M. J. Freyberg

Max Planck Institute for Extraterrestrial Physics, Arching, Bavaria, Germany

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Publications (199)284.77 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We perform ray-tracing simulations aimed at investigating the impact on the overall sensitivity of eROSITA of possible small errors in the mechanical shaping and positioning of the baffle rings above the mirror modules, to estimate to what extent they may contribute to degrade the efficiency of the baffle in eliminating the stray-light at the focal plane as well as to increase at the same time the vignetting, then reducing the effective area of the mirrors. Through the simulations we identify the ranges of acceptable tolerances.
    Proc SPIE 05/2013;
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    ABSTRACT: The Ni electroforming replication process has been used successfully by Beppo-SAX, JET-X/SWIFT, and XMM- Newton, to produce their gold-coated X-ray mirrors. The important feature of the technique is that, also with thin substrates, it is possible to achieve a good angular resolution, which is important for obtaining high signal-to-noise ratios in deep observations and imaging extended sources, while the assembly and integration of the monolithic shells is a relatively easy task. Two approaches can be used for the up grade of this technique also to the case of mirrors with multilayer coating, to be used in future hard X-ray missions: i) the direct replication of the mirror shell, after the deposition of the multilayer film on the master (mandrel) surface followed by the electroforming of the Ni walls, ii) the application of the multilayer film to the internal surface of Ni mirror shells, previously realized by replication. In this paper the last results achieved in Italy in the context of an activity aiming at the development of the former of the two methods will be presented and discussed.
    Citterio,Oberto; O'Dell, Stephen L.: Optics for EUV, X-Ray, and Gamma-Ray Astronomy II, SPIE - The International Society for Optical Engineering, 590008-1-590008-12 (2005). 04/2013; 5900:590008.
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    ABSTRACT: The recently discovered 522.5 s pulsar transient in the SMC - Suzaku J0102-7204 - (ATel #4628), was identified with the Be/X-ray binary XMM J010247.4-720449 (ATel #3761, ATel #4648). With new XMM-Newton data we can confirm both, pulsation period of Suzaku J0102-7204 and the identification with the Be/X-ray binary 2XMM J010247.4-720449.
    The Astronomer's Telegram. 01/2013;
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    ABSTRACT: A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.
    Nature 12/2012; · 38.60 Impact Factor
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    ABSTRACT: eROSITA is the primary instrument on the Russian SRG mission. In the first four years of scientific operation after its launch, foreseen for 2014, it will perform a deep survey of the entire X-ray sky. In the soft X-ray band (0.5-2 keV), this will be about 20 times more sensitive than the ROSAT all sky survey, while in the hard band (2-10 keV) it will provide the first ever true imaging survey of the sky at those energies. Such a sensitive all-sky survey will revolutionize our view of the high-energy sky, and calls for major efforts in synergic, multi-wavelength wide area surveys in order to fully exploit the scientific potential of the X-ray data. The design-driving science of eROSITA is the detection of very large samples (~10^5 objects) of galaxy clusters out to redshifts z>1, in order to study the large scale structure in the Universe, test and characterize cosmological models including Dark Energy. eROSITA is also expected to yield a sample of around 3 millions Active Galactic Nuclei, including both obscured and un-obscured objects, providing a unique view of the evolution of supermassive black holes within the emerging cosmic structure. The survey will also provide new insights into a wide range of astrophysical phenomena, including accreting binaries, active stars and diffuse emission within the Galaxy, as well as solar system bodies that emit X-rays via the charge exchange process. Finally, such a deep imaging survey at high spectral resolution, with its scanning strategy sensitive to a range of variability timescales from tens of seconds to years, will undoubtedly open up a vast discovery space for the study of rare, unpredicted, or unpredictable high-energy astrophysical phenomena. In this living document we present a comprehensive description of the main scientific goals of the mission, with strong emphasis on the early survey phases.
