera-INAF, Milan (Italy); Smith, Malcolm G., E-mail: mtrichas@cfa.harvard.edu [Cerro Tololo Interamerican Observatory, La Serena (Chile); and others

    2012-06-01

    From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z {approx} 5.5 and galaxies out to z {approx} 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While {approx}58% of X-ray Seyferts (10{sup 42} erg s{sup -1} < L{sub 2-10keV} <10{sup 44} erg s{sup -1}) require a starburst event (>5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L{sub 2-10keV} >10{sup 44} erg s{sup -1}) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO

  5. 7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS

    CERN Document Server

    Hofmann, F; Nandra, K; Clerc, N; Gaspari, M

    2016-01-01

    Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters of galaxies. The line has been discussed as a possible decay signature of 7.1 keV sterile neutrinos, which have been proposed as a dark matter candidate. We aim at putting constraints on the proposed line emission in a large sample of Chandra-observed clusters and obtain limits on the mixing-angle in a 7.1 keV sterile neutrino dark matter scenario. For a sample of 33 high-mass clusters of galaxies we merge all observations from the Chandra data archive. Each cluster has more than 100 ks of combined exposure. The resulting high signal-to-noise spectra are used to constrain the flux of an unidentified line emission at 3.55 keV in the individual spectra and a merged spectrum of all clusters. We obtained very detailed spectra around the 3.55 keV range and limits on an unidentified emission line. Assuming all dark matter were made of 7.1 keV sterile neutrinos the upper limits on the mixing angle are $\\rm{sin^2(2\\Theta...

  6. Chandra Characterization of X-ray Emission in the Young F-Star Binary System HD 113766

    CERN Document Server

    Lisse, C M; Wolk, S J; Günther, H M; Chen, C H; Grady, C A

    2016-01-01

    Using Chandra we have obtained imaging X-ray spectroscopy of the 10 to 16 Myr old F-star binary HD 113766. We individually resolve the binary components for the first time in the X-ray and find a total 0.3 to 2.0 keV luminosity of 2.2e29 erg/sec, consistent with previous RASS estimates. We find emission from the easternmost, infrared-bright, dusty member HD 113766A to be only 10% that of the western, infrared-faint member HD 113766B. There is no evidence for a 3rd late-type stellar or sub-stellar member of HD113766 with Lx > 6e25 erg s-1 within 2 arcmin of the binary pair. The ratio of the two stars Xray luminosity is consistent with their assignments as F2V and F6V by Pecaut et al. (2012). The emission is soft for both stars, kTApec = 0.30 to 0.50 keV, suggesting X-rays produced by stellar rotation and/or convection in young dynamos, but not accretion or outflow shocks which we rule out. A possible 2.8 +/- 0.15 (2{\\sigma}) hr modulation in the HD 113766B X-ray emission is seen, but at very low confidence and...

  7. A Chandra observation of the accretion-driven millisecond X-ray pulsar XTE J0929-314 in quiescence

    CERN Document Server

    Wijnands, R; Heinke, C O; Miller, J M; Lewin, W H G; Wijnands, Rudy; Homan, Jeroen; Heinke, Craig O.; Miller, Jon M.; Lewin, Walter H. G.

    2004-01-01

    We observed the accretion-driven millisecond X-ray pulsar XTE J0929-314 in its quiescent state using Chandra. XTE J0929-314 is the second such source to be observed in quiescence, after SAX J1808.4-3658. We detected 22 source photons (in the energy range 0.3-8 keV) in ~24.4 ksec, resulting in a background-corrected count rate of 9+/-2 x 10^{-4} counts s^{-1}. This small number of photons detected did not allow for a detailed spectral analysis of the quiescent spectrum, but we can demonstrate that the spectrum is harder than simple thermal emission which is usually presumed to arise from a cooling neutron star that has been heated during the outbursts. Assuming a power-law model for the X-ray spectrum, we obtain a power-law index of 2.2+/-0.6 and an unabsorbed X-ray flux of 6.5^{+2.8}_{-2.1} x 10^{-15} ergs s^{-1} cm^{-2} (for the energy range 0.5-10 keV), resulting in a 0.5-10 keV X-ray luminosity of 8+/-3 x 10^{31} (d/10 kpc)^2 ergs s^{-1}, with d the distance toward the source in kpc. No thermal component c...

  8. The X-ray Spectrum of the Rapid Burster using the Chandra HETGS

    CERN Document Server

    Marshall, H L; Fox, D; Miller, J M; Guerriero, R; Morgan, E; Van der Klis, M; Bildsten, L; Dotani, T; Lewin, W H G

    2001-01-01

    We present observations of the Rapid Burster (RB, also known as MXB 1730-335) using the Chandra High Energy Transmission Grating Spectrometer. The average interval between type II (accretion) bursts was about 40 s. There was one type I (thermonuclear flash) burst and about 20 "mini-bursts" which are probably type II bursts whose peak flux is 10-40% of the average peak flux of the other type II bursts. The time averaged spectra of the type II bursts are well fit by a blackbody with a temperature of kT = 1.6 keV, a radius of 8.9 km for a distance of 8.6 kpc, and an interstellar column density of 1.7e22 per sq. cm. No narrow emission or absorption lines were clearly detected. The 3 sigma upper limits to the equivalent widths of any features are < 10 eV in the 1.1-7.0 keV band and as small as 1.5 eV near 1.7 keV. We suggest that Comptonization destroys absorption features such as the resonance line of Fe XXVI.

  9. Chandra and XMM-Newton Observations of the First Quasars: X-Rays from the Age of Cosmic Enlightenment

    Science.gov (United States)

    Vignali, C.; Brandt, W. N.; Schneider, D. P.; Anderson, S. F.; Fan, X.; Gunn, J. E.; Kaspi, S.; Richards, G. T.; Strauss, Michael A.

    2003-06-01

    We report on Chandra and XMM-Newton observations of a sample of 13 quasars at z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present sample complements previous X-ray studies of z>=4 quasars, in which the majority of the objects are optically more luminous and at lower redshifts. All but two of our quasars have been detected in the X-ray band, thus doubling the number of z>=4.8 X-ray-detected quasars. The two nondetections are likely to be due to a short exposure time (SDSSp J033829.31+002156.3) and to the presence of intrinsic absorption (SDSSp J173744.87+582829.5). We confirm and extend to the highest redshifts the presence of a correlation between AB1450(1+z) magnitude and soft X-ray flux for z>=4 quasars and the presence of a steeper optical-to-X-ray spectral energy distribution (parameterized by αox) for high-luminosity, high-redshift quasars than for lower luminosity, lower redshift quasars. The second effect is likely due to the known anticorrelation between αox and rest-frame 2500 Å luminosity, whose significance is confirmed via partial correlation analysis. The joint ~2.5-36 keV rest-frame spectrum of the z>4.8 SDSS quasars observed thus far by Chandra is well parameterized by a power law with photon index Γ=1.84+0.31-0.30; this photon index is consistent with those of z~0-3 quasars and that obtained from joint spectral fitting of z~4.1-4.5 optically luminous Palomar Digital Sky Survey quasars. No evidence for widespread intrinsic X-ray absorption has been found (NH<~4.0×1022 cm-2 on average at 90% confidence). We also obtained Hobby-Eberly Telescope (HET) photometric observations for eight of our target quasars. None of these shows significant (greater than 30%) optical variability over the time interval of a few years (in the observed frame) between the SDSS and HET observations.

  10. The Effect of Variability on X-Ray Binary Luminosity Functions: Multiple-epoch Observations of NGC 300 with Chandra

    Science.gov (United States)

    Binder, B.; Gross, J.; Williams, B. F.; Eracleous, M.; Gaetz, T. J.; Plucinsky, P. P.; Skillman, E. D.

    2017-01-01

    We have obtained three epochs of Chandra ACIS-I observations (totaling ∼184 ks) of the nearby spiral galaxy NGC 300 to study the logN–logS distributions of its X-ray point-source population down to ∼2 × 10‑15 erg s‑1 cm‑2 in the 0.35–8 keV band (equivalent to ∼1036 erg s‑1). The individual epoch logN–logS distributions are best described as the sum of a background active galactic nucleus (AGN) component, a simple power law, and a broken power law, with the shape of the logN–logS distributions sometimes varying between observations. The simple power law and AGN components produce a good fit for “persistent” sources (i.e., with fluxes that remain constant within a factor of ∼2). The differential power-law index of ∼1.2 and high fluxes suggest that the persistent sources intrinsic to NGC 300 are dominated by Roche-lobe-overflowing low-mass X-ray binaries. The variable X-ray sources are described by a broken power law, with a faint-end power-law index of ∼1.7, a bright-end index of ∼2.8–4.9, and a break flux of ∼ 8× {10}-15 erg s‑1 cm‑2 (∼4 × 1036 erg s‑1), suggesting that they are mostly outbursting, wind-fed high-mass X-ray binaries, although the logN–logS distribution of variable sources likely also contains low-mass X-ray binaries. We generate model logN–logS distributions for synthetic X-ray binaries and constrain the distribution of maximum X-ray fluxes attained during outburst. Our observations suggest that the majority of outbursting X-ray binaries occur at sub-Eddington luminosities, where mass transfer likely occurs through direct wind accretion at ∼1%–3% of the Eddington rate.

  11. X-Ray Spectra of Young Pulsars and Their Wind Nebulae: Dependence on Spin-Down Energy Loss Rate

    Science.gov (United States)

    Gotthelf, E. V.

    2003-01-01

    An observational model is presented for the spectra of young rotation-powered pulsars and their nebulae based on a study of nine bright Crab-like pulsar systems observed with the Chandra X-ray observatory. A significant correlation is discovered between the X-ray spectra of these pulsars and that of their associated pulsar wind nebulae, both of which are observed to be a function of the spin-down energy loss rate, E. The 2-10 keV spectra of these objects are well characterized by an absorbed power-law model with photon indices, Gamma, in the range of 0.6 < Gamma (sub PSR) < 2.1 and 1.3 < Gamma(sub PWN) < 2.3, for the pulsars and their nebulae, respectively. A linear regression fit relating these two sets of indexes yields Gamma(sub PWN) = 0.91 +/- 0.18 + (0.66 +/- 0.11) Gamma (sub PSR), with a correlation coefficient of r = 0.97. The spectra of these pulsars are found to steepen as Gamma = Gamma(sub max) + alpha E (exp -1/2), with Gamma(sub max) providing an observational limit on the spectral slopes of young rotation-powered pulsars. These results reveal basic properties of young pulsar systems, allow new observational constraints on models of pulsar wind emission, and provide a means of predicting the energetics of pulsars lacking detected pulsations.

  12. The x ray variability of NGC6814: Power spectra

    Science.gov (United States)

    Done, C.; Madejski, G. M.; Mushotsky, R. F.; Turner, T. J.; Koyama, K.; Kunieda, H.

    1992-01-01

    Simulation techniques are used to obtain the X-ray variability power spectrum of unevenly sampled GINGA data from NGC6814. A simple power law is not an adequate description of the power spectrum, with the residuals showing excess power on timescales consistent with the periodicity seen in EXOSAT observations of this object. However the shape of the folded lightcurve is very different, with 3 main peaks, two of which are separated by an extremely sharp dip instead of the single peak and small harmonic structure observed by EXOSAT. Using the dip as a fiducial mark, a second GINGA observation of this source taken one year later is found to be consistent with being completely periodic and phase coherent with this first GINGA observation. Thus the period is consistent with being constant over a period of 6 years, but phase coherence is only maintained on timescales of approximately 1 year. Over 75 percent of the total source variability is due to the periodic component (r.m.s. amplitude of 36 percent). The residual variability can be described as the more usual 'flicker noise' f(exp -1.1) powerlaw. This shows no apparent high frequency break on timescales greater than 300 seconds. Subtle differences in the shape of the folded light curve with energy, and the very large amount of power in the periodic component suggest occultation as its origin, though amplification of variability from an X-ray emitting 'hot spot' at the disk inner radius through gravitational lensing is also possible. The former suffers from the very arbitrary nature of the periodic timescale, while the latter is unattractive as it cannot simply explain the lack of high frequency break in the residual power. That these models probably fail to provide an adequate explanation may be due to the added complexity of anisotropy of the X-ray emission, suggested by the discrepancy between the lack of soft photons implied by the flat spectrum and the copious source of soft photons available from reprocessing in

  13. Broadband X-ray spectra of the ultraluminous x-ray source Holmberg IX X-1 observed with NuSTAR, XMM-Newton, and Suzaku

    DEFF Research Database (Denmark)

    Walton, D. J.; Harrison, F. A.; Grefenstette, B. W.;

    2014-01-01

    We present results from the coordinated broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 performed by NuSTAR, XMM-Newton, and Suzaku in late 2012. These observations provide the first high-quality spectra of Holmberg IX X-1 above 10 keV to date, extending the X...

  14. X-ray spectra induced by slow highly charged Arq+ ions in collision with Nb surface

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The X-ray spectra of Nb surface induced by Arq+ (q =16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar16+ ion was neutralized below the metal surface. The K shell electron of Ar16+ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar17+ is three magnitude orders larger than that of Ar16+.

  15. X-ray spectra induced by slow highly charged Arq+ ions in collision with Nb surface

    Institute of Scientific and Technical Information of China (English)

    YANG ZhiHu; GAO ZhiMing; ZHANG XiaoAn; ZHU KeXin; YU DeYang; CAI XiaoHong; CUI Ying; CHEN XiMeng; SONG ZhangYong; SHAO JianXiong; RUAN FangFang; ZHANG HongQiang; DU Juan; LIU YuWen

    2008-01-01

    The X-ray spectra of Nb surface induced by Arq+ (q = 16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar16+ ion was neutralized below the metal surface. The K shell electron of Ar16+ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar17+ is three magnitude orders larger than that of Ar16+.

  16. A Joint Chandra and Swift View of the 2015 X-Ray Dust Scattering Echo of V404 Cygni

    CERN Document Server

    Heinz, S; Smith, R; Brandt, W N; Jonker, P G; Plotkin, R M; Neilsen, J

    2016-01-01

    We present a combined analysis of the Chandra and Swift observations of the 2015 X-ray echo of V404 Cygni. Using stacking analysis, we identify eight separate rings in the echo. We reconstruct the soft X-ray lightcurve of the June 2015 outburst using the high-resolution Chandra images and cross-correlations of the radial intensity profiles, indicating that about 70% of the outburst fluence occurred during the bright flare at the end of the outburst on MJD 57199.8.By deconvolving the intensity profiles with the reconstructed outburst lightcurve, we show that the rings correspond to eight separate dust concentrations with precise distance determinations. We further show that the column density of the clouds varies significantly across the field of view, with the centroid of most of the clouds shifted toward the Galactic plane, relative to the position of V404 Cyg, invalidating the assumption of uniform cloud column typically made in attempts to constrain dust properties from light echoes. We present a new XSPEC...

  17. Chandra Characterization of X-Ray Emission in the Young F-Star Binary System HD 113766

    Science.gov (United States)

    Lisse, C. M.; Christian, D. J.; Wolk, S. J.; Günther, H. M.; Chen, C. H.; Grady, C. A.

    2017-02-01

    Using Chandra, we have obtained imaging X-ray spectroscopy of the 10–16 Myr old F-star binary HD 113766. We individually resolve the 1.″4 separation binary components for the first time in the X-ray and find a total 0.3–2.0 keV luminosity of 2.2 × 1029 erg s‑1, consistent with previous RASS estimates. We find emission from the easternmost, infrared-bright, dusty member HD 113766A to be only ∼10% that of the western, infrared-faint member HD 113766B. There is no evidence for a 3rd late-type stellar or substellar member of HD 113766 with Lx > 6 × 1025 erg s‑1 within 2‧ of the binary pair. The ratio of the two stars’ X-ray luminosity is consistent with their assignments as F2V and F6V by Pecaut et al. The emission is soft for both stars, kTApec = 0.30–0.50 keV, suggesting X-rays produced by stellar rotation and/or convection in young dynamos, but not accretion or outflow shocks, which we rule out. A possible 2.8 ± 0.15 (2σ) hr modulation in the HD 113766B X-ray emission is seen, but at very low confidence and of unknown provenance. Stellar wind drag models corresponding to Lx ∼ 2 × 1029 erg s‑1 argue for a 1 mm dust particle lifetime around HD 113766B of only ∼90,0000 years, suggesting that dust around HD 113766B is quickly removed, whereas 1 mm sized dust around HD 113766A can survive for >1.5 × 106 years. At 1028–1029 erg s‑1 X-ray luminosity, astrobiologically important effects, like dust warming and X-ray photolytic organic synthesis, are likely for any circumstellar material in the HD 113766 systems.

  18. Chandra X-ray observations of the hyper-luminous infrared galaxy IRAS F15307+3252

    Science.gov (United States)

    Hlavacek-Larrondo, J.; Gandhi, P.; Hogan, M. T.; Gendron-Marsolais, M.-L.; Edge, A. C.; Fabian, A. C.; Russell, H. R.; Iwasawa, K.; Mezcua, M.

    2017-01-01

    Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with LIR > 1013 L⊙. They are thought to be closer counterparts of the more distant sub-millimeter galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100 ks), a classical HyLIRG located at z = 0.93 and hosting a radio-loud AGN (L1.4 GHz ˜ 3.5 × 1025 W Hz-1). The Chandra images reveal the presence of extended (r = 160 kpc), asymmetric X-ray emission in the soft 0.3-2.0 keV band that has no radio counterpart. We therefore argue that the emission is of thermal origin originating from a hot intragroup or intracluster medium virializing in the potential. We find that the temperature (˜2 keV) and bolometric X-ray luminosity (˜3 × 1043 erg s-1) of the gas follow the expected LX-ray-T correlation for groups and clusters, and that the gas has a remarkably short cooling time of 1.2 Gyr. In addition, VLA radio observations reveal that the galaxy hosts an unresolved compact steep-spectrum (CSS) source, most likely indicating the presence of a young radio source similar to 3C186. We also confirm that the nucleus is dominated by a redshifted 6.4 keV Fe Kα line, strongly suggesting that the AGN is Compton-thick. Finally, Hubble images reveal an overdensity of galaxies and sub-structure in the galaxy that correlates with soft X-ray emission. This could be a snapshot view of on-going groupings expected in a growing cluster environment. IRAS F15307+3252 might therefore be a rare example of a group in the process of transforming into a cluster.

  19. X-ray outflows of active galactic nuclei warm absorbers: A 900 ks Chandra simulated spectrum

    CERN Document Server

    Ramirez-Velasquez, J M

    2016-01-01

    We report on the performance of the statistical, X-ray absorption lines identification procedure XLINE-ID. As illustration, it is used to estimate the time averaged gas density $n_H(r)$ of a representative AGN's warm absorber ($T\\approx 10^5$~K) X-ray simulated spectrum. The method relies on three key ingredients: (1) a well established emission continuum level; (2) a robust grid of photoionisation models spanning several orders of magnitude in gas density ($n_H$), plasma column density ($N_H$), and in ionization states; (3) theoretical curves of growth for a large set of atomic lines. By comparing theoretical and observed equivalent widths of a large set of lines, spanning highly ionized charge states from O, Ne, Mg, Si, S, Ar, and the Fe L-shell and K-shell, we are able to infer the location of the X-ray warm absorber.

  20. Galaxy Cluster Scaling Relations between Bolocam Sunyaev-Zel'dovich Effect and Chandra X-ray Measurements

    CERN Document Server

    Czakon, N G; Mantz, A; Golwala, S R; Downes, T P; Koch, P M; Lin, K -Y; Molnar, S M; Moustakas, L A; Mroczkowski, T; Pierpaoli, E; Shitanishi, J A; Siegel, S; Umetsu, K

    2014-01-01

    We present scaling relations between the integrated Sunyaev-Zel'dovich Effect (SZE) signal, $Y_{\\rm SZ}$, its X-ray analogue, $Y_{\\rm X}$$\\equiv$$M_{\\rm gas}$$T_{\\rm X}$, and total mass, $M_{\\rm tot}$, for the 45 galaxy clusters in the Bolocam X-ray-SZ (BOXSZ) sample. All parameters are integrated within $r_{2500}$. $Y_{2500}$ values are measured using SZE data collected with Bolocam, operating at 140 GHz at the Caltech Submillimeter Observatory (CSO). The temperature, $T_{\\rm X}$, and mass, $M_{\\rm gas,2500}$, of the intracluster medium are determined using X-ray data collected with \\emph{Chandra}, and $M_{\\rm tot}$ is derived from $M_{\\rm gas}$ using a constant gas mass fraction. Our analysis accounts for several potential sources of bias, including: selection effects, contamination from radio point sources, and the loss of SZE signal due to noise filtering and beam-smoothing effects. We measure the $Y_{2500}$-$Y_{\\rm X}$ scaling to have a logarithmic slope of $0.84\\pm0.07$, and a fractional intrinsic scatt...

  1. Revealing the heavily obscured AGN population of High Redshift 3CRR Sources with Chandra X-ray Observations

    CERN Document Server

    Wilkes, Belinda J; Haas, Martin; Barthel, Peter; Leipski, Christian; Willner, S P; Worrall, D M; Birkinshaw, Mark; Antonucci, Robert; Ashby, M L N; Chini, Rolf; Fazio, G G; Lawrence, Charles; Ogle, Patrick; Schulz, Bernhard

    2013-01-01

    Chandra observations of a complete, flux-limited sample of 38 high-redshift (10) indicating obscuration (log N_H ~ 22-24 cm^-2). These properties and the correlation between obscuration and radio core-fraction are consistent with orientation-dependent obscuration as in Unification models. About half the NLRGs have soft X-ray hardness ratios and/or high [OIII] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC1068). The ratios of unobscured to Compton-thin (10^{22} 1.5 x 10^{24} cm^-2) is 2.5:1.4:1 in this high luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for AGN at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is ~ 60deg and the obscuring material covers 30deg of which ~ 12deg is Compton thick. The multi-wavelength prope...

  2. The Effect of Variability on X-Ray Binary Luminosity Functions: Multiple Epoch Observations of NGC 300 with Chandra

    CERN Document Server

    Binder, Breanna; Williams, Benjamin F; Eracleous, Michael; Gaetz, Terrance J; Plucinsky, Paul P; Skillman, Evan D

    2016-01-01

    We have obtained three epochs of Chandra ACIS-I observations (totaling $\\sim$184 ks) of the nearby spiral galaxy NGC~300 to study the logN-logS distributions of its X-ray point source population down to $\\sim$2$\\times$10$^{-15}$ erg s$^{-1}$ cm$^{-2}$ in the 0.35-8 keV band (equivalent to $\\sim$10$^{36}$ erg s$^{-1}$). The individual epoch logN-logS distributions are best described as the sum of a background AGN component, a simple power law, and a broken power law, with the shape of the logN-logS distributions sometimes varying between observations. The simple power law and AGN components produce a good fit for "persistent" sources (i.e., with fluxes that remain constant within a factor of $\\sim$2). The differential power law index of $\\sim$1.2 and high fluxes suggest that the persistent sources intrinsic to NGC~300 are dominated by Roche lobe overflowing low mass X-ray binaries. The variable X-ray sources are described by a broken power law, with a faint-end power law index of $\\sim$1.7, a bright-end index ...

  3. A Chandra observation of the neutron star X-ray transient and eclipsing binary MXB 1659-29 in quiescence

    CERN Document Server

    Wijnands, R; Miller, J M; Homan, J; Wachter, S; Lewin, W H G; Wijnands, Rudy; Nowak, Mike; Miller, Jon M.; Homan, Jeroen; Wachter, Stefanie; Lewin, Walter H. G.

    2003-01-01

    After almost 2.5 years of actively accreting, the neutron star X-ray transient and eclipsing binary MXB 1659-29 returned to quiescence in 2001 September. We report on a Chandra observation of this source taken a little over a month after this transition. The source was detected at an unabsorbed 0.5-10 keV flux of only (2.7 - 3.6) x 10^{-13} erg cm^-2 s^-1, which implies a 0.5-10 keV X-ray luminosity of approximately (3.2 - 4.3) x 10^{33} (d/10 kpc)^2 erg s^-1, with d is the distance to the source in kpc. Its spectrum had a thermal shape and could be well fitted by either a blackbody with a temperature kT of ~0.3 keV or with a neutron star atmosphere model with a kT of ~0.1 keV. The luminosity and spectral shape of MXB 1659-29 are very similar to those observed of the other neutron star X-ray transients when they are in their quiescent state. The source was variable during our observation, exhibiting a complete eclipse of the inner part of the system by the companion star. Dipping behavior was observed before ...

  4. Measuring the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Albert, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pollock, B. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shaw, J. L. [Univ. of California, Los Angeles, CA (United States); Marsh, K. A. [Univ. of California, Los Angeles, CA (United States); Ralph, J. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chen, Y. -H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Alessi, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pak, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Clayton, C. E. [Univ. of California, Los Angeles, CA (United States); Glenzer, S. H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Joshi, C. [Univ. of California, Los Angeles, CA (United States)

    2014-07-22

    This paper presents a new technique to measure the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator. Measurements are performed with a stacked image plates spectrometer, capable of detecting broadband x-ray radiation up to 1 MeV. It can provide measurements of the betatron x-ray spectrum at any angle of observation (within a 40 mrad cone) and of the beam profile. A detailed description of our data analysis is given, along with comparison for several shots. As a result, these measurements provide useful information on the dynamics of the electrons are they are accelerated and wiggled by the wakefield.

  5. First Principles Calculations for X-ray Resonant Spectra and Elastic Properties

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yongbin [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    In this thesis, we discuss applications of first principles methods to x-ray resonant spectra and elastic properties calculation. We start with brief reviews about theoretical background of first principles methods, such as density functional theory, local density approximation (LDA), LDA+U, and the linear augmented plane wave (LAPW) method to solve Kohn-Sham equations. After that we discuss x-ray resonant scattering (XRMS), x-ray magnetic circular dichroism (XMCD) and the branching problem in the heavy rare earths Ledges. In the last chapter we discuss the elastic properties of the second hardest material AlMgB14.

  6. On the Weak-Wind Problem in Massive Stars: X-Ray Spectra Reveal a Massive Hot Wind in mu Columbae

    Science.gov (United States)

    Huenemoerder, David P.; Oskinova, Lidia M.; Ignace, Richard; Waldron, Wayne L.; Todt, Helge; Hamaguchi, Kenji; Kitamoto, Shunji

    2012-01-01

    Mu Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there actually is a massive hot wind. The X-ray emission measure indicates that the outflow is an order of magnitude greater than that derived from UV lines and is commensurate with the nominal wind-luminosity relationship for O stars. Therefore, the "weak-wind problem"--identified from cool wind UV/optical spectra--is largely resolved by accounting for the hot wind seen in X-rays. From X-ray line profiles, Doppler shifts, and relative strengths, we find that this weak-wind star is typical of other late O dwarfs. The X-ray spectra do not suggest a magnetically confined plasma-the spectrum is soft and lines are broadened; Suzaku spectra confirm the lack of emission above 2 keV. Nor do the relative line shifts and widths suggest any wind decoupling by ions. The He-like triplets indicate that the bulk of the X-ray emission is formed rather close to the star, within five stellar radii. Our results challenge the idea that some OB stars are "weak-wind" stars that deviate from the standard wind-luminosity relationship. The wind is not weak, but it is hot and its bulk is only detectable in X-rays.

  7. The spatial distribution of X-ray selected AGN in the Chandra deep fields: a theoretical perspective

    CERN Document Server

    Marulli, Federico; Branchini, Enzo; Gilli, Roberto; Moscardini, Lauro; Springel, Volker

    2009-01-01

    We study the spatial distribution of X-ray selected AGN in the framework of hierarchical co-evolution of supermassive black holes and their host galaxies and dark matter haloes. To this end, we have applied the model developed by Croton et al.(2006), De Lucia & Blaizot(2007) and Marulli et al.(2008) to the output of the Millennium Run and obtained hundreds of realizations of past light-cones from which we have extracted realistic mock AGN catalogues that mimic the Chandra deep fields. We find that the model AGN number counts are in fair agreement with observations, except at fluxes <1e-15 erg/cm^2/s. The spatial two-point correlation function predicted by the model is well described by a power-law relation out to 20 Mpc/h, in close agreement with observations. Our model matches the correlation length r_0 of AGN in the Chandra Deep Field North but underestimates it in the Chandra Deep Field South. When fixing the slope to gamma = 1.4, as in Gilli et al. (2005), the statistical significance of the mismat...

  8. Chandra observation of an ultraluminous X-ray source from the Galaxy NGC 12911

    CERN Document Server

    Luna, Juan C

    2009-01-01

    I report the analysis of an ultraluminous X-ray source (ULX) located in the galaxy NGC 1291. This X-ray point source is denominated IXO6 in the Catalog of Candidate IXO (Colbert & Ptak). An Intermediate-luminosity X-ray Object (IXO) is defined as an off-nuclear, compact object with luminosity Lx [2-10keV] >= 1039 erg s-1. The cutoff Lx is defined as a value greater than the Eddington luminosity of a 1.4 Mo black hole (10 38.3 erg s-1). IXO is an early denomination of what is call now a ULX point source. The Catalog was derived from a ROSAT survey and represents 87 IXOS in 54 galaxies. IXO6 was selected because of being positioned in the outer disk of the galaxy, with no near X-ray source neighbors. The study of this ULX pretends to confirm certain assumptions related to this class of objects (Roberts et al.)

  9. Comparison between X-ray photoelectron and X-ray absorption spectra of an environmental aerosol sample measured by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, J.; Yamamoto, T. [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto (Japan); Tohno, S. [Department of Socio-Environmental Energy Science, Graduate School of Energy Science, Kyoto University, Uji, Kyoto (Japan); Kitajima, Y. [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba (Japan)

    1999-01-04

    Sulfur X-ray photoelectron spectra (XPS) and X-ray absorption spectra (XAS) of an aerosol sample collected by an Andersen sampler were measured using a synchrotron beam line. While the XPS was more surface sensitive than XAS, the detection limit of XAS was better than that of XPS. It was concluded that the XAS was more suitable for the chemical state analysis of sulfur in aerosol samples than XPS. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  10. X-ray spectra for mamography; Espectros de rayos X para mamografia

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Manzanares A, E.; Ramirez G, J.; Hernandez V, R.; Hernandez D, V.M.; Salas L, M.A. [UAZ, A.P. 336, 98000 Zacatecas (Mexico)]. e-mail: fermineutron@yahoo.com

    2008-07-01

    By means of Monte Carlo methods the X-ray spectra that produce Mammography equipment have been obtained. The mammographs are widely used with the purpose of diagnosing the cancer of the mammary glands. Different makers and mammographs models are distinguished by the voltage capacity and the current, exist as well as in the target type and filter. The targets that are used are Mo, Rh and W and the filters are Mo, Rh, Al and Be. In this work the results obtained by means of the MCNP code of the X-ray spectra take place when an electron beam of 28 keV is made impact on Mo, Rh and W targets, as well as the spectra that result of filtering these X rays using different types of filters. The resulting spectra contain the continuous spectrum of the stopping radiation, as well as the X rays characteristic of the used target. The utility of estimating the spectra of X rays by means of Monte Carlo is that it can use to estimate the absorbed dose by the gland, as well as the absorbed dose by other organs. It also allows to calculate the detector response. (Author)

  11. Invisible structures in the X-ray absorption spectra of actinides

    NARCIS (Netherlands)

    Kvashnina, Kristina O.; De Groot, Frank M F

    2014-01-01

    The X-ray absorption spectra of actinides are discussed with an emphasis on the fundamental effects that influence their spectral shape, including atomic multiplet theory, charge transfer theory and crystal field theory. Many actinide spectra consist of a single peak and it is shown that the use of

  12. Measuring x-ray spectra of flash radiographic sources [PowerPoint

    Energy Technology Data Exchange (ETDEWEB)

    Gehring, Amanda Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Espy, Michelle A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Haines, Todd Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mendez, Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moir, David C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sedillo, Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Shurter, Roger P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Volegov, Petr Lvovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Webb, Timothy J [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-11-02

    The x-ray spectra of flash radiographic sources are difficult to measure. The sources measured were Radiographic Integrated Test Stand-6 (370 rad at 1 m; 50 ns pulse) and Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) (550 rad at 1 m; 50 ns pulse). Features of the Compton spectrometer are described, and spectra are shown. Additional slides present data on instrumental calibration.

  13. Chandra Cluster Cosmology Project. II. Samples and X-Ray Data Reduction

    DEFF Research Database (Denmark)

    Vikhlinin, A.; Burenin, R. A.; Ebeling, H.;

    2009-01-01

    We discuss the measurements of the galaxy cluster mass functions at z ≈ 0.05 and z ≈ 0.5 using high-quality Chandra observations of samples derived from the ROSAT PSPC All-Sky and 400 deg2 surveys. We provide a full reference for the data analysis procedures, present updated calibration of relati...

  14. Radiative Spectra from Disk Corona and Inner Hot Flow in Black Hole X-ray Binaries

    CERN Document Server

    Kawabata, Ryoji

    2010-01-01

    To understand the origin of hard X-ray emissions from black hole X-ray binaries during their low/hard states, we calculate the X-ray spectra of black-hole accretion flow for the following three configurations of hot and cool media: (a) an inner hot flow and a cool outer disk (inner hot flow model), (b) a cool disk sandwiched by disk coronae (disk corona model), and (c) the combination of those two (hybrid model). The basic features we require for successful models are (i) significant hard X-ray emission whose luminosity exceeds that of soft X-rays, (ii) high hard X-ray luminosities in the range of (0.4 - 30) times 10^{37} erg s^{-1}, and (iii) the existence of two power-law components in the hard X-ray band with the photon indices of Gamma_s ~ 2 > Gamma_h, where Gamma_s and Gamma_h are the photon indices of the softer (10 keV) power-law components, respectively. Contribution by non-thermal electrons nor time-dependent evolution are not considered. We find that Models (a) and (b) can be ruled out, since the sp...

  15. Comparison of simulated and measured spectra of an industrial 450 kV X-ray tube

    Science.gov (United States)

    Miceli, A.; Thierry, R.; Bettuzzi, M.; Flisch, A.; Hofmann, J.; Sennhauser, U.; Casali, F.

    2007-09-01

    An accurate knowledge of the X-ray source spectrum is required in order to optimize X-ray Computed Tomography systems. A simulation model based on the Monte Carlo code GEANT4 was developed to determine the X-ray spectrum generated by a 450 kV tube. The X-ray spectra were measured using a Cadmium Telluride stack detector. The measured spectra were corrected for spurious detector effects and detector efficiency. The X-ray spectra simulated by GEANT4 were validated by comparison with X-ray spectra measured at 350, 400 and 450 kV. We observed a good agreement between the simulated and the measured X-ray spectra. In addition, we simulated and measured attenuation curves using aluminium and copper filtration. The comparison of the attenuation curves shows an excellent agreement.

  16. X-ray spectra induced by 129Xeq+ impacting the metal surface

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using the slow highly charged ions 129 Xe q+ (q=25,26,27;initial kinetic T0≤4.65 keV/a.u.)to impact Au surface,the Au atomic Mαcharacteristic X-ray spectrum is induced.The result shows that as long as the charge state of projectile is high enough,the heavy atomic characteristic X-ray can be effectively excited even though the incident beam is very weak(nA magnitude),and the X-ray yield per ion is in the order of 10-8and increases with the kinetic energy and potential energy of projectile.By measuring the Au Mα-X-ray spectra,Au atomic N-level lifetime is estimated at about 1.33×10-18s based on Heisenberg uncertainty relation.

  17. Theoretical spectra of nonmagnetized low-mass X-ray binaries

    Science.gov (United States)

    Czerny, Bozena; Czerny, Michal; Grindlay, Jonathan E.

    1986-01-01

    Theoretical X-ray spectra of low-mass X-ray binaries with negligible magnetic fields are presented. The geometry of the X-ray emitting region, the energetic efficiency of the accretion in the disk and in the boundary layer which leads to a relation between the disk and the boundary layer luminosities, and the irradiation of the disk by the boundary layer are studied. The model of the radiation spectrum emerging from the neutron star and the innermost part of the disk is presented. The relativistic and Doppler effects and their influence on the spectrum as a function of inclination angle are discussed. A simple method for comparing the spectrum model with observations by studying the hardness ratio is given, and the results for three X-ray sources in globular clusters observed by the Einstein satellite are presented. The range of applicability of the spectrum models is also discussed.

  18. X-ray spectra induced by 129Xeq+ impacting the metal surface

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using the slow highly charged ions 129Xeq+ (q = 25, 26, 27; initial kinetic T0≤4.65 keV/a.u.) to impact Au surface, the Au atomic Mα characteristic X-ray spectrum is induced. The result shows that as long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10-8 and increases with the kinetic energy and potential energy of projectile. By measuring the Au Mα-X-ray spectra, Au atomic N-level lifetime is estimated at about 1.33×10-18 s based on Heisenberg uncertainty relation.

  19. X-ray reflected spectra from accretion disk models.II. Diagnostic tools for X-ray observations

    CERN Document Server

    Garcia, J; Mushotzky, R F

    2011-01-01

    We present a comprehensive study of the emission spectra from accreting sources. We use our new reflection code to compute the reflected spectra from an accretion disk illuminated by X-rays. This set of models covers different values of ionization parameter, solar iron abundance and photon index for the illuminating spectrum. These models also include the most complete and recent atomic data for the inner-shell of the iron and oxygen isonuclear sequences. We concentrate our analysis to the 2-10 keV energy region, and in particular to the iron K-shell emission lines. We show the dependency of the equivalent width (EW) of the Fe K$\\alpha$ with the ionization parameter. The maximum value of the EW is $\\sim 800$ eV for models with log $\\xi\\sim 1.5$, and decreases monotonically as $\\xi$ increases. For lower values of $\\xi$ the Fe K$\\alpha$ EW decreases to a minimum near log $\\xi\\sim 0.8$. We produce simulated CCD observations based on our reflection models. For low ionized, reflection dominated cases, the 2-10 keV...

  20. An indirect method of X-ray spectra measurement by simultaneous attenuations of the scattered beam

    Energy Technology Data Exchange (ETDEWEB)

    Mainardi, Raul T. [Facultad de Matematica, Astronomia y Fisica (FaMAF), Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA-Cordoba (Argentina)], E-mail: mainardi@famaf.unc.edu.ar; Bonzi, Edgardo V. [Facultad de Matematica, Astronomia y Fisica (FaMAF), Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA-Cordoba (Argentina)

    2008-05-15

    Direct and indirect methods of X-ray spectra determination present obstacles to their practical use since they must position either the collimator-detector assembly or the attenuators-ionization chamber, respectively, along the X-ray beam direction. These arrangements require considerable space and in many instances the detectors promptly saturate. An indirect procedure, which overcomes the aforementioned problems, is developed. It consists of the scattering of the X-ray beam from a carbon disk, which is detected simultaneously by several detectors placed away from the beam. The X-ray flux reaching each of these detectors is attenuated in metal sheets of different thicknesses, thus obtaining simultaneously the attenuation curve values. A set of analytical equations are derived to calculate attenuation curves by taking into account all the absorption and elastic and inelastic scattering processes that a beam of photons undergoes when going from the X-ray tube to the detector. Users, even those who are not well acquainted with computer programming, can easily obtain the X-ray spectrum by a least square fitting of a measured attenuation curve to a previously derived analytical expression. A simulated Monte Carlo program of photon transport from the X-ray tube to the detector provided simulated attenuation curves data. Analytically calculated and simulated attenuation curves for the same input spectrum wholly overlap and furthermore, reconstructed spectra from both sets of curves for different kilovoltages are also in full agreement. Finally, in addition to the importance of having the detectors out of the beam direction, the proposed arrangement features other main advantages, namely, only one X-ray tube shot is needed to obtain the required data, the physical processes involved are very well known, analytical equations are easily interpreted, and the measuring apparatuses can be comparatively simple to assemble and operate.

  1. Cross-calibration of the X-ray instruments onboard the Chandra, INTEGRAL, RXTE, Suzaku, Swift, and XMM-Newton observatories using G21.5-0.9

    Science.gov (United States)

    Tsujimoto, M.; Guainazzi, M.; Plucinsky, P. P.; Beardmore, A. P.; Ishida, M.; Natalucci, L.; Posson-Brown, J. L. L.; Read, A. M.; Saxton, R. D.; Shaposhnikov, N. V.

