Engineering topics

Szymkowiak, A. E.

Publications and source records attributed to Szymkowiak, A. E..

At least 37 records · Page 2

NASA NTRS1988

Einstein Observatory solid state detector observations of cooling flows in clusters of galaxies

Einstein Observatory (EO) solid state spectrometer results for the cooling flows in nine clusters of galaxies are discussed. An analysis of the data using three separate models provides strong evidence for the existence of cool components in the centers of these clusters. The obtained distribution of emission versus temperature for M87 is found to agree well with that determined from data obtained by the EO focal Plane Crystal Spectrometer.

Mushotzky, R. F.↗

NASA NTRS1988

High resolution X-ray spectroscopy using microcalorimeters

The use of microcalorimeters for high-resolution, high quantum efficiency, nondispersive X-ray spectroscopy has been demonstrated over the past few years. In this paper, the principles of X-ray calorimetry are reviewed, and the results of ongoing X-ray tests using microcalorimetry are summarized. An approach to building an X-ray calorimeter spectrometer is discussed.

Kelley, R. L.↗

NASA NTRS1986

Thermal detectors for high resolution spectroscopy

Cryogenic microcalorimeters can be made sensitive enough to measure the energy deposited by a single particle or X-ray photon with an accuracy of about one electron volt. It may also be possible to construct detectors of several-kilograms mass whose resolution is only a few times worse than this. Data from relatively crude test devices are in good agreement with thermal performance calculations, and a total system noise of 11 eV FWHM has been obtained for a silicon detector operating at 98 mK. Observations of 35 eV FWHM for 6-keV X-rays with a different device have been made.

Mccammon, D.↗

NASA NTRS1986

The X-ray spectrum of SN 1006

The supernova (SN) of A.D. 1006 represents the brightest in recorded history. The X-ray observations of its remnant appear to be full of puzzles. The present paper has the objective to reevaluate published X-ray data on SN 1006, using detailed nonequilibrium spectral computations and a self-consistent hydrodynamic SNR model. In a summary of the main conclusions, it is pointed out that an observed power-law continuum can be understood as mainly free-free emission from a reverse shock into SN ejecta with an initially uniform density profile. The spectral index is correctly predicted by such a model. Most of the continuum is produced by fully ionized gas in the dense outer layers of ejecta. The X-ray spectrum is not consistent with a solar composition or a uniform composition but is consistent with a layered composition of ejecta containing carbon on the outside, and processed heavy elements on the inside. There is no difficulty in including a large mass of iron.

Hamilton, A. J. S.↗

NASA NTRS1986

The X-ray spectrum of Tycho

Baade (1945) has identified Tycho's supernova (SN) of A.D. 1572 as Type I, taking into account an analysis of the light curve recorded by Tycho. However, in spite of the obvious interest of Tycho's spectrum, to date the spectrum remains poorly understood. The present study is concerned with a reevaluation of the X-ray spectrum of Tycho. Attention is given to detailed nonequilibrium calculations and a self-consistent hydrodynamic model for ejecta consisting of pure heavy elements moving into a uniform external medium. The model provides a satisfactory fit to the spectrum, and avoids any requirement for a large mass of material in Tycho. It is demonstrated that the observed iron line emission is compatible with the presence of perhaps 0.7 solar mass of iron, of which 0.3 solar mass is shocked.

Hamilton, A. J. S.↗

NASA NTRS1986

The GSFC/Wisconsin X-ray spectroscopy investigation for AXAF

A novel device is described which combines the high quantum efficiency of a photoelectric detector with the high energy resolution of a dispersive spectrometer in a system that operates simultaneously over the whole AXAF bandpass. It is basically an X-ray calorimeter, in which the temperature rise of an X-ray absorber following the deposition of energy from a single X-ray photon can be measured to an accuracy expected to be of order one part in 1000 at 6 keV.

Holt, S. S.↗

NASA NTRS1985

X-ray spectra of young Type I supernova remnants - Exploded white dwarfs?