    09/2012;
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    ABSTRACT: We report on our activities, currently in progress, aimed at performing accelerator experiments with soft protons and hyper-velocity dust particles. They include tests of different types of X-ray detectors and related components (such as filters) and measurements of scattering of soft protons and hyper-velocity dust particles off X-ray mirror shells. These activities have been identified as a goal in the context of a number of ongoing space projects in order to assess the risk posed by environmental radiation and dust and qualify the adopted instrumentation with respect to possible damage or performance degradation. In this paper we focus on tests for the Silicon Drift Detectors (SDDs) used aboard the LOFT space mission. We use the Van de Graaff accelerators at the University of T\"ubingen and at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, for soft proton and hyper-velocity dust tests respectively. We present the experimental set-up adopted to perform the tests, status of the activities and some very preliminary results achieved at present time.
    09/2012;
  • Michael J. Freyberg, Konrad Dennerl
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    ABSTRACT: eROSITA is a German X-ray astronomical observatory on-board Spectrum-Roentgen-Gamma (SRG) with an expected launch in 2014 and operation at libration point L2. It consists of 7 identical mirror modules with 7 identical CCD cameras as focal plane instrumentation. It will observe the X-ray sky in the 0.25 - 10 keV range (4 yr all-sky survey, then pointed observations). Another instrument aboard SRG, ART-XC, will extend the spectral range to higher energies. We describe how the on-ground calibration is planned for the PANTER and PUMA X-ray test facilities, with respect to maximum scientific exploitation, in combination with an in-orbit calibration. This will be performed within one module and between the 7 eROSITA modules. If XMM-Newton will still be operational, a dedicated cross-calibration campaign is envisaged. The selection of the celestial targets and the procedure of the measurements with the internal Fe-55 calibration source are outlined.
    Proc SPIE 09/2012;
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    ABSTRACT: Soft protons can be a major source of degradation of the performances of instrumentation in space, in particular for CCDs. It was learned from the experience of Chandra and XMM-Newton that they can be funneled through the mirrorshells of an X-ray telescope down to the focal plane and hit detectors. This seems the favoured mechanism, since in general a detector placed at the focal plane is completely shielded from environmental soft protons except that in correspondance of the aperture field of view. However, the bombardment of high-energy cosmic rays can induce spallation reactions in the shield itself and other materials present at the focal plane. These processes generate secondary hadrons at softer energy, which can escape the target and reach the detectors. The products of spallation are mainly protons and neutrons. Neutrons can also have an impact on the performances of a Silicon-based detector. We study the production of secondary hadrons in the case of the pn-CCDs aboard eROSITA and the DEPFET Wide Field Imager aboard ATHENA, calculate expected doses over the missions duration and discuss possible effects on these detectors.
    Proc SPIE 09/2012;
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    ABSTRACT: The Point Spread Function (PSF) of the eROSITA miror modules is specified to have an on-axis Half Energy Width (HEW) of 15 arcsec. This is only slightly larger than the eROSITA pixel size of 75 microns, which corresponds to 9.6 arcsec at the PANTER test facility, where the PSF is being measured with a prototype of the eROSITA CCD. We have developed a fast algorithm which provides a substantially higher spatial resolution by utilizing the information contained in the charge ratios of split events. By applying this algorithm to measurements where the CCD is systematically shifted in subpixel increments (typically in a 12x12 pattern), we are able to achieve an effective resolution of ~2 arcsec for specific pixel patterns. This algorithm can also be used to compute the two dimensional probability distribution for detecting a photon from an incident point-like beam, for each combination of photon energy, low energy threshold, selected pixel patterns, and subpixel scan properties. These maps allow us to deconvolve the measured PSF and thus to minimize the influence of the spatial detector resolution on the determination of the eROSITA mirror HEW. After launch, the algorithm for improving the spatial resolution by reconstructing the subpixel position will also be applied to the science data.