    2011-01-01

    Context. For many years, X-ray astronomy missions have used the Crab nebula as a celestial calibration source for the X-ray flux and spectral shape. However, the object is often too bright for current and future missions equipped with instruments with improved sensitivity. Aims: We use G21.5-0.9, a pulsar-wind nebula with a time-constant power-law spectrum and a flux of a few milli-Crab in the X-ray band, as a viable, fainter substitute to the Crab. Using this source, we conduct a cross-calibration study of the instruments onboard currently active observatories: Chandra ACIS, Suzaku XIS, Swift XRT, and XMM-Newton EPIC (MOS and pn) for the soft-band, and INTEGRAL IBIS-ISGRI, RXTE PCA, and Suzaku HXD-PIN for the hard band. Methods: We extract spectra from all instruments and fit under the same astrophysical assumptions. We compare the spectral parameters of the G21.5-0.9 model: power-law photon index, H-equivalent column density of the interstellar photoelectric absorption, and flux in the soft (2-8 keV) or hard (15-50 keV) energy band. Results: We identify systematic differences in the best-fit parameter values unattributable to statistical scatter of the data alone. We interpret these differences as due to residual cross-calibration problems. The differences can be as large as 20% and 9% for the soft-band flux and power-law index, respectively, and 46% for the hard-band flux. The results are plotted and tabulated as a useful reference for future calibration and scientific studies using multiple missions. This work is based on the activity of the International Astronomical Consortium for High Energy Calibration (IACHEC).

  2. On X-ray tube spectra, the dependence on the angular and electron energy of X-rays from the targets

    Science.gov (United States)

    Shaltout, A. A.

    2007-03-01

    An algorithm was developed for the theoretical intensities of both X-ray continuum and characteristic K-radiation (K{α 1}, K{α 2}, K{α }, K{β 1}, K{β 2}, K{β 3}, K{β 13}, K{β 4} and K{β 5}) of different target materials (Cr, Cu, Rh, Mo, W, Ag and Au) at different electron incidence angles (0.01circ 90circ), different take-off angles of the photon emission (0.01circ 90circ) and different X-ray tube voltages. It was found that the intensities of continuum and characteristic X-rays increase with increasing take-off angle and the take-off angle is inversely proportional to the absorption path of X-rays in the target. At take-off angles of 20circ or more, the flux of the X-ray spectra remains practically independent of the take-off angle. Furthermore, at the optimum electron incidence angle and take-off angle of emitted X-ray photons, the dependence of X-ray tube spectra on applied voltage was also investigated.

  3. Lifetime-vibrational interference effects in resonantly excited x-ray emission spectra of CO

    Energy Technology Data Exchange (ETDEWEB)

    Skytt, P.; Glans, P.; Gunnelin, K. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    The parity selection rule for resonant X-ray emission as demonstrated for O{sub 2} and N{sub 2} can be seen as an effect of interference between coherently excited degenerate localized core states. One system where the core state degeneracy is not exact but somewhat lifted was previously studied at ALS, namely the resonant X-ray emission of amino-substituted benzene (aniline). It was shown that the X-ray fluorescence spectrum resulting from excitation of the C1s at the site of the {open_quotes}aminocarbon{close_quotes} could be described in a picture separating the excitation and the emission processes, whereas the spectrum corresponding to the quasi-degenerate carbons could not. Thus, in this case it was necessary to take interference effects between the quasi-degenerate intermediate core excited states into account in order to obtain agreement between calculations and experiment. The different vibrational levels of core excited states in molecules have energy splittings which are of the same order of magnitude as the natural lifetime broadening of core excitations in the soft X-ray range. Therefore, lifetime-vibrational interference effects are likely to appear and influence the band shapes in resonant X-ray emission spectra. Lifetime-vibrational interference has been studied in non-resonant X-ray emission, and in Auger spectra. In this report the authors discuss results of selectively excited soft X-ray fluorescence spectra of molecules, where they focus on lifetime-interference effects appearing in the band shapes.

  4. Implications of the Detection of X-rays From Pluto by Chandra for Its Solar Wind - Neutral Atmosphere Interaction

    Science.gov (United States)

    Lisse, C. M.

    2016-12-01

    Using the Chandra X-Ray Observatory, we have obtained low-resolution imaging X-ray spectrophotometry of the Pluto system in support of the New Horizons (NH) flyby. In a total of 174 ksec of on-target time, we measured 8 photons from 0.31 to 0.60 keV in a co-moving 11 x 11 pixel2 box (the 90% flux aperture for fixed background sources in the field) measuring 121,000 x 121,000 km2 (or 100 x 100 RPluto) at Pluto. The Pluto photons do not have the spectral shape of the background, are coincident with a 90% flux aperture co-moving with Pluto, and are not confused with any background source, so we consider them as sourced from the Pluto system. Allowing for background, we find a net signal of 6.8 counts and a statistical noise level of 1.2 counts, for a detection of Pluto at > 99.95%. The mean 0.31 - 0.60 keV X-ray power from Pluto is 200 +200/-100 MW, in the middle range of X-ray power levels seen for other known solar system emission sources: auroral precipitation, solar X-ray scattering, and charge exchange (CXE) between solar wind (SW) ions and atmospheric neutrals. We eliminate auroral effects as a source, as Pluto has no known magnetic field and the NH/Alice UV spectrometer detected no airglow from Pluto during the flyby. Atmospheric haze particles could produce resonant scattering of solar X-rays from Pluto, but the energy signature of the detected photons does not match the solar spectrum and estimates of Pluto's scattered X-ray emission are 2 to 3 orders of magnitude lower than seen in our observations. CXE-driven emission from hydrogenic and heliogenic SW carbon, nitrogen, and oxygen ions can produce the energy signature seen, and the 6 x 1025 neutral gas escape rate from Pluto deduced from NH data (Gladstone et al. 2016) can support the 3.0 +3.0/-1.5 x 1024 X-ray photons/s emission rate required by our observations. Using the SW proton density and speed measured by the NH/SWAP instrument in the vicinity of Pluto at the time of the photon emissions, we find a

  5. Many-body effects on the x-ray spectra of metals

    Energy Technology Data Exchange (ETDEWEB)

    Satpathy, Sashi Sekhar [Univ. of Illinois, Urbana-Champaign, IL (United States)

    1982-01-01

    The effects of band structure, of a solid surface, of temperature, and of disorder on the many-electron x-ray spectra of metals are evaluated in a change-of-mean-field approximation using a one-dimensional nearest-neighbor tight-binding model of a metal. The x-ray spectral shapes are determined by both the band structure and the final-state interactions. The effect of the band being non-free-electron-like is not felt at the x-ray threshold, but away from it such effects are noticeable. When the core hole is created at the surface, the spectra at the edge exhibit a Nozieres-de Dominicis-type singularity with the appropriate surface phase-shifts. At energies away from the edge, the one-particle effects are prominent with the x-ray emission and absorption spectra closely reflecting the local one-electron density of states. The recoil spectrum of a Fermi sea at a non-zero temperature has less asymmetry than the zero-temperature case. It was found that at ordinary temperatures the reduction of the asymmetry due to the thermal distribution of one-electron states is not very significant. Finally, using a one-dimensional Anderson model, the effect of lattice disorder on the x-ray absorption spectra is studied for the first time. There are two effects: (1) the strong infrared divergence peak is gradually quenched as disorder is increased, and (2) the threshold is broadened because the threshold energies for absorption at different sites in the crystal depend on the varying local lattice environment. It is proposed that the x-ray spectra may be useful as a tool for studying the degree of electron localization in disordered many-electron systems.

  6. Precise Localization of the Soft Gamma Repeater SGR 1627-41 with Chandra and the Anomalous X-Ray Pulsar AXP 1E1841-045 with Chandra

    Science.gov (United States)

    Wachter, Stefanie; Patel, Sandeep K.; Kouveliotou, Chryssa; Bouchet, Patrice; Ozel, Feryal; Tennant, Allyn F.; Woods, Peter M.; Hurley, Kevin; Becker, Werner; Slane, Patrick

    2004-01-01

    We present precise localizations of AXP 1E184-045 and SGR 1627-41 with Chandra. We obtained new infrared observations of SGR 1627-41 and reanalyzed archival observations of AXP 1E1841-045 in order to refine their positions and search for infrared counterparts. A faint source is detected inside the error circle of AXP 1E1841-045. In the case of SGR 1627-41, several sources are located within the error radius of the X-ray position, and we discuss the likelihood of one of them being the counterpart. We compare the properties of our candidates to those of other known anomalous X-ray pulsar (AXP) and soft gamma repeater (SGR) counterparts. We find that the counterpart candidates for SGR 1627-41 and SGR 1806-20 would have to be intrinsically much brighter than AXPs in order to have counterparts detectable with the observational limits currently available for these sources. To confirm the reported counterpart of SGR 1806-20, we obtained new infrared observations during the 2003 July burst activation of the source. No brightening of the suggested counterpart is detected, implying that the counterpart of SGR 1806-20 remains yet to be identified.

  7. A search for effects on chemical isomerism in muonic X-ray spectra of propyl alcohol

    CERN Document Server

    Brandão d'Oliveira, A; Von Egidy, T

    1974-01-01

    The intensities of muonic X-ray transitions in n-propyl alcohol and isopropyl alcohol were measured. The experiment was performed at the muon channel of the 600 MeV synchrocyclotron at CERN. The spectra were evaluated by means of a standard computer program and by a technique to observe small differences between the propyl-alcohol spectra. No differences in the muonic spectra were observed within rather small experimental errors. (16 refs).

  8. Chandra and ASCA X-ray Observations of the Radio Supernova SN1979C IN NGC 4321

    CERN Document Server

    Ray, A; Schlegel, E M

    2001-01-01

    We report on the X-ray observation of the radio selected supernova SN1979C carried out with ASCA in 1997 December and serendipitously available from a Chandra Guaranteed Time Observation in 1999 November. The supernova, of type SN II-Linear (SN IIL), was first observed in the optical and occurred in the weakly barred, almost face on spiral galaxy NGC 4321 (M100). The galaxy, a member of the Virgo S cluster, is at a distance of 17.1 Mpc, and contains at least three other supernovae discovered in this century. The useful exposure time was ~25 ks for the Solid-State Imaging Spectrometer (SIS), ~28 ks for the Gas Scintillation Imaging Spectrometer (GIS), and ~2.5 ks for Chandra's Advanced CCD Imaging Spectrometer (ACIS). No point source was detected at the radio position of SN1979C in a 3' diameter half power response circle in the ASCA data. The background and galaxy subtracted SN signal had a 3sigma upper limit to the flux of 6.3x10^-14 ergs/s/cm^-2 in the full ASCA SIS band (0.4-10.0 keV) and a 3sigma upper li...

  9. X-ray calibration of SZ scaling relations with the ACCEPT catalogue of galaxy clusters observed by Chandra

    CERN Document Server

    Comis, B; Conte, A; Lamagna, L; De Gregori, S

    2011-01-01

    We explore the scaling relation between the flux of the Sunyaev-Zel'dovich (SZ) effect and the total mass of galaxy clusters using already reduced Chandra X-ray data present in the ACCEPT (Archive of Chandra Cluster Entropy Profile Tables) catalogue. The analysis is conducted over a sample of 226 objects, examining the relatively small scale corresponding to a cluster overdensity equal to 2500 times the critical density of the background universe, at which the total masses have been calculated exploiting the hydrostatic equilibrium hypothesis. Core entropy (K0) is strongly correlated with the central cooling time, and is therefore used to identify cooling-core (CC) objects in our sample. Our results confirm the self-similarity of the scaling relation between the integrated Comptonization parameter (Y) and the cluster mass, for both CC and NCC (non-cooling-core) clusters. The consistency of our calibration with recent ones has been checked, with further support for Y as a good mass proxy. We also investigate t...

  10. A detailed analysis of the high-resolution X-ray spectra of NGC 3516: variability of the ionized absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Huerta, E. M.; Krongold, Y.; Jimenez-Bailon, E. [Departamento de Astronomia Extragalactica y Cosmologia, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-264, 04510 Mexico D.F. (Mexico); Nicastro, F. [Osservatorio Astronomico di Roma-INAF, Via di Frascati 33, I-00040 Monte Porzio Catone, RM (Italy); Mathur, S. [Astronomy Department, The Ohio State University, Enarson Hall, 140 West 18th Avenue, Columbus, OH 43210 (United States); Longinotti, A. L. [European Space Astronomy Centre of ESA, E-28691, Madrid (Spain)

    2014-09-20

    The 1.5 Seyfert galaxy NGC 3516 presents a strong time variability in X-rays. We re-analyzed the nine observations performed in 2006 October by XMM-Newton and Chandra in the 0.3 to 10 keV energy band. An acceptable model was found for the XMM-Newton data fitting the EPIC-PN and RGS spectra simultaneously; later, this model was successfully applied to the contemporary Chandra high-resolution data. The model consists of a continuum emission component (power law + blackbody) absorbed by four ionized components (warm absorbers), and 10 narrow emission lines. Three absorbing components are warm, producing features only in the soft X-ray band. The fourth ionization component produces Fe XXV and Fe XXVI in the hard-energy band. We study the time response of the absorbing components to the well-detected changes in the X-ray luminosity of this source and find that the two components with the lower ionization state show clear opacity changes consistent with gas close to photoionization equilibrium. These changes are supported by the models and by differences in the spectral features among the nine observations. On the other hand, the two components with higher ionization state do not seem to respond to continuum variations. The response time of the ionized absorbers allows us to constrain their electron density and location. We find that one component (with intermediate ionization) must be located within the obscuring torus at a distance 2.7 × 10{sup 17} cm from the central engine. This outflowing component likely originated in the accretion disk. The three remaining components are at distances larger than 10{sup 16}-10{sup 17} cm. Two of the absorbing components in the soft X-rays have similar outflow velocities and locations. These components may be in pressure equilibrium, forming a multi-phase medium, if the gas has metallicity larger than the solar one (≳ 5 Z {sub ☉}). We also search for variations in the covering factor of the ionized absorbers (although partial

  11. X-ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminous z>4 Quasars with Chandra

    CERN Document Server

    Vignali, C; Schneider, D P; Kaspi, S

    2005-01-01

    We report on Chandra observations of a sample of 11 optically luminous (Mb4 quasars known and hence represent ideal witnesses of the end of the "dark age ''. Nine quasars are detected by Chandra, with ~2-57 counts in the observed 0.5-8 keV band. These detections increase the number of X-ray detected AGN at z>4 to ~90; overall, Chandra has detected ~85% of the high-redshift quasars observed with snapshot (few kilosecond) observations. PSS 1506+5220, one of the two X-ray undetected quasars, displays a number of notable features in its rest-frame ultraviolet spectrum, the most prominent being broad, deep SiIV and CIV absorption lines. The average optical-to-X-ray spectral index for the present sample (=-1.88+/-0.05) is steeper than that typically found for z>4 quasars but consistent with the expected value from the known dependence of this spectral index on quasar luminosity. We present joint X-ray spectral fitting for a sample of 48 radio-quiet quasars in the redshift range 3.99-6.28 for which Chandra observati...

  12. Probing symmetry and symmetry breaking in resonant soft-x-ray fluorescence spectra of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Glans, P.; Gunnelin, K.; Guo, J. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Conventional non-resonant soft X-ray emission brings about information about electronic structure through its symmetry and polarization selectivity, the character of which is governed by simple dipole rules. For centro-symmetric molecules with the emitting atom at the inversion center these rules lead to selective emission through the required parity change. For the more common classes of molecules which have lower symmetry or for systems with degenerate core orbitals (delocalized over identical sites), it is merely the local symmetry selectivity that provides a probe of the local atomic orbital contribution to the molecular orbital. For instance, in X-ray spectra of first row species the intensities essentially map the p-density at each particular atomic site, and, in a molecular orbital picture, the contribution of the local p-type atomic orbitals in the LCAO description of the molecular orbitals. The situation is different for resonant X-ray fluorescence spectra. Here strict parity and symmetry selectivity gives rise to a strong frequency dependence for all molecules with an element of symmetry. In addition to symmetry selectivity the strong frequency dependence of resonant X-ray emission is caused by the interplay between the shape of a narrow X-ray excitation energy function and the lifetime and vibrational broadenings of the resonantly excited core states. This interplay leads to various observable effects, such as linear dispersion, resonance narrowing and emission line (Stokes) doubling. Also from the point of view of polarization selectivity, the resonantly excited X-ray spectra are much more informative than the corresponding non-resonant spectra. Examples are presented for nitrogen, oxygen, and carbon dioxide molecules.

  13. X-ray ionization yields and energy spectra in liquid argon

    CERN Document Server

    Bondar, A; Dolgov, A; Shekhtman, L; Sokolov, A

    2015-01-01

    The main purpose of this work is to provide reference data on X-ray ionization yields and energy spectra in liquid Ar to the studies in the field of Cryogenic Avalanche Detectors (CRADs) for rare-event experiments, based on noble-gas liquids. We present the results of two related researches. First, the X-ray recombination coefficients in the energy range of 10-1000 keV and ionization yields at different electric fields are determined in liquid Ar, based on the results of a dedicated experiment. Second, the energy spectra of pulsed X-rays in liquid Ar in the energy range of 15-40 keV, obtained in given experiments including that with the two-phase CRAD, are interpreted and compared to those calculated using a dedicated computer program, to correctly determine the incident X-ray energy. The X-ray recombination coefficients and ionization yields have for the first time been presented for liquid Ar in systematic way.

  14. X-ray ionization yields and energy spectra in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Bondar, A.; Buzulutskov, A. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Dolgov, A. [Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Shekhtman, L.; Sokolov, A. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

    2016-04-21

    The main purpose of this work is to provide reference data on X-ray ionization yields and energy spectra in liquid Ar to the studies in the field of Cryogenic Avalanche Detectors (CRADs) for rare-event and other experiments, based on liquid Ar detectors. We present the results of two related researches. First, the X-ray recombination coefficients in the energy range of 10–1000 keV and ionization yields at different electric fields, between 0.6 and 2.3 kV/cm, are determined in liquid Ar based on the results of a dedicated experiment. Second, the energy spectra of pulsed X-rays in liquid Ar in the energy range of 15−40 keV, obtained in given experiments including that with the two-phase CRAD, are interpreted and compared to those calculated using a computer program, to correctly determine the absorbed X-ray energy. The X-ray recombination coefficients and ionization yields have for the first time been presented for liquid Ar in systematic way.

  15. Transmission properties of barite mortar using X-ray spectra measured with Cd Te detector

    Energy Technology Data Exchange (ETDEWEB)

    Santos, J. C.; Mariano, L.; Costa, P. R. [Universidade de Sao Paulo, Instituto de Fisica, Rua do Matao Travessa R. 187, Cidade Universitaria, 05508-090 Sao Paulo (Brazil); Tomal, A., E-mail: josilene@usp.br [Universidade Federal de Goias, Instituto de Fisica, Campus Samambaia, 74001-970 Goiania (Brazil)

    2014-08-15

    Current methods for calculating X-ray shielding barriers do not take into account spectral distribution of the beam transmitted by the protective material. This consideration is important in dose estimations for radiation workers and general public in diagnostic radiology facilities. The aim of the present study was to estimate barite mortar attenuation curves using X-ray spectra weighted by a workload distribution. These curves were described in units of ambient dose equivalent (H (10)), since it is the radiation quantity adopted by IAEA for dose assessment in medical environment. Attenuation curves were determined using the optimized model for shielding evaluation presented by Costa and Caldas (2002). Workload distribution presented by Simpkin (1996), measured primary spectra and mass attenuation coefficients of barite mortar were used as input data in this model. X-ray beams in diagnostic energy range were generated by an industrial X-ray tube with 3 mm of aluminum additional filtration. Primary experimental spectra were measured by a Cd Te detector and corrected by the response function of detector by means of a stripping procedure. Air kerma measurements were performed using an ionization chamber for normalization purpose of the spectra. The corrected spectra presented good agreement with spectra generated by a semi-empirical model. The variation of the ambient dose equivalent as a function of barite mortar thickness was calculated. Using these data, it was estimated the optimized thickness of protective barrier needed for shielding a particular area in an X-ray imaging facility. The results obtained for primary protective barriers exhibit qualitative agreement with those presented in literature. (Author)

  16. X-ray MCD spectra and distortions at Fe2+ L2,3 edges

    NARCIS (Netherlands)

    Wang, Xin; Groot, F.M.F. de; Cramer, S.P.

    1996-01-01

    We have shown from ligand field multiplet calculations that the shape of X-ray magnetic circular dichroism (XMCD) spectra changes drastically with the distortion parameter Ds. The temperature dependence study of XMCD makes it possible to determine both Ds and spin-orbit coupling.

  17. EXPLORING X-RAY BINARY POPULATIONS IN COMPACT GROUP GALAXIES WITH CHANDRA

    Energy Technology Data Exchange (ETDEWEB)

    Tzanavaris, P.; Hornschemeier, A. E. [Laboratory for X-ray Astrophysics, NASA/Goddard Spaceflight Center, Mail Code 662, Greenbelt, MD 20771 (United States); Gallagher, S. C.; Lenkić, L. [Department of Physics and Astronomy and Centre for Planetary and Space Exploration, The University of Western Ontario, London, ON N6A 3K7 (Canada); Desjardins, T. D. [Department of Physics and Astronomy, 177 Chem.-Phys. Building, University of Kentucky, 505 Rose Street, Lexington KY 40506-0055202 (United States); Walker, L. M. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Johnson, K. E. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Mulchaey, J. S. [The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)

    2016-02-01

    We obtain total galaxy X-ray luminosities, L{sub X}, originating from individually detected point sources in a sample of 47 galaxies in 15 compact groups of galaxies (CGs). For the great majority of our galaxies, we find that the detected point sources most likely are local to their associated galaxy, and are thus extragalactic X-ray binaries (XRBs) or nuclear active galactic nuclei (AGNs). For spiral and irregular galaxies, we find that, after accounting for AGNs and nuclear sources, most CG galaxies are either within the ±1σ scatter of the Mineo et al. L{sub X}–star formation rate (SFR) correlation or have higher L{sub X} than predicted by this correlation for their SFR. We discuss how these “excesses” may be due to low metallicities and high interaction levels. For elliptical and S0 galaxies, after accounting for AGNs and nuclear sources, most CG galaxies are consistent with the Boroson et al. L{sub X}–stellar mass correlation for low-mass XRBs, with larger scatter, likely due to residual effects such as AGN activity or hot gas. Assuming non-nuclear sources are low- or high-mass XRBs, we use appropriate XRB luminosity functions to estimate the probability that stochastic effects can lead to such extreme L{sub X} values. We find that, although stochastic effects do not in general appear to be important, for some galaxies there is a significant probability that high L{sub X} values can be observed due to strong XRB variability.

  18. The Chandra Local Volume Survey I: The X-ray Point Source Populations of NGC 55, NGC 2403, and NGC 4214

    CERN Document Server

    Binder, B; Eracleous, M; Plucinsky, P P; Gaetz, T J; Anderson, S F; Skillman, E D; Dalcanton, J J; Kong, A K H; Weisz, D R

    2015-01-01

    We present comprehensive X-ray point source catalogs of NGC~55, NGC~2403, and NGC~4214 as part of the Chandra Local Volume Survey. The combined archival observations have effective exposure times of 56.5 ks, 190 ks, and 79 ks for NGC~55, NGC~2403, and NGC~4214, respectively. When combined with our published catalogs for NGC 300 and NGC 404, our survey contains 629 X-ray sources total down to a limiting unabsorbed luminosity of $\\sim5\\times10^{35}$ erg s$^{-1}$ in the 0.35-8 keV band in each of the five galaxies. We present X-ray hardness ratios, spectral analysis, radial source distributions, and an analysis of the temporal variability for the X-ray sources detected at high significance. To constrain the nature of each X-ray source, we carried out cross-correlations with multi-wavelength data sets. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections to provide preliminary classifications for each X-ray source as a likely X-ray binary, background AGN, su...

  19. THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

    Energy Technology Data Exchange (ETDEWEB)

    Montez, R. Jr. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37212 (United States); Kastner, J. H.; Freeman, M. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, Rochester, NY 14623 (United States); and others

    2015-02-10

    We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively ''hard'' (≥0.5 keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, L {sub X}, that appear uncorrelated with the CSPN bolometric luminosity, L {sub bol} and (2) lower-temperature plasmas with L {sub X}/L {sub bol} ∼ 10{sup –7}. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.

  20. Near-infrared counterparts to Chandra X-ray sources toward the Galactic Center. II. Discovery of Wolf-Rayet stars and O supergiants

    CERN Document Server

    Mauerhan, Jon C; Morris, Mark R; Stolovy, Susan R; Cotera, Angela S

    2009-01-01

    We present new identifications of infrared counterparts to the population of hard X-ray sources near the Galactic center detected by the Chandra X-ray Observatory. We have confirmed 16 new massive stellar counterparts to the X-ray population, including nitrogen-type (WN) and carbon-type (WC) Wolf-Rayet stars, and O supergiants. For the majority of these sources, the X-ray photometry is consistent with thermal emission from plasma having temperatures in the range of kT=1-8 keV or non-thermal emission having power-law indices in the range of -1X-ray luminosities in the range of Lx~1e32-1e34 erg/s. Several sources have exhibited X-ray variability of several factors between separate observations. The X-ray properties are not a ubiquitous feature of single massive stars but are typical of massive binaries, in which the high-energy emission is generated by the collision of supersonic winds, or by accretion onto a compact companion. However, the possibility of intrinsic hard X-ray generation from...

  1. Normal incidence X-ray telescope power spectra of X-ray emission from solar active regions. I - Observations. II - Theory

    Science.gov (United States)

    Gomez, Daniel O.; Martens, Petrus C. H.; Golub, Leon

    1993-01-01

    Fourier analysis is applied to very high resolution image of coronal active regions obtained by the Normal Incidence X-Ray Telescope is used to find a broad isotropic power-law spectrum of the spatial distribution of soft X-ray intensities. Magnetic structures of all sizes are present down to the resolution limit of the instrument. Power spectra for the X-ray intensities of a sample of topologically different active regions are found which fall off with increasing wavenumber as 1/k-cubed. A model is presented that relates the basic features of coronal magnetic fluctuations to the subphotospheric hydrodynamic turbulence that generates them. The model is used to find a theoretical power spectrum for the X-ray intensity which falls off with increasing wavenumber as 1/k-cubed. The implications of a turbulent regime in active regions are discussed.

  2. Investigating ChaMPlane X-ray sources in the Galactic Bulge with Magellan LDSS2 spectra

    OpenAIRE

    Koenig, Xavier; Grindlay, Jonathan E.; Berg, Maureen van den; Laycock, Silas; Zhao, Ping; Hong, Jaesub; Schlegel, Eric M.

    2008-01-01

    We have carried out optical and X-ray spectral analyses on a sample of 136 candidate optical counterparts of X-ray sources found in five Galactic-bulge fields included in our Chandra Multi-wavelength Plane Survey. We use a combination of optical spectral fitting and quantile X-ray analysis to obtain the hydrogen column density towards each object, and a three-dimensional dust model of the Galaxy to estimate the most probable distance in each case. We present the discovery of a population of s...

  3. Spectra Transmitted by Mortar Barite in x-ray Qualities Applied in Diagnostic Radiology as Shielding

    Science.gov (United States)

    Almeida, A. T., Jr.; Araújo, F. G. S.; Nogueira, M. S.; Santos, M. A. P.

    2016-07-01

    Concrete which contains water, cement and aggregate, is widely used in building construction such as medical hospitals. The CdZnTe spectrometry system was used to acquire the transmitted spectra in the RQR qualities and the stripping procedure was performed by taking into account both the contributions of efficiency and x-ray escape fraction, experimentally determined. The samples were prepared in rectangular plate format with dimensions of (5 x 5) cm with thicknesses varying from 0.2cm to 2cm and exposed to x-ray beams generated. The HVL and the mean energy in this energy range was determined.

  4. A ubiquitous absorption feature in the X-ray spectra of BL Lacertae objects

    Science.gov (United States)

    Madejski, Greg M.; Mushotzky, Richard F.; Weaver, Kimberly A.; Arnaud, Keith A.; Urry, C. Megan

    1991-01-01

    The paper presents the broadband (0.5-20-keV) X-ray spectra of five X-ray bright BL Lac objects observed with the Einstein Observatory Solid State Spectrometer (SSS) and Monitor Proportional Counter (MPC) detectors. The combination of moderate energy resolution and broad spectral coverage makes it possible to confirm the presence of an absorption feature at an energy of 650 eV in the BL Lac object PKS 2155-304, originally reported by Canizares and Kruper (1984) based on higher resolution Einstein Objective Grating Spectrometer (OGS) data.

  5. The spectra of accretion discs in low-mass X-ray binaries

    CERN Document Server

    Ross, R R

    1995-01-01

    We present self-consistent models for the radiative transfer in Shakura-Sunyaev accretion discs in bright low-mass X-ray binaries (LMXB). Our calculations include the full effects of incoherent Compton scattering and the vertical temperature structure within the disc, as well as the effects of Doppler blurring and gravitational redshift. We find that the observed X-ray spectra are well fit by exponentially cutoff power-law models. The difference between the observed total spectrum and our calculated disc spectrum should reveal the spectrum of the disc/neutron star boundary layer and other emitting regions considered to be present in LMXB.

  6. Resonant Auger Destruction and Iron K-Alpha Spectra in Compact X-ray Sources

    OpenAIRE

    Liedahl, Duane A.

    2005-01-01

    We examine the effects of resonant Auger destruction in modifying the intensities and flux distributions of K-alpha spectra from iron L-shell ions. Applications include X-ray irradiated stellar winds in X-ray binaries and accretion disk atmospheres. Using detailed atomic models, we find that resonant Auger destruction is selective, in that only a subset of the emitted K-alpha lines is highly attenuated. We also show that that the local excitation conditions can have a dramatic effect on the K...

  7. Spectra transmitted by mortar barite in X-Ray qualities applied in diagnostic radiology as shielding

    Energy Technology Data Exchange (ETDEWEB)

    Almeida Junior, Airton T., E-mail: airton.almeida@fundacentro.gov.br [Fundacaoo Jorge Duprat Figueiredo de Seguranca e Medicina do Trabalho (FUNDACENTRO), Belo Horizonte, MG (Brazil); Araujo, F.G.S. [Universidade Federal de Ouro Preto (REDEMAT/UFOP), MG (Brazil); Nogueira, M.S., E-mail: mnogue@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Santos, M.A.P. [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)

    2015-07-01

    Concrete which contains water, cement and aggregate, is widely used in building construction such as medical hospitals. The CdZnTe spectrometry system was used to acquire the transmitted spectra in the RQR qualities and the stripping procedure was performed by taking into account both the contributions of efficiency and x-ray escape fraction, experimentally determined. The samples were prepared in rectangular plate format with dimensions of (5 x 5) cm with thicknesses varying from 0.2cm to 2cm and exposed to x-ray beams generated. The HVL and the mean energy in this energy range was determined. (author)

  8. Characterization of neutron yield and x-ray spectra of a High Flux Neutron Generator (HFNG)

    Science.gov (United States)

    Nnamani, Nnaemeka; HFNG Collaboration

    2015-04-01

    The High Flux Neutron Generator (HFNG) is a DD plasma-based source, with a self-loading target intended for fundamental science and engineering applications, including 40 Ar/39 Ar geochronology, neutron cross section measurements, and radiation hardness testing of electronics. Our first estimate of the neutron yield, based on the population of the 4.486 hour 115 In isomer gave a neutron yield of the order 108 n/sec; optimization is ongoing to achieve the design target of 1011 n/sec. Preliminary x-ray spectra showed prominent energy peaks which are likely due to atomic line-emission from back-streaming electrons accelerated up to 100 keV impinging on various components of the HFNG chamber. Our x-ray and neutron diagnostics will aid us as we continue to evolve the design to suppress back-streaming electrons, necessary to achieve higher plasma beam currents, and thus higher neutron flux. This talk will focus on the characterization of the neutron yield and x-ray spectra during our tests. A collimation system is being installed near one of the chamber ports for improved observation of the x-ray spectra. This work is supported by NSF Grant No. EAR-0960138, U.S. DOE LBNL Contract No. DE-AC02-05CH11231, U.S. DOE LLNL Contract No. DE-AC52-07NA27344, and the UC Office of the President Award 12-LR-238745.

  9. Target optimization for desired X-ray spectra produced by laser plasma accelerated electrons

    Science.gov (United States)

    Lobok, Maxim; Brantov, Andrey; Bychenkov, Valery

    2016-10-01

    Different regimes of electron acceleration from low-density targets are investigated using three-dimensional numerical simulations. Multiple spatial target density profiles were examined, including laser pre-pulse modified targets. The size of the plasma corona is shown to be one of the main parameters characterizing the temperature and number of hot electrons, which determine the yield of X-ray radiation and its hardness. The generation of X-ray radiation by laser accelerated electrons, which impact the converter target located behind the laser target, was studied. The X-ray spectra were computed using Monte-Carlo simulations. This work was partially supported by the Russian Foundation for Basic Research 16-02-00088-a.

  10. PHASE-RESOLVED X-RAY SPECTRA OF MAGNETARS AND THE CORONAL OUTFLOW MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Hascoët, Romain; Beloborodov, Andrei M. [Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street, New York, NY 10027 (United States); Den Hartog, Peter R., E-mail: hascoet@astro.columbia.edu [Stanford University HEPL/KIPAC, 452 Lomita Mall, Stanford, CA 94305-4085 (United States)

    2014-05-01

    We test a model recently proposed for the persistent hard X-ray emission from magnetars. In the model, hard X-rays are produced by a decelerating electron-positron flow in the closed magnetosphere. The flow decelerates as it radiates its energy away via resonant scattering of soft X-rays, then it reaches the top of the magnetic loop and annihilates there. We test the model against observations of three magnetars: 4U 0142+61, 1RXS J1708-4009, and 1E 1841-045. We find that the model successfully fits the observed phase-resolved spectra. We derive constraints on the angle between the rotational and magnetic axes of the neutron star, the object inclination to the line of sight, and the size of the active twisted region filled with the plasma flow. Using the fit of the hard X-ray component of the magnetar spectrum, we revisit the remaining soft X-ray component. We find that it can be explained by a modified two-temperature blackbody model. The hotter blackbody is consistent with a hot spot covering 1%-10% of the neutron star surface. Such a hot spot is expected at the base of the magnetospheric e {sup ±} outflow, as some particles created in the e {sup ±} discharge flow back and bombard the stellar surface.

  11. Phase-resolved X-ray spectra of magnetars and the coronal outflow model

    CERN Document Server

    Hascoet, R; Hartog, P R den

    2014-01-01

    We test a model recently proposed for the persistent hard X-ray emission from magnetars. In the model, hard X-rays are produced by a decelerating electron-positron flow in the closed magnetosphere. The flow decelerates as it radiates its energy away via resonant scattering of soft X-rays, then it reaches the top of the magnetic loop and annihilates there. We test the model against observations of three magnetars: 4U 0142+61, 1RXS J1708-4009, and 1E 1841-045. We find that the model successfully fits the observed phase-resolved spectra. We derive constraints on the angle between the rotational and magnetic axes of the neutron star, the object inclination to the line of sight, and the size of the active twisted region filled with the plasma flow. Using the fit of the hard X-ray component of the magnetar spectrum, we revisit the remaining soft X-ray component. We find that it can be explained by a modified two-temperature blackbody model. The hotter blackbody is consistent with a hot spot covering 1-10% of the ne...

  12. Chandra X-Ray Observations of Young Clusters. III. NGC 2264 and the Orion Flanking Fields

    CERN Document Server

    Rebull, L M; Micela, G; Ramírez, S V; Sciortino, S; Stauffer, J R; Strom, S E; Wolff, S C

    2006-01-01

    Chandra observations of solar-like pre-main sequence (PMS) stars in the Orion Flanking Fields (age ~1 Myr) and NGC 2264 (~3 Myr) are compared with the results of the COUP survey of similar objects in the ONC (~0.5 Myr). The correlations between log Lx and mass found for PMS stars on convective tracks in these clusters are consistent with the relationships found for the ONC, indicating little change in the median values of either log Lx or log Lx/Lbol during the first ~3-5 Myr of evolution down convective tracks. The fraction of stars with extreme values of Lx, more than 10 times higher than the average for a given Lbol or with log Lx/Lbol greater than the canonical saturation value of -2.9, is however larger by a factor of two in the younger ONC when compared with the Orion FF and NGC 2264. PMS stars in NGC 2264 on radiative tracks have Lx/Lbol values that are systematically lower by a factor of ~10 times than those found for stars of similar mass on convective tracks. The dramatic decrease in flux from conve...

  13. The Puzzling Detection of X-rays From Pluto by Chandra

    CERN Document Server

    Lisse, C M; Wolk, S J; Bagenal, F; Stern, S A; Gladstone, G R; Cravens, T E; Hill, M E; Kollmann, P; Weaver, H A; Strobel, D F; Elliott, H A; McComas, D J; Binzel, R P; Snios, B T; Bhardwaj, A; Chutjian, A; Young, L A; Olkin, C B; Ennico, K A

    2016-01-01

    Using Chandra ACIS-S, we have obtained imaging Xray spectrophotometry of the Pluto system in support of the New Horizons flyby on 14 July 2015. 174 ksec of observations were obtained on 4 visits in Feb 2014 to Aug 2015. We measured a net signal of 6.8 counts and a noise level of 1.2 counts in a comoving 11 x 11 pixel box (100 x 100 R_Pluto) in the 0.31 to 0.60 keV passband for a detection at > 99.95 C.L. The Pluto photons do not match the background spectrum, are coincident with a 90% flux aperture comoving with Pluto, and are not sky source confused. The mean 0.31 to 0.60 keV Xray power from Pluto is 200 MW, in the midrange of Xray power levels seen for known solar system emission sources: auroral precipitation, solar Xray scattering, and charge exchange (CXE) between solar wind (SW) ions & atmospheric neutrals. We eliminate auroral effects as a source, as Pluto has no known magnetic field & the New Horizons Alice UV spectrometer detected no airglow from Pluto during the flyby. Nano-scale atmospheric...

  14. MOG Weak Field Approximation: A Modified Gravity Compatible with Chandra X-ray Clusters

    CERN Document Server

    Moffat, J W

    2013-01-01

    We use the covariant Scalar-Vector-Tensor theory of gravity (so-called MOG), in the weak field approximation limit to study the dynamics of clusters of galaxies. The ionized gas density and the temperature profile of the clusters are our observables, which have been measured by the Chandra telescope for the nearby clusters. The MOG effective gravitational potential in the weak field approximation is composed of attractive Newtonian and repulsive Yukawa terms. Two parameters $\\alpha$ and $\\mu$ in the effective potential determine the asymptotic gravitational constant and the mass of the vector field, respectively. These parameters have been fixed by fitting MOG dynamics to the rotation curves of galaxies. Our analysis shows that the internal dynamics of clusters can be well explained within $1\\sigma$ with a virial theorem in the framework of MOG, such that the best fit for the ratio of the dynamical mass to the baryonic mass is: $M_{\\rm dyn}/M_{\\rm b} = 0.98^{+0.02}_{-0.02}$. This result means that MOG is a th...

  15. The High Resolution X-ray Spectrum of SS 433 using the Chandra HETGS

    CERN Document Server

    Marshall, H L; Schulz, N S; Marshall, Herman L.; Canizares, Claude R.; Schulz, Norbert S.

    2001-01-01

    We present observations of SS 433 using the Chandra High Energy Transmission Grating Spectrometer. Many emission lines of highly ionized elements are detected with the relativistic blue and red Doppler shifts. The lines are measurably broadened to 1700 km/s (FWHM) and the widths do not depend significantly on the characteristic emission temperature, suggesting that the emission occurs in a freely expanding region of constant collimation with opening angle of 1.23 +/- 0.06 deg. The blue shifts of lines from low temperature gas are the same as those of high temperature gas within our uncertainties, again indicating that the hottest gas we observe to emit emission lines is already at terminal velocity. Fits to the emission line fluxes give a range of temperatures in the jet from 5e6 to 1e8 K. We derive the emission measure as a function of temperature for a four component model that fits the line flux data. Using the density sensitive Si XIII triplet, the characteristic electron density is 1e14 cm^{-3}, where th...

