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Kellogg, E.

Publications and source records attributed to Kellogg, E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

The Outer X-ray and Radio Jets in R Aquarii

The symbiotic star R Aquarii has been known to emit collimated outflow in the form of jets for many years. We report on five years of observations in x-rays and radio using Chandra, VLA and XMM-Newton. We discuss the evolution of the outer thermal jets, including new observations performed in June and October 2005. We see motion of the NE x-ray jet at a projected velocity of about 600 km (sup -1). The SW x-ray jet has almost disappeared between 2000.7 and 2004.0. An XMM grating spectrum of the NE jet confirms the existence of O VII He-like lines, and offers the possibility of doing plasma density diagnostics. We comment on on the physics of cooling in the SW jet and implications for the density of the x-ray emitting gas, the heating mechanism, and mass and kinetic energy in the jets and its implications for the system as a whole. This work was supported by NASA and NSF.

Kellogg, E.↗
NASA NTRS2007

A Study of the Mass Loss Rates of Symbiotic Star Systems

The amount of mass loss in symbiotic systems is investigated, specifically mass loss via the formation of jets in R Aquarii (R Aqr). The jets in R Aqr have been observed in the X-ray by Chandra over a four year time period. The jet changes on times scales of a year and new outflows have been observed. Understanding the amount of mass and the frequency of ejection further constrain the ability of the white dwarf in the system to accrete enough mass to become a Type la supernova progenitor. The details of multi-wavelength studies, such as speed, density and spatial extent of the jets will be discussed in order to understand the mass balance in the binary system. We examine other symbiotic systems to determine trends in mass loss in this class of objects.

Korreck, K. E.↗
NASA NTRS1997

Absolute Calibration of the AXAF Telescope Effective Area

The prelaunch calibration of AXAF encompasses many aspects of the telescope. In principle, all that is needed is the complete point response function. This is, however, a function of energy, off-axis angle of the source, and operating mode of the facility. No single measurement would yield the entire result. Also, any calibration made prior to launch will be affected by changes in conditions after launch, such as the change from one g to zero g. The reflectivity of the mirror and perhaps even the detectors can change as well, for example by addition or removal of small amounts of material deposited on their surfaces. In this paper, we give a broad view of the issues in performing such a calibration, and discuss how they are being addressed in prelaunch preparation of AXAF. As our title indicates, we concentrate here on the total throughput of the observatory. This can be thought of as the integral of the point response function, i.e. the encircled energy, out ot the largest practical solid angle for an observation. Since there is no standard x-ray source in the sky whose flux is known to the -1% accuracy we are trying to achieve, we must do this calibration on the ground. we also must provide a means for monitoring any possible changes in this calibration from pre-launch until on-orbit operation can transfer the calibration to a celestial x-ray source whose emission is stable. In this paper, we analyze the elements of the absolute throughput calibration, which we call Effective Area. We review the requirements for calibrations of components or subsystems of the AXAF facility, including mirror, detectors, and gratings. We show how it is necessary to calibrate this ground-based detection system at standard man-made x-ray sources, such as electron storage rings. We present the status of all these calibrations, with indications of the measurements remaining to be done, even though the measurements on the AXAF flight optics and detectors will have been completed by the time this paper is presented. We evaluate progress toward the goal of making 1% measurements of the absolute x-ray flux from astrophysical sources, so that comparisons can be made with their emission at other wavelengths, in support of observations such as the Sunyaev-Zeldovitch effect, which can give absolute distance measurements independent of the traditional distance measuring techniques in astronomy.

Kellogg, E.↗
NASA NTRS1993

Summary of AXAF calibration requirements

The following summarizes requirements on the High Resolution Mirror Assembly (HRMA) and HRMA/SI calibration. The lists of calibration measurements assume that the HRMA meets the CTT requirement that the XRCF test environment shall have not more than a 10 percent effect on the encircled energy in 1 arcsec and that it can be calibrated to 1 percent. This implies that the offloading scheme has been implemented in the HRMA. It should be remembered that there are additional calibrations needed for: aspect system; tracking; gyros; other parts of the PCAS; spacecraft timing and checks on timing accuracy for all SIs after integration in the spacecraft; ficucial lights and periscope; alignments; optical metrology data: lengths and diameters with errors on mirror elements and optical interferometer data on surface figure; and throughput and imaging stability test: an end-to-end test that can be used after the XRCF to verify that the x-ray throughput and imaging quality have not been degraded. The tables presented give a summary of the integration times for HRMA and HRMA/SI calibration.