    Proc SPIE 09/2012;
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    ABSTRACT: Due to the particle background and radiation damage in orbit, the CCDs aboard X-ray astronomical satellites (such as eROSITA) tend to degrade in their performance, especially in the charge transfer inefficiency (CTI). The on-board Calibration Source based on Fe-55 will be used to monitor the CTI and the gain. It provides Mn-Kα (5.89 keV) and Mn-Kβ (6.49 keV) lines (accompanied by Auger electrons), but also the Al-K (1.49 keV) and Ti-Kα (4.51 keV) and Ti-Kβ (4.93 keV) fluorescence lines from a target made of aluminum and a contribution of titanium. Measurements with the Calibration Source will be used to compare the on-board CTI with the CTI measured on ground and to modify the CTI correction. We summarize the design and trade-off analysis of the internal eROSITA calibration source and present results obtained with TRoPIC (eROSITA prototype camera) at the PANTER X-ray test facility in the energy range 0.5-250 keV. Various geometries have been tested to optimize the homogeneity of the calibration lines in the focal plane, the overall efficiency, and the line ratios between Mn-K and Al-K. Additionally, multi-component target materials (titanium and silver in addition to aluminum) have been tested. Moreover, the required source strength has been determined to obtain enough photons from the source after several years when radiation damage becomes significant and the source intensity has decayed (T1/2 ~ 999 d). Finally, also measurements to determine the electron content have been performed.
    Proc SPIE 09/2012;
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    ABSTRACT: Reliable timing calibration is essential for the accurate comparison of XMM-Newton light curves with those from other observatories, to ultimately use them to derive precise physical quantities. The XMM-Newton timing calibration is based on pulsar analysis. However, as pulsars show both timing noise and glitches, it is essential to monitor these calibration sources regularly. To this end, the XMM-Newton observatory performs observations twice a year of the Crab pulsar to monitor the absolute timing accuracy of the EPIC-pn camera in the fast Timing and Burst modes. We present the results of this monitoring campaign, comparing XMM-Newton data from the Crab pulsar (PSR B0531+21) with radio measurements. In addition, we use five pulsars (PSR J0537-69, PSR B0540-69, PSR B0833-45, PSR B1509-58 and PSR B1055-52) with periods ranging from 16 ms to 197 ms to verify the relative timing accuracy. We analysed 38 XMM-Newton observations (0.2-12.0 keV) of the Crab taken over the first ten years of the mission and 13 observations from the five complementary pulsars. All the data were processed with the SAS, the XMM-Newton Scientific Analysis Software, version 9.0. Epoch folding techniques coupled with \chi^{2} tests were used to derive relative timing accuracies. The absolute timing accuracy was determined using the Crab data and comparing the time shift between the main X-ray and radio peaks in the phase folded light curves. The relative timing accuracy of XMM-Newton is found to be better than 10^{-8}. The strongest X-ray pulse peak precedes the corresponding radio peak by 306\pm9 \mus, which is in agreement with other high energy observatories such as Chandra, INTEGRAL and RXTE. The derived absolute timing accuracy from our analysis is \pm48 \mus.
    Astronomy and Astrophysics 04/2012; · 5.08 Impact Factor
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    ABSTRACT: We present the analysis of the bright X-ray binary 4U 1820-30, based mainly on XMM-Newton-RGS data, but using complementary data from XMM-Epic, Integral, and Chandra-HETG, to investigate different aspects of the source. The broad band continuum is well fitted by a classical combination of black body and Comptonized emission. The continuum shape and the high flux of the source (L/L_Edd\sim0.16) are consistent with a "high state" of the source. We do not find significant evidence of iron emission at energies >=6.4 keV. The soft X-ray spectrum contain a number of absorption features. Here we focus on the cold-mildly ionized gas. The neutral gas column density is N_H\sim1.63x10^21 cm^-2. The detailed study of the oxygen and iron edge reveals that those elements are depleted, defined here as the ratio between dust and the total ISM cold phase, by a factor 0.20\pm0.02 and 0.87\pm0.14, respectively. Using the available dust models, the best fit points to a major contribution of Mg-rich silicates, with metallic iron inclusion. Although we find that a large fraction of Fe is in dust form, the fit shows that Fe-rich silicates are disfavored. The measured Mg:Fe ratio is 2.0\pm0.3. Interestingly, this modeling may point to a well studied dust constituent (GEMS), sometimes proposed as a silicate constituent in our Galaxy. Oxygen and iron are found to be slightly over- and under-abundant, respectively (1.23 and 0.85 times the solar value) along this line of sight. We also report the detection of two absorption lines, tentatively identified as part of an outflow of mildly ionized gas (\xi\sim-0.5) at a velocity of \sim1200 km/s.