It is argued that the X-ray spectra of young Type I supernova remnants can be understood consistently in terms of thermal emission mainly from a reverse shock into initially uniform density ejecta. The inferred mass of ejecta is then consistent with 1.4 solar mass in SN 1006, Tycho, and Kepler. A substantial mass of iron, perhaps 0.8 solar mass, may be present provided that the ejecta are chemically inhomogeneous, with iron confined to inner layers of ejecta. The marked difference between the X-ray spectra of SN 1006 and Tycho is explained by the lower interstellar density around SN 1006.

Hamilton, A. J. S.↗

NASA NTRS1985

X-ray spectra of supernova remnants

X-ray spectra were obtained from fields in three supernova remnants with the solid state spectrometer of the HEAO 2 satellite. These spectra, which contain lines from K-shell transitions of several abundant elements with atomic numbers between 10 and 22, were compared with various models, including some of spectra that would be produced by adiabatic phase remnants when the time-dependence of the ionization is considered.

Szymkowiak, A. E.↗

NASA NTRS1985

Thermal detectors as single photon X-ray spectrometers

In a thermal detector employed for X-ray spectroscopy applications, the energy of an X-ray is converted to heat in a small mass, and the energy of that X-ray inferred from the size of the temperature rise. The present investigation is concerned with the possibility to make an extremely low heat capacity calorimeter which can be employed as a thermal detector. Several types of calorimeters were fabricated and tested at temperatures as low as approximately 0.05 K. The obtained devices make use of thermistors constructed of melt-doped silicon, nuclear transmutation doped (NTD) germanium, and ion-implanted silicon with a variety of materials for the support and electrical leads. The utility of these microcalorimeters as X-ray spectrometers could be verified.

Moseley, S. H.↗

NASA NTRS1983

X-ray properties of the Be/X-ray system 28 0114+650 = LSI +65deg 010

Results are presented from experiments on the Einstein Observatory, HEAO 1, and OSO 8 on the temporal and spectral properties of 2S 0114+650. In a 12 hr Einstein monitor proportional counter and solid state spectrometer observation, two episodes of flaring occurred by an order of magnitude over about 1 hr. Variability on shorter time scales showed a preferred period of 14.9 minutes, but periodic pulsations were not seen in the HEAO 1 and OSO 8 data. The spectra above 1 keV were typical of accreting X-ray pulsars; the power law was E exp -alpha with alpha of about 1.2 for the number spectrum up to a cutoff at 14 keV. There is some evidence that the spectrum is steeper when the source is quiescent at low luminosity, but no large spectral changes attended the flares. Absorption column densities were consistent with interstellar reddening of the proposed companion, the Be star LSI +65 deg010. In the minute and hour variability and in the spectral character, 2S0114+650 is similar to other Be star-neutron star binary X-ray sources. Variations over several days in the OSO 8 data suggest orbital effects.

Koenigsberger, G.↗

NASA NTRS1983

G29.7-0.3: another supernova remnant with an identity crisis

New radio and X-ray observations of the galactic supernova remnant G29.7-0.3 show that it is composed of two spectrally distinct components: a steep-spectrum, incomplete shell 3 arcmin in extent enclosing a flat-spectrum, X-ray emitting region 30 arcsec across. Thus, G29.7-0.3 joins the ranks of supernova remnants which exhibit a combination of Crab-like and shell remnant attributes. The Crab-like core has the highest ratio of X-ray radio luminosity of all the Crab-like remnants observed to date, suggesting that it is an extremely young object.

