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  • 1
    Electronic Resource
    Electronic Resource
    Analysis and interpretation of soft X-ray photographs of coronal active regions taken with Fresnel zone plates (1978)
    Springer
    Solar physics 57 (1978), S. 345-367 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Soft X-ray photographs of the Sun taken at O vii 21.6 Å and in a spectral band ranging from 13.2 to 22.1 Å have been analysed in order to establish spatially resolved maps of temperature and emission measure for several active regions in the corona. The photographs were taken on 11 March, 1971, and on 2 March, 1972, with Fresnel zone plate cameras which were flown on ESRO and NRL sounding rockets. In Part I of this paper we first deal with those aspects of the instrumentation which are important for setting up a suitable image analysis procedure. We discuss the characteristics of the wavelength dependent image formation by zone plates combined with absorption filters. Results of the calibration of the X-ray film are given. Then we describe a specific iterative data reduction procedure and finally present the resulting maps of temperature and emission measure for a selected active region. In Part II corresponding results for further active regions will be given and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160108
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  • 2
    Electronic Resource
    Electronic Resource
    An analysis of electron density fluctuations in air shower cores and the question of large transverse momenta (1970)
    Springer
    The European physical journal 230 (1970), S. 1-17 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron density distributions in air shower cores recorded with the 32 m2 neon hodoscope of the Kiel array have been analysed, looking for the existence of significant multicores which might result from large transverse momentum emission of high energy particles. The shower sizes are between 104 and 5×106 particles, corresponding to primary energies up to a few times 107 GeV. Several spurious effects simulating multicores have been found, but there are no indications for the existence of large transverse momenta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01394578
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  • 3
    Electronic Resource
    Electronic Resource
    Neutronensterne als Quellen kosmischer Röntgenstrahlung (1979)
    Springer
    Naturwissenschaften 66 (1979), S. 286-293 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract Unlike single neutron stars which appear as radio pulsars, neutron stars in close binary systems emit intense X-radiation. These superdense objects are of interest not only as the end stages of stellar evolution but also as physical laboratories which are dominated by superstrong gravitational and magnetic fields and in which matter densities and temperatures attain extreme values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00441270
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  • 4
    Electronic Resource
    Electronic Resource
    A Fully Depleted pn-Junction CCD for Infrared-, UV- and X- ray detection (1998)
    Springer
    Experimental astronomy 8 (1998), S. 89-96 
    Details
    ISSN: 1572-9508
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper describes the performance of the Fully Depleted pn-junction CCD (pn-CCD) system, developed for ESA's XMM-satellite mission for soft x-ray imaging and spectroscopy in the single photon counting mode in the 100 eV to 10 keV photon range. The 58 mm x 60 mm large pn-CCD array, designed and fabricated at the Semiconductor Lab (Halbleiterlabor) of the Max-Planck-Institut, uses pn-junctions for registers and as backside structure. This concept naturally enables full depletion of the detector volume independent of the silicon wafer's resistivity and thickness, and as such make it an efficient detector for the x-ray region and the infrared. For high detection efficiency in the soft x-ray region and UV, an ultrathin pn-CCD backside deadlayer has been realized. Each pn-CCD-channel is equipped with its own on-chip JFET amplifier which, in combination with the CAMEX-amplifier and multiplexing chip, facilitates parallel readout and fast data rate: the cooled pn-CCD system can be read out at a data rate up to 3 MHz with an electronic noise floor of ENC 〈 5 e-.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008008808704
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  • 5
    Electronic Resource
    Electronic Resource
    Simulated ROSAT observations of clusters of galaxies (1990)
    Springer
    Experimental astronomy 1 (1990), S. 365-388 
    Details
    ISSN: 1572-9508
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Detailed simulations have been made of the search for clusters of galaxies during the ROSAT all-sky x-ray survey (0.1–2 keV). The simulations use a conservative estimate of the cluster luminosity function to create an x-ray catalog specifying cluster position, redshift, flux, temperature and angular extent. This is used in combination with realistic models of the ROSAT scanning motion and of the background due to particles, cosmic x-rays and scattered solar x-rays, to build a simulated ROSAT data base. The data base has been subjected to the ROSAT source search algorithms and the results analyzed. Two cases were considered, a 2-degree wide great circle strip representing the general survey, and a region within 10 degrees of the ecliptic pole, where the exposure is unusually high. We present estimates of the minimum number of clusters to be detected, the fraction recognized as extended x-ray sources, and the minimum detectable energy flux from clusters during the survey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426719
