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NASA NTRS1985

Characterization of X-ray sources detected in a deep Einstein exposure of the field around 3C 295

An extensive set of optical and radio observations is presented that characterize the X-ray sources detected in an extremely deep Einstein Observatory exposure of the 3C 295 region. A total of five X-ray sources was found. This number is consistent with the only previous log N - log S result published at these flux levels. One of the sources was a galactic star. The four extragalactic sources are active galactic nuclei (three Seyferts and one QSO). Two of the sources are Seyfert galaxies in the 3C 295 cluster, one of which was previously unknown. The number of Seyfert galaxies in the cluster that is found from this complete X-ray survey is inconsistent with that expected from the fraction of low-redshift active galactic nuclei in their clusters.

Henry, J. P.↗
NASA NTRS1985

Einstein observations of selected regions of the Cygnus Loop

The imaging proportional counter on the Einstein X-ray Observatory is used to obtain high quality soft X-ray maps of two 40 x 40 arcmin regions of the Cygnus Loop. One region covers the western shock front; the other is centered on the southern diffuse extension. After careful correction for background and detector gain variations these two regions were subdivided for X-ray spectral analysis. In both cases the spectra of the brightest X-ray emitting areas are characterized by temperatures of about 2 million K, whereas the spectra of the fainter diffuse regions are indicative of higher temperatures (T greater than about 4 million K) and suggest the presence of a second, hard component. These results, together with the correlation of the X-ray spatial distribution with the optical and radio maps, are discussed in terms of current models of supernova remnant evolution. The evidence suggests that the Cygnus Loop is the result of a Type II supernova of a star of initial mass of less than about 20 solar masses.

Charles, P. A.↗
NASA NTRS1985

A statistical analysis of the Einstein normal galaxy sample. I - Spiral and irregular galaxies

The results of a statistical analysis of 48 spiral and irregular galaxies observed with the Einstein Observatory are reported. It is found that the X-ray luminosity is not directly correlated with the mass of the galaxies, but is strongly correlated with the blue luminosity. This suggests that most X-ray sources, including low-mass binaries, are binary systems belonging to both old disk and young arm Population I components. A real bulge population of X-ray sources exists that can contribute significantly to the X-ray luminosity of early-type spirals. The X-ray emission from a sample of 29 relatively isolated, normal elliptical and S0 galaxies is also studied, and the results are compared to those for the above sample to investigate the origin of the X-ray emission in early-type galaxies and the possible emission mechanisms. The influence of a powerful radio source and the onset of nuclear activity are also examined.

Fabbiano, G.↗
NASA NTRS1985

X-ray observations of GX 1 + 4 with the monitor proportional counter on board the Einstein Observatory

The results of X-ray observations of GX 1 + 4 with the monitor proportional counter on board the Einstein Observatory (HEAO 2) are presented. Using data from the time interval processor, the value of the approximately 2 minute pulse period at the time of the observations was determined. Previous determinations are discussed, along with evidence for a suggested value of approximately 4 minutes for the pulse period. The phase of first harmonic of the Fourier decomposition of pulse profile is stable within its errors but the phases of higher harmonics are not. The spin-up time scale is determined to be approximately 40 years.

Elsner, R. F.↗
NASA NTRS1985

Observations of four nearby galaxies with the Einstein Observatory

Four nearby galaxies, NGC 205, NGC 6822, the dwarf elliptical galaxy in Uras Major, and Maffei 1, were studied with the imaging instruments on the Einstein Observatory, and the results are reported. Fifteen X-ray sources were discovered, eight of which may not be associated with the target galaxies. No X-ray source was found in NGC 205, and one was found in NGC 6822, probably the optical supernova remnant Hodge 12. There are at most three sources in the Ursa Minor galaxy. There is probably an extended source associated with the Maffei 1 galaxy.

Markert, T. H.↗
NASA NTRS1986

Constraints on neutron star models of gamma-burst sources from the Einstein Observatory

Six Einstein observations of five gamma-ray burst sources are presented and discussed. With one possible exception, no point source was detected in any of the observations. The data are interpreted in the framework of neutron star models for gamma bursters. Upper limits are derived for the surface temperatures of the neutron stars assumed to be responsible for the bursts. It is shown that the lack of soft X-ray emission may impose stringent constraints on accretion rates onto neutron stars.