    Astronomy and Astrophysics 12/2011; · 5.08 Impact Factor
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    ABSTRACT: The establishment of Silicon Pore Optics (SPO) as the technology of choice for the implementation of future large X-ray space optics has opened up the road to its use in all classes of X-ray missions with varying scientific goals. This interest has given us the possibility to broaden the design parameter space which is normally considered for SPO optics. In doing so a number of classical space X-ray optics design issues (e.g., field of view, stray light, baffling, aberrations) have been tackled. In this paper we report on recent results achieved in this effort. Particular attention will be given to the issues of stray light and baffling, a topic upon which a combination of analytical, simulation, and data analysis means can be effectively brought to bear. Missions considering the use of SPO optics have requirements spanning more than two orders of magnitude in energy, and a factor 20 in focal length. The possibilities that can be considered and the trade offs that must be made when applying SPO to such a wide range of optical designs will be illustrated, and some of the possible solutions discussed.
    Proc SPIE 09/2011;
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    ABSTRACT: The New Hard X-ray Mission (NHXM) is a space X-ray telescope project focused on the 0.2 to 80 keV energy band, coupled to good imaging, spectroscopic and polarimetry detectors. The mission is currently undergoing the Phase B study and it has been proposed to ESA as a small-size mission to be further studied in the context of the M3 call; even if the mission was not downselected for this call, its study is being continued by ASI. The required performance is reached with a focal length of 10 m and with four mirror modules, each of them composed of 70 NiCo electroformed mirror shells. The reflecting coating is a broadband graded multilayer film, and the focal plane is mounted onto an extensible bench. Three of the four modules are equipped with a camera made of two detectors positioned in series, a Silicon low energy detector covering the range 0.2 to 15 keV and a high energy detector based on CdTe sensitive from 10 keV up to 120 keV. The fourth module is dedicated to the polarimetry to be performed with enhanced imaging capabilities. In this paper the latest development in the design and manufacturing of the optics is presented. The design has been optimized in order to increase as much as possible the effective area in the high-energy band. The manufacturing of the mirror shells benefits from the latest development in the mandrel production (figuring and polishing), in the multilayer deposition and in the integration improvements.
    Optics for EUV, X-Ray, and Gamma-Ray Astronomy V; 09/2011
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    ABSTRACT: The International X-ray Observatory (IXO) is a candidate mission in the ESA Space Science Programme Cosmic Vision 1525, and was studied as a joint mission with NASA and JAXA. Considering the programmatic evolution of the international context, the mission is being reformulated as an ESA-led mission, under the name of ATHENA (Advanced Telescope for High Energy Astrophysics), with possible participation of NASA and JAXA. The mission is building on the novel Silicon Pore Optics (SPO) technology to achieve the required performance for this demanding astrophysics observatory. This technology is being developed by an industrial consortium, and involves also several research institutes [1-12]. A second optics technology, slumped glass optics (SGO), which is being developed in Europe and the USA, was the backup technology for IXO, and additionally work is progressing on improved reflective coatings and X-ray test facilities [13-17].