Becker, R. H.↗

NASA NTRS1982

X-ray properties of the Be/X-ray systems 2S0114+650 = LSI+65 deg 010

Results are presented from experiments on the Einstein Observatory, HEAO-1 and OSO-8 on the temporal and spectral properties of 2S0114+650. In a 12 hour Einstein MPC and SSS observation two episodes of flaring occurred by an order of magnitude over about 1 hour. Variability on shorter time scales showed a preferred period of 14.9 minutes, but periodic pulsations were not seen in the HEAO-1 and OSO-8 data. There is some evidence that the spectrum is steeper when the source is quiescent at low luminosity, but no large spectral changes attended the flares. Absorption column densities were consistent with interstellar reddening of the proposed companion, the Be star LSI+65 deg 010. In the minute and hour variability and in the spectral character, 2S0114+650 is similar to other Be star-neutron star binary X-ray sources. Variations over several days in the OSO-8 data suggest orbital effects.

Koenigsberger, G.↗

NASA NTRS1982

X-ray spectral classification of supernova remnants in the Large Magellanic Cloud

The solid state spectrometer on the Einstein Observatory was used to measure the 0.6-4.5 keV X-ray spectra of six prominent supernova remnants in the Large Magellanic Cloud, namely, N132D, N63A, N49, 0525-66.0, N157B, and 0540-69.3. Thermal emission is detected from the first four remnants and is similar in nature to that observed from young galactic SNRs. In contrast, N157B and 0540-69.3 have featureless X-ray spectra which are well described by power-law models. The present data support a synchrotron origin for the X-rays from N157B and 0540-69.3, although an alternative emission mechanism is considered for the latter object.

Clark, D. H.↗

NASA NTRS1982

An X-ray study of two Crablike supernova remnants - 3C 58 and CTB 80

The instruments on the Einstein Observatory have been used to study the X-ray properties of two Crablike SNRs: 3C 58 and CTB 80. Images of the objects are similar, showing an extended plateau of emission surrounding a pronounced central maximum consistent with the presence of a point source. The X-ray spectrum of 3C 58 is consistent with a power law of spectral index 0.5 + 0.5 or -0.2 modified by absorption in a hydrogen column density N sub H of (2 + or - 0.5) x 10 to the 21st/sq cm. These data suggest an analogy with the Crab Nebula, where the extended X-ray emission is nonthermal and the pointlike emission emanates from a central neutron star. Quantitative comparisons of the X-ray and radio properties for six Crablike remnants indicate significant differences which may reflect an evolutionary sequence.

Becker, R. H.↗

NASA NTRS1982

On syntheses of the X-ray background with power-law sources

The conditions under which the combined emission from power-law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low-luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit steeper spectra at higher energies.

De Zotti, G.↗

NASA NTRS1982

X-ray spectroscopy and imagery of supernova remnants with the Einstein Observatory

The two complementary spectroscopic instruments of the Einsten Observatory make possible X-ray spectroscopy of SNRs with considerably increased sensitivity and spectral resolution. The Solid State Spectrometer is a cryogenically cooled detector with 160 eV resolution, which suffices not only for the separation of lines due to different elements, but also the resolution of H-like, He-like and neutral lines from the same element for Si and above. The Focal Plane Crystal Spectrometer uses Bragg crystals to achieve excellent spectral resolution, but at the expense of sensitivity. Both instruments operate over most of the 0.2-4 keV energy band of the Einstein telescope, and are able to detect most of the important X-ray lines except the K lines of Fe and Ni.

Winkler, P. F.↗

NASA NTRS1981

High resolution X-ray and radio images of the Crab-like supernova remnant G21.5-0.9

The Crab-like supernova remnant G21.5-0.9 has been imaged at 6 cm wavelength with the VLA and between 0.1-4 keV with the Einstein Observatory. Both the X-ray and radio images show a centrally peaked distribution of extended emission with no indication of a pointlike component. In contrast, the linearly polarized radio emission is distributed in a ring with a distinct central minimum. The electric vectors of the polarized radio emission are oriented circumferentially. The data support a Crab-like model for G21.5-0.9, but one in which a lower percentage of the radiated flux is emitted as X-rays relative to the Crab Nebula.

Becker, R. H.↗

NASA NTRS1981

On syntheses of the X-ray background with power-law sources

The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

Dezotti, G.↗