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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1983

Rapid X-ray variability from the Seyfert 1 Galaxy NGC 4051

Strong variable X-ray emission from the nearby low luminosity Seyfert 1 galaxy NGC 4051 was discovered during observations with the imaging proportional counter of the Einstein Observatory. During one 2304 second observation, the X-ray flux more than doubled in an approximately linear fashion, and a 70% increase for 150 seconds was seen during another 968 second observation. Evidence is presented which demonstrates that the X-ray spectrum of NGC 4051 is unusually soft compared to Seyfert 1 galaxies or QSOs. The emission mechanism is probably not synchrotron or synchrotron self-Compton, but the emission can be plausibly explained by various black hole accretion models.

Marshall, F. E.↗
NASA NTRS1984

Binary modulation and transient periodic variations in X-ray emission from the AM Her binary H 0139 - 68

A detailed timing analysis of HEAO-1 and Einstein satellite soft X-ray data on the AM Her-type binary H 0139 - 68 indicates that the X-ray flux is modulated at the 113.6363-min period of its optical counterpart, and that the X-ray source shows high and low states. Transient X-ray pulsations with a period of about 275 sec are noted in the Imaging Proportional Counter (IPC) data during the high state, and the rapid X-ray flickering observed in the IPC light curve is characterized by an average e-folding autocorrelation time of about 10-20 sec. The present optical and X-ray data preclude the presence of an accretion disk in the primary system.

Singh, K. P.↗
NASA NTRS1983

Rapid X-ray variability from the Seyfert 1 galaxy NGC 4051

Strong variable X-ray emission from the nearby low luminosity Seyfert 1 galaxy NGC 4051 was discovered during observations with the imaging proportional counter of the Einstein Observatory. During one 2304 second observation, the X-ray flux more than doubled in an approximately linear fashion, and a 70 percent increase for 150 seconds was seen during another 968 second observation. Evidence is presented which demonstrates that the X-ray spectrum of NGC 4051 is unusually soft compared to Seyfert 1 galaxies or QSOs. The emission mechanism is probably not synchrotron or synchrotron self-Compton, but the emission can be plausibly explained by various black hole accretion models. Previously announced in STAR as N83-23265

Marshall, F. E.↗
NASA NTRS1985

Backside charging of the CCD

Until recently, the usefulness of the charge coupled device (CCD) as an imaging sensor was thought to be restricted to within rather narrow boundaries of the visible and near IR spectrum. However, since the discovery of backside charging the full potential of CCD performance is now realized. Indeed, the technique of backside charging not only allows the CCD to be used directly in the UV, EUV, and soft X-ray regimes, it has opened up new opportunities in optimizing charge collection processes as well. The technique of backside charging is discussed, and its properties, use, and potential in the future as it applies to the CCD are described.

Janesick, J.↗
NASA NTRS1979

Observation of soft X-ray emission from the supernova remnant HB9

The number of known X-ray emitting supernova remnants in our galaxy has significantly grown as a result of the soft X-ray survey by the HEAO-1 spacecraft. The HEAO-1 A-2 experiment has observed soft X-ray emission from the old supernova remnant HB9 which lies close to the previously identified X-ray source, Capella. Spectral data and the low optical obscuration in the direction of the remnant suggest that HB9 is a good candidate for detecting Fe XIV coronal forbidden-line emission. Mapping of the coronal line emission in association with the imaging X-ray data expected from HEAO-2 would allow the temperature profile of the emitting shell to be determined in a manner similar to that used by Tuohy, Nousek, and Garmire (1979) for the Cygnus Loop, which is in a similar evolutionary phase to HB9.

Tuohy, I. R.↗
NASA NTRS1981

Simultaneous X-ray and optical observations of an Ursae Majoris during a low state

In November 1975, AN UMa was detected as a soft X-ray source with a 0.1-0.4 keV flux which was modulated with the orbital cycle. In order to investigate further this orbital dependence and to correlate it with existing photometric and spectroscopic observations to aid in determining the geometry of the system, simultaneous X-ray and optical observations were made throughout several cycles of AN UMa. The system was in a low optical state during the observations. The X-ray observations were made with the Imaging Proportional Counter on the Einstein Observatory, yielding measurements over an available energy range of 0.1-4 keV. Attention is given to total X-ray flux, the X-ray light curve, optical and infrared data, and model implications.

Szkody, P.↗
NASA NTRS1973

Study of X-ray optics

The testing is reported of a polished Kanigen coated beryllium mirror in a soft X-ray telescope to be flown on a Skylark sounding rocket. This test involved inserting the telescope in a 220 foot long vacuum line and taking photographs of an X-ray resolution source. These photographs were then used to evaluate the performance of the telescope mirror as a function of distance from the focal plane and the angular distance off the telescope axis. A second test was made in which a point source was used to study the imaging characteristics by means of a pinhole and proportional counter placed in the telescope focal plane. A third test was conducted using a position sensitive detector. The efficiency and resolution was increased by polishing.