  16. Chandra Studies of the X-ray Gas Properties of Fossil Systems

    CERN Document Server

    Qin, Zhenzhen

    2015-01-01

    We study ten galaxy groups and clusters suggested in the literature to be "fossil system (FS)" based on \\chandra\\ observations. According to the $M_{500}-T$ and $L_{\\rm X}-T$ relations, the gas properties of FSs are not physically distinct from ordinary galaxy groups or clusters. We also first study the $f_{\\rm gas,~2500}-T$ relation and find that the FS exhibits same as ordinary systems. The gas densities of FSs within $0.1r_{200}$, are $\\sim 10^{-3}$ cm$^{-3}$, which is the same order as galaxy clusters. The entropies within $0.1r_{200}$ ($S_{0.1r_{200}}$) of FSs are systematically lower than those in ordinary galaxy groups which is consistent with previous report, but we find their $S_{0.1r_{200}}-T$ relation is more similar to galaxy clusters. The derived mass profiles of FSs are consistent with the Navarro, Frenk, \\& White model in $(0.1-1)r_{200}$, and the relation between scale radius $r_{\\rm s}$ and characteristic mass density $ta_{\\rm c}$ indicates the self-similarity of dark matter halos of FSs....

  17. Chandra Studies of the X-ray gas properties of fossil systems

    Science.gov (United States)

    Qin, Zhen-Zhen

    2016-03-01

    We study ten galaxy groups and clusters suggested in the literature to be “fossil systems (FSs)” based on Chandra observations. According to the M500 - T and LX - T relations, the gas properties of FSs are not physically distinct from ordinary galaxy groups or clusters. We also first study the fgas, 2500 - T relation and find that the FSs exhibit the same trend as ordinary systems. The gas densities of FSs within 0.1r200 are ˜ 10-3 cm-3, which is the same order of magnitude as galaxy clusters. The entropies within 01r200 (S0.1r200) of FSs are systematically lower than those inordinary galaxy groups, which is consistent with previous reports, but we find their S0.1r200 - T relation is more similar to galaxy clusters. The derived mass profiles of FSs are consistent with the Navarro, Frenk and White model in (0.1 - 1)r200, and the relation between scale radius rs and characteristic mass density δc indicates self-similarity of dark matter halos of FSs. The ranges of rs and δc for FSs are also close to those of galaxy clusters. Therefore, FSs share more common characteristics with galaxy clusters. The special birth place of the FS makes it a distinct type of galaxy system.

  18. Evolution of Hard X-Ray Spectra Along the Branches in Cir X-1

    CERN Document Server

    Ding, G Q; Li, T P

    2003-01-01

    Using the data from the PCA and HEXTE on board the RXTE satellite, we investigate the evolution of the 3-200 keV spectra of the peculiar low mass X-ray binary (LMXB) Cir X-1 along the branches on its hardness-intensity diagram (HID) from the vertical horizontal branch (VHB), through the horizontal horizontal branch (HHB) and normal branch (NB), to the flaring branch (FB). We detect a power-law hard component in the spectra. It is found that the derived photon indices ($\\Gamma$) of the power-law hard component are correlated with the position on the HID. The power-law component dominates the X-ray emission of Cir X-1 in the energy band higher than $\\sim 20$ keV. The fluxes of the power-law component are compared with those of the bremsstrahlung component in the spectra. A possible origin of the power-law hard component is discussed.

  19. The Field X-ray AGN Fraction to z=0.7 from the Chandra Multiwavelength Project and the Sloan Digital Sky Survey

    CERN Document Server

    Haggard, Daryl; Anderson, Scott F; Constantin, Anca; Aldcroft, Tom L; Kim, Dong-Woo; Barkhouse, Wayne A

    2010-01-01

    We employ the Chandra Multiwavelength Project (ChaMP) and the Sloan Digital Sky Survey (SDSS) to study the fraction of X-ray-active galaxies in the field out to z = 0.7. We utilize spectroscopic redshifts from SDSS and ChaMP, as well as photometric redshifts from several SDSS catalogs, to compile a parent sample of more than 100,000 SDSS galaxies and nearly 1,600 Chandra X-ray detections. Detailed ChaMP volume completeness maps allow us to investigate the local fraction of active galactic nuclei (AGN), defined as those objects having broad-band X-ray luminosities L_X (0.5-8 keV) > 10^42 erg s^-1, as a function of absolute optical magnitude, X-ray luminosity, redshift, mass, and host color/morphological type. In five independent samples complete in redshift and i-band absolute magnitude, we determine the field AGN fraction to be between 0.16 +/- 0.06% (for z M_i > -20) and 3.80 +/- 0.92% (for z < 0.7 and M_i < -23). We find striking agreement between our ChaMP/SDSS field AGN fraction and the Chandra clu...

  20. Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra

    Science.gov (United States)

    West, Brent F.; Wolfram, Kenneth D.; Becker, Peter A.

    2017-02-01

    The availability of the unprecedented spectral resolution provided by modern X-ray observatories is opening up new areas for study involving the coupled formation of the continuum emission and the cyclotron absorption features in accretion-powered X-ray pulsar spectra. Previous research focusing on the dynamics and the associated formation of the observed spectra has largely been confined to the single-fluid model, in which the super-Eddington luminosity inside the column decelerates the flow to rest at the stellar surface, while the dynamical effect of gas pressure is ignored. In a companion paper, we have presented a detailed analysis of the hydrodynamic and thermodynamic structure of the accretion column obtained using a new self-consistent model that includes the effects of both gas and radiation pressures. In this paper, we explore the formation of the associated X-ray spectra using a rigorous photon transport equation that is consistent with the hydrodynamic and thermodynamic structure of the column. We use the new model to obtain phase-averaged spectra and partially occulted spectra for Her X-1, Cen X-3, and LMC X-4. We also use the new model to constrain the emission geometry, and compare the resulting parameters with those obtained using previously published models. Our model sheds new light on the structure of the column, the relationship between the ionized gas and the photons, the competition between diffusive and advective transport, and the magnitude of the energy-averaged cyclotron scattering cross-section.

  1. Maximising the mileage from the Chandra podcasts

    Science.gov (United States)

    Arcand, K. K.; Watzke, M.

    2008-06-01

    NASA's Chandra X-ray Observatory captures X-ray images and measures spectra of many highenergy cosmic phenomena. There is a constant challenge to devise new and appropriate means to bring these potentially esoteric science results and concepts in a digestible way to the public. One of the ideas to address this challenge became the Chandra podcast.

  2. Direct Measurement of Mammographic X-Ray Spectra with a Digital CdTe Detection System

    Directory of Open Access Journals (Sweden)

    Giuseppe Raso

    2012-06-01

    Full Text Available In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP system, for high-rate X-ray spectroscopy in mammography (1–30 keV. The DPP system performs a height and shape analysis of the detector pulses, sampled and digitized by a 14-bit, 100 MHz ADC. We show the results of the characterization of the detection system both at low and high photon counting rates by using monoenergetic X-ray sources and a nonclinical X-ray tube. The detection system exhibits excellent performance up to 830 kcps with an energy resolution of 4.5% FWHM at 22.1 keV. Direct measurements of clinical molybdenum X-ray spectra were carried out by using a pinhole collimator and a custom alignment device. A comparison with the attenuation curves and the half value layer values, obtained from the measured and simulated spectra, from an ionization chamber and from a solid state dosimeter, also shows the accuracy of the measurements. These results make the proposed detection system a very attractive tool for both laboratory research, calibration of dosimeters and advanced quality controls in mammography.

  3. The Chandra COSMOS Legacy Survey: Energy Spectrum of the Cosmic X-Ray Background and Constraints on Undetected Populations

    Science.gov (United States)

    Cappelluti, Nico; Li, Yanxia; Ricarte, Angelo; Agarwal, Bhaskar; Allevato, Viola; Tasnim Ananna, Tonima; Ajello, Marco; Civano, Francesca; Comastri, Andrea; Elvis, Martin; Finoguenov, Alexis; Gilli, Roberto; Hasinger, Günther; Marchesi, Stefano; Natarajan, Priyamvada; Pacucci, Fabio; Treister, E.; Urry, C. Megan

    2017-03-01

    Using Chandra observations in the 2.15 deg2 COSMOS-legacy field, we present one of the most accurate measurements of the Cosmic X-ray Background (CXB) spectrum to date in the [0.3–7] keV energy band. The CXB has three distinct components: contributions from two Galactic collisional thermal plasmas at kT ∼ 0.27 and 0.07 keV and an extragalactic power law with a photon spectral index Γ = 1.45 ± 0.02. The 1 keV normalization of the extragalactic component is 10.91 ± 0.16 keV cm‑2 s‑1 sr‑1 keV‑1. Removing all X-ray-detected sources, the remaining unresolved CXB is best fit by a power law with normalization 4.18 ± 0.26 keV cm‑2 s‑1 sr‑1 keV‑1 and photon spectral index Γ = 1.57 ± 0.10. Removing faint galaxies down to {i}{AB}∼ 27{--}28 leaves a hard spectrum with {{Γ }}∼ 1.25 and a 1 keV normalization of ∼1.37 keV cm‑2 s‑1 sr‑1 keV‑1. This means that ∼91% of the observed CXB is resolved into detected X-ray sources and undetected galaxies. Unresolved sources that contribute ∼8%–9% of the total CXB show marginal evidence of being harder and possibly more obscured than resolved sources. Another ∼1% of the CXB can be attributed to still undetected star-forming galaxies and absorbed active galactic nuclei. According to these limits, we investigate a scenario where early black holes totally account for non-source CXB fraction and constrain some of their properties. In order to not exceed the remaining CXB and the z∼ 6 accreted mass density, such a population of black holes must grow in Compton-thick envelopes with {N}H > 1.6 × 1025 cm‑2 and form in extremely low-metallicity environments ({Z}ȯ )∼ {10}-3.

  4. X-ray emission of SNRs in nonuniform medium: properties of thermal and nonthermal spectra

    Science.gov (United States)

    Petruk, O.

    2006-05-01

    In this report we consider two effects in the thermal and nonthermal spectra of supernova remnants (SNRs) which could be caused by the nonuniform ISM: i) the mimicry of the thermal X-ray spectrum of SNRs under the nonthermal one and ii) artificial broadening of the high-energy end of the nonthermal X-ray spectrum of SNRs. 1.There is possibility that the nonthermal features in the X-ray spectrum of some supernova remnants may be in fact of the thermal origin. Observed spectrum from SNRs is a superposition of ``individual'' spectra from different small volumes along the line of sight. The plasma is under different conditions in different places in SNR. The thermal X-ray spectrum of emission from a volume with high enough gradients of density and temperature may mimic under nonthermal one. This effect is studied with special attention to the case of supernova remnant evolution in the nonuniform interstellar medium like near molecular cloud. The mimicry-effect may be responsible for the nonthermal properties of X-ray spectra in those SNRs where nonthermal flux in photons with energy nonuniform interstellar medium. Time dependence of the maximum energy of electrons accelerated by the shock is also not able to make the observed spectrum considerably broader. The only possibility to produce broadening in the spectrum is the variation of the maximum energy of electrons over the surface of SNR. In such a case, the obliquity dependence of injection efficiency and/or magnetic field strength make also effect on the shape of the spectrum but their role is of the second order.

  5. An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: The AGN Fraction and X-ray Properties of Submillimeter Galaxies

    CERN Document Server

    Wang, S X; Luo, B; Smail, I; Alexander, D M; Danielson, A L R; Hodge, J A; Karim, A; Lehmer, B D; Simpson, J M; Swinbank, A M; Walter, F; Wardlow, J L; Xue, Y Q; Chapman, S C; Coppin, K E K; Dannerbauer, H; De Breuck, C; Menten, K M; van der Werf, P

    2013-01-01

    The large gas and dust reservoirs of submm galaxies (SMGs) could potentially provide ample fuel to trigger an Active Galactic Nucleus (AGN), but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available submillimeter surveys. Here we set improved constraints on the AGN fraction and X-ray properties of the SMGs with ALMA and Chandra observations in the Extended Chandra Deep Field-South (E-CDF-S). This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submm-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA E-CDF-S Submillimeter Survey (ALESS). We found 10 X-ray sources associated with SMGs (median redshift z = 2.3), of which 8 were identified as AGNs using several techniques that enable cross-checking. The other 2 X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by the...

  6. A Chandra Perspective On Galaxy-Wide X-ray Binary Emission And Its Correlation With Star Formation Rate And Stellar Mass: New Results From Luminous Infrared Galaxies

    CERN Document Server

    Lehmer, B D; Bauer, F E; Brandt, W N; Goulding, A D; Jenkins, L P; Ptak, A; Roberts, T P

    2010-01-01

    We present new Chandra observations that complete a sample of seventeen (17) luminous infrared galaxies (LIRGs) with D < 60 Mpc and low Galactic column densities of N_H < 5 X 10^20 cm^-2. The LIRGs in our sample have total infrared (8-1000um) luminosities in the range of L_IR ~ (1-8) X 10^11 L_sol. The high-resolution imaging and X-ray spectral information from our Chandra observations allow us to measure separately X-ray contributions from active galactic nuclei (AGNs) and normal galaxy processes (e.g., X-ray binaries and hot gas). We utilized total infrared plus UV luminosities to estimate star-formation rates (SFRs) and K-band luminosities and optical colors to estimate stellar masses (M*) for the sample. Under the assumption that the galaxy-wide 2-10 keV luminosity (LX) traces the combined emission from high mass X-ray binaries (HMXBs) and low mass X-ray binaries (LMXBs), and that the power output from these components are linearly correlated with SFR and M*, respectively, we constrain the relation ...

  7. Effect of Viewing Angle on Super-Soft-Source X-Ray Spectra

    Science.gov (United States)

    Ness, Jan-Uwe

    2012-09-01

    The advent of the X-ray grating spectrometers has given new momentum to the studies of Super-Soft-Source (SSS) X-ray spectra in high resolution. Earlier CCD-type spectra only allow determinations of effective temperatures while in the grating spectra, lines and continuum can be resolved. I have studied the X-ray grating spectra of eight classical novae during their SSS phase, two of them candidates for recurrent novae, two established recurrent novae, and four permanent SSSs including the prototypes Cal 83 and Cal 87. I discovered two categories of SSSs: those dominated by emission lines (SSSe) and by absorption line (SSSa). All spectra contain photospheric continuum emission, indicated by the shape of a blackbody. For the majority of SSSe, the inclination angle is known, which are all greater than 75 degrees. I argue that the SSSe are high-inclination systems in which photospheric X-ray emission from the central source is partially blocked and scattered via Thompson scattering, which preserves the spectral shape of the continuum. Since the electrons in the scattering medium move at high velocities, photospheric absorption lines are smeared out and are therefore not seen. Additional emission lines are produced by resonant line scattering. The fact that only high inclination systems show these effects of scattering, the scattering material must be concentrated to the ecliptic plane. While in permanent SSSs, the accretion disk can explain this behavior, this result implies that in novae, the reformation of the accretion disk has already progressed to an advanced stage during their SSS phase. I argue that also the novae in low-inclination angle systems possess a reformed accretion disk. The viewing angle dependence requires non-symmetrical modeling approaches. Early disk reformation can also explain high-amplitude variations that have frequently been observed during the early SSS phase.

  8. An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis

    Science.gov (United States)

    Edmonds, Peter D.; Gilliland, Ronald L.; Heinke, Craig O.; Grindlay, Jonathan E.

    2003-10-01

    We report time series and variability information for the optical identifications of X-ray sources in 47 Tucanae reported in Paper I (at least 22 cataclysmic variables [CVs] and 29 active binaries). The radial distribution of the CVs is indistinguishable from that of the millisecond pulsars (MSPs) detected by Freire et al. A study of the eight CVs with secure orbital periods (two obtained from the Chandra study of Grindlay et al.) shows that the 47 Tuc CVs have fainter accretion disks, in the V band, than field CVs with similar periods. These faint disks and the faint absolute magnitudes (MV) of the 47 Tuc CVs suggests they have low accretion rates. One possible explanation is that the 47 Tuc objects may be a more representative sample of CVs, down to our detection threshold, than the CVs found in the field (where many low accretion rate systems are believed to be undiscovered), showing the advantages of deep globular cluster observations. The median FX/Fopt value for the 47 Tuc CVs is higher than that of all known classes of field CV, partly because of the faint MV values and partly because of the relatively high X-ray luminosities (LX). The latter are only seen in DQ Her systems in the field, but the 47 Tuc CVs are much fainter optically than most field DQ Her's. Previous work by Edmonds et al. has shown that the four brightest CVs in NGC 6397 have optical spectra and broadband colors that are consistent with DQ Her's having lower than average accretion rates. Some combination of magnetic behavior and low accretion rates may be able to explain our observations, but the results at present are ambiguous, since no class of field CV has distributions of both LX and MV that are consistent with those of the 47 Tuc CVs. The radial distribution of the X-ray detected active binaries is indistinguishable from that of the much larger sample of optical variables (eclipsing and contact binaries and BY Dra variables) detected in previous Wide Field Planetary Camera 2 (WFPC2

  9. Monitoring the Health and Safety of the ACIS Instrument On-Board the Chandra X-ray Observatory

    CERN Document Server

    Virani, S N; De Pasquale, J M; Plucinsky, P P; Virani, Shanil N.; Ford, Peter G.; Pasquale, Joseph M. De; Plucinsky, Paul P.

    2002-01-01

    The Chandra X-ray Observatory (CXO), NASA's latest ``Great Observatory'', was launched on July 23, 1999 and reached its final orbit on August 7, 1999. The CXO is in a highly elliptical orbit, approximately 140,000 km x 10,000 km, and has a period of approximately 63.5 hours (~2.65 days). Communication with the CXO nominally consists of 1-hour contacts spaced 8-hours apart. Thus, once a communication link has been established, it is very important that the health and safety status of the scientific instruments as well as the Observatory itself be determined as quickly as possible. In this paper, we focus exclusively on the automated health and safety monitoring scripts developed for the Advanced CCD Imaging Spectrometer (ACIS) to use during those 1-hour contacts. ACIS is one of the two focal plane instruments on-board the CXO. We present an overview of the real-time ACIS Engineering Data Web Page and the alert schemes developed for monitoring the instrument status during each communication contact. A suite of ...

  10. Cosmic Ray Acceleration at the Forward Shock in Tycho's Supernova Remnant: Evidence from Chandra X-ray Observations

    CERN Document Server

    Warren, J S; Badenes, C; Ghavamian, P; McKee, C F; Moffett, D; Plucinsky, P P; Rakowski, C; Reynoso, E; Slane, P O

    2005-01-01

    We present evidence for cosmic ray acceleration at the forward shock in Tycho's supernova remnant (SNR) from three X-ray observables: (1) the proximity of the contact discontinuity to the forward shock, or blast wave, (2) the morphology of the emission from the rim of Tycho, and (3) the spectral nature of the rim emission. We determine the locations of the blast wave (BW), contact discontinuity (CD), and reverse shock (RS) around the rim of Tycho's supernova remnant using a principal component analysis and other methods applied to new Chandra data. The azimuthal-angle-averaged radius of the BW is 251". For the CD and RS we find average radii of 241" and 183", respectively. Taking account of projection effects, we find ratios of 1:0.93:0.70 (BW:CD:RS). We show these values to be inconsistent with adiabatic hydrodynamical models of SNR evolution. The CD:BW ratio can be explained if cosmic ray acceleration of ions is occurring at the forward shock. The RS:BW ratio, as well as the strong Fe Ka emission from the T...

  11. Measurements of X-ray doses and spectra produced by picosecond laser-irradiated solid targets.

    Science.gov (United States)

    Yang, Bo; Qiu, Rui; Yu, Minghai; Jiao, Jinlong; Lu, Wei; Yan, Yonghong; Zhang, Bo; Zhang, Zhimeng; Zhou, Weimin; Li, Junli; Zhang, Hui

    2017-02-09

    Experiments have shown that high-intensity laser interaction with a solid target can generate significant X-ray doses. This study was conducted to determine the X-ray doses and spectra produced for picosecond laser-irradiated solid targets. The photon doses and X-ray spectra in the laser forward and side directions were measured using an XG III ps 300 TW laser system. For laser intensities of 7×10(18)-4×10(19)W/cm(2), the maximum photon dose was 16.8 mSv at 50cm with a laser energy of ~153J on a 1-mm Ta target. The photon dose in the forward direction increased more significantly with increasing laser intensity than that in the side direction. For photon energies >300keV, the X-ray spectrum can be fit with an effective temperature distribution of the exponential form, dN/dE = k× exp(-E/Tx). The X-ray temperature Tx increased with the laser intensity in the forward direction with values of 0.46-0.75MeV. Tx was less strongly correlated with the laser intensity in the side direction with values of 0.29-0.32MeV. The escaping electron spectrum was also measured. The measured electron temperature was correlated with the electron temperature predicted by the ponderomotive law. The observations in this experiment were also investigated numerically. A good agreement was observed between the experimental and simulation results.

  12. K X-ray satellite spectra of Ti, V, Cr and Mn induced by photons

    Indian Academy of Sciences (India)

    M V R Murti; S S Raju; B Seetharami Reddy; V Koteswara Rao; L S Mombaswala; T Seshi Reddy; S Lakshminarayana; K Premachand

    2008-04-01

    K X-ray emission spectra of Ti, V, Cr and Mn generated by photon excitation have been studied with a crystal spectrometer. The measured energy shifts of K satellite relative to the diagram line are compared with values obtained by electron excitation and with different theoretical estimates. The present experimental values of KL1/KL0 relative intensities are compared with values obtained by electron excitation.

  13. New Insights into the X-Ray Spectra of Heliumlike and Neonlike Ions

    Energy Technology Data Exchange (ETDEWEB)

    Beiersdorfer, P; Chen, H; Hey, D; May, M; Osterheld, A; Reed, K; Scofield, J; Thorn, D; Bitter, M; Boyce, K R; Brown, G V; Gendreau, K C; Kelley, R L; Porter, F S; Stahle, C K; Szymkowiak, A E; Olson, R E; Lepson, J K; Gu, M F; Behar, E; Kahn, S M

    2002-04-11

    Recent measurements of the K-shell and L-shell x-ray spectra of highly charged helium-like and neon-like ions are presented that were performed on the Livermore electron beam ion traps and the Princeton tokamaks. These measurements provide new insights into collisional and indirect line formation processes, identifications of forbidden lines, and a new plasma line diagnostic of magnetic field strength.

  14. Reflection spectra from an accretion disc illuminated by a neutron star X-ray burst

    CERN Document Server

    Ballantyne, D R

    2004-01-01

    Recent time-resolved X-ray spectra of a neutron star undergoing a superburst revealed an Fe K line and edge consistent with reprocessing from the surrounding accretion disc. Here, we present models of X-ray reflection from a constant density slab illuminated by a blackbody, the spectrum emitted by a neutron star burst. The calculations predict a prominent Fe K line and a rich soft X-ray line spectrum which is superimposed on a strong free-free continuum. The lines slowly vanish as the ionization parameter of the slab is increased, but the free-free continuum remains dominant at energiesless than 1 keV. The reflection spectrum has a quasi-blackbody shape only at energies greater than 3 keV. If the incident blackbody is added to the reflection spectrum, the Fe K equivalent width varies between 100 and 300 eV depending on the ionization parameter and the temperature, kT, of the blackbody. The equivalent width is correlated with kT, and therefore we predict a strong Fe K line when an X-ray burst is at its brighte...

  15. The Chandra Planetary Nebulae Survey (ChanPlaNS): III. X-ray Emission from the Central Stars of Planetary Nebulae

    CERN Document Server

    Montez, R; Balick, B; Behar, E; Blackman, E; Bujarrabal, V; Chu, Y -H; Corradi, R L M; De Marco, O; Frank, A; Freeman, M; Frew, D J; Guerrero, M A; Jones, D; Lopez, J A; Miszalski, B; Nordhaus, J; Parker, Q A; Sahai, R; Sandin, C; Schonberner, D; Soker, N; Sokoloski, J L; Steffen, M; Toalá, J A; Ueta, T; Villaver, E; Zijlstra, A

    2014-01-01

    We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey (ChanPlaNS) observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively "hard" ($\\geq0.5$~keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically-thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, $L_{\\rm X}$, that appear uncorrelated with the CSPN bolometric luminosity, $L_{\\rm bol}$; and (2) lower-temperature plasmas with $L_{\\rm X}/L_{\\rm bol}\\sim10^{-7}$. We suggest these two classes correspond to the physical processes of magnetically active binary comp...

  16. The Evolution of Normal Galaxy X-ray Emission Through Cosmic History: Constraints from the 6 Ms Chandra Deep Field-South

    CERN Document Server

    Lehmer, B D; Mineo, S; Brandt, W N; Eufrasio, R T; Fragos, T; Hornschemeier, A E; Luo, B; Xue, Y Q; Bauer, F E; Gilfanov, M; Ranalli, P; Schneider, D P; Shemmer, O; Tozzi, P; Trump, J R; Vignali, C; Wang, J -X; Yukita, M; Zezas, A

    2016-01-01

    We present measurements of the evolution of normal-galaxy X-ray emission from $z \\approx$ 0-7 using local galaxies and galaxy samples in the 6 Ms Chandra Deep Field-South (CDF-S) survey. The majority of the CDF-S galaxies are observed at rest-frame energies above 2 keV, where the emission is expected to be dominated by X-ray binary (XRB) populations; however, hot gas is expected to provide small contributions to the observed- frame < 1 keV emission at $z < 1$. We show that a single scaling relation between X-ray luminosity ($L_{\\rm X}$) and star-formation rate (SFR) is insufficient for characterizing the average X-ray emission at all redshifts. We establish that scaling relations involving not only SFR, but also stellar mass ($M_\\star$) and redshift, provide significantly improved characterizations of the average X-ray emission from normal galaxy populations at $z \\approx$ 0-7. We further provide the first empirical constraints on the redshift evolution of X-ray emission from both low-mass XRB (LMXB) an...

  17. Theory of pump–probe ultrafast photoemission and X-ray absorption spectra

    Energy Technology Data Exchange (ETDEWEB)

    Fujikawa, Takashi, E-mail: tfujikawa@faculty.chiba-u.jp; Niki, Kaori

    2016-01-15

    Highlights: • Pump–probe ultrafast XAFS and XPS spectra are theoretically studied. • Keldysh Green's function theory is applied. • Important many-body effects are explicitly included. - Abstract: Keldysh Green's function approach is extensively used in order to derive practical formulas to analyze pump–probe ultrafast photoemission and X-ray absorption spectra. Here the pump pulse is strong enough whereas the probe X-ray pulse can be treated by use of a perturbation theory. We expand full Green's function in terms of renormalized Green's function without the interaction between electrons and probe pulse. The present theoretical formulas allow us to handle the intrinsic and extrinsic losses, and furthermore resonant effects in X-ray Absorption Fine Structures (XAFS). To understand the radiation field screening in XPS spectra, we have to use more sophisticated theoretical approach. In the ultrafast XPS and XAFS analyses the intrinsic and extrinsic loss effects can interfere as well. In the XAFS studies careful analyses are necessary to handle extrinsic losses in terms of damped photoelectron propagation. The nonequilibrium dynamics after the pump pulse irradiation is well described by use of the time-dependent Dyson orbitals. Well above the edge threshold, ultrafast photoelectron diffraction and extended X-ray absorption fine structure (EXAFS) provide us with transient structural change after the laser pump excitations. In addition to these slow processes, the rapid oscillation in time plays an important role related to pump electronic excitations. Near threshold detailed information could be obtained for the combined electronic and structural dynamics. In particular high-energy photoemission and EXAFS are not so influenced by the details of excited states by pump pulse. Random-Phase Approximation (RPA)-boson approach is introduced to derive some practical formulas for time-dependent intrinsic amplitudes.

  18. High-Resolution {\\it Chandra} Spectroscopy of tau Scorpii A Narrow-Line X-ray Spectrum From a Hot Star

    CERN Document Server

    Cohen, D H; MacFarlane, J J; Miller, N A; Cassinelli, J P; Owocki, S P; Liedahl, D A; Cohen, David H.; Messi\\`{e}res, Genevi\\`{e}ve E. de; Farlane, Joseph J. Mac; Miller, Nathan A.; Cassinelli, Joseph P.; Owocki, Stanley P.; Liedahl, Duane A.

    2003-01-01

    Long known to be an unusual early-type star by virtue of its hard and strong X-ray emission, tau Scorpii poses a severe challenge to the standard picture of O star wind-shock X-ray emission. The Chandra HETGS spectrum now provides significant direct evidence that this B0.2 star does not fit this standard wind-shock framework. The many emission lines detected with the Chandra gratings are significantly narrower than what would be expected from a star with the known wind properties of tau Sco, although they are broader than the corresponding lines seen in late-type coronal sources. While line ratios are consistent with the hot plasma on this star being within a few stellar radii of the photosphere, from at least one He-like complex there is evidence that the X-ray emitting plasma is located more than a stellar radius above the photosphere. The Chandra spectrum of tau Sco is harder and more variable than those of other hot stars, with the exception of the young magnetized O star theta Ori C. We discuss these new...

  19. New Constraints on Dark Energy from Chandra X-rayObservations of the Largest Relaxed Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Allen, S.W.; Rapetti, D.A.; /KIPAC, Menlo Park; Schmidt, R.W.; /Heidelberg, Astron. Rechen Inst.; Ebeling, H.; /Inst. Astron., Honolulu; Morris, G.; /KIPAC, Menlo Park; Fabian, A.C.; /Cambridge U., Inst. of Astron.

    2007-06-06

    We present constraints on the mean matter density, {Omega}{sub m}, dark energy density, {Omega}{sub DE}, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT > 5keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the 6 lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measure {Omega}{sub m}=0.28{+-}0.06 (68% confidence, using standard priors on the Hubble Constant, H{sub 0}, and mean baryon density, {Omega}{sub b}h{sup 2}). Analyzing the data for all 42 clusters, employing only weak priors on H{sub 0} and {Omega}{sub b}h{sup 2}, we obtain a similar result on {Omega}{sub m} and detect the effects of dark energy on the distances to the clusters at {approx}99.99% confidence, with {Omega}{sub DE}=0.86{+-}0.21 for a non-flat LCDM model. The detection of dark energy is comparable in significance to recent SNIa studies and represents strong, independent evidence for cosmic acceleration. Systematic scatter remains undetected in the f{sub gas} data, despite a weighted mean statistical scatter in the distance measurements of only {approx}5%. For a flat cosmology with constant w, we measure {Omega}{sub m}=0.28{+-}0.06 and w=-1.14{+-}0.31. Combining the fgas data with independent constraints from CMB and SNIa studies removes the need for priors on {Omega}{sub b}h{sup 2} and H{sub 0} and leads to tighter constraints: {Omega}{sub m}=0.253{+-}0.021 and w=-0.98{+-}0.07 for the same constant-w model. More general analyses in which we relax the assumption of flatness and/or allow evolution in w remain consistent with the cosmological constant paradigm. Our analysis includes conservative allowances for systematic uncertainties. The small systematic scatter and tight constraints bode well for future dark energy studies using the f{sub gas} method.

  20. HEAO 1 A-2 low-energy detector X-ray spectra of the Cygnus Loop

    Science.gov (United States)

    Leahy, D. A.; Fink, R.; Nousek, J.

    1990-01-01

    The Cygnus Loop supernova remnant was observed by the A-2 low-energy detector (LED) proportional counters on the HEAO 1 satellite. Recent improvements to the non-X-ray background rejection and detector response simulation have allowed production of the most accurate spectra of the Cygnus Loop to date. Three separate regions of the Cygnus Loop were observed. Single-temperature, Raymond-Smith models are inadequate to describe the spectra, but two component model fits are good. Temperature, column density, and emission measure variations across the Cygnus Loop are found. These results are interpreted and compared with previous work.

  1. HIGHER ORDER SPECIATION EFFECTS ON PLUTONIUM L3 X-RAY ABSORPTION NEAR EDGE SPECTRA.

    Energy Technology Data Exchange (ETDEWEB)

    Conradson, Steven D.; Abney, Kent D.; Begg, Bruce D.; Brady, Erik D.; Clark, David L.; den Auwer, Christophe; Ding, Mei; Dorhout, Peter K.; Espinosa-Faller, Francisco J.; Gordon, Pamela L.; Hess, Nancy J.; Hess, Ryan F.; Keogh, D. Webster; Lander, Gerard H.; Lupinetti, Anthony J.; Neu, Mary P.; Palmer, Phillip D.; Paviet-Hartmann, Patricia; Reilly, Sean D.; Runde, Wolfgang H.; Tait, C. Drew; Veirs, D. Kirk

    2003-06-09

    Pu L{sub 3} X-ray Near Edge Absorption Spectra for Pu(0-VII) are reported for more than 50 chalcogenides, chlorides, hydrates, hydroxides, nitrates, carbonates, oxy-hydroxides, and other compounds both as solids and in solution, and substituted in zirconlite, perovksite, and borosilicate glass. This large data base extends the known correlations between the energy and shape of these spectra from the usual association of the XANES with valence and site symmetry to higher order chemical effects. Because of the large number of compounds of these different types a number of novel and unexpected behaviors are observed.

  2. Microcalorimeter/EBIT measurements of X-ray spectra of highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Kink, I.; Porto, J.V.; Gillaspy, J.D. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Laming, J.M. [Naval Research Lab., Washington, DC (United States); Takacs, E. [Massachusetts Inst. of Tech., Cambridge, MA (United States); Silver, E.; Schnopper, H.; Bandler, S.R.; Brickhouse, N.; Murray, S. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Barbera, M. [Osservatorio Astronomico G.S. Vaiana, Palermo (Italy); Madden, N.; Landis, D.; Beeman, J.; Haller, E.E. [Lawrence Berkeley National Lab., CA (United States)

    2001-07-01

    Spectra of highly charged Ar, Kr, Xe and Fe ions, produced in an electron beam ion trap (EBIT), have been recorded in a broad X-ray energy band (0.2 keV to 10 keV) with a microcalorimeter detector. The first analysis of the Kr spectra has been completed and most of the spectral lines have been identified as transitions of B- to Al-like Kr. Line intensity ratios of Fe XVII have been measured and compared with theoretical models. (orig.)

  3. Chandra Discovery of 10 New X-Ray Jets Associated With FR II Radio Core-Selected AGNs in the MOJAVE Sample

    CERN Document Server

    Hogan, Brandon; Kharb, Preeti; Marshall, Herman; Cooper, Nathan

    2011-01-01

    The Chandra X-ray observatory has proven to be a vital tool for studying high-energy emission processes in jets associated with Active Galactic Nuclei (AGN).We have compiled a sample of 27 AGN selected from the radio flux-limited MOJAVE (Monitoring of Jets in AGN with VLBA Experiments) sample of highly relativistically beamed jets to look for correlations between X-ray and radio emission on kiloparsec scales. The sample consists of all MOJAVE quasars which have over 100 mJy of extended radio emission at 1.4 GHz and a radio structure of at least 3" in size. Previous Chandra observations have revealed X-ray jets in 11 of 14 members of the sample, and we have carried out new observations of the remaining 13 sources. Of the latter, 10 have Xray jets, bringing the overall detection rate to ~ 78%. Our selection criteria, which is based on highly compact, relativistically beamed jet emission and large extended radio flux, thus provides an effective method of discovering new X-ray jets associated with AGN. The detect...

  4. Chandra X-ray Observatory Arcsecond Imaging of the Young, Oxygen-rich Supernova Remnant 1E0102.2-7219

    CERN Document Server

    Gaetz, T J; Edgar, R J; Eriksen, K A; Plucinsky, P P; Schlegel, E M; Smith, R K; Butt, Yousaf M.; Edgar, Richard J.; Eriksen, Kristoffer A.; Plucinsky, Paul P.; Schlegel, Eric M.; Smith, Randall K.

    2000-01-01

    We present observations of the young, Oxygen-rich supernova remnant 1E0102.2-7219 taken by the Chandra X-ray Observatory during Chandra's Orbital Activation and Checkout phase. The boundary of the blast wave shock is clearly seen for the first time, allowing the diameter of the remnant and the mean blast wave velocity to be accurately determined. The prominent X-ray bright ring of material may be the result of the reverse shock encountering ejecta; the radial variation of O VII vs. O VIII emission indicates an ionizing shock propagating inwards, possibly through a strong density gradient in the ejecta. We compare the X-ray emission to Australia Telescope Compact Array 6 cm radio observations (Amy and Ball 1993) and to archival Hubble Space Telescope [O III] observations. The ring of radio emission is predominantly inwards of the outer blast wave, consistent with an interpretation as synchrotron radiation originating behind the blast wave, but outwards of the bright X-ray ring of emission. Many (but not all) o...

  5. Chandra observation of an unusually long and intense X-ray flare from a young solar-like star in M78

    CERN Document Server

    Grosso, N; Feigelson, E D; Forbes, T G

    2004-01-01

    LkHA312 has been observed serendipitously with the ACIS-I detector on board Chandra with 26h continuous exposure. This H_alpha emission line star belongs to the star-forming region M78 (NGC2068). From the optical and NIR data, we show that it is a pre-main sequence (PMS) low-mass star with a weak NIR excess. This genuine T Tauri star displayed an X-ray flare with an unusual long rise phase (~8h). The X-ray emission was nearly constant during the first 18h of the observation, and then increased by a factor of 13 during a fast rise phase (~2h), and reached a factor of 16 above the quiescent X-ray level at the end of a gradual phase (~6h) showing a slower rise. To our knowledge this flare, with \\~0.4-~0.5 cts/s, has the highest count rate observed so far with Chandra from a PMS low-mass star. By chance, the source position, 8.2' off-axis, protected this observation from pile-up. We make a spectral analysis of the X-ray emission versus time, showing that the plasma temperature of the quiescent phase and the flare...

  6. A Chandra study of X-ray sources in the field of the z=2.16 radio galaxy MRC 1138-262

    CERN Document Server

    Pentericci, L; Carilli, C L; Harris, D E; Miley, G K; Röttgering, H J A

    2002-01-01

    We present results from a Chandra X-ray Observatory study of the field X-ray source population in the vicinity of the radio galaxy MRC 1138-262. Many serendipitous X-ray sources are detected in an area of 8'x8' around the radio source and 90% are identified in our deep VLT images. The space density of such sources is higher than expected on the basis of the statistics of ROSAT and Chandra deep surveys. The most likely explanation is in terms of a concentration of AGN associated with the protocluster at z=2.16 which was found around the radio galaxy in previous studies. Two sources have a confirmed spectroscopic redshift close to that of the radio galaxy, and for three more sources other observations suggest that they are associated with the protocluster. Four of these five X-ray sources form, together with the radio galaxy, a filament in the plane of the sky. The direction of the filament is similar to that of the radio source axis, the large scale distribution of the other protocluster members, the 150 kpc-s...

  7. Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds

    NARCIS (Netherlands)

    GOEDKOOP, JB; THOLE, BT; VANDERLAAN, G; SAWATZKY, GA; DEGROOT, FMF; FUGGLE, JC; de Groot, Frank

    1988-01-01

    We present atomic calculations for the recently discovered magnetic x-ray dichroism (MXD) displayed by the 3d x-ray-absorption spectra of rare-earth compounds. The spectral shapes expected at T=0 K for linear polarization parallel and normal to the local magnetic field is given, together with the te

  8. Beyond Chandra (towards the X-ray Surveyor mission): possible solutions for the implementation of very high angular resolution X-ray telescopes in the new millennium based on fused silica segments

    Science.gov (United States)

    Pareschi, G.; Basso, S.; Civitani, M. M.; Ghigo, M.; Parodi, G.; Pelliciari, C.; Salmaso, B.; Spiga, D.; Vecchi, G.