Pizzichini, G.↗
NASA NTRS1985

Einstein observations of the Vela supernova remnant - The spatial structure of the hot emitting gas

Spatially resolved (aproximately 1 arcmin) X-ray maps of the Vela supernova remnant have been constructed in two spectral bands, 0.2-1.0 keV and 0.8-2.0 keV, from a series of 36 separate observations with the Imaging Proportional Counter of the Einstein Observatory. The maps exhibit substantial structure on all angular scales. Spectral analysis shows that the emission from the remnant can be consistently described as thermal radiation from hot gas which is nonuniform in density and temperature, but which is in approximate pressure equilibrium. It is found that p/k is approximately 3-4 x 10 to the 5th/cu cm K. The soft X-ray emission exhibits a high degree of correlation with the optical filamentary structure, in the sense that the most prominent filaments either tightly surround or are coincident with the brightest X-ray regions. This suggests that the softest X-radiation may originate in 'warm' gas which is evaporated from the denser clouds responsible for the optical and ultraviolet filaments. Such an interpretation is quantitatively investigated, and shown to be only marginally consistent with the observations.

Kahn, S. M.↗
NASA NTRS1985

Einstein observations of Vela X and the Vela pulsar

The imaging detectors of the Einstein X-ray observatory have been used to study the Vela pulsar and its surrounding region. Although the pulsar is a relatively strong source of X-rays, there are not detectable pulsations at the pulsar period; the pulsed X-ray luminosity is less than approximately 10 to the 31st ergs/s in the 0.1-4.5 keV band. Nor is there evidence for other types of variability in the pulsar's X-ray emission. The images reveal structure on four spatial scales: (1) a pointlike object coincident with the pulsar; (2) a relatively bright, approximately 4-arcmin nebula of diffuse emission about the pulsar; (3) an approximately 1-degree nebula of hard emission that lies between the pulsar and the radio feature Vela X; and (4) thermal emission from the entire approximately 5-degree Vela supernova remnant. Spectral data from the small nebula are well fitted by a synchrotron model. Under the assumption that emission from the pulsar itself is thermal blackbody radiation, the surface temperature of the neutron star is calculated to be 1 million K.

Harnden, F. R., Jr.↗
NASA NTRS1986

Observations of quasi-periodic oscillations from GX 5 - 1 and Cygnus X-2 with the Einstein (HEAO 2) Observatory

The bright galactic bulge X-ray source GX 5 - 1 was observed in April 1979 with the Monitor Proportional Counter on board the Einstein (HEAO 2) Observatory. Analysis of the high time resolution data from the Time Interval Processor confirms the recent Exosat discovery of quasi-periodic oscillations in the X-ray emission from GX 5 - 1. In addition, the summed 0.4 s power spectrum shows the low-frequency red noise component also discovered in the Exosat data. Low-frequency structure is also clearly present in data taken from the bright galaxtic X-ray source Cyg X-2 in December 1978. The expected power spectrum for quasi-periodic oscillations was calculated, including the low-frequency red noise component, using a simple shot noise model with oscillating shots.

Elsner, R. F.↗
NASA NTRS1987

A statistical analysis of the Einstein normal galaxy sample. III - Radio and X-ray properties of elliptical and S0 galaxies

Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed.

Fabbiano, G.↗
NASA NTRS1987

Persistent emission and bursts from Aquila X-1 observed by Einstein

A two-component model is applied to an X-ray outburst from Aql X-1 recorded by the Einstein Observatory in March-April 1979. The model treats such outbursts as a combination of a soft, multicolor component (accretion disk) and a hard-blackbody component (boundary layer emission). Evaluation of the light curves indicates that the bursts were caused by an increase in the accretion rate. The calculations also suggest that the system observed is inclined at a 33 deg angle.

Czerny, M.↗
NASA NTRS1987

X-ray studies of quasars with the Einstein Observatory. IV - X-ray dependence on radio emission

The X-ray properties of a sample of 114 radio-loud quasars observed with the Einstein Observatory are examined, and the results are compared with those obtained from a large sample of radio-quiet quasars. The results of statistical analysis of the dependence of X-ray luminosity on combined functions of optical and radio luminosity show that the dependence on both luminosities is important. However, statistically significant differences are found between subsamples of flat radio spectra quasars and steep radio spectra quasars with regard to dependence of X-ray luminosity on only radio luminosity. The data are consistent with radio-loud quasars having a physical component, not directly related to the optical luminosity, which produces the core radio luminosity plus 'extra' X-ray emission.