Froechtenigt, J. F.↗
NASA NTRS1982

An unbiased survey of field star X-ray emission

To determine the X-ray luminosity function of normal stars, 1700 stars brighter than 10th magnitude were surveyed by the imaging proportional counter aboard the Einstein Observatory. Seventy star positions were found to contain excess X-ray counting rates. The number of stars per square degree in a number of magnitude intervals was calculated as a function of spectral type and luminosity class, and the total number of stars for each spectral type brighter than magnitude 9.5 derived in this manner was compared with the 1700-star sample. The agreement is good, as is that between the surface density of soft X-ray sources and the number of stellar emitters predicted from the field star survey. It is concluded that stars probably do not contribute significantly to the diffuse soft X-ray background. The findings are consistent with the notion that stellar age and/or rotation velocity are important determinants of stellar X-ray emission level.

Helfand, D. J.↗
NASA NTRS1982

X-ray observations to detect hot coronae around galaxies

X-ray observations were made of two nearby edge-on spiral galaxies with the Imaging Proportional Counter (IPC) on the Einstein Observatory in an effort to detect hot (1,000,000 K), gaseous galactic coronae. No diffuse emission from galactic coronae was detected. Upper limits to diffuse emission (0.3-2.9 keV) are 10 to the 39th ergs/sec (NGC 3628) and 2 x 10 to the 38th ergs/sec (NGC 4244). The measurements indicate that less than 1/1000 of the energy supplied by supernovae in these galaxies appears as soft X-rays. The energy from supernovae may be radiated away by cool gas (less than 600,000 K) whose emission is undetectable by the Einstein Observatory, or the energy may be carried away by a hot wind (10,000,000 K) which radiates inefficiently. Serendipitous X-ray sources from the two IPC fields are listed.

Bregman, J. N.↗
NASA NTRS1982

The impulsive and gradual phases of a solar limb flare as observed from the solar maximum mission satellite

Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25-300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30-0.3 keV range. The ultraviolet observations were images with a 10 arcsec spatial resolution in the line of O V and Fe XXI. The hard X-ray and O V data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as materials was ejected into the corona. Impulsive excitation was observed up to 30,000 km above the solar surface at specific points in the flare loop. The Fe XXI observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient.

Poland, A. I.↗
NASA NTRS1979

Rocket studies of solar corona and transition region

The XSST (X-Ray Spectrometer/Spectrograph Telescope) rocket payload launched by a Nike Boosted Black Brant was designed to provide high spectral resolution coronal soft X-ray line information on a spectrographic plate, as well as time resolved photo-electric records of pre-selected lines and spectral regions. This spectral data is obtained from a 1 x 10 arc second solar region defined by the paraboloidal telescope of the XSST. The transition region camera provided full disc images in selected spectral intervals originating in lower temperature zones than the emitting regions accessible to the XSST. A H-alpha camera system allowed referencing the measurements to the chromospheric temperatures and altitudes. Payload flight and recovery information is provided along with X-ray photoelectric and UV flight data, transition camera results and a summary of the anomalies encountered. Instrument mechanical stability and spectrometer pointing direction are also examined.

Acton, L. W.↗
NASA NTRS1980

X-ray studies of quasars and active galaxies with the Einstein Observatory

Preliminary results of the first six months of an X-ray survey of active galaxies and quasars performed with the imaging proportional counter on board the Einstein Observatory are presented. Consideration is given to detections of Seyfert galaxies, N galaxies, BL Lac objects and quasars, and properties of selected representative objects are discussed in detail. The statistical properties, including class averages and correlation coefficients, of the various X-ray active galaxies are calculated in an attempt to determine the relation of X-ray properties to the similarities and differences between the various classes of galaxies. Evidence is obtained for a continuity of high-energy behavior among all active galaxies, and it is noted that they all exhibit flux variability, often on a short time scale. The soft X-ray emission can be explained in terms of the synchrotron self-Compton model, or alternatively by thermal emission from hot gas. A significant correlation is obtained between the X-ray and optical fluxes for all objects considered, indicating that optical quasar counts may be used to infer the contribution of quasars to the diffuse X-ray background.

Ku, W. H.-M.↗
NASA NTRS1980

X-ray properties of quasars

The X-ray properties of 111 catalogued quasars have been examined with the imaging proportional counter on board the Einstein Observatory. Thirty-five of the objects, of redshift between 0.064 and 3.53, were detected as X-ray sources. The 0.5-4.5-keV X-ray properties of these quasars are correlated with their optical and radio continuum properties and with their redshifts and variability characteristics. The X-ray luminosity of quasars tends to be highest for those objects which are bright in the optical and radio regimes and which exhibit optically violent variability. These observations suggest that quasars should be divided into two classes on the basis of radio luminosities, spectra, evolution and underlying morphology and that quasars can make up a significant portion of the diffuse soft X-ray background only if the slope of the optical quasar log N-log S relation is steeper than 2 to m sub b of about 21.5.