    2016-07-01

    An important challenge for the X-ray astronomy of the new millennium is represented by the implementation of an Xray telescope able to maintain the exquisite angular resolution of Chandra (with a sub-arcsec HEW, on-axis) but, at the same time, being characterized by a much larger throughput and grasp. A mission with similar characteristics is represented by the X-ray Surveyor Mission. The project has been recently proposed in USA and is being currently studied by NASA. It will host an X-ray telescope with an effective area of more than 2 square meters at 1 keV (i.e. 30 times greater than Chandra) and a 15-arcminutes field-of-view, with 1-arcsecond or better half-power diameter (versus the 4 arcmin diameter of Chandra). While the scientific reasons for implementing a similar mission are clear, being related to compelling problems like e.g. the formation and subsequent growth of black hole seeds at very high redshift or the identification of the first galaxy groups and proto-clusters, the realization of a grazing-angle optics system able to fulfil these specs remain highly challenging. Different technologies are being envisaged, like e.g. the use of adjustable segmented mirrors (with use of piezoelectric or magneto-restrictive film actuators on the back surface) or the direct polishing of a variety of thin substrates or the use of innovative correction methods like e.g. differential deposition, ionfiguring or the correction of the profile via controlled stress films. In this paper we present a possible approach based on the direct polishing (with final ion figuring correction of the profile) of thin SiO2 segmented substrates (typically 2 mm thick), discussing different aspects of the technology under implementation and presenting some preliminary results.

  9. Krypton K-shell X-ray spectra recorded by the HENEX spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Seely, J.F. [Naval Research Laboratory, Space Science Division, Washington DC 20375 (United States)]. E-mail: john.seely@nrl.navy.mil; Back, C.A. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Constantin, C. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Lee, R.W. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Chung, H.-K. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Hudson, L.T. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Szabo, C.I. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Henins, A. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Holland, G.E. [SFA Inc., 9315 Largo Drive West Suite 200, Largo MD 20774 (United States); Atkin, R. [Tiger Innovations, L.L.C., 3610 Vacation Lane, Arlington VA 22207 (United States); Marlin, L. [Naval Research Laboratory, Space Science Division, Washington DC 20375 (United States)

    2006-05-15

    High-resolution X-ray spectra were recorded by the High-Energy Electronic X-ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1-20keV energy range and one quartz(10-11) transmission crystal (Laue geometry) covering the 11-40keV range. The time-integrated spectral images were recorded on five CMOS X-ray detectors. In the spectra recorded from krypton-filled gasbag and hohlraum targets, the helium-like K-shell transitions n=1-2, 1-3, and 1-4 appeared in the 13-17keV energy range. A number of additional spectral features were observed at energies lower than the helium-like n=1-3 and n=1-4 transitions. Based on computational simulations of the spectra using the FLYCHK/FLYSPEC codes, which included opacity effects, these additional features are identified to be inner-shell transitions from the Li-like through N-like krypton charge states. The comparisons of the calculated and observed spectra indicate that these transitions are characteristic of the plasma conditions immediately after the laser pulse when the krypton density is 2x10{sup 18}cm{sup -3} and the electron temperature is in the range 2.8-3.2keV. These spectral features represent a new diagnostic for the charge state distribution, the density and electron temperature, and the plasma opacity. Laboratory experiments indicate that it is feasible to record K-shell spectra from gold and higher Z targets in the >60keV energy range using a Ge(220) transmission crystal.

  10. Solar quiescent Active Region temperature distribution inferred from the Miniature Solar X-ray Solar Spectrometer (MinXSS) CubeSat soft X-ray spectra, Hinode X-ray Telescope (XRT) soft X-ray filter images and EUV measurements.

    Science.gov (United States)

    Moore, C. S.; Woods, T. N.; Caspi, A.; Mason, J. P.

    2016-12-01

    Soft X-rays serve as an important diagnostic tool for hot (T > 106 K) solar coronal plasma elemental composition, elemental ionization states, density of emitting plasma and dynamical events triggered by magnetic field structures. Spectrally resolved, solar disc averaged, soft X-ray spectra from the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat combined with spatially resolved soft X-ray filter images from the Hinode X-ray Telescope (XRT) and complimentary EUV data can yield unique inferences of the quiescent (non-flaring) active regions' emitting plasma temperature distribution and chemical composition. This talk will discuss how the MinXSS spectra and Hinode XRT images from the sparsely measured 0.7 - 10 keV ( 0.124 - 1.77 nm) region, can augment estimations of active region temperature distribution and elemental abundance variations that are currently being assessed primarily from typical EUV and hard X-ray observations.

  11. Determination of x-ray spectra including characteristic line intensities from attenuation data

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, M.; Mainardi, R.T. (Universidad Nacional de Cordoba (Argentina). Facultad de Matematica, Astronomia y Fisica)

    1984-11-01

    The Laplace pair transform method for the determination of X-ray spectral shapes has been modified by adding characteristic lines, assuming that the energy of each line is known. Their intensities are parameters to be determined by this extended method. A numerical simulation procedure was used to obtain attenuation data and from this all relevant parameters were determined: four parameters were allocated to the continuum plus one for each line considered. Measured X-ray spectral distributions taken from the literature were used both to generate attenuation data and also to verify the spectrum reconstruction procedure. Percentage differences from both sets of data are less than 8% and they were used to check the goodness of fit of the reconstructed spectra.

  12. Cosmic-Ray Acceleration at the Forward Shock in Tycho's Supernova Remnant: Evidence from Chandra X-Ray Observations

    Science.gov (United States)

    Warren, Jessica S.; Hughes, John P.; Badenes, Carles; Ghavamian, Parviz; McKee, Christopher F.; Moffett, David; Plucinsky, Paul P.; Rakowski, Cara; Reynoso, Estela; Slane, Patrick

    2005-11-01

    We present evidence for cosmic-ray acceleration at the forward shock in Tycho's supernova remnant (SNR) from three X-ray observables: (1) the proximity of the contact discontinuity to the forward shock, or blast wave, (2) the morphology of the emission from the rim of Tycho, and (3) the spectral nature of the rim emission. We determine the locations of the blast wave (BW), contact discontinuity (CD), and reverse shock (RS) around the rim of Tycho's supernova remnant using a principal component analysis and other methods applied to new Chandra data. The azimuthal-angle-averaged radius of the BW is 251". For the CD and RS we find average radii of 241" and 183", respectively. Taking account of projection effects, we find ratios of 1:0.93:0.70 (BW:CD:RS). We show these values to be inconsistent with adiabatic hydrodynamic models of SNR evolution. The CD:BW ratio can be explained if cosmic-ray acceleration of ions is occurring at the forward shock. The RS:BW ratio, as well as the strong Fe Kα emission from the Tycho ejecta, imply that the RS is not accelerating cosmic rays. We also extract radial profiles from ~34% of the rim of Tycho and compare them to models of surface brightness profiles behind the BW for a purely thermal plasma with an adiabatic shock. The observed morphology of the rim is much more strongly peaked than predicted by the model, indicating that such thermal emission is implausible here. Spectral analysis also implies that the rim emission is nonthermal in nature, lending further support to the idea that Tycho's forward shock is accelerating cosmic rays.

  13. Effects of characteristic x rays on the noise power spectra and detective quantum efficiency of photoconductive x-ray detectors.

    Science.gov (United States)

    Zhao, W; Ji, W G; Rowlands, J A

    2001-10-01

    The effects of K fluorescence on the imaging performance of photoconductor-based x-ray imaging systems are investigated. A cascaded linear systems model was developed, where a parallel cascaded process was implemented to take into account the effect of K-fluorescence reabsorption on the modulation transfer function (MTF), noise power spectrum (NPS), and the spatial frequency dependent detective quantum efficiency [DQE(f)] of an imaging system. The investigation was focused on amorphous selenium (a-Se), which is the most highly developed photoconductor material for x-ray imaging. The results were compared to those obtained with Monte Carlo simulation using the same imaging condition and detector parameters, so that the validity of the cascaded linear system model could be confirmed. Our results revealed that K-fluorescence reabsorption in a-Se is responsible for a 18% drop in NPS at high spatial frequencies with an incident x-ray photon energy of E=20 keV (which is just above the K edge of 12.5 keV). When E increases to 60 keV, the effects of K-fluorescence reabsorption on NPS decrease to approximately 12% at high spatial frequencies. Because the high frequency drop is present in both MTF and NPS, the effect of K fluorescence on DQE(f) is minimal, especially for E that is much higher than the K edge. We also applied the cascaded linear system model to a newly developed compound photoconductor, lead iodide (PbI2), and found that at 60 keV there is a high frequency drop in NPS of 19%. The calculated NPS were compared to previously published measurements of PbI2 detectors.

  14. Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies using X-ray Emission: Results from the CHANDRA Deep Fields

    Science.gov (United States)

    Lehmer, B.D; Brandt, W.N.; Schneider, D.P.; Steffen, A.T.; Alexander, D.M.; Bell, E.F.; Hornschemeier, A.E.; McIntosh, D.H.; Bauer, F.E.; Gilli, R.; Mainieri, V.; Silverman, J.D.; Tozzi, P.; Wolf, C.

    2008-01-01

    We report on the X-ray evolution over the last approx.9 Gyr of cosmic history (i.e., since z = 1.4) of late-type galaxy populations in the Chandra Deep Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S. respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists of 2568 galaxies. which were identified using rest-frame optical colors and HST morphologies. We utilized X-ray stacking analyses to investigate the X-ray emission from these galaxies, emphasizing the contributions from normal galaxies that are not dominated by active galactic nuclei (AGNs). Over this redshift range, we find significant increases (factors of approx. 5-10) in the X-ray-to-optical mean luminosity ratio (L(sub x)/L(sub B)) and the X-ray-to-stellar-mass mean ratio (L(sub x)/M(sub *)) for galaxy populations selected by L(sub B) and M(sub *), respectively. When analyzing galaxy samples selected via SFR, we find that the mean X-ray-to-SFR ratio (L(sub x)/SFR) is consistent with being constant over the entire redshift range for galaxies with SFR = 1-100 Solar Mass/yr, thus demonstrating that X-ray emission can be used as a robust indicator of star-formation activity out to z approx. 1.4. We find that the star-formation activity (as traced by X-ray luminosity) per unit stellar mass in a given redshift bin increases with decreasing stellar mass over the redshift range z = 0.2-1, which is consistent with previous studies of how star-formation activity depends on stellar mass. Finally, we extend our X-ray analyses to Lyman break galaxies at z approx. 3 and estimate that L(sub x)/L(sub B) at z approx. 3 is similar to its value at z = 1.4.

  15. X-ray spectra of high temperature tungsten plasma calculated with collisional radiative model

    Institute of Scientific and Technical Information of China (English)

    Wang Jun; Zhang Hong; Cheng Xin-Lu

    2013-01-01

    Tungsten is regarded as an important candidate of plasma facing material in international thermonuclear experimental reactor (ITER),so the determination and modeling of spectra of tungsten plasma,especially the spectra at high temperature were intensely focused on recently.In this work,using the atomic structure code of Cowan,a collisional radiative model (CRM) based on the spin-orbit-split-arrays is developed.Based on this model,the charge state distribution of tungsten ions is determined and the soft X-ray spectra from high charged ions of tungsten at different temperatures are calculated.The results show that both the average ionization charge and line positions are well agreed with others calculations and measurements with discrepancies of less than 0.63% and 1.26%,respectively.The spectra at higher temperatures are also reported and the relationship between ion abundance and temperature is predicted in this work.

  16. Changes in X-ray photoelectron spectra of yttria-tetragonal zirconia polycrystal by ion sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Eiko; Yoshinari, Masao [Tokyo Dental College, Oral Health Science Center, Tokyo, Chiyoda-ku (Japan)

    2016-04-15

    This paper reports changes in X-ray photoelectron spectroscopy spectra of yttria-tetragonal zirconia polycrystal (Y-TZP) brought about by Ar ion sputtering. The changes in the core-level spectra of Y-TZP suggest that preferential sputtering of oxygen occurred. A new peak was observed near 0 eV binding energy accompanied with changes in the core-level spectra by the sputtering. After 18 h in a high vacuum following the sputtering, the spectra changed by the sputtering were returned to their original shapes. In contrast, the color of Y-TZP was changed from white to pale brown by X-ray irradiation and was changed from pale brown to dark gray by ion sputtering. However, when the new peak near 0 eV decreased after 18 h, no color change was observed. Therefore, it is thought that the new peak was mainly derived from electrons trapped in various kinds of oxygen vacancies created by the sputtering in other than color centers. (orig.)

  17. XMM-Newton and Chandra X-ray follow-up observations of the VHE gamma-ray source HESS J1507-622

    CERN Document Server

    Tibolla, O; Kosack, K

    2014-01-01

    Context. The discovery of the unique source HESS J1507-622 in the very high energy (VHE) range (100 GeV-100 TeV) opened new possibilities to study the parent population of ultra-relativistic particles found in astrophysical sources and underlined the possibility of new scenarios/mechanisms crucial for understanding the underlying astrophysical processes in nonthermal sources. Aims. The follow-up X-ray (0.2 - 10 keV) observations on HESS J1507-622 are reported, and possibilities regarding the nature of the VHE source and that of the newly discovered X-ray sources are investigated. Methods.We obtained bservations with the X-ray satellites XMM-Newton and Chandra. Background corrections were applied to the data to search for extended diffuse emission. Since HESS J1507-622 covers a large part of the field of view of these instruments, blank-sky background fields were used. Results. The discovery of several new X-ray sources and a new, faint, extended X-ray source with a flux of ~6e-14 erg cm^-2 s^-1 is reported. I...

  18. Harnessing the full power of the widest Chandra field: average accretion rates of black holes in SDSS galaxies through X-ray stacking

    Science.gov (United States)

    Goulding, Andy D.; Greene, Jenny E.; Hickox, Ryan C.; Alexander, David M.; Forman, William R.; Jones, Christine; Lehmer, Bret

    2017-08-01

    Galaxy-scale bars are expected to provide an effective means for driving material towards the central region in spiral galaxies, and possibly feeding supermassive black holes (BHs). I will present our latest results on a statistically-complete study of the effect of bars on average BH accretion. From a well-selected sample of over 50,000 spiral galaxies extracted from the Sloan Digital Sky Survey, we separate those sources considered to contain galaxy-scale bars from those that do not. Using the first 16 years worth of data taken by the Chandra X-ray Observatory, we identify X-ray luminous AGN and perform the widest-area X-ray stacking analysis to date on the remaining X-ray undetected sources. Through our X-ray stacking, we derive a time-averaged look at accretion for galaxies at fixed stellar mass and star formation rate, finding that the average nuclear accretion rates of galaxies with bar structures are fully consistent with those lacking bars, and robustly concluding that large-scale bars have little or no effect on the average growth of BHs in nearby (z < 0.15) galaxies over gigayear timescales.

  19. Optical spectra of 5 new Be/X-ray Binaries in the Small Magellanic Cloud and the link of the supergiant B[e] star LHA 115-S 18 with an X-ray source

    CERN Document Server

    Maravelias, Grigoris; Antoniou, Vallia; Hatzidimitriou, Despoina

    2013-01-01

    The Small Magellanic Cloud (SMC) is well known to harbor a large number of High-Mass X-ray Binaries (HMXBs). The identification of their optical counterparts provides information on the nature of the donor stars and can help to constrain the parameters of these systems and their evolution. We obtained optical spectra for a number of HMXBs identified in previous Chandra and XMM-Newton surveys of the SMC using the AAOmega/2dF fiber-fed spectrograph at the Anglo-Australian Telescope. We find 5 new Be/X-ray binaries (BeXRBs; including a tentative one), by identifying the spectral type of their optical counterparts, and we confirm the spectral classification of an additional 15 known BeXRBs. We compared the spectral types, orbital periods, and eccentricities of the BeXRB populations in the SMC and the Milky Way and we find marginal evidence for difference between the spectral type distributions, but no statistically significant differences for the orbital periods and the eccentricities. Moreover, our search reveal...

  20. A comprehensive analysis of the hard X-ray spectra of bright Seyfert galaxies

    Science.gov (United States)

    Lubiński, P.; Beckmann, V.; Gibaud, L.; Paltani, S.; Papadakis, I. E.; Ricci, C.; Soldi, S.; Türler, M.; Walter, R.; Zdziarski, A. A.

    2016-05-01

    Hard X-ray spectra of 28 bright Seyfert galaxies observed with INTEGRAL were analysed together with the X-ray spectra from XMM-Newton, Suzaku and RXTE. These broad-band data were fitted with a model assuming a thermal Comptonization as a primary continuum component. We tested several model options through a fitting of the Comptonized continuum accompanied by a complex absorption and a Compton reflection. Both the large data set used and the model space explored allowed us to accurately determine a mean temperature kTe of the electron plasma, the Compton parameter y and the Compton reflection strength R for the majority of objects in the sample. Our main finding is that a vast majority of the sample (20 objects) is characterized by kTe 200 keV. The median kTe for entire sample is 48_{-14}^{+57} keV. The distribution of the y parameter is bimodal, with a broad component centred at ≈0.8 and a narrow peak at ≈1.1. A complex, dual absorber model improved the fit for all data sets, compared to a simple absorption model, reducing the fitted strength of Compton reflection by a factor of about 2. Modest reflection (median R ≈ 0.32) together with a high ratio of Comptonized to seed photon fluxes point towards a geometry with a compact hard X-ray emitting region well separated from the accretion disc. Our results imply that the template Seyferts spectra used in the population synthesis models of active galactic nuclei (AGN) should be revised.

  1. On the origin of X-ray spectra in luminous blazars

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, Marek; Janiak, Mateusz; Moderski, Rafał [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland); Nalewajko, Krzysztof [JILA, University of Colorado and National Institute of Standards and Technology, UCB 440, Boulder, CO 80309 (United States); Madejski, Greg M., E-mail: sikora@camk.edu.pl, E-mail: mjaniak@camk.edu.pl [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States)

    2013-12-10

    Gamma-ray luminosities of some quasar-associated blazars imply jet powers reaching values comparable to the accretion power even if assuming very strong Doppler boosting and very high efficiency of gamma-ray production. With much lower radiative efficiencies of protons than of electrons, and the recent reports of very strong coupling of electrons with shock-heated protons indicated by particle-in-cell simulations, the leptonic models seem to be strongly favored over the hadronic ones. However, the electron-proton coupling combined with the external-radiation-Compton (ERC) models of gamma-ray production in leptonic models predict extremely hard X-ray spectra, with energy indices α {sub x} ∼ 0. This is inconsistent with the observed 2-10 keV slopes of blazars, which cluster around α {sub x} ∼ 0.6. This problem can be resolved by assuming that electrons can be efficiently cooled down radiatively to non-relativistic energies, or that blazar spectra are entirely dominated by the synchrotron self-Compton (SSC) component up to at least 10 keV. Here, we show that the required cooling can be sufficiently efficient only at distances r < 0.03 pc. SSC spectra, on the other hand, can be produced roughly co-spatially with the observed synchrotron and ERC components, which are most likely located roughly at a parsec scale. We show that the dominant SSC component can also be produced much further than the dominant synchrotron and ERC components, at distances of ≳ 10 pc. Hence, depending on the spatial distribution of the energy dissipation along the jet, one may expect to see γ-ray/optical events with either correlated or uncorrelated X-rays. In all cases the number of e{sup +}e{sup –} pairs per proton is predicted to be very low. The direct verification of the proposed SSC scenario, and particularly the question of the co-spatiality of the SSC component with other spectral components, requires sensitive observations in the hard X-ray band. This is now possible with the

  2. Application of direct peak analysis to energy dispersive x-ray fluorescence spectra

    Energy Technology Data Exchange (ETDEWEB)

    Nielson, K.K.

    1977-07-01

    A modified Covell method for direct peak analysis has been applied to energy dispersive x-ray fluorescence spectra. The method is background independent and is well-suited to computerized data reduction. It provides acceptable precision, minimizes errors from instrumental gain shift, and permits peak overlap correction. Peak overlap errors exhibit both positive and negative nodes as a function of peak separation distance, and are corrected using concentration ratios determined from thin, single-element standards. Peak precisions and overlaps are evaluated as a function of window width to aid in width selection. Least-square polynomial smoothing prior to peak analysis significantly improves peak area precisions without significantly affecting their accuracies.

  3. Analysis of KLL Auger spectra excited by X-rays from Ni and Cu metal surfaces

    Science.gov (United States)

    Egri, S.; Kövér, L.; Cserny, I.; Novák, M.; Drube, W.

    2016-02-01

    Ni and Cu KLL Auger spectra excited by X-rays from polycrystalline metal foils were measured with good energy resolution and intensity earlier. Auger spectra of 3d transition metals contain satellite peaks due to the atomic excitation processes. Because of the complexity of the measured spectral shape a complete explanation of the spectra was not given in the previous works. A new analysis of the measured spectra is presented here, with improved description of effects of inelastic electron scattering of the electrons in the solid sample and using complex peak shapes to model the satellite structure that follows each diagram line. The energy loss part of measured spectra due to the bulk plasmon excitations, surface plasmon excitations and intrinsic loss processes was removed using the Partial Intensity Analysis method based on energy loss distributions obtained from experimental reflection electron energy loss spectra of the same Cu and Ni metal foils. Relative Auger-transition energies derived from measured spectra of copper are in good agreement with previous experimental works and the results of cluster molecular orbital multielectron (DV-ME) calculations. The intensity ratio I(3P2/3P0) shows better agreement with the result of relativistic calculations than in previous works. In the case of nickel the relative Auger-transition energies are in good agreement with the previous results. According to the new evaluation four satellite peaks were identified on the low energy side of each diagram line in the Auger spectra of Ni.

  4. Monitoring Chandra observations of the quasi-persistent neutron-star X-ray transient MXB 1659-29 in quiescence: the cooling curve of the heated neutron-star crust

    CERN Document Server

    Wijnands, R; Miller, J M; Lewin, W H G; Wijnands, Rudy; Homan, Jeroen; Miller, Jon M.; Lewin, Walter H. G.

    2004-01-01

    We have observed the quasi-persistent neutron-star X-ray transient and eclipsing binary MXB 1659-29 in quiescence on three occasions with Chandra. The purpose of our observations was to monitor the quiescent behavior of the source after its last prolonged (~2.5 years) outburst which ended in September 2001. The X-ray spectra of the source are consistent with thermal radiation from the neutron-star surface. We found that the bolometric flux of the source decreased by a factor of 7-9 over the time-span of 1.5 years between our first and last Chandra observations. The effective temperature also decreased, but by a factor of 1.6-1.7. The decrease in time of the bolometric flux and effective temperature can be described using exponential decay functions, with e-folding times of ~0.7 and ~3 years, respectively. Our results are consistent with the hypothesis that we observed a cooling neutron-star crust which was heated considerably during the prolonged accretion event and which is still out of thermal equilibrium w...

  5. Electron Heating and Cosmic Rays at a Supernova Shock from Chandra X-ray Observations of E0102.2-7219

    CERN Document Server

    Hughes, J P; Decourchelle, A; Hughes, John P.; Rakowski, Cara E.; Decourchelle, Anne

    2000-01-01

    In this Letter we use the unprecedented spatial resolution of the Chandra X-ray Observatory to carry out, for the first time, a measurement of the post-shock electron temperature and proper motion of a young SNR, specifically to address questions about the post-shock partition of energy among electrons, ions, and cosmic rays. The expansion rate, 0.100 +/- 0.025 percent per yr, and inferred age, ~1000 yr, of E0102.2-7219, from a comparison of X-ray observations spanning 20 years, are fully consistent with previous estimates based on studies of high velocity oxygen-rich optical filaments in the remnant. With a radius of 6.4 pc for the blast wave estimated from the Chandra image, our expansion rate implies a blast wave velocity of ~6000 km/s and a range of electron temperatures 2.5 - 45 keV, dependent on the degree of collisionless electron heating. Analysis of the Chandra ACIS spectrum of the immediate post-shock region reveals a thermal plasma with abundances and column density typical of the Small Magellanic ...

  6. A CHANDRA-VLA INVESTIGATION OF THE X-RAY CAVITY SYSTEM AND RADIO MINI-HALO IN THE GALAXY CLUSTER RBS 797

    Energy Technology Data Exchange (ETDEWEB)

    Doria, Alberto [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany); Gitti, Myriam; Brighenti, Fabrizio [Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, Bologna 40127 (Italy); Ettori, Stefano [Astronomical Observatory of Bologna-INAF, via Ranzani 1, I-40127 Bologna (Italy); Nulsen, Paul E. J.; McNamara, Brian R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-07-01

    We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and Very Large Array (VLA) data. RBS 797 (z = 0.35) is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the presence of a cool core and indicate a higher metallicity along the cavity directions. This is likely due to the active galactic nucleus outburst, which lifts cool metal-rich gas from the center along the cavities, as seen in other systems. We find indications that the cavities are hotter than the surrounding gas. Moreover, the new Chandra images show bright rims contrasting with the deep, X-ray deficient cavities. The likely cause is that the expanding 1.4 GHz radio lobes have displaced the gas, compressing it into a shell that appears as bright cool arms. Finally, we show that the large-scale radio emission detected with our VLA observations may be classified as a radio mini-halo, powered by the cooling flow, as it nicely follows the trend P{sub radio} versus P{sub CF} predicted by the reacceleration model.

  7. Performance as Promised: How the Chandra X-ray Observatory Accomplished One of Nasa's Most Challenging Missions for Billions of Dollars Less than Originally Planned

    Science.gov (United States)

    Davidson, Greg; Hefner, Keith

    2004-01-01

    As the nation looks toward bold new ventures in space, the Chandra X-ray Observatory program offers an example of how billion-dollar missions can be successfully developed within tightening fiscal constraints. Chandra experienced many of challenges facing bold space programs (state-of-the-art technical requirements and budget-induced slips and restructurings), and yet the Chandra team achieved nearly all the originally envisioned performance for dramatically lower cost. This was accomplished by a combination of team- work, systems engineering, advanced technology insertion, and effective approaches for program implementation. A thorough tradeoff of science utility vs. cost led to the selection of a highly elliptical orbit with uncrewed robotic delivery, deployment, and maintenance. Progressive, focused technology demonstrations were accomplished prior to commitment of major resources to critical elements of the system design, such as the high resolution mirror assembly (HRMA). Pathfinder hardware was developed to reduce risks. A variety of schedule risk reduction measures were implemented and resulted in the X-ray calibration taking place exactly within five days of its originally planned date after after five years of development. The team worked together in an effective manner to contain requirements creep. reductions such as the ACIS-2 chip device. It is estimated that the above combination of measures achieved the avoidance of over $4B in costs, while enabling a highly successful mission.

  8. A Chandra - VLA Investigation of the X-ray Cavity System and Radio Mini-Halo in the Galaxy Cluster RBS 797

    CERN Document Server

    Doria, Alberto; Ettori, Stefano; Brighenti, Fabrizio; Nulsen, Paul E J; McNamara, Brian R

    2012-01-01

    We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and VLA data. RBS 797 (z = 0.35), is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the presence of a cool core and indicate an higher metallicity along the cavity directions. This is likely due to the AGN outburst, which lifts cool metal-rich gas from the center along the cavities, as seen in other systems. We find indications that the cavities are hotter than the surrounding gas. Moreover, the new Chandra images show bright rims contrasting with the deep, X-ray deficient cavities. The likely cause is that the expanding 1.4 GHz radio lobes have displaced the gas, compressing it into a shell that appears as bright cool arms. Finally we show that the large-scale radio emission detected with our VLA observations may be classified as a radio mini-halo, powered by the cooling flow (CF), as it nicely follows the trend P_radio vs. P_CF predicted by the...

  9. Improved DQE by means of X-ray spectra and scintillator optimization for FFDM

    Science.gov (United States)

    Job, Isaias D.; Taie-Nobraie, Nima; Colbeth, Richard E.; Mollov, Ivan; Gray, Keith D.; Webb, Chris; Pavkovich, John M.; Zoghi, Fred; Tognina, Carlo A.; Roos, Pieter G.

    2012-03-01

    The focus of this work was to improve the DQE performance of a full-field digital mammography (FFDM) system by means of selecting an optimal X-ray tube anode-filter combination in conjunction with an optimal scintillator configuration. The flat panel detector in this work is a Varian PaxScan 3024M. The detector technology is comprised of a 2816 row × 3584 column amorphous silicon (a-Si) photodiode array with a pixel pitch of 83μm. The scintillator is cesium iodide and is deposited directly onto the photodiode array and available with configurable optical and x-ray properties. Two X-ray beam spectra were generated with the anode/filter combinations, Molybdenum/Molybdenum (Mo/Mo) and Tungsten/Aluminum (W/Al), to evaluate the imaging performance of two types of scintillators, high resolution (HR) type and high light output (HL) type. The results for the HR scintillator with W/Al anode-filter (HRW/ Al) yielded a DQE(0) of 67%, while HR-Mo/Mo was lower with a DQE(0) of 50%. In addition, the DQE(0) of the HR-W/Al configuration was comparable to the DQE(0) of the HL-Mo/Mo configuration. The significance of this result is the HR type scintillator yields about twice the light output with the W/Al spectrum, at about half the dose, as compared to the Mo/Mo spectrum. The light output or sensitivity was measured in analog-to-digital convertor units (ADU) per dose. The sensitivities (ADU/uGy) were 8.6, 16.8 and 25.4 for HR-Mo/Mo, HR-W/Al, HL-Mo/Mo, respectively. The Nyquist frequency for the 83 μm pixel is 6 lp/mm. The MTF at 5 lp/mm for HR-Mo/Mo and HR-W/Al were equivalent at 37%, while the HL-Mo/Mo MTF was 24%. According to the DQE metric, the more favorable anodefilter combination was W/Al with the HR scintillator. Future testing will evaluate the HL-W/Al configuration, as well as other x-ray filters materials and other scintillator optimizations. While higher DQE values were achieved, the more general conclusion is that the imaging performance can be tuned as required by

  10. X-ray spectra from magnetar candidates - III. Fitting SGRs/AXPs soft X-ray emission with non-relativistic Monte Carlo models

    CERN Document Server

    Zane, S; Turolla, R; Nobili, L

    2009-01-01

    Within the magnetar scenario, the "twisted magnetosphere" model appears very promising in explaining the persistent X-ray emission from the Soft Gamma Repeaters and the Anomalous X-ray Pulsars (SGRs and AXPs). In the first two papers of the series, we have presented a 3D Monte Carlo code for solving radiation transport as soft, thermal photons emitted by the star surface are resonantly upscattered by the magnetospheric particles. A spectral model archive has been generated and implemented in XSPEC. Here we report on the systematic application of our spectral model to different XMM-Newton and Integral observations of SGRs and AXPs. We find that the synthetic spectra provide a very good fit to the data for the nearly all the source (and source states) we have analyzed.

  11. A wavelet analysis for the X-ray absorption spectra of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Penfold, T. J. [Ecole polytechnique Federale de Lausanne, Laboratoire de spectroscopie ultrarapide, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland); Ecole polytechnique Federale de Lausanne, Laboratoire de chimie et biochimie computationnelles, ISIC, FSB-BCH, CH-1015 Lausanne (Switzerland); SwissFEL, Paul Scherrer Inst, CH-5232 Villigen (Switzerland); Tavernelli, I.; Rothlisberger, U. [Ecole polytechnique Federale de Lausanne, Laboratoire de chimie et biochimie computationnelles, ISIC, FSB-BCH, CH-1015 Lausanne (Switzerland); Milne, C. J.; Abela, R. [SwissFEL, Paul Scherrer Inst, CH-5232 Villigen (Switzerland); Reinhard, M.; Nahhas, A. El; Chergui, M. [Ecole polytechnique Federale de Lausanne, Laboratoire de spectroscopie ultrarapide, ISIC, FSB-BSP, CH-1015 Lausanne (Switzerland)

    2013-01-07

    We present a Wavelet transform analysis for the X-ray absorption spectra of molecules. In contrast to the traditionally used Fourier transform approach, this analysis yields a 2D correlation plot in both R- and k-space. As a consequence, it is possible to distinguish between different scattering pathways at the same distance from the absorbing atom and between the contributions of single and multiple scattering events, making an unambiguous assignment of the fine structure oscillations for complex systems possible. We apply this to two previously studied transition metal complexes, namely iron hexacyanide in both its ferric and ferrous form, and a rhenium diimine complex, [ReX(CO){sub 3}(bpy)], where X = Br, Cl, or ethyl pyridine (Etpy). Our results demonstrate the potential advantages of using this approach and they highlight the importance of multiple scattering, and specifically the focusing phenomenon to the extended X-ray absorption fine structure (EXAFS) spectra of these complexes. We also shed light on the low sensitivity of the EXAFS spectrum to the Re-X scattering pathway.

  12. Energy dispersive X-ray diffraction to identify explosive substances: Spectra analysis procedure optimization

    Energy Technology Data Exchange (ETDEWEB)

    Crespy, C., E-mail: charles.crespy@insa-lyon.f [CNDRI-Insa Lyon, Universite de Lyon, F-69621, Villeurbanne cedex (France); Duvauchelle, P., E-mail: philippe.duvauchelle@insa-lyon.f [CNDRI-Insa Lyon, Universite de Lyon, F-69621, Villeurbanne cedex (France); Kaftandjian, V.; Soulez, F. [CNDRI-Insa Lyon, Universite de Lyon, F-69621, Villeurbanne cedex (France); Ponard, P. [Thales Components and Subsystems, 2 rue Marcel Dassault 78491, Velizy cedex (France)

    2010-11-21

    To detect the presence of explosives in packages, automated systems are required. Energy dispersive X-ray diffraction (EDXRD) represents a powerful non-invasive tool providing information on the atomic structure of samples. In this paper, EDXRD is investigated as a suitable technique for explosive detection and identification. To this end, a database has been constructed, containing measured X-ray diffraction spectra of several explosives and common materials. In order to quantify spectral resolution influence, this procedure is repeated with two different detectors which have different spectral resolution. Using our database, some standard spectrum analysis procedures generally used for this application have been implemented. Regarding to the results, it is possible to conclude on the robustness and the limits of each analysis procedure. The aim of this work is to define a robust and efficient sequence of EDXRD spectra analysis to discriminate explosive substances. Since our explosive substances are crystalline, the first step consists in using characteristic of the spectrum to estimate a crystallinity criterion which allows to remove a large part of common materials. The second step is a more detailed analysis, it consists in using similarity criterion and major peaks location to differentiate explosive from crystalline common materials. The influence of the spectral resolution on the detection is also examined.

  13. X-Ray Spectra from MHD Simulations of Accreting Black Holes

    Science.gov (United States)

    Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

    2012-01-01

    We present the results of a new global radiation transport code coupled to a general relativistic magneto-hydrodynamic simulation of an accreting, nonrotating black hole. For the first time, we are able to explain from first principles in a self-consistent way the X-ray spectra observed from stellar-mass black holes, including a thermal peak, Compton reflection hump, power-law tail, and broad iron line. Varying only the mass accretion rate, we are able to reproduce the low/hard, steep power-law, and thermal-dominant states seen in most galactic black hole sources. The temperature in the corona is T(sub e) 10 keV in a boundary layer near the disk and rises smoothly to T(sub e) greater than or approximately 100 keV in low-density regions far above the disk. Even as the disk's reflection edge varies from the horizon out to approximately equal to 6M as the accretion rate decreases, we find that the shape of the Fe Ka line is remarkably constant. This is because photons emitted from the plunging region are strongly beamed into the horizon and never reach the observer. We have also carried out a basic timing analysis of the spectra and find that the fractional variability increases with photon energy and viewer inclination angle, consistent with the coronal hot spot model for X-ray fluctuations.

  14. X-ray bursting neutron star atmosphere models: spectra and color corrections

    CERN Document Server

    Suleimanov, V; Werner, K

    2010-01-01

    X-ray bursting neutron stars in low mass X-ray binaries constitute an appropriate source class to constrain masses and radii of neutron stars, but a sufficiently extended set of corresponding model atmospheres is necessary for these investigations. We computed such a set of model atmospheres and emergent spectra in a plane-parallel, hydrostatic, and LTE approximation with Compton scattering taken into account. The models were calculated for six different chemical compositions: pure hydrogen and pure helium atmospheres, and atmospheres with solar mix of hydrogen and helium, and various heavy element abundances Z = 1, 0.3, 0.1, and 0.01 Z_sun. For each chemical composition the models are computed for three values of surface gravity, log g =14.0, 14.3, and 14.6, and for 20 values of the luminosity in units of the Eddington luminosity, L/L_Edd, in the range 0.001--0.98. The emergent spectra of all models are redshifted and fitted by a diluted blackbody in the RXTE/PCA 3--20 keV energy band, and corresponding valu...

  15. What can we learn from EPIC X-ray spectra of Seyfert 1 galaxies?

    CERN Document Server

    Pounds, K; Pounds, Ken; Reeves, James

    2002-01-01

    The EPIC detectors on XMM-Newton provide the most sensitive broad band (0.3-12 keV) X-ray spectra to date. Observations of 6 Seyfert 1 galaxies, covering a wide luminosity range, are examined with the aim of identifying the primary X-ray continuum and constraining superimposed emission and absorption features. A soft excess emission component is seen in every case, but with a spectral form which differs markedly with luminosity across our sample. Current interpretations of the soft excess range from intrinsic thermal emission from the accretion disc to reprocessing of harder radiation absorbed in the disc skin. Visual examination of the broad-band EPIC spectra suggest that the luminosity trend in the observed spectral profiles may be governed primarily by differences in the line-of-sight absorption. In that case the underlying continuum could have a common form across the sample. Examination of spectral features in the Fe K band confirm the common presence of a narrow emission line at 6.4 keV. Modelling of th...

  16. A comprehensive analysis of the hard X-ray spectra of bright Seyfert galaxies

    CERN Document Server

    Lubinski, P; Gibaud, L; Paltani, S; Papadakis, I E; Ricci, C; Soldi, S; Türler, M; Walter, R; Zdziarski, A A

    2016-01-01

    Hard X-ray spectra of 28 bright Seyfert galaxies observed with INTEGRAL were analyzed together with the X-ray spectra from XMM-Newton, Suzaku and RXTE. These broad-band data were fitted with a model assuming a thermal Comptonization as a primary continuum component. We tested several model options through a fitting of the Comptonized continuum accompanied by a complex absorption and a Compton reflection. Both the large data set used and the model space explored allowed us to accurately determine a mean temperature kTe of the electron plasma, the Compton parameter y and the Compton reflection strength R for the majority of objects in the sample. Our main finding is that a vast majority of the sample (20 objects) is characterized by kTe 200 keV. The median kTe for entire sample is 48(-14,+57) keV. The distribution of the y parameter is bimodal, with a broad component centered at ~0.8 and a narrow peak at ~1.1. A complex, dual absorber model improved the fit for all data sets, compared to a simple absorption mo...

  17. X-ray photoemission spectra for Al(x)Ga(1-x)As

    Science.gov (United States)

    Ireland, P. J.; Kazmerski, L. L.; Fisher, R. F.

    1984-06-01

    X-ray photoelectron spectroscopy (XPS) is used in both a qualitative and quantitative fashion to study the Al(x)Ga(1-x)As alloy. Gallium and aluminum atoms are always bonded to the arsenic atom. As the concentration of Al increases, a notable shift in the As-3d level could be expected as Ga and Al both have different electronegativities. Spectra taken on molecular beam epitaxially grown samples do not show this shift in the As-3d core level. The composition of the films have been measured with an electron probe, and these results agree very well with the XPS quantitative data. Standard spectra are presented for films with x = 0.16, 0.23, 0.32, 0.46, and 0.65.

  18. Relativistic Accretion Disk Models of High State Black Hole X-ray Binary Spectra

    CERN Document Server

    Davis, S W; Hubeny, I; Turner, N J; Davis, Shane W.; Blaes, Omer M.; Hubeny, Ivan; Turner, Neal J.