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  • 6
    Electronic Resource
    Electronic Resource
    X-Ray Emission From Comet Hale–Bopp (1997)
    Springer
    Earth, moon and planets 77 (1997), S. 283-291 
    Details
    ISSN: 1573-0794
    Keywords: Comets ; individual, X-rays ; solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The discovery of X-ray emission from comets has created a number of questions about the physical mechanism producing the radiation. There are now a variety of explanations for the emission, from thermal bremsstrahlung of electrons off neutrals or dust, to charge exchange induced emission from solar wind ions, to scattering of solar X-rays from attogram dust, to reconnection of solar magnetic field lines. In an effort to understand this new phenomenon, we observed but failed to detect in the X-ray the very dusty and active comet C/Hale-Bopp 1995 O1 over a two year period, September 1996 to December 1997, using the ROSAT HRI imaging photometer at 0.1–2.0 keV and the ASCA SIS imaging spectrometer at 0.5–10.0 keV. The results of our Hale-Bopp non-detections, when combined with spectroscopic imaging 0.08–1.0 keV observations of the comet by EUVE and BeppoSAX, show that the emission has the same spectral shape and strong variability seen in other comets. Comparison of the ROSAT photometry of the comet to our ROSAT database of 8 comets strongly suggests that the overall X-ray faintness of the comet was due to an emission mechanism coupled to gas, and not dust, in the comet’s coma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006274812124
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  • 7
    Electronic Resource
    Electronic Resource
    Temporal intensity fluctuations of Her X-1 around 100 sec time scales (1985)
    Springer
    Space science reviews 40 (1985), S. 339-345 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Her X-1 has been observed with EXOSAT for one 35d cycle between March 1 and April 5, 1984 at about 4 day intervals. During three observations, absorption dips were encountered showing fluctuations with time scales in the several hundred seconds range. The data are interpreted with a model where random superposition of absorbing blobs or inhomogeneous structures within the accretion disk, in the line of sight, cause these intensity variations. The calculations give a measure of the extent of the disk both in vertical and radial directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00212906
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  • 8
    Electronic Resource
    Electronic Resource
    EXOSAT observations of the bright X-ray source GX9+1 (1985)
    Springer
    Space science reviews 40 (1985), S. 367-370 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results of the spectral and timing analysis of an observation of GX9+1/4U1758-205 performed with the Medium Energy Experiment aboard EXOSAT. During our observation the source flux varied irregularly in time scales from minutes to hours. No periodic emission in the period range from 16 msec to 2000 sec was found with an upper limit of around 1% (3 σ) for the pulsed fraction. The hardness ratio shows a correlated change with the flux intensity (Sco X-1 behaviour). The spectrum could be fitted by a double component model, a black body component (kT=1.16–1.26 keV) together with a thermal bremsstrahlung law (kT=13–15keV). The black-body temperature-black-body flux relation follows a Stefan Boltzmann law with RBB=15.3 km*D/10 kpc. No iron line was detected. The upper limit for the line equivalent width of a 6.7 keV iron emission line is 40 eV (1σ). The X-ray spectral behaviour of GX9+1 indicates, that this source belongs to the class of Low-Mass X-ray Binaries (LMXB).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00179842
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  • 9
    Electronic Resource
    Electronic Resource
    Observability of magnetically strongly shifted iron line emission from X-ray pulsars (1981)
    Springer
    Space science reviews 30 (1981), S. 337-340 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As an application of our extensive calculations of energies and intensities of atomic lines in very intense magnetic fields of the order of 1011-1013 G we discuss the possibility of observing magnetically strongly shifted iron lines in the spectra of pulsating X-ray sources. Careful estimates of the relevant parameters lead us to the conclusion that it would be profitable to look for magnetically shifted iron line enission in magnetic neutron stars of low luminosity using spectrometers working in the energy range 10 – 100 keV with sensitivities of 10−4 cm−2 s−1 and energy resolutions E/ΔE ∼ 10 – 100.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246042
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  • 10
    Electronic Resource
    Electronic Resource
    Hard X-ray balloon observations of compact galactic and extragalactic X-ray sources (1981)
    Springer
    Space science reviews 30 (1981), S. 311-323 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A balloon program in hard X-ray astronomy (20–200 keV) is jointly pursued by the Astronomisches Institut der Universität Tübingen (AIT) and the Max Planck-Institute für Extraterrestrische Physik in Garching (MPE). Since 1973 nine successful balloon flights have been performed from Texas and Australia. Here results on Centaurus A and on several galactic binary X-ray sources are summarized. In particular the high energy photon spectrum of Hercules X-1 and the evidence for the cyclotron line feature which was discovered by us in 1976 is reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246037
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