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Mushotzky, R. F.

Publications and source records attributed to Mushotzky, R. F..

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

X-ray spectral constraints on the broad-line cloud geometry of NGC 4151

X-ray spectral data from NGC 4151 taken with the Einstein Solid-State Spectrometer (SSS) and the HEAO 1 A-2 experiment cannot be simply reconciled with absorption from a uniform column of cold gas. The SSS data can, however, be explained in terms of a clumped absorber with approximately 10% uncovered fraction and factor-of-two overabundances in Z equal to or greater than 14 elements relative to solar oxygen. It is shown that these and previously reported spectral and variability data can be quantitatively reconciled with absorption arising in the cold clouds responsible for the broad optical line emission if the cloud dimensions are small compared to the central source size. It is suggested that the lack of significant X-ray absorption observed from much higher luminosity Seyferts and quasars is a natural consequence of the proposed picture for NGC 4151.

Holt, S. S.↗
NASA NTRS1980

Quasi-simultaneous observations of the BL Lac object MK 501 in X-ray, UV, visible, IR and radio frequencies

Quasi-simultaneous observations of the BL Lacertae (Lac) objects MK 501 were performed for the first time at X-ray, ultraviolet, visible, infrared, and radio frequencies. The observed spectral slope from the X-ray to UV regions is positive and continuous, but that from the mid UV to visible light region becomes gradually flat and possibly turns down toward lower frequencies; the optical radio emission can not be accounted for by a single power law. Several theoretical models were considered for the emission mechanism. A quantitative comparison was performed with the synchrotron-self-Compton model; the total spectrum is found consistent with this model. The spectrum from visible light to X-ray is consistent with synchrotron radiation or with inverse-Compton scattering by a hot thermal cloud of electrons. The continuity of the spectral slope from X-ray to UV implied by the current data suggests that the previous estimates of the total luminosity of this BL Lac object is underestimated by a factor of about three or four.

Kondo, D. M.↗
NASA NTRS1980

X-ray observations of the Seyfert 1 galaxies AKN 120 and MCG 8-11-11

A new X-ray source, H0523-00, with the optically variable Seyfert 1 galaxy AKN 120 is identified. The source has a 2-10 keV X-ray flux of 2 x 10 to the -11th ergs/sq cm s which corresponds to a 2-10 keV X-ray luminosity of 10 to the 44th ergs/s. X-ray observations over a 1.5 year time span combined with contemporaneous optical photometry show a decrease in the optical with no corresponding decrease in the X-ray. In contrast, similar observations of MCG 8-11-11 show a contemporaneous decrease in optical and X-ray fluxes. It is noted that the infrared and X-ray spectral slopes for these two objects are similar, with the optical being steeper by roughly one unit.

Mushotzky, R. F.↗
NASA NTRS1980

HEAO 1 identification of the X-ray emitting poor cluster of galaxies, AWM 7

The X-ray source 2A 0251 + 413 is identified with the AWM 7 group of galaxies. The source is extended, with a FWHM of roughly 9 arcmin if an isothermal sphere profile is assumed. The spectrum is best fitted by thermal bremsstrahlung at 4.0 + or - 0.5 keV, with a significant Fe line emission of equivalent width 0.63 keV centered at 6.6 keV. This temperature is consistent with a measured dispersion velocity of 600 km/s of the central galaxies.

Schwartz, D. A.↗
NASA NTRS1980

Variable X-ray spectra of BL Lac objects: HEAO-1 observations of PKS 0548-322 and 2A 1219+305

X-ray spectra for the BL Lac objects PKS 0548-322 and 2A 1219+305 measured with the HEAO-1 A2 detectors during pointing maneuvers on September 30, 1978 and May 31, 1978 respectively are presented. Both fit single power law components with low energy absorption. For 2A 1219+305, a thermal bremsstrahlung form gives an unacceptable fit. From a comparison with other statistically poorer observations taken at 6 month intervals while the satellite was in its normal scanning mode, it is found that the sources exhibit spectral variability. A summary of measurements of the 5 BL Lac objects detected with the A2 experiment is presented and it is concluded that X-ray spectral changes in this class of source are common. Their general X-ray spectral characteristics distinguish BL Lac objects from other classes of X-ray emitting active galactic nuclei. Analysis of their total spectra indicates that most of the energy is emitted in the 5 to 100 eV band.