Worrall, D. M.↗
NASA NTRS1987

Einstein observations of EF Eridani (2A 0311-227) - The textbook example of AM Herculis-type systems

Hard and soft X-ray spectra of the AM Herculis star EF Eridani obtained with the Einstein Observatory are found to be fitted by a thermal bremsstrahlung spectrum with kT of about 20 keV, and a blackbody spectrum with kT of between 16 and about 33 eV, respectively. EF Eri is shown to behave almost exactly as predicted by simple theory, with its soft X-ray luminosity not exceeding the hard X-ray luminosity by more than a factor of three, and both spectra originating from the same active pole of the accreting white dwarf. The data are consistent with a model involving an accretion stream penetrating deep into the magnetosphere of the white dwarf, such that accretion occurs along nonpolar field lines, and an 'X-ray auroral oval' emission is formed on the surface of the white dwarf.

Beuermann, K.↗
NASA NTRS1987

Hot DA white dwarfs seen with Einstein, an ultrahot H- and He-poor white dwarf, and Zanstra temperatures of planetary nebula nuclei

Einstein observations of hot DA white dwarfs are analyzed using model atmospheres. It is found that, for a relatively limited sample of stars, that hot He-poor stars like HZ 43 are indeed the exception, and that there is an apparent correlation between He/H ratio and increasing temperature. The seventh brightest soft X-ray source in the HEAO-A1 catalog, H1504+65, turns out to be an ultrahot white dwarf star, with a temperature of approximately 160,000 K, showing spectral features of the Zanstra method for determining the temperatures of central stars of planetary nebulae demonstrates that the H I Zanstra temperatures are indeed reliable and suggests that a substantial fraction of these central stars have He/H ratios which are considerably less than the solar value.

Shipman, Harry L.↗
NASA NTRS1987

Deep Einstein X-ray imagery of the Small Magellanic Cloud

Deep Einstein IPC imagery of about 50 percent of the main body and 'wing' of the SMC has been obtained and analyzed. The four X-ray images have exposure times between 12,000 and 24,000 s and reveal a total of 25 X-ray sources. Twelve of these sources are new detections. Two, possibly three, sources with soft spectra may be newly discovered supernova remnants. The rest of the sources have harder spectra and intrinsic X-ray luminosities in the range log L(x) = 34.0-35.0 and are most likely stellar objects in the SMC. These luminosities are much lower than that found for typical Galactic X-ray binaries, and a factor of 100 larger than the range for 'normal' galactic O and B stars.

Bruhweiler, Frederick C.↗
NASA NTRS1987

Torsion as a source of expansion in a Bianchi type-I universe in the self-consistent Einstein-Cartan theory of a perfect fluid with spin density

It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.

Bradas, James C.↗
NASA NTRS1987

Equation-of-state spinning fluids in the Einstein-Cartan theory

The relativistic fluid equations may be completed in two physically distinct methods. One method assumes the mass, rho, (or particle number) is conserved, while the other method assumes an equation of state of the form P = P(rho). A variational principle for the mass conservation method both with and without an intrinsic spin for the fluid was constructed earlier (Ray and Smalley, 1982 and 1983). A variational principle for the fluid described by an equation of state both with and without spin is formulated. In all cases the variational principle is set in the Einstein-Cartan metric-torsion U4 geometry. The results for general relativity follow as a special case.

Ray, John R.↗
NASA NTRS1987

Einstein Observatory survey of X-ray emission from solar-type stars - The late F and G dwarf stars

Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes of sources is consistent with the superposition of individual components in multiple-component systems, whose X-ray properties are similar to those of the single-component sources. The X-ray emission of the stars in our sample is well correlated with their chromospheric CA II H-K line emission and with their projected equatorial rotational velocity. Comparison of the X-ray luminosity function constructed for the sample of the dG stars of the local population with the corresponding functions derived elsewhere for the Hyades, the Pleiades, and the Orion Ic open cluster confirms that the level of X-ray emission decreases with stellar age.

Maggio, A.↗