Ku, W. H.-M.↗
NASA NTRS1981

The Einstein Observatory and future X-ray telescopes

A history of the events leading to the development and flight of the Einstein Observatory is given. The advantages of using grazing-incidence telescopes for solar and extrasolar X-ray astronomy is first discussed and followed by a description of the HEAO program. The Einstein Observatory marks a departure from the manner in which X-ray investigations are carried out, from individual experiments to the shared use of large facilities. The Observatory has achieved a sensitivity to point sources of 10 to the -14th erg/sq cm-sec in the 1-3 keV band, a flux 500 times smaller than previously detected and about 10 million times smaller than that of the first extrasolar source detected in 1962. The design philosophy of the Observatory entails three principles: (1) the unified scientific approach, (2) the establishment of spacecraft requirements at lowest acceptable levels that still allow operating flexibility, and (3) the idea of 'soft' rather than 'hard' failure. The mirror design, including the high resolution imager, the imaging proportional counter, and the solid-state and focal plane crystal spectrometers, is also given. An account of the struggle to gain acceptance by the scientific community and the funding agencies of the need for the Einstein Observatory mission is discussed. Finally, results of observations made by the Observatory are presented in detail, along with plans for future observation experiments.

Giacconi, R.↗
NASA NTRS1972

Quantitative micro-luminescence and related studies of fine and/or glassy lunar surface materials

Papers on Raman and soft X-ray spectroscopy of lunar glasses and electron microscopy of lunar fines are presented. Individual particles of glasses from Apollo 11, 12, 14, and 15 samples were analyzed separately. Silicon emission shifts vary between parent rock types and can be interpreted as a range of Si-O distances from 1.612 to 1.637 A. Aluminum emission shifts relate to the amount of 4- and 6-coordinated Al in the glass. Raman spectra show broadened bands. Certain bands recur in many specimens and relate to the main normative minerals for the glass bulk composition, olivine, pyroxene, and anorthite. Quantitative size and shape analyses were carried out on six Apollo 14 and 15 samples of fines by computer evaluation of scanning electron microspace images. For the size range of 0.50 to 30 micron diameter, the distributions are log-normal on a number count basis. Aspect ratios range from 0.1 to 1.0 with an average value of about 0.6. The aspect ratios and a shape complexity factor vary only slightly among the samples.

Roy, R.↗
NASA NTRS1979

Evidence for X-ray emission from Kepler's supernova remnant

Evidence for weak soft X-ray emission from the remnant of Kepler's supernova has been acquired by the low energy detectors of the A 2 experiment on HEAO 1. A soft X-ray source has been detected using a narrow field of view sensitive to X rays between 0.2 and 3 keV and is found to be the only constant X-ray source within the error box containing Kepler's supernova remnant. The intensity of the X-ray source is calculated to be about 6.3 x 10 to the -2 counts/sq cm sec, with an intrinsic X-ray luminosity in the energy range 0.3 to 3 keV of about 28 x 10 to the 35 erg/sec if, as is widely believed, the remnant is at a distance of 4 kpc. Observations from HEAO 2 will allow the detection to be confirmed, the source to be imaged and its spectrum to be determined.

Tuohy, I. R.↗
NASA NTRS1982

Further observational evidence for a coronal boundary line in the cool star region of the H-R diagram

Soft X-ray emission was detected from Gamma Hya and 37 Com, at levels of 6-8 x 10 to the -13th ergs/sq cm per sec, during 0.2-4.0 keV observations of eight G-K giant stars obtained with the Einstein Observatory's Imaging Proportional Counter. Upper limits of about 3 x 10 to the 13th ergs/sq cm per sec were determined for the remaining stars. These results are judged to strengthen the Ayres et al (1981) findings that stellar coronae whose temperature is greater than one million K are either very weak or entirely absent among red giants and supergiants, while a large range in coronal emission exists among the yellow giant and supergiant stars.

Haisch, B. M.↗
NASA NTRS1983

X-ray and microwave observations of active regions

Coordinated high-resolution (1-3 arcsec) observations of two active solar regions (H 421 and H 419) on November 16, 1979, are reported: soft-X-ray filtergrams from a sounding rocket flight, VLA total-intensity and circular-polarization microwave (6-cm) radio maps, KPNO full-disk photospheric magnetograms, and BBSO H-alpha data. The images were converted to 4.8-arcsec/mm-scale transparencies and coaligned on the basis of sunspot positions for comparison. The two active regions are characterized in detail, and intensity, size, and polarization data for the brightest microwave components (BMC) are listed. It is found that 19 of the 32 BMC are farther than 5 arcsec from any sunspot, and that X-ray-emitting structures only rarely correspond to sunspots, or BMC. About one third of the BMC are located at the feet or legs of coronal loops smaller than about 50,000 km. The limitations implied by these obervations for proposed thermal-bremsstrahlung, thermal-gyro-resonance, and nonthermal microwave-emission mechanisms are discussed.

Webb, D. F.↗