Worrall, D. M.↗
NASA NTRS1980

The HEAO A-2 survey of Abell clusters and the X-ray luminosity function

The HEAO A-2 all sky data base was surveyed for 2-10KeV X-rau emission from the 225 Abell clusters og galaxies listed in Abell's (1958) catalog which are of distance class four or less, and are within the fraction of the sky surveyed completely by Abell. Thirty-two identifications of clusters with X-ray sources were made, for which 2-10 KeV fluxes and 90% error boxes are presented. Twelve of these identification are new. The X-ray luminosity function was derived for this statistically complete sample and the best exponential fit was found to be f(L) = 20.2 x 10 to the minus 8 power exp (-l(44)/1.9) per cu Mpc 2-10KeV. The relationship between X-ray luminosity and richness was examined and a correlation was found for richness classes 0, 1, and 2. The relationship of X-rau luminosity, Bautz-Morgan type, and Rood-Sastry type was examined. It was found that BM type I's and RS type cD and B have the greatest average luminosity. The contribution of clusters to the X-ray background was calculated from the luminosity function and was found to be 5%, and with 90% certainty, less than 8% in the 2-10 KeV band pass.

Mckee, J. D.↗
NASA NTRS1980

HEAO 1 spectra of X-ray emitting Seyfert 1 galaxies

The paper presents the 2-50-keV X-ray spectra and time variability information on seven Seyfert 1 galaxies NGC 3783, NGC 4151, NGC 5548, NGC 6814, MK 509, MCG 8-11-11, and ESO 141-G55, obtained with the A2(2) experiment on HEAO 1. It is concluded that the spectra of Seyfert 1 galaxies can be well represented by flat power laws of high-temperature thermal breamsstrahlung models with relatively low column densities.

Mushotzky, R. F.↗
NASA NTRS1980

The diffuse X-ray background spectrum from 3 to 50 keV

The spectrum of the extragalactic diffuse X-ray background has been measured with the GSFC Cosmic X-ray Experiment on HEAO 1 for regions of the sky away from known point sources and more than 20 deg from the galactic plane. A total exposure of 80 sq m-s-sr is available at present. Free-free emission from an optically thin plasma of 40 plus or minus 5 keV provides an excellent description of the observed spectrum from 3 to 50 keV. This spectral shape is confirmed by measurements from five separate layers of three independent detectors. With an estimated absolute precision of about 10%, the intensity of the emission at 10keV is 3.2 keV/keV/sq cm/s/sr, a value consistent with the average of previously reported spectra. A uniform hot intergalactic medium of approximately 36% of the closure density of the universe would produce such a flux, although nonuniform models indicating less total matter are probably more realistic.

Marshall, F. E.↗
NASA NTRS1980

Elemental abundances in a Type I supernova remnant

The solid-state spectrometer (SSS) on the HEAO 2 (Einstein) X-ray observatory observed the X-ray spectrum of Tycho's SNR. The observations show a relative excess of line emission from Si, S, and Ar by not less than 6 compared to that expected from a plasma of solar composition in collisional equilibrium and by a factor of not less than 3 compared to Cas A. Similar excesses are not found for line emission from Mg and Fe. The data suggest that the SN observed by Tycho in 1572 produced significant amounts of Si group elements but did not eject large amounts of Fe as predicted by some models of Type I SN events.