    2004-01-01

    We present calculations of non-LTE, relativistic accretion disk models applicable to the high/soft state of black hole X-ray binaries. We include the effects of thermal Comptonization and bound-free and free-free opacities of all abundant ion species. We present spectra calculated for a variety of accretion rates, black hole spin parameters, disk inclinations, and stress prescriptions. We also consider nonzero inner torques on the disk, and explore different vertical dissipation profiles, including some which are motivated by recent radiation MHD simulations of magnetorotational turbulence. Bound-free metal opacity generally produces significantly less spectral hardening than previous models which only considered Compton scattering and free-free opacity. It also tends to keep the effective photosphere near the surface, resulting in spectra which are remarkably independent of the stress prescription and vertical dissipation profile, provided little dissipation occurs above the effective photosphere. We provide...

  19. Unidentified line in x-ray spectra of the Andromeda galaxy and Perseus galaxy cluster.

    Science.gov (United States)

    Boyarsky, A; Ruchayskiy, O; Iakubovskyi, D; Franse, J

    2014-12-19

    We report a weak line at 3.52±0.02  keV in x-ray spectra of the Andromeda galaxy and the Perseus galaxy cluster observed by the metal-oxide-silicon (MOS) and p-n (PN) CCD cameras of the XMM-Newton telescope. This line is not known as an atomic line in the spectra of galaxies or clusters. It becomes stronger towards the centers of the objects; is stronger for Perseus than for M31; is absent in the spectrum of a deep "blank sky" data set. Although for each object it is hard to exclude that the feature is due to an instrumental effect or an atomic line, it is consistent with the behavior of a dark matter decay line. Future (non-)detections of this line in multiple objects may help to reveal its nature.

  20. Application of the Monte Carlo method to analyze materials used in flat panel detectors to obtain X-ray spectra

    Science.gov (United States)

    Gallardo, Sergio; Pozuelo, Fausto; Querol, Andrea; Ródenas, José; Verdú, Gumersindo

    2014-06-01

    An accurate knowledge of the photon spectra emitted by X-ray tubes in radiodiagnostic is essential to better estimate the imparted dose to patients and to improve the quality image obtained with these devices. In this work, it is proposed the use of a flat panel detector together with a PMMA wedge to estimate the actual X-ray spectrum using the Monte Carlo method and unfolding techniques. The MCNP5 code has been used to model different flat panels (based on indirect and direct methods to produce charge carriers from absorbed X-rays) and to obtain the dose curves and system response functions. Most of the actual flat panel devices use scintillator materials that present K-edge discontinuities in the mass energy-absorption coefficient, which strongly affect the response matrix. In this paper, the applicability of different flat panels for reconstructing X-ray spectra is studied. The effect of the mass energy-absorption coefficient of the scintillator material has been studied on the response matrix and consequently, in the reconstructed spectra. Different unfolding methods are tested to reconstruct the actual X-ray spectrum knowing the dose curve and the response function. It has been concluded that the regularization method MTSVD is appropriate to unfold X-ray spectra in all the scintillators studied.

  1. Observations of the Crab Nebula with the Chandra X-Ray Observatory During the Gamma-Ray Flare of 2011 April

    Science.gov (United States)

    Weisskopf, Martin C.

    2012-01-01

    Recently, using the AGILE and Fermi satellites, gamma-ray flares have been discovered from the direction of the Crab Nebula (Tavani et al. 2011, Abdo et al. 2011). We have been using the Chandra X-Ray observatory to monitor the Crab on a monthly cadence since just after the 2010 September gamma-ray flare. We were fortunate to trigger series of pre-planned target of opportunity observations during the 2011 April flare. We present the results of these observations and address some implications both for now and for the future.

  2. X-ray properties of radio-selected star forming galaxies in the Chandra-COSMOS survey

    OpenAIRE

    Ranalli, P.; Comastri, A.; Zamorani, G.; Cappelluti, N.; Civano, F.; Georgantopoulos, I.; Gilli, R.; Schinnerer, E.; Smolcic, V.; Vignali, C.

    2012-01-01

    X-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4 GHz in the VLA-COSMOS survey, classified by Smolcic et al. (2008) according to their o...

  3. X-Ray Spectra of The High-Mass X-RAY Binary 4U~1700-37 using BeppoSAX, Suzaku and RXTE Observations

    CERN Document Server

    Seifina, Elena; Shaposhnikov, Nikolai

    2016-01-01

    We present an X-ray spectral analysis of the high-mass binary 4U~1700-37 during its hard-soft state evolution. We use the BeppoSAX, Suzaku and RXTE (Rossi X-ray Timing Explorer), Suzaku and BeppoSAX observations for this investigation. We argue that the X-ray broad-band spectra during all spectral states can be adequately reproduced by a model, consisting of a low-temperature Blackbody component, two Comptonized components both due to the presence of a Compton cloud (CC) that up-scatters seed photons of $T_{s1}$~< 1.4 keV, and $T_{s2}<$1 keV, and an iron-line component. We find using this model that the photon power-law index is almost constant, $\\Gamma_{1}\\sim 2$ for all spectral states. However, $\\Gamma_{2}$ shows a behavior depending on the spectral state. Namely, $\\Gamma_{2}$ is quasi-constant at the level of $\\Gamma_{2}\\sim 2$ while the CC plasma temperature $kT^{(2)}_e$ is less than 40 keV; on the other hand, $\\Gamma_{2}$ is in the range of $1.3<\\Gamma_{2}<2$, when $kT^{(2)}_e$ is greater th...

  4. Broadband X-ray Spectra of the Ultraluminoux X-ray Source Holmberg IX X-1 observed with NuSTAR, XMM-Newton and Suzaku

    CERN Document Server

    Walton, D J; Grefenstette, B W; Miller, J M; Bachetti, M; Barret, D; Boggs, S E; Christensen, F E; Craig, W W; Fabian, A C; Fuerst, F; Hailey, C J; Madsen, K K; Parker, M L; Ptak, A; Rana, V; Stern, D; Webb, N A; Zhang, W W

    2014-01-01

    We present results from the coordinated broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 performed by NuSTAR, XMM-Newton and Suzaku in late 2012. These observations provide the first high-quality spectra of Holmberg IX X-1 above 10 keV to date, extending the X-ray coverage of this remarkable source up to ~30 keV. Broadband observations were undertaken at two epochs, between which Holmberg IX X-1 exhibited both flux and strong spectral variability, increasing in luminosity from Lx = (1.94+/-0.03)e40 erg/s to Lx = (3.38+/-0.03)e40 erg/s. Neither epoch exhibits a spectrum consistent with emission from the standard low/hard accretion state seen in Galactic black hole binaries, that would have been expected if Holmberg IX X-1 harbors a truly massive black hole accreting at substantially sub-Eddington accretion rates. The NuSTAR data confirm that the curvature observed previously in the 3-10 keV bandpass does represent a true spectral cutoff. During each epoch, the spectrum app...

  5. The Broadband XMM-Newton and NuSTAR X-ray Spectra of Two Ultraluminous X-ray Sources in the Galaxy IC 342

    DEFF Research Database (Denmark)

    Rana, Vikram; Harrison, Fiona A.; Bachetti, Matteo

    2015-01-01

    We present results for two Ultraluminous X-ray Sources (ULXs), IC 342 X-1 and IC 342 X-2, using two epochs of XMM-Newton and NuSTAR observations separated by ∼7 days. We observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3-30 keV luminosities being $1.......04+0.08/-0.06 x 1040 erg s-1 for IC 342 X-1 and 7.40±0.20 x 1039 erg s-1for IC 342 X-2, so that both were observed in a similar, luminous state. Both sources have a high absorbing column in excess of the Galactic value. Neither source has a spectrum consistent with a black hole binary in low/hard state, and both...... ULXs exhibit strong curvature in their broadband X-ray spectra. This curvature rules out models that invoke a simple reflection-dominated spectrum with a broadened iron line and no cutoff in the illuminating power-law continuum. X-ray spectrum of IC 342 X-1 can be characterized by a soft disk...

  6. Chandra Detection of the First X-ray Forest along the Line of Sight To Mkn 421

    CERN Document Server

    Nicastro, F; Elvis, M; Drake, J; Fiore, F; Fang, T; Fruscione, A; Krongold, Y; Marshall, H; Williams, R; Nicastro, Fabrizio; Mathur, Smita; Elvis, Martin; Drake, Jeremy; Fiore, Fabrizio; Fang, Taotao; Fruscione, Antonella; Krongold, Yair; Marshall, Herman; Williams, Rik

    2005-01-01

    We present the first >=3.5 sigma (conservative) or >=5.8 sigma (sum of lines significance) detection of two Warm-Hot Intergalactic Medium (WHIM) filaments at z>0, which we find along the line of sight to the blazar Mkn 421. These systems are detected through highly ionized resonant metal absorption in high quality Chandra-ACIS and -HRC Low Energy Transmission Grating (LETG) spectra of Mkn 421, obtained following our two Target of Opportunity requests during two outburst phases. The two intervening WHIM systems that we detect, have OVII and NVII columns of N(OVII)=(1.0 +/- 0.3) x 1e15 cm-2} N(NVII)=(0.8 +/- 0.4) x 1e15 cm-2, and N(OVII)=(0.7 +/- 0.3) x 1e15 cm-2, N(NVII)=(1.4 +/- 0.5) x 1e15 cm-2 respectively. From the detected number of WHIM filaments along this line of sight we can estimate the number of OVII filaments per unit redshift with columns larger than 7e14 cm-2, dP(OVII)/dz(N(OVII)>=7e14) = 67^{+88}_{-43}, consistent, within the large 1-sigma errors, with the hydrodynamical simulation predictions o...

  7. How realistic UV spectra and X-rays suppress the abundance of direct collapse black holes

    Science.gov (United States)

    Latif, M. A.; Bovino, S.; Grassi, T.; Schleicher, D. R. G.; Spaans, M.

    2015-01-01

    Observations of high-redshift quasars at z > 6 indicate that they harbour supermassive black holes (SMBHs) of a billion solar masses. The direct collapse scenario has emerged as the most plausible way to assemble SMBHs. The nurseries for the direct collapse black holes are massive primordial haloes illuminated with an intense UV flux emitted by Population II (Pop II) stars. In this study, we compute the critical value of such a flux (J_{21}^crit) for realistic spectra of Pop II stars through three-dimensional cosmological simulations. We derive the dependence of J_{21}^crit on the radiation spectra, on variations from halo to halo, and on the impact of X-ray ionization. Our findings show that the value of J_{21}^crit is a few times 104 and only weakly depends on the adopted radiation spectra in the range between Trad = 2 × 104and105 K. For three simulated haloes of a few times 107 M⊙, J_{21}^crit varies from 2 × 104 to 5 × 104. The impact of X-ray ionization is almost negligible and within the expected scatter of J_{21}^crit for background fluxes of JX, 21 ≤ 0.1. The computed estimates of J_{21}^crit have profound implications for the quasar abundance at z = 10 as it lowers the number density of black holes forming through an isothermal direct collapse by a few orders of magnitude below the observed black hole density. However, the sites with moderate amounts of H2 cooling may still form massive objects sufficient to be compatible with observations.

  8. The Broadband XMM-Newton and NuSTAR X-Ray Spectra of Two Ultraluminous X-Ray Sources in the Galaxy IC 342

    Science.gov (United States)

    Rana, Vikram; Harrison, Fiona A.; Bachetti, Matteo; Walton, Dominic J.; Furst, Felix; Barret, Didier; Miller, Jon M.; Fabian, Andrew C.; Boggs, Steven E.; Christensen, Finn C.; Craig, William W.; Grefenstette, Brian W.; Hailey, Charles J.; Madsen, Kristin K.; Ptak, Andrew F.; Stern, Daniel; Webb, Natalie A.; Zhang, William W.

    2015-02-01

    We present results for two ultraluminous X-ray sources (ULXs), IC 342 X-1 and IC 342 X-2, using two epochs of XMM-Newton and NuSTAR observations separated by ~7 days. We observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3-30 keV luminosities being 1.04+0.08-0.06 × 1040 erg s-1 for IC 342 X-1 and 7.40 ± 0.20 × 1039 erg s-1 for IC 342 X-2, so that both were observed in a similar, luminous state. Both sources have a high absorbing column in excess of the Galactic value. Neither source has a spectrum consistent with a black hole binary in low/hard state, and both ULXs exhibit strong curvature in their broadband X-ray spectra. This curvature rules out models that invoke a simple reflection-dominated spectrum with a broadened iron line and no cutoff in the illuminating power-law continuum. X-ray spectrum of IC 342 X-1 can be characterized by a soft disk-like blackbody component at low energies and a cool, optically thick Comptonization continuum at high energies, but unique physical interpretation of the spectral components remains challenging. The broadband spectrum of IC 342 X-2 can be fit by either a hot (3.8 keV) accretion disk or a Comptonized continuum with no indication of a seed photon population. Although the seed photon component may be masked by soft excess emission unlikely to be associated with the binary system, combined with the high absorption column, it is more plausible that the broadband X-ray emission arises from a simple thin blackbody disk component. Secure identification of the origin of the spectral components in these sources will likely require broadband spectral variability studies.

  9. X-ray Spectra and Pulse Frequency Changes in SAX J2103.5+4545

    CERN Document Server

    Baykal, A; Swank, J H

    2002-01-01

    The November 1999 outburst of the transient pulsar SAX J2103.5+4545 was monitored with the large area detectors of the Rossi X-Ray Timing Explorer until the pulsar faded after a year. The 358 s pulsar was spun up for 150 days, at which point the flux dropped quickly by a factor of 7, the frequency saturated and, as the flux continued to decline, a weak spin-down began. The pulses remained strong during the decay and the spin-up/flux correlation can be fit to the Ghosh and Lamb derivations for the spin-up caused by accretion from a thin, pressure-dominated disk, for a distance 3.2 kpc and a surface magnetic field 1.2 10^{13} Gauss. During the bright spin-up part of the outburst, the flux was subject to strong orbital modulation, peaking 3 days after periastron of the eccentric 12.68 day orbit, while during the faint part, there was little orbital modulation. The X-ray spectra were typical of accreting pulsars, describable by a cut-off power-law, with an emission line near the 6.4 keV of K alpha fluorescence fr...

  10. The influence of magnetic field geometry on magnetars X-ray spectra

    CERN Document Server

    Viganò, D; Zane, S; Turolla, R; Pons, J A; Miralles, J A

    2011-01-01

    Nowadays, the analysis of the X-ray spectra of magnetically powered neutron stars or magnetars is one of the most valuable tools to gain insight into the physical processes occurring in their interiors and magnetospheres. In particular, the magnetospheric plasma leaves a strong imprint on the observed X-ray spectrum by means of Compton up-scattering of the thermal radiation coming from the star surface. Motivated by the increased quality of the observational data, much theoretical work has been devoted to develop Monte Carlo (MC) codes that incorporate the effects of resonant Compton scattering in the modeling of radiative transfer of photons through the magnetosphere. The two key ingredients in this simulations are the kinetic plasma properties and the magnetic field (MF) configuration. The MF geometry is expected to be complex, but up to now only mathematically simple solutions (self-similar solutions) have been employed. In this work, we discuss the effects of new, more realistic, MF geometries on syntheti...

  11. On the origin of cyclotron lines in the spectra of X-ray pulsars

    Directory of Open Access Journals (Sweden)

    Mushtukov A. A.

    2014-01-01

    Full Text Available Cyclotron resonance scattering features are observed in the spectra of some X-ray pulsars and show significant changes in the line energy with the pulsar luminosity. In a case of bright sources, the line centroid energy is anti-correlated with the luminosity. Such a behaviour is often associated with the onset and growth of the accretion column, which is believed to be the origin of the observed emission and the cyclotron lines. However, this scenario inevitably implies large gradient of the magnetic field strength within the line-forming region, and it makes the formation of the observed line-like features problematic. Moreover, the observed variation of the cyclotron line energy is much smaller than could be anticipated for the corresponding luminosity changes. We argue that a more physically realistic situation is that the cyclotron line forms when the radiation emitted by the accretion column is reflected from the neutron star surface. The idea is based on the facts that a substantial part of column luminosity is intercepted by the neutron star surface and the reflected radiation should contain absorption features. The reflection model is developed and applied to explain the observed variations of the cyclotron line energy in a bright X-ray pulsar V 0332+53 over a wide range of luminosities.

  12. Chandra and HST Imaging of the Quasars PKS B0106+013 and 3C 345: Inverse Compton X-Rays and Magnetized Jets

    Science.gov (United States)

    Kharb, P.; Lister, M. L.; Marshall, H. L.; Hogan, B. S.

    2012-04-01

    We present results from deep (~70 ks) Chandra/ACIS observations and Hubble Space Telescope (HST) Advanced Camera for Surveys F475W observations of two highly optically polarized quasars belonging to the MOJAVE blazar sample, viz., PKS B0106+013 and 1641+399 (3C 345). These observations reveal X-ray and optical emissions from the jets in both sources. X-ray emission is detected from the entire length of the 0106+013 radio jet, which shows clear bends or wiggles—the X-ray emission is brightest at the first prominent kiloparsec jet bend. A picture of a helical kiloparsec jet with the first kiloparsec-scale bend representing a jet segment moving close(r) to our line of sight, and getting Doppler boosted at both radio and X-ray frequencies, is consistent with these observations. The X-ray emission from the jet end, however, peaks at about 0farcs4 (~3.4 kpc) upstream of the radio hot spot. Optical emission is detected both at the X-ray jet termination peak and at the radio hot spot. The X-ray jet termination peak is found upstream of the radio hot spot by around 0farcs2 (~1.3 kpc) in the short projected jet of 3C 345. HST optical emission is seen in an arc-like structure coincident with the bright radio hot spot, which we propose is a sharp (apparent) jet bend instead of a terminal point, that crosses our line of sight and consequently has a higher Doppler beaming factor. A weak radio hot spot is indeed observed less than 1'' downstream of the bright radio hot spot, but has no optical or X-ray counterpart. By making use of the parsec-scale radio and the kiloparsec-scale radio/X-ray data, we derive constraints on the jet Lorentz factors (Γjet) and inclination angles (θ): for a constant jet speed from parsec to kiloparsec scales, we obtain a Γjet of ~70 for 0106+013 and ~40 for 3C 345. On relaxing this assumption, we derive a Γjet of ~2.5 for both the sources. Upper limits on θ of ~13° are obtained for the two quasars. Broadband (radio-optical-X-ray) spectral

  13. Comparison of hard X-ray spectra obtained by spectrometers on Hinotori and SMM and detection of 'superhot' component

    Science.gov (United States)

    Nitta, Nariaki

    1988-01-01

    Hard X-ray spectra in solar flares obtained by the broadband spectrometers aboard Hinotori and SMM are compared. Within the uncertainty brought about by assuming the typical energy of the background X-rays, spectra by the Hinotori spectrometer are usually consistent with those by the SMM spectrometer for flares in 1981. On the contrary, flares in 1982 persistently show 20-50-percent higher flux by Hinotori than by SMM. If this discrepancy is entirely attributable to errors in the calibration of energy ranges, the errors would be about 10 percent. Despite such a discrepancy in absolute flux, in the the decay phase of one flare, spectra revealed a hard X-ray component (probably a 'superhot' component) that could be explained neither by emission from a plasma at about 2 x 10 to the 7th K nor by a nonthermal power-law component. Imaging observations during this period show hard X-ray emission nearly cospatial with soft X-ray emission, in contrast with earlier times at which hard and soft X-rays come from different places.

  14. Uncertainty analysis in the simulation of X-ray spectra in the diagnostic range using the MCNP5 code.

    Science.gov (United States)

    Gallardo, S; Querol, A; Ródenas, J; Verdú, G

    2011-01-01

    An accurate knowledge of the photonic spectra emitted by X-ray tubes in radiodiagnostics is essential to better estimate the imparted dose to patients and to improve the image quality obtained with these devices. In this work, several X-ray spectra have been simulated using the MCNP5 code to simulate X-ray production in a commercial device. To validate the Monte Carlo results, simulated spectra have been compared to those extracted from the IPEM 78 database. The uncertainty associated to some geometrical features of the tube and its effect on the simulated spectra has been analyzed using the Noether-Wilks formula. This analysis has been focused on the thickness of collimators, filters, shielding and barrel shutter. Furthermore, results show that the uncertainty due to geometrical parameters (0.98% in terms of Root Mean Squared) is higher than the statistical uncertainty associated to the MCNP5 calculations.

  15. REVEALING THE HEAVILY OBSCURED ACTIVE GALACTIC NUCLEUS POPULATION OF HIGH-REDSHIFT 3CRR SOURCES WITH CHANDRA X-RAY OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Wilkes, Belinda J.; Kuraszkiewicz, Joanna; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Haas, Martin; Chini, Rolf [Astronomisches Institut, Ruhr-University, D-44801 Bochum (Germany); Barthel, Peter [Kapteyn Institute, University of Groningen, 9747 AD Groningen (Netherlands); Leipski, Christian [MPIA, D-69117 Heidelberg (Germany); Worrall, D. M.; Birkinshaw, Mark [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); Antonucci, Robert [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Lawrence, Charles [JPL, Pasadena, CA 91109 (United States); Ogle, Patrick [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Schulz, Bernhard [IPAC, Caltech, Pasadena, CA 91125 (United States)

    2013-08-10

    Chandra observations of a complete, flux-limited sample of 38 high-redshift (1 < z < 2), low-frequency-selected (and so unbiased in orientation) 3CRR radio sources are reported. The sample includes 21 quasars (=broad-line radio galaxies) and 17 narrow-line radio galaxies (NLRGs) with matched 178 MHz radio luminosity (log L{sub R}(5 GHz) {approx}44-45). The quasars have high radio core fraction, high X-ray luminosities (log L{sub X} {approx}45-46), and soft X-ray hardness ratios (HR {approx}-0.5) indicating low obscuration. The NLRGs have lower core fraction, lower apparent X-ray luminosities (log L{sub X} {approx}43-45), and mostly hard X-ray hardness ratios (HR >0) indicating obscuration (N{sub H} {approx}10{sup 22}-10{sup 24} cm{sup -2}). These properties and the correlation between obscuration and radio core fraction are consistent with orientation-dependent obscuration as in unification models. About half the NLRGs have soft X-ray hardness ratios and/or a high [O III] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC 1068). The ratios of unobscured to Compton-thin (10{sup 22} cm{sup -2} < N{sub H}(int) <1.5 Multiplication-Sign 10{sup 24} cm{sup -2}) to CT (N{sub H}(int) >1.5 Multiplication-Sign 10{sup 24} cm{sup -2}) is 2.5:1.4:1 in this high-luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for active galactic nuclei at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is {approx}60 Degree-Sign and the obscuring material covers 30 Degree-Sign , {approx}12 Degree-Sign of which is CT. The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10-1000 Multiplication-Sign higher than indicated by their X-ray hardness ratios, and their true L{sub X} values are

  16. Effects of domain size on x-ray absorption spectra of boron nitride doped graphenes

    Science.gov (United States)

    Li, Xin; Hua, Weijie; Wang, Bo-Yao; Pong, Way-Faung; Glans, Per-Anders; Guo, Jinghua; Luo, Yi

    2016-08-01

    Doping is an efficient way to open the zero band gap of graphene. The control of the dopant domain size allows us to tailor the electronic structure and the properties of the graphene. We have studied the electronic structure of boron nitride doped graphenes with different domain sizes by simulating their near-edge X-ray absorption fine structure (NEXAFS) spectra at the N K-edge. Six different doping configurations (five quantum dot type and one phase-separated zigzag-edged type) were chosen, and N K-edge NEXAFS spectra were calculated with large truncated cluster models by using the density functional theory with hybrid functional and the equivalent core hole approximation. The opening of the band gap as a function of the domain size is revealed. We found that nitrogens in the dopant boundary contribute a weaker, red-shifted π* peak in the spectra as compared to those in the dopant domain center. The shift is related to the fact that these interfacial nitrogens dominate the lowest conduction band of the system. Upon increasing the domain size, the ratio of interfacial atom decreases, which leads to a blue shift of the π* peak in the total NEXAFS spectra. The spectral evolution agrees well with experiments measured at different BN-dopant concentrations and approaches to that of a pristine h-BN sheet.

  17. Bifurcation timescales in power spectra of black hole binaries and ultraluminous X-ray sources

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    For black hole binaries(BHBs) and active galactic nuclei(AGNs),bifurcation timescales(BTs) Δtb exist,below which time-domain power is significantly higher than the corresponding Fourier power.Quasi-periodic oscillations(QPOs) are removed from the Fourier spectra of BHBs.A relationship between BT,black hole mass and bolometric luminosity is derived.Strong anti-correlation between BT and luminosity of Cyg X-1 is found.After removing the QPOs,BTs are also obtained for two ultraluminous X-ray sources(ULXs),M82 X-1 and NGC5408 X-1.The results support that they harbor intermediate mass black holes(IMBHs).

  18. Multielectron excitations in x-ray absorption spectra of Rb and Kr

    Energy Technology Data Exchange (ETDEWEB)

    Kodre, A. [Faculty of Mathematics and Physics, University of Ljubljana (Slovenia); J. Stefan Institute, Ljubljana (Slovenia)]. E-mail: alojz.kodre@fmf.uni-lj.si; Arcon, I. [J. Stefan Institute, Ljubljana (Slovenia); Nova Gorica Polytechnics, Nova Gorica (Slovenia); Padeznik-Gomilsek J. [Faculty of Mechanical Engineering, University of Maribor, Maribor (Slovenia); Preseren, R. [Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana (Slovenia); Frahm, R. [Bergische Universitaet Gesamthochschule Wuppertal, Fachbereich 8-Physik, Wuppertal (Germany)

    2002-08-28

    In the K-edge x-ray absorption of rubidium vapour and gaseous krypton, comprehensive spectra of collective excitations down to the relative probability of 5x10{sup -5} are extracted. After removal of the asymptotic Victoreen trend, the region {approx}100 eV above the edge exhibits a steep decrease of the absorption coefficient attributed to core relaxation and post-collision interaction in the Auger decay. With an exponential model for the decrease, the entire spectrum of multielectron excitations is recognized as a succession of consecutive resonant, shake-up and shake-off channels. They can be identified as coexcitations of electrons from successively deeper subshells, from 5s down to 3s. The identification of excited states is aided by a quantitative modelling of subshell contributions and by natural-width deconvolution. The valence and subvalence coexcitations are shown to follow the pattern of the lighter homologues potassium and argon. (author)

  19. X-Ray CT of Highly-Attenuating Objects: 9- or 15- MV Spectra?

    Energy Technology Data Exchange (ETDEWEB)

    Stone, G; Trebes, J; Perry, R; Schneberk, D; Logan, C

    2005-08-29

    We imaged-highly attenuating test objects in three dimensions with 9-MV (at LLNL) and 15-MV (at Hill Air Force Base) x-ray spectra. While we used the same detector and motion control, there were differences that we could not control in the two radiography bays and in the sources. The results show better spatial resolution for the 9-MV spectrum and better contrast for the 15-MV spectrum. The 15-MV data contains a noise pattern that obfuscates the data. It is our judgment that if sufficient attention were given to design of the bay, beam dump, collimation, filtration and linac spot size; a 15-MV imaging system using a flat panel could be developed with spatial resolution of 5 lp/mm and contrastive performance better than we have demonstrated using a 9-MV spectrum.

  20. X-ray photoelectron spectra structure and chemical bonding in AmO2

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2015-01-01

    Full Text Available Quantitative analysis was done of the X-ray photoelectron spectra structure in the binding energy range of 0 eV to ~35 eV for americium dioxide (AmO2 valence electrons. The binding energies and structure of the core electronic shells (~35 eV-1250 eV, as well as the relativistic discrete variation calculation results for the Am63O216 and AmO8 (D4h cluster reflecting Am close environment in AmO2 were taken into account. The experimental data show that the many-body effects and the multiplet splitting contribute to the spectral structure much less than the effects of formation of the outer (0-~15 eV binding energy and the inner (~15 eV-~35 eV binding energy valence molecular orbitals. The filled Am 5f electronic states were shown to form in the AmO2 valence band. The Am 6p electrons participate in formation of both the inner and the outer valence molecular orbitals (bands. The filled Am 6p3/2 and the O 2s electronic shells were found to make the largest contributions to the formation of the inner valence molecular orbitals. Contributions of electrons from different molecular orbitals to the chemical bond in the AmO8 cluster were evaluated. Composition and sequence order of molecular orbitals in the binding energy range 0-~35 eV in AmO2 were established. The experimental and theoretical data allowed a quantitative scheme of molecular orbitals for AmO2, which is fundamental for both understanding the chemical bond nature in americium dioxide and the interpretation of other X-ray spectra of AmO2.

  1. The discovery of lensed radio and X-ray sources behind the Frontier Fields cluster MACS J0717.5+3745 with the JVLA and Chandra

    CERN Document Server

    van Weeren, R J; Jones, C; Forman, W R; Andrade-Santos, F; Bonafede, A; Brüggen, M; Bulbul, E; Clarke, T E; Churazov, E; David, L; Dawson, W A; Donahue, M; Goulding, A; Kraft, R P; Mason, B; Merten, J; Mroczkowski, T; Murray, S S; Nulsen, P E J; Rosati, P; Roediger, E; Randall, S W; Sayers, J; Umetsu, K; Vikhlinin, A; Zitrin, A

    2015-01-01

    We report on high-resolution JVLA and Chandra observations of the HST Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0-6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample we find 7 lensed sources with amplification factors larger than $2$. None of these sources are identified as multiply-lensed. Based on the radio luminosities, the majority of these sources are likely star forming galaxies with star formation rates of 10-50 M$_\\odot$ yr$^{-1}$ located at $1 \\lesssim z \\lesssim 2$. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely AGN, given their $2-10$ keV X-ray luminosities of $\\sim 10^{43-44}$ erg s$^{-1}$. From the derived radio luminosity function, we find evidence...

  2. Hunting for X-ray Outbursts from Galactic Nuclei

    Science.gov (United States)

    Brandt, W. N.

    2005-09-01

    Transient X-ray outbursts from galactic nuclei are likely caused by inevitable fueling events of nuclear supermassive black holes when a star, planet, or gas cloud is tidally disrupted and partially accreted. We propose to extend current studies of such events by searching for new X-ray outbursts with harder X-ray spectra, lower X-ray luminosities, and higher redshifts. We will pursue a two-pronged strategy utilizing a combination of (1) about 380 fields with moderate-depth coverage by both Chandra and XMM-Newton and (2) deep Chandra surveys, primarily the Chandra Deep Fields. Aside from their innate interest, our results will be useful for planning future missions such as the Black Hole Finder Probe, Lobster, ROSITA, and LISA.

  3. Examining molecular clouds in the Galactic Centre region using X-ray reflection spectra simulations

    Science.gov (United States)

    Walls, M.; Chernyakova, M.; Terrier, R.; Goldwurm, A.

    2016-12-01

    In the centre of our Galaxy lies a supermassive black hole, identified with the radio source Sagittarius A⋆. This black hole has an estimated mass of around 4 million solar masses. Although Sagittarius A⋆ is quite dim in terms of total radiated energy, having a luminosity that is a factor of 1010 lower than its Eddington luminosity, there is now compelling evidence that this source was far brighter in the past. Evidence derived from the detection of reflected X-ray emission from the giant molecular clouds in the Galactic Centre region. However, the interpretation of the reflected emission spectra cannot be done correctly without detailed modelling of the reflection process. Attempts to do so can lead to an incorrect interpretation of the data. In this paper, we present the results of a Monte Carlo simulation code we developed in order to fully model the complex processes involved in the emerging reflection spectra. The simulated spectra can be compared to real data in order to derive model parameters and constrain the past activity of the black hole. In particular, we apply our code to observations of Sagittarius B2, in order to constrain the position and density of the cloud and the incident luminosity of the central source. The results of the code have been adapted to be used in XSPEC by a large community of astronomers.

  4. How realistic UV spectra and X-rays suppress the abundance of direct collapse black holes

    CERN Document Server

    Latif, M A; Grassi, T; Schleicher, D R G; Spaans, M

    2014-01-01

    Observations of high redshift quasars at $z>6$ indicate that they harbor supermassive black holes (SMBHs) of a billion solar masses. The direct collapse scenario has emerged as the most plausible way to assemble SMBHs. The nurseries for the direct collapse black holes are massive primordial halos illuminated with an intense UV flux emitted by population II stars. In this study, we compute the critical value of such a flux ($J_{21}^{\\rm crit}$) for realistic spectra of pop II stars through three-dimensional cosmological simulations. We derive the dependence of $J_{21}^{\\rm crit}$ on the radiation spectra, on variations from halo to halo, and on the impact of X-ray ionization. Our findings show that the value of $J_{21}^{\\rm crit}$ is a few times $\\rm 10^4$ and only weakly depends on the adopted radiation spectra in the range between $T_{\\rm rad}=2 \\times 10^4-10^5$ K. For three simulated halos of a few times $\\rm 10^{7}$~M$_{\\odot}$, $J_{21}^{\\rm crit}$ varies from $\\rm 2 \\times 10^4 - 5 \\times 10^4$. The impa...

  5. Examining molecular clouds in the Galactic Centre region using X-ray reflection spectra simulations

    CERN Document Server

    Walls, Michael; Terrier, Regis; Goldwurm, Andrea

    2016-01-01

    In the centre of our galaxy lies a super-massive black hole, identified with the radio source Sagittarius A*. This black hole has an estimated mass of around 4 million solar masses. Although Sagittarius A* is quite dim in terms of total radiated energy, having a luminosity that is a factor of $10^{10}$ lower than its Eddington luminosity, there is now compelling evidence that this source was far brighter in the past. Evidence derived from the detection of reflected X-ray emission from the giant molecular clouds in the galactic centre region. However, the interpretation of the reflected emission spectra cannot be done correctly without detailed modelling of the reflection process. Attempts to do so can lead to an incorrect interpretation of the data. In this paper we present the results of a Monte Carlo simulation code we developed in order to fully model the complex processes involved in the emerging reflection spectra. The simulated spectra can be compared to real data in order to derive model parameters and...

  6. Deep Chandra observations of NGC 7457, the X-ray point source populations of a low mass early-type galaxy

    Science.gov (United States)

    Peacock, Mark B.; Zepf, Stephen E.; Kundu, Arunav; Maccarone, Thomas J.; Lehmer, Bret D.; Gonzalez, Anthony H.; Maraston, Claudia

    2017-01-01

    We present the X-ray point source population of NGC 7457 based on 124 ks of Chandra observations. Previous deep Chandra observations of low mass X-ray binaries (LMXBs) in early-type galaxies have typically targeted the large populations of massive galaxies. NGC 7457 is a nearby, early-type galaxy with a stellar luminosity of 1.7× 10^{10} {L_{K⊙}}, allowing us to investigate the populations in a relatively low mass galaxy. We classify the detected X-ray sources into field LMXBs, globular cluster LMXBs, and background AGN based on identifying optical counterparts in new HST/ACS images. We detect 10 field LMXBs within the rext ellipse of NGC 7457 (with semi-major axis ˜ 9.1 kpc, ellipticity = 0.55). The corresponding number of LMXBs with {Lx} > 2 × 10^{37} {{erg s^{-1}}} per stellar luminosity is consistent with that observed in more massive galaxies, ˜7 per 10^{10} {L_{K⊙}}. We detect a small globular cluster population in these HST data and show that its colour distribution is likely bimodal and that its specific frequency is similar to that of other early type galaxies. However, no X-ray emission is detected from any of these clusters. Using published data for other galaxies, we show that this non-detection is consistent with the small stellar mass of these clusters. We estimate that 0.11 (and 0.03) LMXBs are expected per 106 {M_{⊙}} in metal-rich (and metal-poor) globular clusters. This corresponds to 1100 (and 330) LMXBs per 10^{10} {L_{K⊙}}, highlighting the enhanced formation efficiency of LMXBs in globular clusters. A nuclear X-ray source is detected with Lx varying from 2.8-6.8× 10^{38} {{erg s^{-1}}}. Combining this Lx with a published dynamical mass estimate for the central SMBH in NGC 7457, we find that {Lx}/L_{Edd} varies from 0.5 - 1.3 × 10-6.

  7. The Megasecond Chandra X-Ray Visionary Project Observation of NGC 3115 (III): luminosity functions of LMXBs and dependence on stellar environments

    CERN Document Server

    Lin, Dacheng; Wong, Ka-wah; Jennings, Zachary G; Homan, Jeroen; Romanowsky, Aaron J; Strader, Jay; Brodie, Jean P; Sivakoff, Gregory R; Remillard, Ronald A

    2015-01-01

    We have studied the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXBs) in the nearby lenticular galaxy NGC 3115, using the Megasecond Chandra X-Ray Visionary Project Observation. With a total exposure time of ~1.1 Ms, we constructed the XLF down to a limiting luminosity of ~10^36 erg/s, much deeper than typically reached for other early-type galaxies. We found significant flattening of the overall LMXB XLF from dN/dL \\propto L^{-2.2\\pm0.4} above 5.5x10^37 erg/s to dN/dL \\propto L^{-1.0\\pm0.1} below it, though we could not rule out a fit with a higher break at ~1.6x10^38 erg/s. We also found evidence that the XLF of LMXBs in globular clusters (GCs) is overall flatter than that of field LMXBs. Thus our results for this galaxy do not support the idea that all LMXBs are formed in GCs. The XLF of field LMXBs seems to show spatial variation, with the XLF in the inner region of the galaxy being flatter than that in the outer region, probably due to contamination of LMXBs from undetected and/or disrup...

  8. The Hot Interstellar Medium of Normal Elliptical Galaxies. I. A Chandra Gas Gallery and Comparison of X-ray and Optical Morphology

    CERN Document Server

    Diehl, S; Diehl, Steven; Statler, Thomas S.

    2006-01-01

    We present an X-ray analysis of 54 normal elliptical galaxies in the Chandra archive and isolate their hot gas component from the contaminating point source emission. This makes it possible to conduct, for the first time, a complete morphological analysis on the gas alone. A comparison with optical DSS images and published optical photometry shows that the hot gas morphology has surprisingly little in common with the shape of the stellar distribution. In particular, we observe no correlation between optical and X-ray ellipticity, as would be expected if the gas had settled into hydrostatic equilibrium with the underlying gravitational potential. In fact, the observed X-ray ellipticity exceeds the optical ellipticity in many cases. We exclude rotational support as the dominant factor to produce these high ellipticities. Instead, we find that the gas appears to be very disturbed and that the general perception of normal elliptical galaxies hosting calm, hydrostatic gas has to be revised. We conclude that, even ...

  9. The unusual X-ray morphology of NGC4636 revealed by deep Chandra observations: cavities and shocks created by past AGN outbursts

    CERN Document Server

    Baldi, A; Jones, C; Kraft, R; Nulsen, P; Churazov, E; David, L; Giacintucci, S

    2009-01-01

    We present Chandra ACIS-I and ACIS-S observations ($\\sim$200 ks in total) of the X-ray luminous elliptical galaxy NGC 4636, located in the outskirts of the Virgo cluster. A soft band (0.5-2 keV) image shows the presence of a bright core in the center surrounded by an extended X-ray corona and two pronounced quasi-symmetric, 8 kpc long, arm-like features. Each of this features defines the rimof an ellipsoidal bubble. An additional bubble-like feature, whose northern rim is located $\\sim2$ kpc south of the north-eastern arm, is detected as well. We present surface brightness and temperature profiles across the rims of the bubbles, showing that their edges are sharp and characterized by temperature jumps of about 20-25%. Through a comparison of the observed profiles with theoretical shock models, we demonstrate that a scenario where the bubbles were produced by shocks, probably driven by energy deposited off-center by jets, is the most viable explanation to the X-ray morphology observed in the central part of NG...

  10. A Chandra observation of the long-duration X-ray transient KS 1731-260 in quiescence too cold a neutron star?

    CERN Document Server

    Wijnands, R; Markwardt, C B; Lewin, W H G; Van der Klis, M; Wijnands, Rudy; Miller, Jon M.; Markwardt, Craig; Lewin, Walter H. G.; Klis, Michiel van der

    2001-01-01

    After more than a decade of actively accreting at about a tenth of the Eddington critical mass accretion rate, the neutron-star X-ray transient KS 1731-260 returned to quiescence in early 2001. We present a Chandra/ACIS-S observation taken several months after this transition. We detected the source at an unabsorbed flux of ~2 x 10^{-13} erg/s/cm^2 (0.5-10 keV). For a distance of 7 kpc, this results in a 0.5-10 keV luminosity of ~1 x 10^{33} erg/s and a bolometric luminosity approximately twice that. The quiescent luminosity of KS 1731-260 is very similar to that of the other quiescent neutron star systems. However, if this quiescent X-ray luminosity is due to the cooling of the neutron star, this low luminosity may indicate that the source spends several hundreds of years in quiescence in between outbursts for the neutron star to cool. If true, then it might be the first such X-ray transient to be identified and a class of several hundred similar systems might be present in the Galaxy. Alternatively, enhance...