    Proc SPIE 09/2011;
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    ABSTRACT: MPE will provide the X-ray Survey Telescope eROSITA for the Russian Spektrum-Roentgen-Gamma Mission to be launched in 2013. It consists of a compact bundle of 7 co-aligned mirror modules with a focal length of 1600 mm and 54 nested mirror shells each. Therefore, its sensitivity in terms of effective area, field-of-view (61'), and angular resolution (15" HEW on-axis) will yield a high grasp of about 1000 cm2 deg2 around 1 keV with an average angular resolution of ~26" HEW over the field-of-view (30" including optical and spacecraft error contributions). After an extended test program on single mirror shells, assembled test modules (6 shells) and a qualification model we have now started integration of flight mirror modules. We give a résumé on the development and test program including key improvements to the shell integration method. Moreover, we report on the integration progress and present first results on the X-ray performance of partially integrated mirror modules.
    Proc SPIE 09/2011;
  • The X-ray Universe 2011; 08/2011
  • 08/2011;
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    ABSTRACT: X-ray charge-coupled devices (CCDs) are the workhorse detectors of modern X-ray astronomy. Typically covering the 0.3-10.0 keV energy range, CCDs are able to detect photoelectric absorption edges and K shell lines from most abundant metals. New CCDs also offer resolutions of 30-50 (E/ΔE), which is sufficient to detect lines in hot plasmas and to resolve many lines shaped by dynamical processes in accretion flows. The spectral capabilities of X-ray CCDs have been particularly important in detecting relativistic emission lines from the inner disks around accreting neutron stars and black holes. One drawback of X-ray CCDs is that spectra can be distorted by photon "pile-up," wherein two or more photons may be registered as a single event during one frame time. We have conducted a large number of simulations using a statistical model of photon pile-up to assess its impacts on relativistic disk line and continuum spectra from stellar-mass black holes and neutron stars. The simulations cover the range of current X-ray CCD spectrometers and operational modes typically used to observe neutron stars and black holes in X-ray binaries. Our results suggest that severe photon pile-up acts to falsely narrow emission lines, leading to falsely large disk radii and falsely low spin values. In contrast, our simulations suggest that disk continua affected by severe pile-up are measured to have falsely low flux values, leading to falsely small radii and falsely high spin values. The results of these simulations and existing data appear to suggest that relativistic disk spectroscopy is generally robust against pile-up when this effect is modest.
    The Astrophysical Journal 11/2010; 724(2):1441. · 6.73 Impact Factor
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    ABSTRACT: eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian Spektrum-Roentgen-Gamma (SRG) mission which is scheduled for launch in late 2012. eROSITA is fully approved and funded by the German Space Agency DLR and the Max-Planck-Society.The design driving science is the detection of 50-100 thousands Clusters of Galaxies up to redshift z{approx}1.3 in order to study the large scale structure in the Universe and test cosmological models, especially Dark Energy. This will be accomplished by an all-sky survey lasting for four years plus a phase of pointed observations. eROSITA consists of seven Wolter-I telescope modules, each equipped with 54 Wolter-I shells having an outer diameter of 360 mm. This would provide and effective area at 1.5 keV of {approx}1500 cm{sup 2} and an on axis PSF HEW of 15'' which would provide an effective angular resolution of 25''-30''. In the focus of each mirror module, a fast frame-store pn-CCD will provide a field of view of 1 deg. in diameter for an active FOV of {approx}0.83 deg{sup 2}. At the time of writing the instrument development is currently in phase C/D.
    AIP Conference Proceedings. 07/2010; 1248(1).

Publication Stats

2k Citations
284.77 Total Impact Points

Institutions

  • 1997–2013
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
    • Universities Space Research Association
      Houston, Texas, United States
  • 2011
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands
  • 2009
    • California Institute of Technology
      Pasadena, California, United States
  • 1999–2004
    • Nicolaus Copernicus University
      Toruń, Kujawsko-Pomorskie, Poland
  • 2003
    • Massachusetts Institute of Technology
      • Department of Physics
      Cambridge, Massachusetts, United States