Becker, R. H.↗
NASA NTRS1979

X-ray line emission from Capella

X-ray emission-line components from Mg, Si, S, and Fe are unambiguously detected from Capella with the solid-state spectrometer onboard the Einstein Observatory. The X-ray spectrum is inconsistent with an isothermal corona, and requires components between 6-million K and at least 24-million K for an adequate fit. An inhomogeneous corona in which the X-ray emitting plasma is confined to magnetically contained loops appears to be reconcilable with all of the experimental evidence.

Holt, S. S.↗
NASA NTRS1979

X-ray spectrum of Cassiopeia A measured with the Einstein SSS

The solid state spectrometer (SSS) on the Einstein Observatory observed the X-ray spectrum of Cas A between 0.8 and 4.5 keV with a FWHM energy resolution of 160 eV. Line emission consistent with transitions of helium-like ions of Si, S, and Ar was well defined. Comparison between the data and the emission expected from a gas containing two distinct thermal components requires additional line emission from Mg, Al, Ca, and Fe. These results are discussed in the context of both equilibrium and nonequilibrium situations.

Becker, R. H.↗
NASA NTRS1979

A search for X-ray emission from rich clusters, extended halos around clusters, and superclusters

HEAO A-2 X-ray observations of rich clusters, extended halos around clusters, and superclusters are discussed. Concerning the optically richest clusters, results in the 0.2-60 keV energy range show that they appear to be relatively underluminous in X-rays. It is found that X-ray and microwave measurements for some rich clusters and for Abell 576 can be used to meaningfully constrain intracluster gas parameters and H(0); in addition, observations of Abell 576 show its luminosity to be less than earlier estimates. Extended halos around clusters were not detected in the data, and spectral observations of Abell 401 and 2147 reveal that they have typical cluster spectra with iron-line emission, while intensity measurements indicate that supercluster X-ray emission is not required.

Pravdo, S. H.↗
NASA NTRS1979

Search for X-ray emission from bursting radio sources

Results are reported for a systematic search with the A-2 experiment aboard HEAO 1 for X-ray emission from 28 radio sources that were actually bursting at the epoch of the X-ray observations. Two of these sources are found to lie within the positional errors of X-ray sources: the moderately redshifted quasars NRAO 140 and NRAO 530. The positions of 30 historically variable radio sources that were not active at the time of the search are compared with those of detectable X-ray sources, but no X-ray emission is detected from any of these positions. The implications of the results are discussed in terms of models for the radio emission from compact extragalactic sources. Several possible explanations are presented for the general absence of Compton X-ray emission from the bursting radio sources surveyed.

Marscher, A. P.↗
NASA NTRS1979

The X-ray spectrum of the BL Lacertae object PKS 0548-322

X-ray observations of H0548-322 = PKS 0548-322 at energies from 0.15 keV to 24 keV with the HEAO A-2 experiment are reported. The spectrum shows a distinct break in slope near 2 keV, with the indices of power-law energy spectra of 2.2 below and 0.3 above this break. A synchrotron self-Compton model is consistent with radio, optical, and all X-ray data, although a modified synchrotron self-Compton model with added thermal origin for the low-energy X-ray spectrum is also plausible.

Riegler, G. R.↗
NASA NTRS1979

Large-scale structure of X-ray clusters of galaxies

Observations from the A-2 experiment on HEAO-1 are used to search for very large-scale structure (exceeding a degree) in 40 X-ray sources in clusters of galaxies. Significant evidence for extension is found only in the relatively nearby Perseus and Virgo clusters. For the remainder of the sources the results place stringent limits on the flux in any very large component.

Nulsen, P. E. J.↗
NASA NTRS1979

Effect of hard X-rays on the emission lines of Seyfert galaxies and QSOs

Models of photoionized emission-line regions show that inclusion of a hard X-ray component in the ionizing continuum has relatively minor effects on most optical line intensities but helps to explain the strong O VI emission observed from QSOs. The optical-forbidden lines of NGC 4151 indicate roughly solar abundances ratios of N/O/Ne/Fe. The X-ray absorption arises largely in neutral portions of the emission-line clouds.

Shields, G. A.↗