  11. Indirect measurements of X-ray spectra; Mediciones indirectas de espectros de rayos X

    Energy Technology Data Exchange (ETDEWEB)

    Mainardi, R.T. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, X5000HUA Cordoba (Argentina)

    2006-07-01

    To the effects of measuring the spectral distribution of the radiation emitted by the x-ray tubes and electron accelerators, numerous procedures that are grouped in two big categories exist at the present time: direct and indirect methods. The first ones use high resolution detectors that should be positioned, together with the appropriate collimator, in the direction of the x ray beam. The user should be an expert in the use and correction of the obtained data by the different effects that affect the detector operation such as efficiency and resolution in terms of the energy of the detected radiation. The indirect procedures, although its are more simple to use, its also require a considerable space along the beam to position the ionization chamber and the necessary absorbents to construct by this way the denominated attenuation curve. We will analyze the operation principle of the indirect methods and a new proposal in which such important novelties are introduced as the beam dispersion to avoid to measure along the main beam and that of determination of the attenuation curve in simultaneous form. By this way, with a single shot of the tube, the attenuation curve is measured, being necessary at most a shot of additional calibration to know the relative response of the detectors used in the experimental array. The physical processes involved in the obtaining of an attenuation curve are very well well-known and this it finishes it can be theoretically calculated if the analytic form of the spectrum is supposed well-known. Finally, we will see a spectra reconstruction example with the Kramers parametric form and comparisons with numeric simulations carried out with broadly validated programs as well as the possibility of the use of solid state dosemeters in the obtention of the attenuation curve. (Author)

  12. X-ray diffraction, X-ray photoelectron spectra, crystal structure, and optical properties of centrosymmetric strontium borate Sr2B16O26.

    Science.gov (United States)

    Reshak, Ali Hussain; Auluck, S; Kityk, I V; Chen, Xuean

    2009-07-09

    We report results of X-ray diffraction (XRD) and valence band X- ray photoelectron (VB-XPS) spectra for strontium borate Sr(2)B(16)O(26). The X-ray structural analysis shows that the single crystals of Sr(2)B(16)O(26) crystallize in the monoclinic space group P2(1)/c with a = 8.408(1) A, b = 16.672(1) A, c = 13.901(2) A, beta = 106.33(1) degrees , and Z = 4. The crystal structure consists of a 3D network of the complex borate anion [B(16)O(20)O(12/2)](4-), formed by 12 BO(3) triangles and four BO(4) tetrahedra, which can be viewed as three linked [B(3)O(3)O(4/2)](-) triborate groups bonded to one pentaborate [B(5)O(6)O(4/2)](-) group and two BO(3) triangles. Using this structure, we have performed theoretical calculations using the all-electron full potential linearized augmented plane wave (FP-LAPW) method for the band structure, density of states, electron charge density, and the frequency-dependent optical properties. Our experimental VB-XPS of Sr(2)B(16)O(26) is compared with results of our FP-LAPW calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Gamma of the Brillouin zone (BZ) resulting in a direct energy gap of about 5.31 eV. Our measured VB-XPS show reasonable agreement with our calculated total density of states for the valence band that is attributed to the use of the full potential method.

  13. X-Ray Absorption Spectra of Amorphous Ices from GW Quasiparticle Calculation

    Science.gov (United States)

    Kong, Lingzhu; Car, Roberto

    2013-03-01

    We use a GW approach[2] to compute the x-ray absorption spectra of model low- and high-density amorphous ice structures(LDA and HDA)[3]. We include the structural effects of quantum zero point motion using colored-noise Langevin molecular dynamics[4]. The calculated spectra differences in the main and post edge region between LDA and HDA agree well with experimental observations. We attribute these differences to the presence of interstitial molecules within the first coordination shell range in HDA. This assignment is further supported by a calculation of the spectrum of ice VIII, a high-pressure structure that maximizes the number of interstitial molecules and, accordingly, shows a much weaker post-edge feature. We further rationalize the spectral similarity between HDA and liquid water, and between LDA and ice Ih in terms of the respective similarities in the H-bond network topology and bond angle distributions. Supported by grants DOE-DE-SC0005180, DOE DE-SC0008626 and NSF-CHE-0956500.

  14. HEXTE Studies of Sco X-1 Spectra Detections of Hard X-Ray Tails Beyond 200 keV

    CERN Document Server

    D'Amico, F; Rothschild, R E; Peterson, L E; Gruber, D E; Pelling, M R; Tomsick, J A

    2001-01-01

    Using the HEXTE experiment on-board the RXTE satellite, we performed a search for hard X-ray tails in Sco X-1 spectra. We found strong evidence for the presence of such a non-thermal component on several occasions. Using the PCA/RXTE we were able to track the position of the source along the Z diagram, and we observed that the presence of the hard X-ray tail is not confined to a particular region. However, we found a correlation between the power law index of the non-thermal component and the position of the source in the Z diagram, suggesting that the hard X-ray spectrum (i.e., E > 50 keV) becomes flatter as the mass accretion rate increases. We were also able to study the temporal variation of the appearance/absence of the hard X-ray component. With our derived luminosities, we were also able to test the idea that X-ray luminosities can be used to distinguish between X-ray binary systems containing neutron stars and black holes.

  15. THE BROADBAND XMM-NEWTON AND NuSTAR X-RAY SPECTRA OF TWO ULTRALUMINOUS X-RAY SOURCES IN THE GALAXY IC 342

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Vikram; Harrison, Fiona A.; Walton, Dominic J.; Furst, Felix; Grefenstette, Brian W.; Madsen, Kristin K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bachetti, Matteo; Barret, Didier; Webb, Natalie A. [Université de Toulouse, UPS-OMP, IRAP, Toulouse (France); Miller, Jon M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Fabian, Andrew C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, Finn C. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Hailey, Charles J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Ptak, Andrew F.; Zhang, William W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2015-02-01

    We present results for two ultraluminous X-ray sources (ULXs), IC 342 X-1 and IC 342 X-2, using two epochs of XMM-Newton and NuSTAR observations separated by ∼7 days. We observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3-30 keV luminosities being 1.04{sub −0.06}{sup +0.08}×10{sup 40} erg s{sup –1} for IC 342 X-1 and 7.40 ± 0.20 × 10{sup 39} erg s{sup –1} for IC 342 X-2, so that both were observed in a similar, luminous state. Both sources have a high absorbing column in excess of the Galactic value. Neither source has a spectrum consistent with a black hole binary in low/hard state, and both ULXs exhibit strong curvature in their broadband X-ray spectra. This curvature rules out models that invoke a simple reflection-dominated spectrum with a broadened iron line and no cutoff in the illuminating power-law continuum. X-ray spectrum of IC 342 X-1 can be characterized by a soft disk-like blackbody component at low energies and a cool, optically thick Comptonization continuum at high energies, but unique physical interpretation of the spectral components remains challenging. The broadband spectrum of IC 342 X-2 can be fit by either a hot (3.8 keV) accretion disk or a Comptonized continuum with no indication of a seed photon population. Although the seed photon component may be masked by soft excess emission unlikely to be associated with the binary system, combined with the high absorption column, it is more plausible that the broadband X-ray emission arises from a simple thin blackbody disk component. Secure identification of the origin of the spectral components in these sources will likely require broadband spectral variability studies.

  16. ANALYSIS OF X-RAY SPECTRA EMITTED FROM THE VENUS ECR ION SOURCE

    Energy Technology Data Exchange (ETDEWEB)

    Benitez, J.; Leitner, D.

    2008-01-01

    The Versatile Electron Cyclotron resonance ion source for Nuclear Science (VENUS), located at Lawrence Berkeley National Lab’s 88-inch cyclotron, extracts ion beams from a plasma created by ionizing a gas with energetic electrons. Liquid-helium cooled superconducting coils produce magnetic fi elds that confi ne the plasma and high microwave frequencies heat the electrons enough to allow for successive ionizations of the neutral gas atoms. The combination of strong plasma confi nement and high microwave frequencies results in VENUS’ production of record breaking ion beam currents and high charge state distributions. While in operation, VENUS produces signifi cant quantities of bremsstrahlung, in the form of x-rays, primarily through two processes: 1) electron-ion collisions within the plasma, and 2) electrons are lost from the plasma, collide with the plasma chamber wall, and radiate bremsstrahlung due to their sudden deceleration. The bremsstrahlung deposited into the plasma chamber wall is absorbed by the cold mass used to maintain superconductivity in the magnets and poses an additional heat load on the cryostat. In order for VENUS to reach its maximum operating potential of 10 kW of 28 GHz microwave heating frequency, the heat load posed by the emitted bremsstrahlung must be understood. In addition, studying the bremsstrahlung under various conditions will help further our understanding of the dynamics within the plasma. A code has been written, using the Python programming language, to analyze the recorded bremsstrahlung spectra emitted from the extraction end of VENUS. The code outputs a spectral temperature, which is relatively indicative of the temperature of the hot electrons, and total integrated count number corresponding to each spectra. Bremsstrahlung spectra are analyzed and compared by varying two parameters: 1) the heating frequency, 18 GHz and 28 GHz, and 2) the ratio between the minimum magnetic fi eld and the resonant magnetic fi eld, .44 and

  17. X-ray magnetic circular dichroism spectra and distortions at Fe2+ L(2,3) edges

    NARCIS (Netherlands)

    Wang, X.; de Groot, F.M.F.; Cramer, S.P.

    1996-01-01

    We have shown from ligand field multiplet calculations that the shape of X-ray magnetic circular dichroism (XMCD) spectra changes drastically with the distortion parameter Ds. The temperature dependence study of XMCD makes it possible to determine both Ds and spin-orbit coupling.

  18. CALCULATION OF MAGNETIC-X-RAY DICHROISM IN 4D AND 5D ABSORPTION-SPECTRA OF ACTINIDES

    NARCIS (Netherlands)

    OGASAWARA, H; KOTANI, A; THOLE, BT

    1991-01-01

    We present atomic calculations of the magnetic dichroism in 4d and 5d x-ray-absorption (XAS) spectra of trivalent actinide ions. The calculations are carried out for both linearly and circularly polarized light at zero temperature. Large magnetic dichroism is predicted for 5d XAS with

  19. X-ray magnetic circular dichroism spectra and distortions at Fe2+ L(2,3) edges

    NARCIS (Netherlands)

    Wang, X.; de Groot, F.M.F.; Cramer, S.P.

    We have shown from ligand field multiplet calculations that the shape of X-ray magnetic circular dichroism (XMCD) spectra changes drastically with the distortion parameter Ds. The temperature dependence study of XMCD makes it possible to determine both Ds and spin-orbit coupling.

  20. A Chandra X-ray analysis of Abell 1664: cooling, feedback, and star formation in the central cluster galaxy

    NARCIS (Netherlands)

    Kirkpatrick, C.C.; McNamara, B.R.; Rafferty, D.A.; Nulsen, P.E.J.; Bîrzan, L.; Kazemzadeh, F.; Wise, M.W.; Gitti, M.; Cavagnolo, K.W.

    2009-01-01

    The brightest cluster galaxy (BCG) in the Abell 1664 cluster is unusually blue and is forming stars at a rate of similar to 23 M-circle dot yr(-1). The BCG is located within 5 kpc of the X-ray peak, where the cooling time of 3.5 x 10(8) yr and entropy of 10.4 keV cm(2) are consistent with other star

  1. A Chandra X-ray Analysis of Abell 1664: Cooling, Feedback and Star Formation in the Central Cluster Galaxy

    CERN Document Server

    Kirkpatrick, C C; Rafferty, D A; Nulsen, P E J; Birzan, L; Kazemzadeh, F; Wise, M W; Gitti, M; Cavagnolo, K W

    2009-01-01

    The brightest cluster galaxy (BCG) in the Abell 1664 cluster is unusually blue and is forming stars at a rate of ~ 23 M_{\\sun} yr^{-1}. The BCG is located within 5 kpc of the X-ray peak, where the cooling time of 3.5x10^8 yr and entropy of 10.4 keV cm^2 are consistent with other star-forming BCGs in cooling flow clusters. The center of A1664 has an elongated, "bar-like" X-ray structure whose mass is comparable to the mass of molecular hydrogen, ~ 10^{10} M_{\\sun} in the BCG. We show that this gas is unlikely to have been stripped from interloping galaxies. The cooling rate in this region is roughly consistent with the star formation rate, suggesting that the hot gas is condensing onto the BCG. We use the scaling relations of Birzan et al. 2008 to show that the AGN is underpowered compared to the central X-ray cooling luminosity by roughly a factor of three. We suggest that A1664 is experiencing rapid cooling and star formation during a low-state of an AGN feedback cycle that regulates the rates of cooling and...

  2. Spectral analysis of the Chandra comet survey

    NARCIS (Netherlands)

    Bodewits, D.; Christian, D. J.; Torney, M.; Dryer, M.; Lisse, C. M.; Dennerl, K.; Zurbuchen, T. H.; Wolk, S. J.; Tielens, A. G. G. M.; Hoekstra, R.

    2007-01-01

    Aims. We present results of the analysis of cometary X-ray spectra with an extended version of our charge exchange emission model (Bodewits et al. 2006). We have applied this model to the sample of 8 comets thus far observed with the Chandra X-ray observatory and acis spectrometer in the 300 - 1000

  3. Evaluation of X-ray spectra transmitted by different concrete compositions

    Science.gov (United States)

    Costa, P. R.; Vieira, D. V.; Naccache, V. K.; Ferreira, K. R.; Priszkulnik, S.

    2015-11-01

    Additional shielding material must frequently be incorporated to medical facilities in order to comply with radiation protection requirements when using radiation sources. Typical materials for shielding walls, floor and ceiling are the lead, concrete and barite. In the present work, a group of four concrete compositions was evaluated by using broad beam transmission curves and transmitted spectra in the range of X-ray energies used for diagnostic imaging. The studied concretes were classified as ordinary concrete (Type C), concrete with addition of hematite (Types H1 and H2) and concrete with addition of steel grit (Type S). Concrete with steel grit shows be more efficient as shielding material of the three heavy types concrete studied. The two mixes of concrete and hematite are practically equivalent from the radioprotection point of view. However, the granulation difference between them might be important to other fields, as shielding is not the only function of concrete in the building structure. Although they are not as efficient as concrete with steel grit, they may be a shielding option in a facility with low shielding requirement.

  4. Revealing O VII from stacked X-ray grating spectra of clusters, groups and elliptical galaxies

    CERN Document Server

    Sanders, J S

    2010-01-01

    We stack 4.6 Ms of high spectral resolution XMM-Newton Reflection Grating Spectrometer spectra from galaxy clusters, groups of galaxies and elliptical galaxies. For those objects with a central temperature of less than 1 keV, we detect O VII for the first time, with a probability of false detection of 2.5x10^-4. The flux ratio of the O VII to Fe XVII lines is 1/4 to 1/8 of the emission expected for isobaric radiative cooling in the absence of heating. There is either a process preventing cooling below 0.5 keV, anomalous O/Fe abundance ratios, absorbing material around the coolest X-ray emitting gas or non-radiative cooling taking place. The mean N VII emission line is strong in the sub-keV sample. As the ratio of the hydrogenic N and O lines is largely independent of temperature, we measure a mean N/O ratio of 4.0 +- 0.6 Solar. Although the continuum around the C VI lines is difficult to measure we can similarly estimate that the C/O ratio is 0.9 +- 0.3 Solar.

  5. Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography*

    Science.gov (United States)

    Paixão, Lucas; Oliveira, Bruno Beraldo; Viloria, Carolina; de Oliveira, Marcio Alves; Teixeira, Maria Helena Araújo; Nogueira, Maria do Socorro

    2015-01-01

    Objective Derive filtered tungsten X-ray spectra used in digital mammography systems by means of Monte Carlo simulations. Materials and Methods Filtered spectra for rhodium filter were obtained for tube potentials between 26 and 32 kV. The half-value layer (HVL) of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F & MAM Detector Platinum and 8201023-C Xi Base unit Platinum Plus w mAs in a Hologic Selenia Dimensions system using a direct radiography mode. Results Calculated HVL values showed good agreement as compared with those obtained experimentally. The greatest relative difference between the Monte Carlo calculated HVL values and experimental HVL values was 4%. Conclusion The results show that the filtered tungsten anode X-ray spectra and the EGSnrc Monte Carlo code can be used for mean glandular dose determination in mammography. PMID:26811553

  6. A practical method for estimating high-energy X-ray spectra using the iterative perturbation principle proposed by Waggener

    CERN Document Server

    Iwasaki, A; Kubota, M; Fujimori, A; Suzaki, K; Abe, Y

    2003-01-01

    We have remodeled the X-ray spectra estimation method, originally proposed by Waggener et al. (Med. Phys. 26(1999)1269), based on the iterative perturbation technique to minimize differences between measured and calculated transmission curves using low Z attenuators. With our approach, the iterative perturbation cycle is repeated until a reasonable spectrum is obtained. Furthermore, the degree of differences between the measured and calculated transmission curves is also checked using high Z attenuators. The present experimental study, conducted using 4, 10 and 15 MV X-ray beams from a linear accelerator, demonstrated that the spectrum varies strongly with the off-axis distance.

  7. Calculation of the Kramers-Kronig transform of X-ray spectra by a piecewise Laurent polynomial method.

    Science.gov (United States)

    Watts, Benjamin

    2014-09-22

    An algorithm is presented for the calculation of the Kramers-Kronig transform of a spectrum via a piecewise Laurent polynomial method. This algorithm is demonstrated to be highly accurate, while also being computationally efficient. The algorithm places no requirements on data point spacing and is capable of integrating across the full spectrum (i.e. from zero to infinity). Further, we present a computer application designed to aid in calculating the Kramers-Kronig transform on near-edge experimental X-ray absorption spectra (extended with atomic scattering factor data) in order to produce the dispersive part of the X-ray refractive index, including near-edge features.

  8. A Chandra Study of the Image Power Spectra of 41 Cool Core and Non-Cool Core Galaxy Clusters

    CERN Document Server

    Zhang, Chenhao; Zhu, Zhenghao; Li, Weitian; Hu, Dan; Wang, Jingying; Gu, Junhua; Gu, Liyi; Zhang, Zhongli; Liu, Chengze; Zhu, Jie; Wu, Xiang-Ping

    2016-01-01

    In this work we propose a new diagnostic to segregate cool core (CC) clusters from non-cool core (NCC) clusters by studying the two-dimensional power spectra of the X-ray images observed with the Chandra X-ray observatory. Our sample contains 41 members ($z=0.01\\sim 0.54$), which are selected from the Chandra archive when a high photon count, an adequate angular resolution, a relatively complete detector coverage, and coincident CC-NCC classifications derived with three traditional diagnostics are simultaneously guaranteed. We find that in the log-log space the derived image power spectra can be well represented by a constant model component at large wavenumbers, while at small wavenumbers a power excess beyond the constant component appears in all clusters, with a clear tendency that the excess is stronger in CC clusters. By introducing a new CC diagnostic parameter, i.e., the power excess index (PEI), we classify the clusters in our sample and compare the results with those obtained with three traditional C...

  9. Chemical and physical parameters from X-ray high resolution spectra of the Galactic nova V959 Mon

    CERN Document Server

    Peretz, U; Behar, E; Bianchini, A; Gallagher, J; Rauch, T; Tofflemire, B; Zemko, P

    2016-01-01

    Two observations of V959 Mon, done using the Chandra X-ray gratings during the late outburst phases (2012 September and December), offer extraordinary insight into the physics and chemistry of this Galactic ONe nova. the X-ray flux was 1.7 x 10(-11) erg/cm(2)/s and 8.6 x 10(-12) erg/cm(2)/s, respectively at the two epochs. The first result, coupled with electron density diagnostics and compared with published optical and ultraviolet observations, indicates that most likely in 2012 September the X-rays originate from a very small fraction of the ejecta, concentrated in very dense clumps. We obtained a fairly good fit to the September spectrum with a model of plasma in collisional ionization equilibrium (CIE) with two components; one at a temperature of 0.78 keV, blueshifted by 710-930 km/s, the other at a temperature of 4.5 keV, mostly contributing to the high-energy continuum. However, we cannot rule out a range of plasma temperatures between these two extremes. In December, the central white dwarf (WD) becam...

  10. WITS-HEX: A renovated code for analysis of PIXE X-ray spectra

    Science.gov (United States)

    Lipworth, A. D.; Annegarn, H. J.; Bauman, S.; Molokomme, T.; Walker, A. J.

    1990-04-01

    The code REX [H.C. Kaufmann and K.R. Akselsson, Adv. X-ray Anal. 18 (1975) 353] and its successor, HEX were developed at Florida State University and University of Lund in the early seventies for quantitative reduction of PIXE spectra. HEX modelled many of the physical processes, including target self-absorption. Lack of adequate documentation and several inherent software related problems hampered widespread adoption and further development. HEX was designed using a hierarchical functional design approach, coded in FORTRAN IV. Its element library and request list are tightly constrained. ANSI standard FORTRAN provides few structured constructs, nor does it support dynamic data structures. HEX has a batch mode of interaction which affords minimal (interim) user interactions. To overcome these limitations we have modernised the program to run on IBM PC compatible computers by using object-oriented design techniques, documented in Program Description Language (pseudo-code) and implemented in a modern programming language, Pascal. Turbo Pascal 5.5 provides an integrated program development environment, a high resolution graphics library, an operating system interface and many software development tools to improve programmer productivity. A menu-based highly interactive screen management library is used for the user interface. A demonstration version is available for user evaluation. Further rigorous testing and the development of user acquired spectra interfacing code will be developed before the first release. The renovated code, WITS-HEX, has extracted the intellectual value embodied in HEX. It will be inherently more stable, reliable, versatile, maintainable and easy to use to facilitate future process modifications.

  11. First-principles calculations of X-ray absorption spectra for warm dense methane

    Science.gov (United States)

    Li, Zi; Wang, Cong; Li, Dafang; Kang, Wei; Zhang, Ping

    2017-09-01

    X-ray absorption spectrum is a powerful tool for atomic structure detection on materials under extreme conditions. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations for warm dense methane under thermodynamical conditions along a Hugoniot curve. From the molecular dynamics trajectories, the detailed atomic structures are examined for each condition. The carbon K-shell X-ray absorption spectrum is calculated, and its change with temperature and pressure is discussed. The methane systems under extreme conditions may contain radicals CHx (x = 1,2,3), molecules CH4, and carbon chains CmHn (m,n >1). These various products show quite different contributions to the total X-ray spectrum due to the different atomic and electronic structures. The change of the total X-ray spectrum along the Hugoniot curve is then attributed to the change of the products induced by the temperature and pressure. Some clear signatures on the X-ray absorption spectrum under different thermodynamical conditions are proposed, which provide useful information for future X-ray experiments.

  12. Ab Initio Calculations of X-ray Spectra : Atomic Multiplet and Molecular Orbital Effects in a Multiconfigurational SCF Approach to the L-Edge Spectra of Transition Metal Complexes

    NARCIS (Netherlands)

    Josefsson, Ida; Kunnus, Kristjan; Schreck, Simon; Foehlisch, Alexander; de Groot, Frank; Wernet, Philippe; Odelius, Michael

    2012-01-01

    A new ab initio approach to the calculation of X-ray spectra is demonstrated. It combines a high-level quantum chemical description of the chemical interactions and local atomic multiplet effects. We show here calculated L-edge X-ray absorption (XA) and resonant inelastic X-ray scattering spectra fo

  13. X-Ray Visions of SS Cygni

    Science.gov (United States)

    Young, D. L.

    2004-12-01

    The Chandra X-Ray Observatory is the most sophisticated X-ray observatory launched by NASA. Chandra is designed to observe X-rays from highenergy regions of the universe, such as X-ray binary stars. On September 14, 2000, triggered by alerts from amateur astronomers worldwide, Chandra observed the outburst of the brightest northern dwarf nova SS Cygni. The cooperation of hundreds of amateur variable star astronomers and the Chandra X-Ray scientists and spacecraft specialists provided proof that the collaboration of amateur and professional astronomers is a powerful tool to study cosmic phenomena.

  14. Shuttle and Transfer Orbit Thermal Analysis and Testing of the Chandra X-Ray Observatory Charge-Couple Device Imaging Spectrometer Radiator Shades

    Science.gov (United States)

    Sharp, John R.

    1999-01-01

    Thermal analyses of the Shuttle and Transfer Orbit of the Advanced X-Ray Astrophysics Facility Charge-Coupled Device (CCD) Imaging Spectrometer (ACIS), one of two science instruments on the Chandra X-Ray Observatory, revealed a low-earth orbit (LEO) overheating problem on the goldized Kapton faces of two radiator shades. The shades were coated with the goldized Kapton to provide a low hemispherical emittance to minimize direct and backloaded heating from the sun and the observatory and high specularity to optimize the coupling to space on two passive radiators which cool the focal plane to -120 C +/- 1 C during on-orbit operations. Since the observatory has a highly elliptical final orbit of 10,000 kilometers by 140,000 kilometers and the ACIS radiators and shades are oriented anti-sun, the high solar absorptance to emittance ratio of the goldized Kapton was not an issue. However, during Shuttle bay-to-earth operations, the short duration solar heating occurring near the eclipse entry and exit resulted in shade temperatures in excess of the cure temperature of the adhesive used to bond the goldized Kapton and honeycomb face-sheets. The detailed thermal analysis demonstrating the LEO overheating as well as the redesign options and thermal testing of a redesigned development unit shade are presented.

  15. Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system I. The non-dip spectrum in the low/hard state

    CERN Document Server

    Hanke, Manfred; Nowak, Michael A; Pottschmidt, Katja; Schulz, Norbert S; Lee, Julia C

    2008-01-01

    We present analyses of a 50 ks observation of the supergiant X-ray binary system Cygnus X-1/HDE 226868 taken with the Chandra High Energy Transmission Grating Spectrometer (HETGS). Cyg X-1 was in its spectrally hard state and the observation was performed during superior conjunction of the black hole, allowing for the spectroscopic analysis of the accreted stellar wind along the line of sight. A significant part of the observation covers X-ray dips as commonly observed for Cyg X-1 at this orbital phase, however, here we only analyze the high count rate non-dip spectrum. The full 0.5-10 keV continuum can be described by a single model consisting of a disk, a narrow and a relativistically broadened Fe Kalpha line, and a power law component, which is consistent with simultaneous RXTE broad band data. We detect absorption edges from overabundant neutral O, Ne and Fe, and absorption line series from highly ionized ions and infer column densities and Doppler shifts. With emission lines of He-like Mg XI, we detect t...

  16. Comparison between X-rays spectra and their effective energies in small animal CT tomographic imaging and dosimetry.

    Science.gov (United States)

    Hamdi, Mahdjoub; Mimi, Malika; Bentourkia, M'hamed

    2016-12-22

    Small animal CT imaging and dosimetry usually rely on X-ray radiation produced by X-ray tubes. These X-rays typically cover a large energy range. In this study, we compared poly-energetic X-ray spectra against estimated equivalent (effective) mono-energetic beams with the same number of simulated photons for small animal CT imaging and dosimetry applications. Two poly-energetic X-ray spectra were generated from a tungsten anode at 50 and 120 kVp. The corresponding effective mono-energetic beams were established as 36 keV for the 50 kVp spectrum and 49.5 keV for the 120 kVp spectrum. To assess imaging applications, we investigated the spatial resolution by a tungsten wire, and the contrast-to-noise ratio in a reference phantom and in a realistic mouse phantom. For dosimetry investigation, we calculated the absorbed dose in a segmented digital mouse atlas in the skin, fat, heart and bone tissues. Differences of 2.1 and 2.6% in spatial resolution were respectively obtained between the 50 and 120 kVp poly-energetic spectra and their respective 36 and 49.5 keV mono-energetic beams. The differences in contrast-to-noise ratio between the poly-energetic 50 kVp spectrum and its corresponding mono-energetic 36 keV beam for air, fat, brain and bone were respectively -2.9, -0.2, 11.2 and -4.8%, and similarly between the 120 kVp and its effective energy 49.5 keV: -11.3, -20.2, -4.2 and -13.5%. Concerning the absorbed dose, for the lower X-ray beam energies, 50 kVp against 36 keV, the poly-energetic radiation doses were higher than the mono-energetic doses. Instead, for the higher X-ray beam energies, 120 kVp and 49.5 keV, the absorbed dose to the bones and lungs were higher for the mono-energetic 49.5 keV. The intensity and energy of the X-ray beam spectrum have an impact on both imaging and dosimetry in small animal studies. Simulations with mono-energetic beams should take into account these differences in order to study biological effects or to be compared to

  17. Galaxy Cluster Thermal X-Ray Spectra Constrain Axion-Like Particles

    CERN Document Server

    Conlon, Joseph P; Powell, Andrew J

    2015-01-01

    Axion-like particles (ALPs) and photons inter-convert in the presence of a magnetic field. At keV energies in the environment of galaxy clusters, the conversion probability can become unsuppressed for light ALPs. Conversion of thermal X-ray photons into ALPs can introduce a step-like feature into the cluster thermal bremsstrahlung spectrum, and we argue that existing X-ray data on galaxy clusters should be sufficient to extend bounds on ALPs in the low-mass region $m_a \\lesssim 1 \\times 10^{-12}\\,{\\rm eV}$ down to $M \\sim 7\\times 10^{11}\\, {\\rm GeV}$, and that for $10^{11}\\, {\\rm GeV} < M \\lesssim 10^{12}$ GeV light ALPs give rise to interesting and unique observational signatures that may be probed by existing and upcoming X-ray (and potentially X-ray polarisation) observations of galaxy clusters.

  18. Comptomization and radiation spectra of X-ray sources. Calculation of the Monte Carlo method

    Science.gov (United States)

    Pozdnyakov, L. A.; Sobol, I. M.; Sonyayev, R. A.

    1980-01-01

    The results of computations of the Comptomization of low frequency radiation in weakly relativistic plasma are presented. The influence of photoabsorption by iron ions on a hard X-ray spectrum is considered.

  19. Chandra Survey in the AKARI North Ecliptic Pole Deep Field. I. X-ray Data, Point-like Source Catalog, Sensitivity Maps, and Number Counts

    CERN Document Server

    Krumpe, M; Brunner, H; Hanami, H; Ishigaki, T; Takagi, T; Markowitz, A G; Goto, T; Malkan, M A; Matsuhara, H; Pearson, C; Ueda, Y; Wada, T

    2014-01-01

    We present data products from the 300 ks Chandra survey in the AKARI North Ecliptic Pole (NEP) deep field. This field has a unique set of 9-band infrared photometry covering 2-24 micron from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ~15 micron, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z~1. We design a source detection procedure, which performs joint Maximum Likelihood PSF fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 square degree. The procedure has been highly optimized and tested by simulations. We provide a point source catalog with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5-7, 0.5-2, 2-7, 2-4, and 4-7 keV bands. The catalog contains 457 X-ray sources and the spurious fraction is estimated to be ~1.7 per cent. Sensitivity and 90 per cent confidence upper flux limit...

  20. X-Ray Absorption with Transmission X-Ray Microscopes

    NARCIS (Netherlands)

    de Groot, F.M.F.

    2016-01-01

    In this section we focus on the use of transmission X-ray microscopy (TXM) to measure the XAS spectra. In the last decade a range of soft X-ray and hard X-ray TXM microscopes have been developed, allowing the measurement of XAS spectra with 10–100 nm resolution. In the hard X-ray range the TXM

  1. Si XII X-ray Satellite Lines in Solar Flare Spectra

    Science.gov (United States)

    Phillips, K. J.; Sylwester, J.; Sylwester, B.; Dubau, J.

    2005-05-01

    We demonstrate the temperature dependence of the intensity ratio of dielectronic satellite lines due to Li-like Si (Si XII) to nearby He-like Si (Si XIII) 1s2 - 1snp(n=3, 4, 5) lines emitted in solar flare X-ray spectra. These lines, which occur in the wavelength range 5.253~Å--5.818~Å, have been observed by the RESIK bent crystal spectrometer on the Russian CORONAS-F solar mission. Line features made up of several strong satellites with transitions 1s2 n'l' - 1s n'l' nl lie near the `parent' Si XIII lines, transition 1s2 1S0 - 1snp 1P1; thus, the feature at 5.818~Å is made up of several blended Si XII satellites with `spectator' electrons n'l'=2s or 2p and nl=3p or 3d, and lies on the long-wavelength side of the Si XIII 1s2 - 1s3p line at 5.681~Å. A similar n=4 satellite feature at 5.565~Å is on the long-wavelength side of the Si XIII 1s2 - 1s4p line at 5.384~Å. The Si XII satellites are formed by dielectronic recombination and direct (inner-shell) excitation. The ratio Is/IHe (Is = Si XII satellite line flux, IHe = Si XIII line flux) depends on electron temperature approximately as Te-1. The atomic data needed to calculate Is/IHe for individual n=3 and n=4 Si XII satellite lines have been calculated and will be presented in this paper; excitation mechanisms including those by dielectronic recombination and inner-shell excitation were included using the SUPERSTRUCTURE and Distorted Wave formalisms. With these and theoretical fluxes of the Si XIII lines, synthetic spectra were calculated and compared with RESIK solar flare spectra. Values of Is/IHe measured from RESIK spectra during the decay of four long-duration solar flares, together with temperatures estimated both from the ratio of the GOES channels and from the ratio of total fluxes in two of the four RESIK channels, enable a comparison to be made with theoretical curves. The agreement with the theoretical curve based on synthetic spectra is within expected uncertainties, and the Te-1 dependence is

  2. Comparison of simulated and measured spectra from an X-ray tube for the energies between 20 and 35 keV

    Science.gov (United States)

    Yücel, M.; Emirhan, E.; Bayrak, A.; Ozben, C. S.; Yücel, E. Barlas

    2015-11-01

    Design and production of a simple and low cost X-ray imaging system that can be used for light industrial applications was targeted in the Nuclear Physics Laboratory of Istanbul Technical University. In this study, production, transmission and detection of X-rays were simulated for the proposed imaging device. OX/70-P dental tube was used and X-ray spectra simulated by Geant4 were validated by comparison with X-ray spectra measured between 20 and 35 keV. Relative detection efficiency of the detector was also determined to confirm the physics processes used in the simulations. Various time optimization tools were performed to reduce the simulation time.

  3. Comparison of simulated and measured spectra from an X-ray tube for the energies between 20 and 35 keV

    Energy Technology Data Exchange (ETDEWEB)

    Yücel, M.; Emirhan, E.; Bayrak, A.; Ozben, C.S.; Yücel, E. Barlas, E-mail: barlase@itu.edu.tr

    2015-11-01

    Design and production of a simple and low cost X-ray imaging system that can be used for light industrial applications was targeted in the Nuclear Physics Laboratory of Istanbul Technical University. In this study, production, transmission and detection of X-rays were simulated for the proposed imaging device. OX/70-P dental tube was used and X-ray spectra simulated by Geant4 were validated by comparison with X-ray spectra measured between 20 and 35 keV. Relative detection efficiency of the detector was also determined to confirm the physics processes used in the simulations. Various time optimization tools were performed to reduce the simulation time.

  4. Soft X-ray absorption spectra of aqueous salt solutions with highly charged cations in liquid microjets

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.

    2010-03-11

    X-ray absorption spectra of 1M aqueous solutions of indium (III) chloride, yttrium (III) bromide, lanthanum (III) chloride, tin (IV) chloride and chromium (III) chloride have been measured at the oxygen K-edge. Relatively minor changes are observed in the spectra compared to that of pure water. SnCl{sub 4} and CrCl{sub 3} exhibit a new onset feature which is attributed to formation of hydroxide or other complex molecules in the solution. At higher energy, only relatively minor, but salt-specific changes in the spectra occur. The small magnitude of the observed spectral changes is ascribed to offsetting perturbations by the cations and anions.

  5. XMM-Newton X-Ray Observation of Jupiter

    Science.gov (United States)

    Waite, J. Hunter

    2005-01-01

    Soft X-ray emission has been observed from the disk of both Jupiter and Saturn as well as from the auroral regions of these planets. The low-latitude disk emission as observed by ROSAT, the Chandra X-Ray Observatory, and XMM-Newton appears to be uniformly distributed across the disk and to be correlated with solar activity. These characteristics suggest that the disk x-rays are produced by: (1) the elastic scattering of solar X-rays by atmospheric neutrals and (2) the absorption of solar X-rays in the carbon K-shell followed by fluorescent emission. The carbon atoms are found in methane molecules located below the homopause. In this paper we present the results of calculations of the scattering albedo for soft x-rays. We also show the calculated x-ray intensity for a range of atmospheric abundances for Jupiter and Saturn and for a number of solar irradiance spectra. The model calculations are compared with recent x-ray observations of Jupiter and Saturn. We conclude that the emission of soft x-rays from the disks of Jupiter and Saturn can be largely explained by the scattering and fluorescence of soft x-rays. We suggest that measured x-ray intensities from the disk regions of Jupiter

  6. H-alpha spectra of dynamic chromospheric processes in five well-observed X-ray flares

    Science.gov (United States)

    Canfield, Richard C.; Penn, Matthew J.; Wulser, Jean-Pierre; Kiplinger, Alan L.

    1990-01-01

    Simultaneous H-alpha and hard X-ray (HXR) spectra were obtained for five solar flares to determine the relationship of H-alpha profiles and the nonthermal part of the flare represented by the hard X-ray burst. All five flares exhibited impulsive-phase redshifted H-alpha in emission, which was temporarily and spatially associated with intense HXR emission and broad impulsive-phase H-alpha wings. A few small regions within two flares showed a blueshifted H-alpha emission which appeared only early in the impulsive phase and was temporally correlated with the HXR emission but not with broad H-alpha wings. Finally, there were both redshifted and blueshifted absorption spectra with properties fully consistent with those known for erupting and untwisting filaments.

  7. First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

    CERN Document Server

    Zhao, Shijun; Kang, Wei; Li, Zi; Zhang, Ping; He, Xian-Tu

    2015-01-01

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to prevent the deviation of pressure from global accumulation along the Hugoniot. In addition, cancellation between electronic kinetic pressure and virial pressure further reduces the deviation. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the $3p$ electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

  8. Exploring the Physics of Type Ia Supernovae Through the X-ray Spectra of their Remnants

    CERN Document Server

    Badenes, C; Bravo, E; Hughes, J P; Hwang, U

    2005-01-01

    We present the results of an ongoing project to use the X-ray observations of Type Ia Supernova Remnants to constrain the physical processes involved in Type Ia Supernova explosions. We use the Tycho Supernova Remnant (SN 1572) as a benchmark case, comparing its observed spectrum with models for the X-ray emission from the shocked ejecta generated from different kinds of Type Ia explosions. Both the integrated spectrum of Tycho and the spatial distribution of the Fe and Si emission in the remnant are well reproduced by delayed detonation models with stratified ejecta. All the other Type Ia explosion models fail, including well-mixed deflagrations calculated in three dimensions.