Kellogg, E.↗
NASA NTRS1993

The X-ray reflectivity of the AXAF VETA-I optics

The study measures the X-ray reflectivity of the AXAF VETA-I optic and compares it with theoretical predictions. Measurements made at energies of 0.28, 0.9, 1.5, 2.1, and 2.3 keV are compared with predictions based on ray trace calculations. Results on the variation of the reflectivity with energy as well as the absolute value of the reflectivity are presented. A synchrotron reflectivity measurement with a high-energy resolution over the range 0.26 to 1.8 keV on a flat Zerodur sample is also reported. Evidence is found for contamination of the flat by a thin layer of carbon on the surface, and the possibility of alteration of the surface composition of the VETA-I mirror, perhaps by the polishing technique. The overall agreement between the measured and calculated effective area of VETA-I is between 2.6 and 10 percent. Measurements at individual energies deviate from the best-fitting calculation to 0.3 to 0.8 percent, averaging 0.6 percent at energies below the high energy cutoff of the mirror reflectivity, and are as high as 20.7 percent at the cutoff.

Kellogg, E.↗
NASA NTRS1992

Calibration of the Verification Engineering Test Article-I (VETA-I) for AXAF using the VETA-I X-ray Detection System

Advanced X-ray Astrophysics Facility (AXAF) X-ray optics testing is conducted by VETA-I, which consists of six nested Wolter type I grazing-incidence mirrors; VETA's X-ray Detection System (VXDS) in turn measures the imaging properties of VETA-I, yielding FWHM and encircled energy of the X-ray image obtained, as well as its effective area. VXDS contains a high resolution microchannel plate imaging X-ray detector and a pinhole scanning system in front of proportional-counter detectors. VETA-I's X-ray optics departs from the AXAF flight configuration in that it uses a temporary holding fixture; its mirror elements are not cut to final length, and are not coated with the metal film used to maximize high-energy reflection.

Kellogg, E.↗
NASA NTRS1979

A high-sensitivity X-ray survey using the Einstein Observatory and the discrete source contribution to the extragalactic X-ray background

Surveys of two fields have been carried out utilizing the X-ray imaging instruments of the Einstein Observatory to a limiting flux of 1.3 x 10 to the -14th ergs/sq cm s in the 1-3 keV band, a several hundred-fold increase in sensitivity with respect to previous surveys. Forty-three objects are observed with positional accuracies varying from 5 to 60 arcsec. Optical and radio studies of candidate counterparts are described. The number-intensity relationship for extragalactic sources is evaluated, and the consequences of the findings are discussed with particular emphasis on the discrete source contribution to the extragalactic X-ray background. It is concluded that a large fraction of the background is due to previously unresolved discrete sources.

Giacconi, R.↗
NASA NTRS1979

Parameter estimation in X-ray astronomy using maximum likelihood

Methods of estimation of parameter values and confidence regions by maximum likelihood and Fisher efficient scores starting from Poisson probabilities are developed for the nonlinear spectral functions commonly encountered in X-ray astronomy. It is argued that these methods offer significant advantages over the commonly used alternatives called minimum chi-squared because they rely on less pervasive statistical approximations and so may be expected to remain valid for data of poorer quality. Extensive numerical simulations of the maximum likelihood method are reported which verify that the best-fit parameter value and confidence region calculations are correct over a wide range of input spectra.

Wachter, K.↗
NASA NTRS1978

Detection of soft X-rays with NEA III-V photocathodes

A description is presented of the results of tests on an X-ray photomultiplier containing a negative electron affinity (NEA) photocathode. This device makes it possible to investigate the response of the NEA photocathode to X-rays of various energies. The obtained data provide a basis for the determination of the photoelectron yield and energy resolution of the considered photocathode as a function of energy in the range from 0.8 to 3 keV. The investigation demonstrates the feasibility of using an NEA III-V photocathode for the detection of soft X-rays.

Bardas, D.↗
NASA NTRS1977

The Photicon

The Photicon is a novel imaging optical detector utilizing a conventional semitransparent photocathode, imaging electrostatic optics, microchannel plates, and a crossed-wire-grid position-sensitive charge detector. Its sensitivity to single optical photons over a two-dimensional area, high-resolution imaging, and timing capability render it useful for recording scintillations from X-ray image converters in X-ray astronomy. A digital word indicating the position of a single photon event is produced; the image can be stored in an array or serially. Spatial resolution to 20 microns in a 25 mm diam active area detector is reported, and modifications to achieve a spectral range of 120-730 nm are mentioned.