  9. Chandra X-Ray Spectroscopy of the Focused Wind in the Cygnus X-1 System. II. The Nondip Spectrum in the Low/Hard State - Modulations with Orbital Phase

    CERN Document Server

    Miškovičová, Ivica; Hanke, Manfred; Nowak, Michael A; Pottschmidt, Katja; Schulz, Norbert S; Grinberg, Victoria; Duro, Refiz; Madej, Oliwia K; Lohfink, Anne M; Rodriguez, Jérôme; Bel, Marion Cadolle; Bodaghee, Arash; Tomsick, John A; Lee, Julia C; Brown, Gregory V; Wilms, Jörn

    2016-01-01

    The accretion onto the black hole in the system HDE 226868/Cygnus X-1 is powered by the strong line driven stellar wind of the O-type donor star. We study the X-ray properties of the stellar wind in the hard state of Cyg X-1 as determined with data from the Chandra High Energy Transmission Gratings. Large density and temperature inhomogeneities are present in the wind, with a fraction of the wind consisting of clumps of matter with higher density and lower temperature embedded in a photoionized gas. Absorption dips observed in the light curve are believed to be caused by these clumps. This work concentrates on the non-dip spectra as a function of orbital phase. The spectra show lines of H-like and He-like ions of S, Si, Na, Mg, Al and highly ionized Fe (Fe xvii-Fe xxiv). We measure velocity shifts, column densities, and thermal broadening of the line series. The excellent quality of these five observations allows us to investigate the orbital phase dependence of these parameters. We show that the absorber is ...

  10. X-ray emission processes in stars

    CERN Document Server

    Testa, Paola

    2010-01-01

    A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the HR diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, evolution of X-ray activity with age), to X-ray generating processes (e.g. accretion, jets, magnetically confined winds) that were poorly understood in the pre-Chandra/XMM-Newton era. I discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysical context, focusing on the role of spectral diagnostics no...

  11. Spectroscopic Studies of X-Ray Binary Pulsars

    Indian Academy of Sciences (India)

    F. Nagase

    2002-03-01

    Several new features of X-ray binary pulsars are revealed from recent observations with ASCA, RXTE, BeppoSAX and other X-ray observatories. Among these, I will review in this paper some recent progress in spectroscopic studies of accreting X-ray pulsars in binary systems (XBPs). First, I will discuss soft excess features observed in the energy spectra of XBPs and propose that it is a common feature for various subclasses of XBPs. Next I will present some recent results of high resolution spectroscopy with ASCA and Chandra.

  12. Constraining black hole masses in low-accreting AGN using X-ray spectra

    CERN Document Server

    Jang, I; Hughes, C; Titarchuk, L

    2014-01-01

    In a recent work we demonstrated that a novel X-ray scaling method, originally introduced for Galactic black holes (GBHs), can be reliably extended to estimate the mass of supermassive black holes accreting at a moderate to high level. Here we investigate the limits of applicability of this method to low-accreting active galactic nuclei, using a control sample with good-quality X-ray data and dynamically measured mass. For low-accreting AGNs, because the basic assumption that the photon index positively correlates with the accretion rate no longer holds the X-ray scaling method cannot be used. Nevertheless, the inverse correlation in the Gamma-Lx/LEdd diagram, found in several low-accreting black holes and confirmed by this sample, can be used to constrain black hole mass within a factor of ~10 from the dynamically determined values. We provide a simple recipe to determine black hole mass using solely X-ray spectral data, which can be used as a sanity check for black hole mass determination based on indirect ...

  13. MAGNETIC-X-RAY DICHROISM - GENERAL FEATURES OF DIPOLAR AND QUADRUPOLAR SPECTRA

    NARCIS (Netherlands)

    CARRA, P; KONIG, H; THOLE, BT; ALTARELLI, M

    1993-01-01

    Sum rules are derived for dipolar linear and quadrupolar circular dichroism in the X-ray region. They relate the intensity of the dichroic signal to the ground state expectation values of orbital and spin dependent effective operators, which act on the valence electrons. The results obtained are

  14. Chandra measurements of a complete sample of X-ray luminous galaxy clusters: the luminosity-mass relation

    Science.gov (United States)

    Giles, P. A.; Maughan, B. J.; Dahle, H.; Bonamente, M.; Landry, D.; Jones, C.; Joy, M.; Murray, S. S.; van der Pyl, N.

    2017-02-01

    We present the results of work involving a statistically complete sample of 34 galaxy clusters, in the redshift range 0.15 ≤ z ≤ 0.3 observed with Chandra. We investigate the luminosity-mass (LM) relation for the cluster sample, with the masses obtained via a full hydrostatic mass analysis. We utilize a method to fully account for selection biases when modelling the LM relation, and find that the LM relation is significantly different from the relation modelled when not account for selection effects. We find that the luminosity of our clusters is 2.2 ± 0.4 times higher (when accounting for selection effects) than the average for a given mass and its mass is 30 per cent lower than the population average for a given luminosity. Equivalently, using the LM relation measured from this sample without correcting for selection biases would lead to the underestimation by 40 per cent of the average mass of a cluster with a given luminosity. Comparing the hydrostatic masses to mass estimates determined from the YX parameter, we find that they are entirely consistent, irrespective of the dynamical state of the cluster.

  15. Detection of X-ray Emission from the Warm-Hot Intergalactic Medium through the Angular Autocorrelation Function with Chandra

    CERN Document Server

    Galeazzi, Massimiliano; Huffenberger, Kevin; Ursino, Eugenio

    2012-01-01

    We have used the angular Autocorrelation Function (AcF) on the angular scale of a few arcminutes to detect and characterize the emission from the Warm-Hot Intergalactic Medium (WHIM) in a pointing with Chandra's ACIS-S instrument. We focused our attention on the energy bands 0.4-0.6 keV, where the WHIM emission is expected to be strongest, due to the redshifted O VII and O VIII lines, and 0.7-0.9 keV, where the WHIM emission is expected to be significantly smaller. After removing identified point sources, and any spurious signal due to detector background and unidentified point sources, in the lower energy band we found a clear AcF signal that we attribute to the WHIM, with a statistical significance of several sigmas (chi2=129, N=31). The attribution of the signal to the WHIM (and not to other spurious emissions, such as unresolved point sources) is confirmed by the higher energy band where the signal is compatible with zero.

  16. Excitation of XPS spectra from nanoscaled particles by local generation of x-rays

    Energy Technology Data Exchange (ETDEWEB)

    Mallinson, Christopher F.; Castle, James E., E-mail: J.castle@surrey.ac.uk [The Surface Analysis Laboratory, Department of Mechanical Engineering Sciences, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2015-09-15

    In preliminary work, the authors have shown that use of an aluminum substrate to support a distribution of copper particles enables their characteristic photoelectrons to be observed within the Auger electron spectrum generated by an incident electron beam. This observation raises the possibility of the use of chemical shifts and the corresponding Auger parameter to identify the chemical states present on the surface of individual submicrometer particles within a mixture. In this context, the technique has an advantage in that, unlike conventional Auger electron spectroscopy, the electron beam does not dwell on the particle but on the substrate adjacent to it. Given the importance, for both medical and toxicological reasons, of the surface composition of such particles, the authors have continued to explore the potential of this development. In this contribution, the authors show that proximal excitation of x-rays is equally successful with magnesium substrates. In some regions of the x-ray photoelectron spectrum, the much larger Auger peaks generated by the electron beam can cause inconvenient clustering of Auger and photoelectron peaks. As in conventional x-ray photoelectron spectroscopy, the ability to switch between Al and Mg sources is useful in such situations. In this context, the authors have extended the studies to iron particles where the authors show that use of Al or Mg substrates, as necessary, can make a contribution to clear identification of individual components in the Fe 2p peaks. For this development in electron spectroscopy to achieve its full potential, it is necessary to optimize the beam conditions used to generate the local x-ray to give good selectivity of a given particle. Measurements made in support of this will be given. Of greater concern is a possible problem of local heating associated with x-ray generation. The authors continue to explore this problem and report some progress in minimizing heating of the particle while maintaining

  17. Analysis of X-ray Spectra of High-Z Elements obtained on Nike with high spectral and spatial resolution

    Science.gov (United States)

    Aglitskiy, Yefim; Weaver, J. L.; Karasik, M.; Serlin, V.; Obenschain, S. P.; Ralchenko, Yu.

    2014-10-01

    The spectra of multi-charged ions of Hf, Ta, W, Pt, Au and Bi have been studied on Nike krypton-fluoride laser facility with the help of two kinds of X-ray spectrometers. First, survey instrument covering a spectral range from 0.5 to 19.5 angstroms which allows simultaneous observation of both M- and N- spectra of above mentioned elements with high spectral resolution. Second, an imaging spectrometer with interchangeable spherically bent Quartz crystals that added higher efficiency, higher spectral resolution and high spatial resolution to the qualities of the former one. Multiple spectral lines with X-ray energies as high as 4 keV that belong to the isoelectronic sequences of Fe, Co, Ni, Cu and Zn were identified with the help of NOMAD package developed by Dr. Yu. Ralchenko and colleagues. In our continuous effort to support DOE-NNSA's inertial fusion program, this campaign covered a wide range of plasma conditions that result in production of relatively energetic X-rays. Work supported by the US DOE/NNSA.

  18. The X-ray spectra of optically selected Seyfert 2 galaxies. Are there any Sy2 galaxies with no absorption?

    CERN Document Server

    Pappa, A; Stewart, G C; Zezas, A L

    2001-01-01

    We present an X-ray spectral analysis of a sample of 8 bona-fide Seyfert 2 galaxies, selected on the basis of their high $[OIII]\\lambda5007$ flux, from the Ho et al. (1997) spectroscopic sample of nearby galaxies. We find that, in general, the X-ray spectra of our Seyfert 2 galaxies are complex, with some our objects having spectra different from the 'typical' spectrum of X-ray selected Seyfert 2 galaxies. Two (NGC3147 and NGC4698) show no evidence for intrinsic absorption. We suggest this is due to the fact that when the torus suppresses the intrinsic medium and hard energy flux, underlying emission from the host galaxy, originating in circumnuclear starbursts, and scattering from warm absorbers contributes in these energy bands more significantly. Our asca data alone cannot discriminate whether low absorption objects are Compton-thick AGN with a strong scattered component or lack an obscuring torus. The most striking example of our low absorption Seyfert 2 is NGC4698. Its spectrum could be explained by eith...

  19. X-ray magnetic and natural circular dichroism from first principles: Calculation of K - and L1-edge spectra

    Science.gov (United States)

    Bouldi, N.; Vollmers, N. J.; Delpy-Laplanche, C. G.; Joly, Y.; Juhin, A.; Sainctavit, Ph.; Brouder, Ch.; Calandra, M.; Paulatto, L.; Mauri, F.; Gerstmann, U.

    2017-08-01

    An efficient first-principles approach to calculate x-ray magnetic circular dichroism (XMCD) and x-ray natural circular dichroism (XNCD) is developed and applied in the near-edge region at the K and L1 edges in solids. Computation of circular dichroism requires precise calculations of x-ray absorption spectra (XAS) for circularly polarized light. For the derivation of the XAS cross section, we used a relativistic description of the photon-electron interaction that results in an additional term in the cross section that couples the electric dipole operator with an operator σ .(ɛ ×r ) that we call the spin position operator. The numerical method relies on pseudopotentials, on the gauge including projected augmented-wave method, and on a collinear spin relativistic description of the electronic structure. We apply the method to calculations of K -edge XMCD spectra of ferromagnetic iron, cobalt, and nickel and of I L1-edge XNCD spectra of α -LiIO3 , a compound with broken inversion symmetry. For XMCD spectra we find that, even if the electric dipole term is the dominant one, the electric quadrupole term is not negligible (8% in amplitude in the case of iron). The term coupling the electric dipole operator with the spin-position operator is significant (28% in amplitude in the case of iron). We obtain a sum rule relating this term to the spin magnetic moment of the p states. In α -LiIO3 we recover the expected angular dependence of the XNCD spectra.

  20. Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography

    Energy Technology Data Exchange (ETDEWEB)

    Paixao, L.; Oliveira, B. B.; Nogueira, M. do S. [Centro de Desenvolvimento da Tecnologia Nuclear, Post-graduation in Science and Technology of Radiations, Minerals and Materials, Pte. Antonio Carlos 6.627, Pampulha, 31270-901 Belo Horizonte (Brazil); Viloria, C. [UFMG, Departamento de Engenharia Nuclear, Post-graduation in Nuclear Sciences and Techniques, Pte. Antonio Carlos 6.627, Pampulha, 31270-901 Belo Horizonte (Brazil); Alves de O, M. [UFMG, Department of Anatomy and Imaging, Prof. Alfredo Balena 190, 30130-100 Belo Horizonte (Brazil); Araujo T, M. H., E-mail: lpr@cdtn.br [Dr Maria Helena Araujo Teixeira Clinic, Guajajaras 40, 30180-100 Belo Horizonte (Brazil)

    2014-08-15

    It is widely accepted that the mean glandular dose (D{sub G}) for the glandular tissue is the more useful magnitude for characterizing the breast cancer risk. The procedure to estimate the D{sub G}, for being difficult to measure it directly in the breast, it is to make the use of conversion factors that relate incident air kerma (K{sub i}) at this dose. Generally, the conversion factors vary with the x-ray spectrum half-value layer and the breast composition and thickness. Several authors through computer simulations have calculated such factors by the Monte Carlo (Mc) method. Many spectral models for D{sub G} computer simulations purposes are available in the diagnostic range. One of the models available generates unfiltered spectra. In this work, the Monte Carlo EGSnrc code package with the C++ class library (eg spp) was employed to derive filtered tungsten x-ray spectra used in digital mammography systems. Filtered spectra for rhodium and aluminium filters were obtained for tube potentials between 26 and 32 kV. The half-value layer of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F and Mam Detector Platinum and 8201023-C Xi Base unit Platinum Plus w m As in a Hologic Selenia Dimensions system using a Direct Radiography mode. Calculated half-value layer values showed good agreement compared to those obtained experimentally. These results show that the filtered tungsten anode x-ray spectra and the EGSnrc Mc code can be used for D{sub G} determination in mammography. (Author)

  1. A Deep Chandra ACIS Study of NGC 4151. I. the X-ray Morphology of the 3 kpc-diameter Circum-nuclear Region and Relation to the Cold Interstellar Medium

    CERN Document Server

    Wang, Junfeng; Risaliti, Guido; Elvis, Martin; Karovska, Margarita; Zezas, Andreas; Mundell, Carole G; Dumas, Gaelle; Schinnerer, Eva

    2011-01-01

    We report on the imaging analysis of 200 ks sub-arcsecond resolution Chandra ACIS-S observations of the nearby Seyfert 1 galaxy NGC 4151. Bright, structured soft X-ray emission is observed to extend from 30 pc to 1.3 kpc in the south-west from the nucleus, much farther than seen in earlier X-ray studies. The terminus of the north-eastern X-ray emission is spatially coincident with a CO gas lane, where the outflow likely encounters dense gas in the host galactic disk. X-ray emission is also detected outside the boundaries of the ionization cone, which indicates that the gas there is not completely shielded from the nuclear continuum, as would be the case for a molecular torus collimating the bicone. In the central r<200 pc region, the subpixel processing of the ACIS data recovers the morphological details on scales of <30~pc (<0.5") first discovered in Chandra HRC images. The X-ray emission is more absorbed towards the boundaries of the ionization cone, as well as perpendicular to the bicone along the...

  2. On the power spectra of the wind-fed X-ray binary pulsar GX 301 - 2

    Science.gov (United States)

    Orlandini, Mauro; Morfill, G. E.

    1992-01-01

    A phenomenological model of accretion which is applied to the wind-fed X-ray binary pulsar GX 301 - 2 is developed, assuming that the accretion onto the neutron star does not occur from a continuous flux of plasma, but from blobs of matter which are threaded by the magnetic field lines onto the magnetic polar caps of the neutron star. These 'lumps' are produced at the magnetospheric limit by magnetohydrodynamical instability, introducing a 'noise' in the accretion process, due to the discontinuity in the flux of matter onto the neutron star. This model is able to describe the change of slope observed in the continuum component of the power spectra of the X-ray binary pulsar GX 301 - 2, in the frequency range 0.01 - 0.1 Hz. The physical properties of the infalling blobs derived in the model are in agreement with the constraints imposed by observations.

  3. X-ray spectra and electronic structure of the Ca3Ga2Ge3О12 compound

    Science.gov (United States)

    Shcherba, I. D.; Kostyk, L. V.; Noga, H.; Bekenov, L. V.; Uskokovich, D.; Jatsyk, B. M.

    2017-09-01

    The band structure of Ca3Ga2Ge3О12 with the garnet structure has been determined for the first time by X-ray emission and photoelectron spectroscopy. It has been established that the bottom of the valence band is formed by Ge d states, which are not dominant in the chemical bonding. Strong hybridization of oxygen 2s states with 4p states of Ga and Ge revealed by the presence of an extra structure in the X-ray emission spectra has been found. The middle of the valence band has been demonstrated to be occupied by d states of Ga, while Ga and Ge 4рstates with a considerable admixture of oxygen 2p states form the top of the valence band.

  4. Identification of Faint Chandra X-ray Sources in the Core-Collapsed Globular Cluster NGC 6397: Evidence for a Bimodal Cataclysmic Variable Population

    CERN Document Server

    Cohn, Haldan N; Couch, Sean M; Anderson, Jay; Cool, Adrienne M; Berg, Maureen van den; Bogdanov, Slavko; Heinke, Craig O; Grindlay, Jonathan E; 10.1088/0004-637X/722/1/20

    2011-01-01

    We have searched for optical identifications for 79 Chandra X-ray sources that lie within the half-mass radius of the nearby, core-collapsed globular cluster NGC 6397, using deep Hubble Space Telescope Advanced Camera for Surveys Wide Field Channel imaging in H-alpha, R, and B. Photometry of these images allows us to classify candidate counterparts based on color-magnitude diagram location. In addition to recovering nine previously detected cataclysmic variables (CVs), we have identified six additional faint CV candidates, a total of 42 active binaries (ABs), two millisecond pulsars (MSPs), one candidate active galactic nucleus, and one candidate interacting galaxy pair. Of the 79 sources, 69 have a plausible optical counterpart. The 15 likely and possible CVs in NGC 6397 mostly fall into two groups: a brighter group of six for which the optical emission is dominated by contributions from the secondary and accretion disk, and a fainter group of seven for which the white dwarf dominates the optical emission. T...

  5. High-Energy Processes in Young Stars: Chandra X-ray Spectroscopy of HDE 283572, RY Tau, and LkCa 21

    CERN Document Server

    Audard, M; Smith, K W; Güdel, M; Pallavicini, R; Audard, Marc; Skinner, Stephen L.; Smith, Kester W.; Guedel, Manuel; Pallavicini, Roberto

    2004-01-01

    Weak-lined T Tauri stars (WTTS) represent the important stage of stellar evolution between the accretion phase and the zero-age main sequence. At this stage, the star decouples from its accretion disk, and spins up to a higher rotation rate than in the preceding classical T Tauri phase. Consequently, dynamo processes can be expected to become even stronger at this stage. High energy processes can have effects on the remaining circumstellar material, possibly including protoplanets and planetesimals, and these effects may account for certain observable properties of asteroids in the current solar system. Chandra observed for 100 ks the WTTS HDE 283572 which probes the PMS stage of massive A-type stars. We present first results of the analysis of its high-resolution X-ray spectrum obtained with the High-Energy Transmission Grating Spectrometer. A wide range of Fe lines of high ionization states are observed, indicating a continuous emission measure distribution. No significant signal is detected longward of the...

  6. A broadband X-ray spectral study of the intermediate-mass black hole candidate M82 X-1 with NuSTAR, Chandra and Swift

    CERN Document Server

    Brightman, Murray; Barret, Didier; Davis, Shane W; Fürst, Felix; Madsen, Kristin K; Middleton, Matthew; Miller, Jon M; Stern, Daniel; Tao, Lian; Walton, Dominic J

    2016-01-01

    M82 X-1 is one of the brightest ultraluminous X-ray sources (ULXs) known, which, assuming Eddington-limited accretion and other considerations, makes it one of the best intermediate-mass black hole (IMBH) candidates. However, the ULX may still be explained by super-Eddington accretion onto a stellar-remnant black hole. We present simultaneous NuSTAR, Chandra and Swift/XRT observations during the peak of a flaring episode with the aim of modeling the emission of M82 X-1 and yielding insights into its nature. We find that thin-accretion disk models all require accretion rates at or above the Eddington limit in order to reproduce the spectral shape, given a range of black hole masses and spins. Since at these high Eddington ratios the thin-disk model breaks down due to radial advection in the disk, we discard the results of the thin-disk models as unphysical. We find that the temperature profile as a function of disk radius ($T(r)\\propto r^{-p}$) is significantly flatter ($p=0.55^{+ 0.07}_{- 0.04}$) than expecte...

  7. Signatures of X-ray reverberation in the power spectra of AGN

    CERN Document Server

    Papadakis, I; Dovciak, M; Epitropakis, A; Emmanoulopoulos, D; Karas, V

    2016-01-01

    We compute fully relativistic disc response functions in the case of the "lamp-post" geometry using the full observed reflection spectrum for various X-ray source heights, disc inclination, and spin values of the central black hole. Since the observed PSD is equal to the product of the intrinsic power spectrum with the "transfer function" (i.e. the Fourier transform of the disc response function), we are able to predict the observed PSDs in the case of X-ray illumination of the inner disc. The observed PSD should show a prominent dip at high frequencies and an oscillatory behaviour, with a decreasing amplitude, at higher frequencies. The reverberation "echo" features should be more prominent in energy bands where the reflection component is more pronounced. The frequency of the dip is independent of energy, and it is mainly determined by the black hole mass and the X-ray source height. The amplitude of the dip increases with increasing black hole spin and inclination angle, as long as the height of the "lamp"...

  8. Autonomous Modelling of X-ray Spectra Using Robust Global Optimization Methods

    Science.gov (United States)

    Rogers, Adam; Safi-Harb, Samar; Fiege, Jason

    2015-08-01

    The standard approach to model fitting in X-ray astronomy is by means of local optimization methods. However, these local optimizers suffer from a number of problems, such as a tendency for the fit parameters to become trapped in local minima, and can require an involved process of detailed user intervention to guide them through the optimization process. In this work we introduce a general GUI-driven global optimization method for fitting models to X-ray data, written in MATLAB, which searches for optimal models with minimal user interaction. We directly interface with the commonly used XSPEC libraries to access the full complement of pre-existing spectral models that describe a wide range of physics appropriate for modelling astrophysical sources, including supernova remnants and compact objects. Our algorithm is powered by the Ferret genetic algorithm and Locust particle swarm optimizer from the Qubist Global Optimization Toolbox, which are robust at finding families of solutions and identifying degeneracies. This technique will be particularly instrumental for multi-parameter models and high-fidelity data. In this presentation, we provide details of the code and use our techniques to analyze X-ray data obtained from a variety of astrophysical sources.

  9. On the soft X-ray spectra of $\\gamma$-loud blazars

    CERN Document Server

    Comastri, A; Ghisellini, G; Molendi, S

    1996-01-01

    ROSAT observations of a large sample of bright gamma-ray (E > 100 MeV) blazars are presented. Results of a detailed spectral analysis in the soft energy distribution with particular emphasis on the relation between X-ray and gamma-ray properties. A significant anti-correlation between X-ray and gamma-ray spectral shapes of flat radio spectrum quasars (FSRQ) and BL Lacs has been discovered. A different shape in the overall energy distributions from radio to gamma-ray energies between FSRQ and BL Lacs is also implied by the correlation of their broad-band spectral indices $\\alpha_{ro}$ and $\\alpha_{x emission and the hard X-ray to gamma-ray emission originate from the same electron population, via, respectively, the synchrotron process and the inverse Compton mechanism. We suggest that a key parameter for understanding the overall energy distributions of both classes of objects is the energy at which the synchrotron emission peaks in a $\

  10. Near-Infrared Spectroscopy of Faint Discrete X-ray Point Sources Constituting the Galactic Ridge X-ray Emission

    CERN Document Server

    Morihana, Kumiko; Dubath, Pierre; Yoshida, Tessei; Suzuki, Kensuke; Ebisawa, Ken

    2016-01-01

    The Galactic Ridge X-ray Emission (GRXE) is apparently extended X-ray emission along the Galactic Plane. The X-ray spectrum is characterized by hard continuum with a strong Fe K emission feature in the 6-7 keV band. A substantial fraction (~80%) of the GRXE in the Fe band was resolved into point sources by deep Chandra imaging observations, thus GRXE is mostly composed of dim Galactic X-ray point sources at least in this energy band. To investigate the populations of these dim X-ray point sources, we carried out Near-Infrared (NIR) follow-up spectroscopic observations in two deep Chandra fields located in the Galactic plane at (l,b)=(0.1{\\arcdeg}, -1.4{\\arcdeg}) and (28.5{\\arcdeg}, 0.0{\\arcdeg}) using NTT/SofI and Subaru/MOIRCS. We obtained well-exposed NIR spectra from 65 objects and found that there are three main classes of Galactic sources based on the X-ray color and NIR spectral features: those having (A) hard X-ray spectra and NIR emission features such as HI(Br{\\gamma}), HeI, and HeII (2 objects), (B)...

  11. Correction of diagnostic x-ray spectra measured with CdTe and CdZnTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, M. [Osaka Univ., Suita (Japan). Medical School; Kanamori, H.; Toragaito, T.; Taniguchi, A.

    1996-07-01

    We modified the formula of stripping procedure presented by E. Di. Castor et al. We added the Compton scattering and separated K{sub {alpha}} radiation of Cd and Te (23 and 27keV, respectively). Using the new stripping procedure diagnostic x-ray spectra (object 4mm-Al) of tube voltage 50kV to 100kV for CdTe and CdZnTe detectors are corrected with comparison of those spectra for the Ge detector. The corrected spectra for CdTe and CdZnTe detectors coincide with those for Ge detector at lower tube voltage than 70kV. But the corrected spectra at higher tube voltage than 70kV do not coincide with those for Ge detector. The reason is incomplete correction for full energy peak efficiencies of real CdTe and CdZnTe detectors. (J.P.N.)

  12. SU-E-I-76: Matching Primary and Scattered X-Ray Spectra for Use in Calculating the Diagnostic Radiation Index of Protection

    Energy Technology Data Exchange (ETDEWEB)

    Pasciak, A [University of Tennessee Medical Center, Knoxville, TN (United States); Jones, A [MD Anderson Cancer Center, Houston, TX (United States); Wagner, L [UT Medical School, Houston, TX (United States)

    2014-06-01

    Purpose: Lightweight lead-free or lead-composite protective garments exploit k-edge interactions to attenuate scattered X-rays. Manufacturers specify the protective value of garments in terms of lead equivalence at a single kVp. This is inadequate, as the protection provided by such garments varies with radiation quality in different use conditions. We present a method for matching scattered X-ray spectra to primary X-ray spectra. The resulting primary spectra can be used to measure penetration through protective garments, and such measurements can be weighted and summed to determine a Diagnostic Radiation Index for Protection (DRIP). Methods: Scattered X-ray spectra from fluoroscopic procedures were modeled using Monte Carlo techniques in MCNP-X 2.7. Data on imaging geometry, operator position, patient size, and primary beam spectra were gathered from clinical fluoroscopy procedures. These data were used to generate scattered X-ray spectra resulting from procedural conditions. Technical factors, including kV and added filtration, that yielded primary X-ray spectra that optimally matched the generated scattered X-ray spectra were identified through numerical optimization using a sequential quadratic programming (SQP) algorithm. Results: The primary spectra generated with shape functions matched the relative flux in each bin of the scattered spectra within 5%, and half and quarter-value layers matched within 0.1%. The DRIP for protective garments can be determined by measuring the penetration through protective garments using the matched primary spectra, then calculating a weighted average according to the expected clinical use of the garment. The matched primary spectra are specified in terms of first and second half-value layers in aluminum and acrylic. Conclusion: Lead equivalence is inadequate for completely specifying the protective value of garments. Measuring penetration through a garment using full scatter conditions is very difficult. The primary spectra

  13. Indirect measure of X-rays spectra using TLDs; Medicion indirecta de espectros de rayos X utilizando TLDs

    Energy Technology Data Exchange (ETDEWEB)

    Bonzi, E. V.; Mainardi, R. T. [Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y Fisica, Av. Haya de la Torre y Av. Medina Allende s/n, Ciudad Universitaria, X5016LEA Cordoba (Argentina)

    2011-10-15

    A methodology of indirect measure of X-rays spectra, emitted by conventional tubes, was developed recently and its feasibility verified in the first place by Monte Carlo simulations. For that case is intended to measure, by means of plastic scintillators, attenuation curves of dispersed beams previously. In this work were carried out measurements of attenuation curves with thermoluminescent dosimeters (TLD) to verify the kindness of the indirect measure method. The attenuation curve was also measured using an ionization chamber brand Capintec (model 192) with the purpose of making a comparison. The results of the attenuation curve measured with both dosimeters present a good resolution inside the statistical fluctuations and the spectral reconstruction using diverse parametric functions is carried out in a quick and simple way with excellent resolutions in the functional form. For this reconstruction method are of fundamental importance the following properties of the used dosimeter: in the first place the repetition of the measures, property that could check; in second place the precision of the measured data and lastly the dosimeter response, this is, the increase of the thermoluminescent signal before an increase of the photons flow of X-rays. This parameter is the gradient of the curve thermoluminescent signal versus the dose imparted to the dosimeter. The measures were realized with a generator of X-rays brand Kevex provided of a conventional tube with tungsten anti cathode that polarizes with high tension to a maximum value of 50 kV and current of 0.5 ma. (Author)

  14. Structure of dimethylphenyl betaine hydrochloride studied by X-ray diffraction, DFT calculation, NMR and FTIR spectra

    Science.gov (United States)

    Szafran, M.; Katrusiak, A.; Dega-Szafran, Z.; Kowalczyk, I.

    2013-01-01

    The structure of dimethylphenyl betaine hydrochloride (1) has been studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra. The crystals are monoclinic, space group P21/c. In the crystal, the Cl- anion is connected with protonated betaine through the O-H⋯Cl- hydrogen bond of 2.943(2) Å. The structures in the gas phase (2) and water solution (3) have been optimized by the B3LYP/6-311++G(d,p) approach and the geometrical results have been compared with the X-ray data of 1. The FTIR spectrum of the solid compound is consistent with the X-ray results. The probable assignments of the anharmonic experimental vibrational frequencies of the investigated chloride (1) based on the calculated harmonic frequencies in water solution (3) are proposed. The correlations between the experimental 1H and 13C NMR chemical shifts (δexp) of 1 in D2O and the magnetic isotropic shielding constants (σcalc) calculated by the GIAO/B3LYP/6-311G++(d,p) approach, using the screening solvation model (COSMO), δexp = a + b σcalc, for optimized molecule 3 in water solution are linear and correctly reproduce the experimental chemical shifts.

  15. X-Ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Ostorero, L.; /Turin U. /INFN, Turin; Moderski, R.; /Warsaw, Copernicus Astron. Ctr. /KIPAC, Menlo Park; Stawarz, L.; /KIPAC, Menlo Park /Jagiellonian U., Astron. Observ.; Diaferio, A.; /Turin U. /INFN, Turin; Kowalska, I.; /Warsaw U. Observ.; Cheung, C.C.; /NASA, Goddard /Naval Research Lab, Wash., D.C.; Kataoka, J.; /Waseda U., RISE; Begelman, M.C.; /JILA, Boulder; Wagner, S.J.; /Heidelberg Observ.

    2010-06-07

    In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the GPS spectral energy distribution (SED) with the source expansion, predicting significant and complex high-energy emission, from the X-ray to the {gamma}-ray frequency domain. Here, we test this model with the broad-band SEDs of a sample of eleven X-ray emitting GPS galaxies with Compact-Symmetric-Object (CSO) morphology, and show that: (i) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism; (ii) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk dominated scenario. We also show that the relation between the hydrogen column densities derived from the X-ray (N{sub H}) and radio (N{sub HI}) data of the sources is suggestive of a positive correlation, which, if confirmed by future observations, would provide further support to our scenario of high-energy emitting lobes.

  16. X-ray spectra and time variability of active galactic nuclei

    Science.gov (United States)

    Mushotzky, Richard F.; Done, Christine; Pounds, Kenneth A.

    1993-01-01

    The history and the present status of X-ray observations of AGN are outlined with reference to Seyfert Is, Seyfert IIs, and quasars. Fe K emission lines, other distortions at E greater tha 6 keV, excess emission below 2 keV, absorption, and ionized material are discussed. The continuum flux variability and line variability in Seyfert Is and the continuum variability in Seyfert IIs are examined. Models and theories of the continuum are reviewed, and the total energy budget of AGN and their similarity to Galactic black holes are also discussed.

  17. Pulsator-like Spectra from Ultraluminous X-Ray Sources and the Search for More Ultraluminous Pulsars

    Science.gov (United States)

    Pintore, F.; Zampieri, L.; Stella, L.; Wolter, A.; Mereghetti, S.; Israel, G. L.

    2017-02-01

    Ultraluminous X-ray sources (ULXs) are a population of extragalactic objects whose luminosity exceeds the Eddington limit for a 10 M ⊙ black hole (BH). Their properties have been widely interpreted in terms of accreting stellar-mass or intermediate-mass BHs. However at least three neutron stars (NSs) have been recently identified in ULXs through the discovery of periodic pulsations. Motivated by these findings we studied the spectral properties of a sample of bright ULXs using a simple continuum model which was extensively used to fit the X-ray spectra of accreting magnetic NSs in the Galaxy. We found that such a model, consisting of a power-law with a high-energy exponential cut-off, fits most of the ULX spectra analyzed here very well, at a level comparable to that of models involving an accreting BH. On these grounds alone we suggest that other non-pulsating ULXs may host NSs. We also found that above 2 keV the spectrum of known pulsating ULXs is harder than that of the majority of the other ULXs of the sample, with only IC 342 X-1 and Ho IX X-1 displaying spectra of comparable hardness. We thus suggest that these two ULXs may host an accreting NS and encourage searches for periodic pulsations in the flux.

  18. X-Ray Reflected Spectra from Accretion Disk Models. III. A Complete Grid of Ionized Reflection Calculations

    Science.gov (United States)

    García, J.; Dauser, T.; Reynolds, C. S.; Kallman, T. R.; McClintock, J. E.; Wilms, J.; Eikmann, W.

    2013-05-01

    We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk. The spectra were computed using an updated version of our code XILLVER that incorporates new routines and a richer atomic database. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index Γ of the illuminating radiation, the ionization parameter ξ at the surface of the disk (i.e., the ratio of the X-ray flux to the gas density), and the iron abundance A Fe relative to the solar value. The ranges of the parameters covered are 1.2 law flux. The models are expected to provide an accurate description of the Fe K emission line, which is the crucial spectral feature used to measure black hole spin. A total of 720 reflection spectra are provided in a single FITS file (http://hea-www.cfa.harvard.edu/~javier/xillver/) suitable for the analysis of X-ray observations via the atable model in XSPEC. Detailed comparisons with previous reflection models illustrate the improvements incorporated in this version of XILLVER.

  19. HEAO 1 A-2 low-energy detector X-ray spectra of the Lupus Loop and SN 1006

    Science.gov (United States)

    Leahy, D. A.; Nousek, J.; Hamilton, A. J. S.

    1991-01-01

    The Lupus Loop and SN 1006 were observed by the A-2 low-energy detector proportional counters on the HEAO 1 satellite as part of the all-sky survey. As a result of a major advance in understanding of detector response and background accurate analysis of the data has become possible. Soft X-ray spectra for both supernova remnants were constructed from the PHA data taken during the scanning observations. Single-temperature and two-temperature Raymond-Smith models were fitted to the observed spectra. In addition, power-law and power-law plus one-temperature models were fitted to the spectrum of SN 1006. Only two-component models provide an adequate description for both Lupus Loop and SN 1006 spectra. The temperatures, column densities, and emission measures are significantly more accurate than previous results.

  20. Akn 564 an unusual component in the X-ray spectra of NLSy1 galaxies

    CERN Document Server

    Turner, T J; Netzer, H; Netzer, Hagai

    1999-01-01

    We present an ASCA observation of the NLSy1 Ark 564. The X-ray light curve shows rapid variability, but no evidence for energy-dependence to these variations, within the 0.6 -- 10 keV bandpass. A strong (EW ~ 70 eV) spectral feature is observed close to 1 keV. A similar feature has been observed in TON S180 (another NLSy1) but has not been observed in broad-line Seyfert galaxies. The feature energy suggests a large contribution from Fe L-shell lines but its intensity is difficult to explain in terms of emission and/or absorption from photoionized gas. Models based on gas in thermal equilibrium with kT ~1 keV provide an alternative parameterization of the soft spectrum. The latter may be interpreted as the hot intercloud medium, undergoing rapid cooling and producing strong Fe L-shell recombination lines. In all cases the physical conditions are rather different from those observed in broad-line Seyferts. The hard X-ray spectrum shows a broad and asymmetric Fe Kalpha line of large equivalent width (~550 eV) wh...

  1. JOINT ANALYSIS OF CLUSTER OBSERVATIONS. II. CHANDRA/XMM-NEWTON X-RAY AND WEAK LENSING SCALING RELATIONS FOR A SAMPLE OF 50 RICH CLUSTERS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Mahdavi, Andisheh [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94131 (United States); Hoekstra, Henk [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Babul, Arif; Bildfell, Chris [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Jeltema, Tesla [Santa Cruz Institute for Particle Physics, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Henry, J. Patrick [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2013-04-20

    We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15% {+-} 6% intrinsic scatter at r{sub 500}{sup WL} (the pseudo-pressure Y{sub X} yields a consistent scatter of 22% {+-} 5%). The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small brightest cluster galaxy (BCG) to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller (<10%) deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure Y{sub X} does not discriminate between the more relaxed and less relaxed populations, making it perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic masses underestimate weak lensing masses by 10% on the average at r{sub 500}{sup WL}; but cool-core clusters are consistent with no bias, while non-cool-core clusters have a large and constant 15%-20% bias between r{sub 2500}{sup WL} and r{sub 500}{sup WL}, in agreement with N-body simulations incorporating unthermalized gas. For non-cool-core clusters, the bias correlates well with BCG ellipticity. We also examine centroid shift variance and power ratios to quantify substructure; these quantities do not correlate with residuals in the scaling relations. Individual clusters have for the most part forgotten the source of their departures from self-similarity.

  2. Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra.

    Science.gov (United States)

    Takegami, Kazuki; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi; Maehata, Itsumi; Kanazawa, Yuki; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

    2016-07-01

    Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1-20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector. Then, with the following two experimental settings, corresponding X-ray spectra were measured with 40-120 kVp and 0.5-1000 mAs at a source-to-detector distance of 100 cm: (1) X-rays penetrating a soft-tissue-equivalent phantom with the OSL dosimeter attached directly on the phantom, and (2) X-rays penetrating only the soft-tissue-equivalent phantom. Next, the energy fluence and errors in the fluence were calculated from the spectra. When the energy fluence with errors concerning these two experimental conditions was estimated to be indistinctive, we defined the condition as the OSL dosimeter not being identified on the X-ray image. Based on our analysis, we determined the identification limit of the dosimeter. We then compared our results with those for the general irradiation conditions used in clinics. We found that the OSL dosimeter could not be identified under the irradiation conditions of abdominal and chest radiography, namely, one can apply the OSL dosimeter to measurement of the exposure dose in the irradiation field of X-rays without disturbing medical images.

  3. A Coordinated X-ray and Optical Campaign on the Nearest Massive Eclipsing Binary, Delta Ori Aa: I. Overview of the X-ray Spectrum

    CERN Document Server

    Corcoran, M F; Pablo, H; Shenar, T; Pollock, A M T; Waldron, W L; Moffat, A F J; Richardson, N D; Russell, C M P; Hamaguchi, K; Huenemoerder, D P; Oskinova, L; Hamann, W -R; Naze, Y; Ignace, R; Evans, N R; Lomax, J R; Hoffman, J L; Gayley, K; Owocki, S P; Leutenegger, M; Gull, T R; Hole, K T; Lauer, J; Iping, R C

    2015-01-01

    We present an overview of four phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system which includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object which can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary, Delta Ori A provides a unique system with which to test the spatial distribution of the X-ray emitting gas around Delta Ori Aa1 via occultation by the photosphere of and wind cavity around the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ksec and covering nearly the entire binary orbit. Companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities simultaneous with the X-ray data to better constrain the system parame...

  4. The X-ray Variability of Eta Car, 1996-2010

    Science.gov (United States)

    Corcoran, Michael F.; Hamaguchi, K.; Gull, T.; Owocki, S.; Pittard, J.

    2010-01-01

    X-ray photometry in the 2-10 keY band of the the supermassive binary star Eta Car has been measured with the Rossi X-ray Timing Explorer from 1996-2010. The ingress to X-ray minimum is consistent with a period of 2024 days. The 2009 X-ray minimum began on January 162009 and showed an unexpectedly abrupt recovery starting after 12 Feb 2009. The X-ray colors become harder about half-way through all three minima and continue until flux recovery. The behavior of the fluxes and X-ray colors for the most recent X-ray minimum, along with Chandra high resolution grating spectra at key phases suggests a significant change in the inner wind of Eta Car, a possible indicator that the star is entering a new unstable phase of mass loss.

  5. The X-ray Variability of Eta Car, 1996-2010

    Science.gov (United States)

    Corcoran, Michael F.; Hamaguchi, K.; Gull, T.; Owocki, S.; Pittard, J.

    2010-01-01

    X-ray photometry in the 2-10 keY band of the the supermassive binary star Eta Car has been measured with the Rossi X-ray Timing Explorer from 1996-2010. The ingress to X-ray minimum is consistent with a period of 2024 days. The 2009 X-ray minimum began on January 162009 and showed an unexpectedly abrupt recovery starting after 12 Feb 2009. The X-ray colors become harder about half-way through all three minima and continue until flux recovery. The behavior of the fluxes and X-ray colors for the most recent X-ray minimum, along with Chandra high resolution grating spectra at key phases suggests a significant change in the inner wind of Eta Car, a possible indicator that the star is entering a new unstable phase of mass loss.

  6. The kinematics and chemical stratification of the type Ia supernova remnant 0519-69.0 : an XMM-Newton and Chandra study

    NARCIS (Netherlands)

    Kosenko, D.; Helder, E.A.; Vink, J.

    2010-01-01

    We present a detailed analysis of the XMM-Newton and Chandra X-ray data of the young type Ia supernova remnant SNR 0519-69.0, which is situated in the Large Magellanic Cloud. We used data from both the Chandra ACIS and XMM-Newton EPIC MOS instruments, and high resolution X-ray spectra obtained with

  7. X-Ray Spectral Analyses of AGNs from the 7Ms Chandra Deep Field-South Survey: The Distribution, Variability, and Evolutions of AGN Obscuration

    Science.gov (United States)

    Liu, Teng; Tozzi, Paolo; Wang, Jun-Xian; Brandt, William N.; Vignali, Cristian; Xue, Yongquan; Schneider, Donald P.; Comastri, Andrea; Yang, Guang; Bauer, Franz E.; Paolillo, Maurizio; Luo, Bin; Gilli, Roberto; Wang, Q. Daniel; Giavalisco, Mauro; Ji, Zhiyuan; Alexander, David M.; Mainieri, Vincenzo; Shemmer, Ohad; Koekemoer, Anton; Risaliti, Guido

    2017-09-01

    We present a detailed spectral analysis of the brightest active galactic nuclei (AGNs) identified in the 7Ms Chandra Deep Field-South (CDF-S) survey over a time span of 16 years. Using a model of an intrinsically absorbed power-law plus reflection, with possible soft excess and narrow Fe Kα line, we perform a systematic X-ray spectral analysis, both on the total 7Ms exposure and in four different periods with lengths of 2–21 months. With this approach, we not only present the power-law slopes, column densities {N}{{H}}, observed fluxes, and absorption-corrected 2–10 keV luminosities L X for our sample of AGNs, but also identify significant spectral variabilities among them on timescales of years. We find that the {N}{{H}} variabilities can be ascribed to two different types of mechanisms, either flux-driven or flux-independent. We also find that the correlation between the narrow Fe line EW and {N}{{H}} can be well explained by the continuum suppression with increasing {N}{{H}}. Accounting for the sample incompleteness and bias, we measure the intrinsic distribution of {N}{{H}} for the CDF-S AGN population and present reselected subsamples that are complete with respect to {N}{{H}}. The {N}{{H}}-complete subsamples enable us to decouple the dependences of {N}{{H}} on L X and on redshift. Combining our data with those from C-COSMOS, we confirm the anticorrelation between the average {N}{{H}} and L X of AGN, and find a significant increase of the AGN-obscured fraction with redshift at any luminosity. The obscured fraction can be described as {f}{obscured}≈ 0.42 {(1+z)}0.60.

  8. Modelling lightcurves and spectra of transient Anomalous X-ray Pulsars

    CERN Document Server

    Zane, S; Turolla, R; Israel, G L; Nobili, L; Stella, L

    2011-01-01

    We present the first detailed joint modelling of both the timing and spectral properties during the outburst decay of transient anomalous X-ray pulsars. We consider the two sources XTE J1810-197 and CXOU J164710.2-455216, and describe the source decline in the framework of a twisted magnetosphere model, using Monte Carlo simulations of magnetospheric scattering and mimicking localized heat deposition at the NS surface following the activity. Our results support a picture in which a limited portion of the star surface close to one of the magnetic poles is heated at the outburst onset. The subsequent evolution is driven both by the cooling/varying size of the heated cap and by a progressive untwisting of the magnetosphere.

  9. Modelling lightcurves and spectra of transient Anomalous X-ray Pulsars

    Science.gov (United States)

    Zane, S.; Albano, A.; Turolla, R.; Israel, G. L.; Nobili, L.; Stella, L.

    2011-09-01

    We present the first detailed joint modelling of both the timing and spectral properties during the outburst decay of transient anomalous X-ray pulsars. We consider the two sources XTE J1810-197 and CXOU J164710.2-455216, and describe the source decline in the framework of a twisted magnetosphere model, using Monte Carlo simulations of magnetospheric scattering and mimicking localized heat deposition at the NS surface following the activity. Our results support a picture in which a limited portion of the star surface close to one of the magnetic poles is heated at the outburst onset. The subsequent evolution is driven both by the cooling/varying size of the heated cap and by a progressive untwisting of the magnetosphere.

  10. X-ray spectra of Hercules X-1. I - Iron line fluorescence from a subrelativistic shell

    Science.gov (United States)

    Pravdo, S. H.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.; Swank, J. H.

    1977-01-01

    The X-ray spectrum of Her X-1 was observed in the energy range from 2 to 24 keV from August 29 to September 3, 1975. Emission features are observed near the K-alpha iron-line energy which exhibit both broadening and a double line structure. The total luminosity in these features is about 4 by 10 to the 35th power ergs/s. Iron line fluorescence from an opaque cool (not exceeding 1 million K) shell of material at the Alfven surface provides the necessary luminosity in this feature. The double line structure and the line energy width can be due to Doppler shifts if the shell is forced to corotate with the pulsar at a radius of at least 800 million cm. Implications of this model regarding physical conditions near Her X-1 are discussed.

  11. Recombination-cascade X-ray spectra of highly charged helium-like ions

    Science.gov (United States)

    Pradhan, A. K.

    1985-01-01

    It is shown that the relative intensity distribution among the X-ray spectral lines of helium-like ions from the n = 2 states produced through recombination processes such as radiative and charge transfer recombination may be given by considering in detail the radiative cascades following recombination. Model calculations are presented with predicted line ratios for Ar XVII and Fe XXV in recombination-dominated noncoronal plasmas. In particular, compared to coronal intensities, the singlet resonance line (w) should be much weaker relative to the triplet intercombination (x, y) and forbidden (z) lines, yielding large values for the ratio G = (x + y + z)/w. Accurate configuration interaction type wave functions are employed to calculate the eigenenergies, transition probabilities, and cascade coefficients. Certain relevant tokamak and astrophysical observations are discussed.

  12. Arcus: The next generation of high-resolution X-ray grating spectra

    Science.gov (United States)

    Smith, Randall

    2014-11-01

    We present the design and scientific motivation for Arcus, an X-ray grating spectrometer mission to be deployed on the International Space Station. This mission will observe structure formation at and beyond the edges of clusters and galaxies, feedback from supermassive black holes, the structure of the interstellar medium and the formation and evolution of stars. Key mission requirements will be R>2500 and >600 cm^2 of effective area at the crucial O VII and O VIII lines, with the full bandpass going from 8-52Å, with an overall minimum resolution of 1300 and effective area >150 cm^2. We will use the silicon pore optics proposed for ESA's Athena mission, paired with off-plane gratings being developed at the University of Iowa and combined with MIT/Lincoln Labs CCDs.

  13. Accuracy of Mass and Radius Determination for Neutron Stars in X-ray Bursters from Simulated LOFT Spectra

    Science.gov (United States)

    Majczyna, A.; Madej, J.; Różańska, A.; Należyty, M.

    2017-06-01

    We present a simulation of an X-ray spectrum of a hot neutron star, as would be seen by the LAD detector on board of LOFT satellite. We also compute a grid of theoretical spectra corresponding to a range of effective temperatures Teff and surface gravities log g with values corresponding to compact stars in Type I X-ray bursters. A neutron star with the mass M=1.64 M⊙ and the radius R=11.95 km (which yields the surface gravity log g=14.30 [cgs] and the surface redshift z=0.30) is used in simulation. Accuracy of mass and radius determination by fitting theoretical spectra to the observed one is found to be M=1.64+0.16-0.02 M⊙ and R=11.95+1.57-0.40 km (2σ). The confidence contours for these two variables are narrow but elongated, and therefore the resulting constraints on the EOS cannot be strong. Note, that in this paper we aim to discuss error contours of NS mass and radius, whereas discussion of EOS is beyond the scope of this work.

  14. Bayesian inference of x-ray diffraction spectra from warm dense matter with the one-component-plasma model

    Science.gov (United States)

    Clérouin, Jean; Desbiens, Nicolas; Dubois, Vincent; Arnault, Philippe

    2016-12-01

    We show that the Bayesian inference of recently measured x-ray diffraction spectra from laser-shocked aluminum [L. B. Fletcher et al., Nat. Photon. 9, 274 (2015), 10.1038/nphoton.2015.41] with the one-component-plasma (OCP) model performs remarkably well at estimating the ionic density and temperature. This statistical approach requires many evaluations of the OCP static structure factor, which were done using a recently derived analytic fit. The atomic form factor is approximated by an exponential function in the diffraction window of the first peak. The electronic temperature is then estimated from a comparison of this approximated form factor with the electronic structure of an average atom model. Out-of-equilibrium states, with electrons hotter than ions, are diagnosed for the spectra obtained early after the pump, whereas at a late time delay the plasma is at thermal equilibrium. Apart from the present findings, this OCP-based modeling of warm dense matter has an important role to play in the interpretation of x-ray Thomson scattering measurements currently performed at large laser facilities.

  15. The MUSCLES Treasury Survey III: X-ray to Infrared Spectra of 11 M and K Stars Hosting Planets

    CERN Document Server

    Loyd, R O Parke; Youngblood, Allison; Schneider, Christian; Brown, Alexander; Hu, Renyu; Linsky, Jeffrey; Froning, Cynthia S; Redfield, Seth; Rugheimer, Sarah; Tian, Feng

    2016-01-01

    We present a catalog of panchromatic spectral energy distributions (SEDs) for 7 M and 4 K dwarf stars that span X-ray to infrared wavelengths (5 {\\AA} - 5.5 {\\mu}m). These SEDs are composites of Chandra or XMM-Newton data from 5 - ~50 {\\AA}, a plasma emission model from ~50 - 100 {\\AA}, broadband empirical estimates from 100 - 1170 {\\AA}, HST data from 1170 - 5700 {\\AA}, including a reconstruction of stellar Ly{\\alpha} emission at 1215.67 {\\AA}, and a PHOENIX model spectrum from 5700 - 55000 {\\AA}. Using these SEDs, we computed the photodissociation rates of several molecules prevalent in planetary atmospheres when exposed to each star's unattenuated flux ("unshielded" photodissociation rates) and found that rates differ among stars by over an order of magnitude for most molecules. In general, the same spectral regions drive unshielded photodissociations both for the minimally and maximally FUV active stars. However, for ozone visible flux drives dissociation for the M stars whereas NUV flux drives dissociati...

  16. Merging Structural Information from X-ray Crystallography, Quantum Chemistry, and EXAFS Spectra: The Oxygen-Evolving Complex in PSII.

    Science.gov (United States)

    Chernev, Petko; Zaharieva, Ivelina; Rossini, Emanuele; Galstyan, Artur; Dau, Holger; Knapp, Ernst-Walter

    2016-10-12

    Structural data of the oxygen-evolving complex (OEC) in photosystem II (PSII) determined by X-ray crystallography, quantum chemistry (QC), and extended X-ray absorption fine structure (EXAFS) analyses are presently inconsistent. Therefore, a detailed study of what information can be gained about the OEC through a comparison of QC and crystallographic structure information combined with the information from range-extended EXAFS spectra was undertaken. An analysis for determining the precision of the atomic coordinates of the OEC by QC is carried out. OEC model structures based on crystallographic data that are obtained by QC from different research groups are compared with one another and with structures obtained by high-resolution crystallography. The theory of EXAFS spectra is summarized, and the application of EXAFS spectra to the experimental determination of the structure of the OEC is detailed. We discriminate three types of parameters entering the formula for the EXAFS spectrum: (1) model-independent, predefined, and fixed; (2) model-dependent that can be computed or adjusted; and (3) model-dependent that must be adjusted. The information content of EXAFS spectra is estimated and is related to the precision of atomic coordinates and resolution power to discriminate different atom-pair distances of the OEC. It is demonstrated how a precise adjustment of atomic coordinates can yield a nearly perfect representation of the experimental OEC EXAFS spectrum, but at the expense of overfitting and losing the knowledge of the initial OEC model structure. Introducing a novel type of penalty function, it is shown that moderate adjustment of atomic coordinates to the EXAFS spectrum limited by constraints avoids overfitting and can be used to validate different OEC model structures. This technique is used to identify the OEC model structures whose computed OEC EXAFS spectra agree best with the measured spectrum. In this way, the most likely S-state and protonation pattern

  17. X-ray Energy Spectra of the Super-soft X-ray Sources CAL87 and RXJ0925.7-4758 Observed with ASCA

    CERN Document Server

    Ebisawa, K; Kotani, T; Asai, K; Dotani, T; Nagase, F; Hartmann, H W; Heise, J; Kahabka, P; Van Teeseling, A

    2000-01-01

    We report observation results of the super-soft X-ray sources (SSS) CAL87 and RXJ0925.7-4758 with the X-ray CCD cameras (Solid-state Imaging Spectrometer; SIS) on-board the ASCA satellite. We have applied theoretical spectral models to CAL87, and constrained the white dwarf mass and intrinsic luminosity as 0.8 - 1.2 M_solar and 4 x 10^{37}- 1.2 x 10^{38} erg s^{-1}, respectively. However, we have found the observed luminosity is an order of magnitude smaller than the theoretical estimate, which indicates the white dwarf is permanently blocked by the accretion disk, and we are observing a scattering emission by a fully ionized accretion disk corona (ADC) whose column density is ~ 1.5 x 10^{23} cm^{-2}. Through simulation, we have shown that the orbital eclipse can be explained by the ADC model, such that a part of the extended X-ray emission from the ADC is blocked by the companion star filling its Roche lobe. We have found that very high surface gravity and temperature, ~ 10^{10} cm s^{-2} and ~ 100 eV respec...

  18. Role of quantum nuclei and local fields in the x-ray absorption spectra of water and ice

    CERN Document Server

    Kong, Lingzhu; Car, Roberto

    2012-01-01

    We calculate the x-ray absorption spectra of liquid water at ambient conditions and of hexagonal ice close to melting, using a static GW approach that includes approximately local field effects. Quantum dynamics of the nuclei is taken into account by averaging the absorption cross section over molecular configurations generated by path integral simulations. We find that inclusion of quantum disorder is essential to bring the calculated spectra in close agreement with experiment. In particular, the intensity of the pre-edge feature, a spectral signature of broken and distorted hydrogen bonds, is accurately reproduced, in water and ice, only when quantum nuclei are considered. The effect of the local fields is less important but non negligible, particularly in ice.

  19. Nonequilibrium ionization models for analysis of x-ray spectra of supernova remnants

    Directory of Open Access Journals (Sweden)

    K. J. Borkowski

    2000-01-01

    Full Text Available Las remanentes de supernova (SNRs son de los objetos m as brillantes en rayos-X que ser an observados por los nuevos sat elites de rayos-X (Chandra, XMM y Astro-E. La emisi on t ermica de las SNRs no puede ser analizada con los c odigos usuales de emisi on de rayos-X porque el plasma de estos objetos no est a en equilibrio de ionizaci on. Se necesitan modelos de ionizaci on fuera de equilibrio (NEI para sacarle provecho a los datos venideros de alta calidad sobre SNRs. Presento un conjunto b asico de modelos NEI para el an alisis de espectros de rayos-X de SNRs; modelos con temperatura constante, con escalas temporales de ionizaci on unicas y generalizadas, choques plano paralelos con temperatura electr onica constante y modelos de Sedov con temperaturas diferentes para iones y electrones.

  20. X-ray emission line spectroscopy of cataclysmic variables. II. Temperatures and densities from line ratios in the Chandra HETG band

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, E. M.; Shipley, H. V. [Department of Physics and Astronomy, University of Texas-San Antonio, San Antonio, TX 78249 (United States); Rana, V. R. [Space Radiation Laboratory, Caltech, Pasadena, CA 91125 (United States); Barrett, P. E. [US Naval Observatory, Washington, DC 20392-5420 (United States); Singh, K. P., E-mail: eric.schlegel@utsa.edu, E-mail: vrana@srl.caltech.edu, E-mail: barrett.paul@usno.navy.mil, E-mail: singh@tifr.res.in [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai (India)

    2014-12-10

    We summarize the results of a line-by-line fitting analysis of the available spectra obtained using the Chandra High-Energy Transmission Grating. We confirm the existence of broad ionization and electron temperature ranges and high number densities in cataclysmic variables (CVs) of all subtypes. Temperatures range from ∼0.4 keV to ∼5-10 keV or more with a broad range detected in any given CV. In other words, single-temperature models do not describe the line emission. Number densities also cover a broad range, from 10{sup 12} to >10{sup 16} cm{sup –3}. We demonstrate that much of the plasma is in a nonequilibrium state; the Fe emission, however, may arise from plasma in the ionization equilibrium.

  1. X-ray luminescence spectra of graded-gap Al xGa 1- xAs structures irradiated by alpha particle

    Science.gov (United States)

    Šilėnas, A.; Požela, J.; Požela, K.; Jucienė, V.; Dapkus, L.

    2011-12-01

    The influence of 241Am alpha particle irradiation on X-ray luminescence spectra of the graded-gap AlxGa1-xAs structures of different thicknesses is investigated. It is observed that the integral X-ray luminescence intensity of nonirradiated thin (15 μm) structure is 1.4 times less than that in the thick (32 μm) structure, and this difference increases to 3 times after 3×1010 cm-2 dose of irradiation by alpha particle. The X-ray luminescence intensity of the energy hνFgg is responsible of that large difference, because it shifts the X-ray generated carriers to the narrow-gap surface with great nonradiative surface recombination rate. The alpha particle irradiation increases nonradiative recombination rate and causes a decrease of the X-ray luminescence intensity of all spectra lines in the thin (15 μm) detector. The most significant drop in X-ray luminescence efficiency is observed from the region at narrow-gap surface after the initial stage (109 cm-2 dose) of alpha particle irradiation. In the 32 μm thick detector, the luminescence intensity of the energy hν=1.8 eV does not change up to 2×1010 cm-2 of alpha particle irradiation dose. That means the high irradiation hardness of the thick graded-gap X-ray detector with optical response.

  2. Local moments and electronic correlations in Fe-based Heusler alloys: Kα x-ray emission spectra measurements

    Energy Technology Data Exchange (ETDEWEB)

    Svyazhin, Artem, E-mail: svyazhin@imp.uran.ru [M.N. Mikheev Institute of Metal Physics, Russian Academy of Sciences – Ural Division, 620990 Yekaterinburg (Russian Federation); Kurmaev, Ernst; Shreder, Elena; Shamin, Sergey [M.N. Mikheev Institute of Metal Physics, Russian Academy of Sciences – Ural Division, 620990 Yekaterinburg (Russian Federation); Sahle, Christoph J. [ESRF – The European Synchrotron, CS40220, 38043 Grenoble Cedex 9 (France)

    2016-09-15

    Heusler alloys are a property-rich class of materials, intensively investigated today from both theoretical and real-world application points of view. In this paper, we attempt to shed light on the role of electronic correlations in the Fe{sub 2}MeAl group (where Me represents all 3d elements from Ti to Ni) of Heusler alloys. For this purpose, we have investigated the local moments of iron by means of the x-ray emission spectroscopy technique. To obtain numerical values of local moments, the Kα-FWHM method has been employed for the first time. In every compound of the group, the presence of a local moment on the Fe atom was detected. As has been revealed, the values of these moments are temperature-independent, pointing to an insufficiency of a pure itinerant approach to magnetism in these alloys. We also comprehensively compare the usage of Kβ main lines and Kα spectra as tools for the probing of local moments and point out the significant advantages of the latter. - Highlights: • Local spin moments of iron in Fe{sub 2}MeAl (Me = Ti … Ni) Heusler alloys were investigated by means of x-ray emission spectroscopy. • Independence of the local moments from temperature confirms their localized nature. • A local moment value of iron in Fe{sub 2}MeAl raises with the atomic number of element Me. • The applicability of the Kα x-ray emission line for extracting local moment values of 3d elements was established.

  3. 1SXPS: A Deep Swift X-Ray Telescope Point Source Catalog with Light Curves and Spectra

    Science.gov (United States)

    Evans, P. A.; Osborne, J. P.; Beardmore, A. P.; Page, K. L.; Willingale, R.; Mountford, C. J.; Pagani, C.; Burrows, D. N.; Kennea, J. A.; Perri, M.; Tagliaferri, G.; Gehrels, N.

    2013-01-01

    We present the 1SXPS (Swift-XRT point source) catalog of 151,524 X-ray point sources detected by the Swift-XRT in 8 yr of operation. The catalog covers 1905 sq deg distributed approximately uniformly on the sky. We analyze the data in two ways. First we consider all observations individually, for which we have a typical sensitivity of approximately 3 × 10(exp -13) erg cm(exp -2) s(exp -1) (0.3-10 keV). Then we co-add all data covering the same location on the sky: these images have a typical sensitivity of approximately 9 × 10(exp -14) erg cm(exp -2) s(exp -1) (0.3-10 keV). Our sky coverage is nearly 2.5 times that of 3XMM-DR4, although the catalog is a factor of approximately 1.5 less sensitive. The median position error is 5.5 (90% confidence), including systematics. Our source detection method improves on that used in previous X-ray Telescope (XRT) catalogs and we report greater than 68,000 new X-ray sources. The goals and observing strategy of the Swift satellite allow us to probe source variability on multiple timescales, and we find approximately 30,000 variable objects in our catalog. For every source we give positions, fluxes, time series (in four energy bands and two hardness ratios), estimates of the spectral properties, spectra and spectral fits for the brightest sources, and variability probabilities in multiple energy bands and timescales.

  4. Spatially Resolved Spectra from a new X-ray Imaging Crystal Spectrometer for Measurements of Ion and Electron Temperature Profiles

    Energy Technology Data Exchange (ETDEWEB)

    Bitter, M; Stratton, B; Roquemore, A; Mastrovito, D; Lee, S; Bak, J; Moon, M; Nam, U; Smith, G; Rice, J; Beiersdorfer, P; Fraenkel, B

    2004-08-10

    A new type of high-resolution X-ray imaging crystal spectrometer is being developed to measure ion and electron temperature profiles in tokamak plasmas. The instrument is particularly valuable for diagnosing plasmas with purely Ohmic heating and rf heating, since it does not require the injection of a neutral beam - although it can also be used for the diagnosis of neutral-beam heated plasmas. The spectrometer consists of a spherically bent quartz crystal and a two-dimensional position-sensitive detector. It records spectra of helium-like argon (or krypton) from multiple sightlines through the plasma and projects a de-magnified image of a large plasma cross-section onto the detector. The spatial resolution in the plasma is solely determined by the height of the crystal, its radius of curvature, and the Bragg angle. This new X-ray imaging crystal spectrometer may also be of interest for the diagnosis of ion temperature profiles in future large tokamaks, such as KSTAR and ITER, where the application of the presently used charge-exchange spectroscopy will be difficult, if the neutral beams do not penetrate to the plasma center. The paper presents the results from proof-of-principle experiments performed with a prototype instrument at Alcator C-Mod.

  5. Soft x-ray spectra and collisional ionization equilibrium of iron ions with data upgrade of electron-ion collisions

    Science.gov (United States)

    Liang, G. Y.; Wei, H. G.; Zhao, G.; Zhong, J. Y.

    2016-06-01

    Line emissivities and ionic fraction in (non-)equilibrium are crucial for understanding the x-ray and extreme ultraviolet (EUV) spectra. These emission originate from electron-impact excitations for a level population of highly charged ions in coronal-like plasma. Recently, a large amount of excitation data was generated within the R-matrix framework by the computational atomic physics community, especially the UK APAP network. These data take resonances in electron-ion collisions into account appropriately, which enhances the effective excitation rates and also the line emissivities in x-ray and EUV regions. For ionization equilibrium data, the earlier compilation by Mazzotta et al (1998 Astron. Astrophys. Supp. Ser. 133 403) was used extensively by the astronomical community until the update by Bryans et al (2006 Astrophys. J. Supp. Ser. 167 343), as well as the compilation of Dere (2007 Astron. Astrophys. 466 771) for electron-impact ionization rates. In past years, many experimental measurements have been performed of highly charged iron ions in heavy-ion storage ring facilities. In this work, we will investigate the line emissivities and ionization equilibrium of highly charged iron ions by using recent theoretical or experimental data of electron-impact excitations and ionizations.

  6. Detection of the X-ray spectra of imploding neon Z-pinch with elliptically bent mica crystal spectrometer

    Institute of Scientific and Technical Information of China (English)

    Jun Shi; Shali Xiao; Hongjian Wang; Xianbin Huang; Libing Yang; Shenye Liu

    2008-01-01

    A wide variety of X-ray and extreme ultraviolet diagnostics are being developed to study on Yang acceler- ator. An elliptically bent crystal spectrometer is designed with a focal length of 1350 mm. A mica crystal with an interplanar spacing of 1.984 nm bent onto an elliptical substrate with eccentricity of 0.9485 is used. The crystal analyzer covers the Bragg angle range from 30° to 60°. The mica crystal can efficiently reflect radiation in multiple orders, covering the entire spectral range from 0.1 to 1.73 nm except for a gap from 0.86 to 1.0 nm. The application experiment is performed on Yang accelerator using the bent mica crystal analyzer. Spectra of neon-puff Z-pinch plasmas are recorded with a X-ray film, showing the H-like and the He-like lines of neon. Each spectrum has been identified and used for the wavelength calibration, and most of the line radiation is contained in the He-α and the L-α lines. The experimental results have demonstrated that the spectral resolution approximates 379.

  7. The X-ray Spectral Evolution of Galactic Black Hole X-ray Binaries Toward Quiescence

    CERN Document Server

    Plotkin, Richard M; Jonker, Peter G

    2013-01-01

    Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio l_x = L_{0.5-10 keV}}/L_{Edd} < 1e-5). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743-322, MAXI J1659-152, and XTE J1752-223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low-hard state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index and l_x in the low-hard state does not continue once a BHXB enters quiescence. Instead, ...

  8. Application of an expectation maximization method to the reconstruction of X-ray-tube spectra from transmission data

    Science.gov (United States)

    Endrizzi, M.; Delogu, P.; Oliva, P.

    2014-12-01

    An expectation maximization method is applied to the reconstruction of X-ray tube spectra from transmission measurements in the energy range 7-40 keV. A semiconductor single-photon counting detector, ionization chambers and a scintillator-based detector are used for the experimental measurement of the transmission. The number of iterations required to reach an approximate solution is estimated on the basis of the measurement error, according to the discrepancy principle. The effectiveness of the stopping rule is studied on simulated data and validated with experiments. The quality of the reconstruction depends on the information available on the source itself and the possibility to add this knowledge to the solution process is investigated. The method can produce good approximations provided that the amount of noise in the data can be estimated.

  9. Soft-X-ray spectra of highly charged Os, Bi, Th, and U ions in an electron beam ion trap

    Energy Technology Data Exchange (ETDEWEB)

    Trabert, E; Beiersdorfer, P; Fournier, K B; Chen, M H

    2004-12-03

    Systematic variation of the electron-beam energy in an electron-beam ion trap has been employed to produce soft-X-ray spectra of Os, Bi, Th, and U with highest charge states ranging up to Ni-like ions. Guided by relativistic atomic structure calculations, the strongest lines have been identified with {Delta}n = 0 (n = 4 to n' = 4) transitions in Rb- to Cu-like ions. The rather weak 4p-4d transitions are much less affected by QED contributions than the dominant 4s-4p transitions. Our wavelength measurements consequently provide benchmarks with and (almost) without QED. Because the radiative corrections are not very sensitive to the number of electrons in the valence shell, our data, moreover, provide benchmarks for the evaluation of electron-electron interactions.

  10. Theoretical characterization of X-ray absorption, emission, and photoelectron spectra of nitrogen doped along graphene edges.

    Science.gov (United States)

    Wang, Xianlong; Hou, Zhufeng; Ikeda, Takashi; Oshima, Masaharu; Kakimoto, Masa-aki; Terakura, Kiyoyuki

    2013-01-24

    K-edge X-ray absorption (XAS), emission (XES), and photoelectron (XPS) spectra of nitrogen doped along graphene edges are systematically investigated by using first-principles methods. In this study we considered pyridinium-like, pyridine-like, cyanide-like, and amine-like nitrogens at armchair and zigzag edges and pyrrole-like nitrogen at armchair edge as well as graphite-like nitrogen at graphene interior site. Our results indicate that nitrogen configuration and its location (armchair or zigzag edge) in nitrogen-doped graphene can be identified via the spectral analysis. Furthermore, some controversial spectral features observed in experiment for N-doped graphene-like materials are unambiguously assigned. The present analysis gives an explanation to the reason why the peak assignment is usually made differently between XPS and XAS.

  11. The x-ray emission spectra of multicharged xenon ions in a gas puff laser-produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Skobelev, I.Yu.; Dyakin, V.M.; Faenov, A.Ya. [Multicharged Ion Spectra Data Center, VNIIFTRI, Mendeleevo (Russian Federation); Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Szczurek, M. [Institute of Optoelectronics, Military University of Technology, Warsaw (Poland); Biemont, E. [Institut de Physique Nucleaire Experimentale, Universite de Liege, Liege (Belgium); Astrophysique et Spectroscopie, Universite de Mons-Hainaut, Mons (Belgium); Quinet, P. [Astrophysique et Spectroscopie, Universite de Mons-Hainaut, Mons (Belgium); Nilsen, J. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Behar, E.; Doron, R.; Mandelbaum, P.; Schwob, J.L. [Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem (Israel)

    1999-01-14

    Emission spectra of multicharged xenon ions produced by a laser gas puff are observed with high spectral resolution in the 8.5-9.5 and 17-19 A wavelength ranges. Three different theoretical methods are employed to obtain 3l-n'l'(n' = 4 to 10) wavelengths and Einstein coefficients for Ni-like Xe{sup 26+}. For the 3d-4p transitions, very good agreement is found between the experimental wavelengths and the various theoretical wavelengths. These accurate energy level measurements can be useful for studying the Ni-like xenon x-ray laser scheme. On the other hand, several intense spectral lines could not be identified as 3l-n'l' lines of Ni-like xenon, despite the very good agreement between the wavelengths and Einstein coefficients calculated for these transitions using the three different methods. (author)

  12. Insoluble Content, Ionic Composition, Density, and X-Ray Diffraction Spectra of 6 Evaporites from Niger Republic

    Directory of Open Access Journals (Sweden)

    Hassidou Saidou

    2015-01-01

    Full Text Available Some physicochemical (insoluble content, ionic composition, density, and X-ray diffraction spectra characteristics of Nigerien evaporites were investigated in this study. The results obtained showed that trona is the main mineral contained in Agadez, Dirkou, Niamey, and Zinder evaporites while thenardite and halite constitute the major minerals in Bilma and Tabalak evaporites, respectively. In addition, all evaporites samples investigated revealed the presence of quartz and halite. Other interesting minerals (calcite, gypsum, sylvite, aphthitalite, nahcolite, illite, burkeite, kaolinite, griceite, and talc were also detected. The use of Agadez, Dirkou, Niamey, and Zinder evaporites as catalyst to accelerate cowpea cooking is due to bicarbonates ions present in trona. Bilma and Tabalak evaporites employed in animal feeding are due to the halite contained in a significant quantity.

  13. The MUSCLES Treasury Survey. III. X-Ray to Infrared Spectra of 11 M and K Stars Hosting Planets

    Science.gov (United States)

    Loyd, R. O. P.; France, Kevin; Youngblood, Allison; Schneider, Christian; Brown, Alexander; Hu, Renyu; Linsky, Jeffrey; Froning, Cynthia S.; Redfield, Seth; Rugheimer, Sarah; Tian, Feng

    2016-06-01

    We present a catalog of panchromatic spectral energy distributions (SEDs) for 7 M and 4 K dwarf stars that span X-ray to infrared wavelengths (5 Å -5.5 μm). These SEDs are composites of Chandra or XMM-Newton data from 5-˜50 Å, a plasma emission model from ˜50-100 Å, broadband empirical estimates from 100-1170 Å, Hubble Space Telescope data from 1170-5700 Å, including a reconstruction of stellar Lyα emission at 1215.67 Å, and a PHOENIX model spectrum from 5700-55000 Å. Using these SEDs, we computed the photodissociation rates of several molecules prevalent in planetary atmospheres when exposed to each star’s unattenuated flux (“unshielded” photodissociation rates) and found that rates differ among stars by over an order of magnitude for most molecules. In general, the same spectral regions drive unshielded photodissociations both for the minimally and maximally FUV active stars. However, for O3 visible flux drives dissociation for the M stars whereas near-UV flux drives dissociation for the K stars. We also searched for an far-UV continuum in the assembled SEDs and detected it in 5/11 stars, where it contributes around 10% of the flux in the range spanned by the continuum bands. An ultraviolet continuum shape is resolved for the star ɛ Eri that shows an edge likely attributable to Si ii recombination. The 11 SEDs presented in this paper, available online through the Mikulski Archive for Space Telescopes, will be valuable for vetting stellar upper-atmosphere emission models and simulating photochemistry in exoplanet atmospheres.

  14. NuSTAR Hard X-ray Survey of the Galactic Center Region II: X-ray Point Sources

    CERN Document Server

    Hong, JaeSub; Hailey, Charles J; Nynka, Melania; Zhang, Shuo; Gotthelf, Eric; Fornasini, Francesca M; Krivonos, Roman; Bauer, Franz; Perez, Kerstin; Tomsick, John A; Bodaghee, Arash; Chiu, Jeng-Lun; Clavel, Maïca; Stern, Daniel; Grindlay, Jonathan E; Alexander, David M; Aramaki, Tsuguo; Baganoff, Frederick K; Barret, David; Barrière, Nicolas; Boggs, Steven E; Canipe, Alicia M; Christensen, Finn E; Craig, William W; Desai, Meera A; Forster, Karl; Giommi, Paolo; Grefenstette, Brian W; Harrison, Fiona A; Hong, Dooran; Hornstrup, Allan; Kitaguchi, Takao; Koglin, Jason E; Madsen, Kristen K; Mao, Peter H; Miyasaka, Hiromasa; Perri, Matteo; Pivovaroff, Michael J; Puccetti, Simonetta; Rana, Vikram; Westergaard, Niels J; Zhang, William W; Zoglauer, Andreas

    2016-01-01

    We present the first survey results of hard X-ray point sources in the Galactic Center (GC) region by NuSTAR. We have discovered 70 hard (3-79 keV) X-ray point sources in a 0.6 deg^2 region around Sgr A* with a total exposure of 1.7 Ms, and 7 sources in the Sgr B2 field with 300 ks. We identify clear Chandra counterparts for 58 NuSTAR sources and assign candidate counterparts for the remaining 19. The NuSTAR survey reaches X-ray luminosities of ~4 x and ~8 x 10^32 erg s^-1 at the GC (8 kpc) in the 3-10 and 10-40 keV bands, respectively. The source list includes three persistent luminous X-ray binaries and the likely run-away pulsar called the Cannonball. New source-detection significance maps reveal a cluster of hard (>10 keV) X-ray sources near the Sgr A diffuse complex with no clear soft X-ray counterparts. The severe extinction observed in the Chandra spectra indicates that all the NuSTAR sources are in the central bulge or are of extragalactic origin. Spectral analysis of relatively bright NuSTAR sources ...

  15. The First Chandra Field

    OpenAIRE

    Weisskopf, Martin C.; Aldcroft, Thomas L.; Cameron, Robert A.; Gandhi, Poshak; Foellmi, Cédric; Elsner, Ronald F.; Patel, Sandeep K.; Wu, Kinwah; O'Dell, Stephen L.

    2005-01-01

    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 Sou...

  16. X-ray Polarimetry

    Science.gov (United States)

    Kallman, T.

    In spite of the recent advances in X-ray instrumentation, polarimetry remains an area which has been virtually unexplored in the last 20 years. The scientific motivation to study polarization has increased during this time: emission models designed to repro- duce X-ray spectra can be tested using polarization, and polarization detected in other wavelength bands makes clear predictions as to the X-ray polarization. Polarization remains the only way to infer geometrical properties of sources which are too small to be spatially resolved. At the same time, there has been recent progress in instrumen- tation which is likely to allow searches for X-ray polarization at levels significantly below what was possible for early detectors. In this talk I will review the history of X-ray polarimetry, discuss some experimental techniques and the scientific problems which can be addressed by future experiments.

  17. Analysis of the high resolution Mg XI x-ray spectra

    Energy Technology Data Exchange (ETDEWEB)

    Siarkowski, M.; Sylwester, J. (Polska Akademia Nauk, Wroclaw. Centrum Badan Kosmicznych); Bromboszcz, G. (Wrolaw Univ. (Poland). Astronomical Inst.); Korneev, V.V.; Mandelshtam, S.L.; Oparin, S.N.; Urnov, A.M.; Zhitnik, I.A. (AN SSSR, Moscow. Fizicheskij Inst.); Vasha, S. (Mongolian Academy of Sciences, Ulan Bator (USSR). Inst. of Physics and Technics)

    1982-04-01

    In this paper, the second in a series dealing with high-resolution spectra (9.14-9.33 A) measured on board the INTERCOSMOS-16 satellite, the analysis of the physical conditions in the coronal part of the McMath 14352 active regions is performed. The temperature structure of the emitting plasma is investigated on the basis of the photon fluxes measured in six selected wavelength bands involving the resonance, intercombination, and forbidden lines of the Mg XI ion and a number of satellite lines. Relative line intensities are discussed in terms of the active region plasma density.

  18. Influence of chemical bonding on X-ray spectra of different aluminium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Bonetto, Rita [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco, Calle 47 No. 257, CC 59, 1900 La Plata (Argentina) and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina (Argentina)]. E-mail: bonetto@quimica.unlp.edu.ar; Trincavelli, Jorge [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000, Cordoba (Argentina) and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina (Argentina)]. E-mail: jorge@quechua.fis.uncor.edu; Vasconcellos, Marcos [Instituto de Fisica, Universidade Federal de Rio Grande do Sul, Campus do Vale, Av. Bento Goncalves 9500, CEP: 91501-970, Porto Alegre (Brazil)]. E-mail: marcos@if.ufrgs.br

    2005-11-15

    Five minerals containing aluminium in different crystal configurations are studied. The different kinds of chemical bonding between aluminium and oxygen originate molecular orbitals with energy levels and transition probabilities varying from one compound to another. This effect appears as shifts and changes in relative intensities of K{alpha} emission lines and as modifications of the K{beta} characteristic spectrum. In the present work, the aluminium K characteristic spectra obtained by means of an electron microprobe with a wavelength dispersive system are compared for topaz, albite, spodumene, biotite and corundum.

    </