Kellogg, E.↗
NASA NTRS1976

High-resolution imaging X-ray detector

The paper describes an X-ray detector using microchannel plates as a photocathode surface and imaging photoelectron multiplier, and a crossed wire grid as a two-dimensional position-sensitive detector. The position resolution is 10 microns. The crossed wire grid consists of 100-micron-diam wires on 200-micron centers. Position sensing is accomplished by electronic interpolation to 1/20 of the wire spacing. The quantum efficiency of the microchannel plates varies from 29% at 0.28 keV to 5% at 3 keV. This detector will provide second-of-arc X-ray imaging in the focal plane of the 342.9-cm focal length grazing-incidence telescope being prepared for the HEAO-B observatory. By addition of suitable photocathodes, it can be used for single-photon imaging light detection in the UV, visible, and near-IR-ranges. In all cases, it gives a very low dark counting rate, allows timing of individual events to 1 microsec or less, and can handle counting rates up to 10,000 per sec.

Kellogg, E.↗
NASA NTRS1975

Studies of cluster X-ray sources, energy spectra for the Perseus, Virgo, and Coma clusters

Final Uhuru X-ray differential-energy spectra are presented for the Perseus, Virgo, and Coma clusters. Power-law and isothermal bremsstrahlung model spectra with low-energy cutoffs are given, and the energy-dependent Gaunt factor is calculated for the bremsstrahlung. The spectra, which are best fits to the Uhuru data between 2 and 10 keV, are compared with previous observations of these sources in the energy range from 0.1 to 100 keV. The problem of parameter estimation is discussed, error bars with 68% confidence are given for the independently determined slope and cutoff parameters, and the 68% confidence limits are plotted for the fitted spectral functions. The data for Perseus above 20 keV marginally favor the bremsstrahlung fit, those for Virgo between 0.25 and 1.0 keV clearly favor that curve, and those for Coma indicate a low-energy turnover or cutoff. Implications of such a cutoff are briefly discussed.

Kellogg, E.↗
NASA NTRS1974

Studies of cluster X-ray sources - Size measurements

An examination is conducted of the nine weaker sources in the list of Kellogg et al. (1973) which are well enough observed to be listed in the 3U catalog compiled by Giacconi et al. (1974). The cluster sizes are presented in a table and chi-square plots versus derived core radius and background counting rate are shown in a graph. X-ray luminosities calculated from the 3U catalog counting rates are presented as a function of X-ray size.

Kellogg, E.↗
NASA NTRS1974

The third Uhuru catalog of X-ray sources

A new edition of the catalog of X-ray sources observed with Uhuru is presented. About 125 days of data have been analyzed for the 3U catalog, yielding a total of 161 X-ray sources. The distribution of sources is similar to that obtained for earlier editions of this catalog. Location error regions for many of the sources previously listed in the 2U catalog have been significantly reduced in size.

Giacconi, R.↗
NASA NTRS1974

Negative affinity X-ray photocathodes

A new X-ray image intensifier is described. The device should eventually have a quantum efficiency which is an order of magnitude greater than that of presently available high spatial resolution X-ray detectors, such as microchannel plates. The new intesifier is based upon a GaAs crystal photocathode which is activated to achieve negative electron affinity. Details concerning the detector concept are discussed together with the theoretical relations involved, X-ray data, and optical data.

Vanspeybroeck, L.↗
NASA NTRS1973

X-ray spectrum of the Tycho supernova

Uhuru satellite data combined with Wisconsin rocket data suggest that the X-ray spectrum of the Tycho supernova remnant is composite and includes a thermal as well as a nonthermal component, the latter being an extension of the radio spectrum. Attempts have been made to fit the low-energy observations (thermal component) with the Tucker and Koren calculations for the solar corona.

Coleman, P. L.↗
NASA NTRS1973

Clusters of galaxies with a wide range of X-ray luminosities.

A search through 125 days of Uhuru data for X-ray emission from X-ray sources associated with Abell clusters is reported. X rays from 16 clusters have been observed. Ten of these are newly discovered and not listed in the previous Uhuru catalog. Seven cases, where the 22 MHz flux has been measured, show a wide spread of relative X-ray and radio luminosity. The discovery of low-richness clusters with high X-ray luminosity provides a possible explanation for some of the unidentified high-latitude X-ray sources.

Kellogg, E.↗