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NASA NTRS1982

Einstein observations of BY Draconis variables and RS CVn binaries

Observations of five BY Draconis variables and four RS Canum Venaticorum systems with the Einstein Observatory are presented. All nine stars were detected. Although the BY Draconis stars have an average X-ray luminosity one to two orders of magnitude lower than the RS CVn binaries, at least three of these systems fit the X-ray/bolometric luminosity ratio-vs-period relation first described by Walter and Bowyer (1981) for RS CVn's. Since one of the BY Draconis stars is almost certainly single, this result lends strong support to the suggestion that rapid rotation, and not duplicity, is the determining factor in defining the level of stellar activity in such stars. In addition, the X-ray data are consistent with the suggestion, made by Vogt and Fekel (1979), that the BY Draconis stars are in the final stages of pre-main-sequence evolution.

Caillault, J.-P.↗
NASA NTRS1982

X-ray observations of peculiar galaxies with the Einstein Observatory

The results of X-ray observations with the Einstein Observatory of 33 galaxies are presented. Almost all of these galaxies, some of which lie in groups and in interactive pairs, display disturbed morphologies. No uniform, well-defined selection criterion can describe the sample galaxies, but almost all lie in a region of the optical color/color diagram that suggests that they are experiencing bursts of star formation. This region is compatible with the locus of Markarian galaxies. The observed sample and the X-ray data are presented, and the X-ray data are discussed and compared with the optical and radio properties of the galaxies. It is concluded that nuclear activity is not the predominant source of X-rays in late-type peculiar galaxies and that the X-ray emission is likely to originate from the Population I galactic component, in particular binary sources and possible young SNR's.

Fabbiano, G.↗
NASA NTRS1982

Einstein X-ray observations of QSO's with absorption-line systems

The detection of X-ray emission from eight QSO's is reported, plus an upper limit to the X-ray flux from one QSO, using the Einstein X-ray Observatory (HEAO-2). Each object in the sample contains at least one absorption-line system that has been identified in its optical spectrum. The present results are combined with those of other investigators to form a sample of 44 absorption-line QSO's (with 2 sub e greater than 1.2) which have been observed in the X-ray. This sample cannot be distinguished, in terms of X-ray properties, from one which consists of QSO's in which no absorption systems have been identified. These results are consistent with extrinsic models for absorption-line clouds, as well as with current versions of intrinsic models.

Junkkarinen, V. T.↗
NASA NTRS1982

Einstein observations of the confused 2A 2315-428 region

Four distinct X-ray sources have been detected by the Einstein Observatory imaging proportional counter in the 2A2315-428 field. The strongest source in the 0.2-3.8 keV band is associated with the Sersic 159-03 cluster, which contains a cD galaxy, and may account for as much as 40% of the observed 2A flux. The rest of the flux is suspected to issue from the weaker but more heavily cut-off galaxy NGC 7582. It is suggested that such a large X-ray absorption column density in NGC 7582 may account for the absence of a broad H-alpha emission component, as has been observed in other narrow-line X-ray galaxies. The weak X-ray flux from NGC 7552 shows together with a reanalysis of previous observations, that the source is not variable, that its X-ray emission is not likely to result from a compact nucleus, and that it may be a starburst galaxy.

Charles, P. A.↗
NASA NTRS1982

Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory

It is noted that only one BL Lac object, designated 1E 1402.3 + 0416, has so far been discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with previously X-ray-discovered BL Lacs, this object is blue and radio weak (17 mJy at 6 cm). It is pointed out that the percentage of BL Lacs in the faint extragalactic X-ray sample (2%) is smaller than the percentage at higher X-ray fluxes (6%). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) rises from 40% to 74%). This is seen as suggesting that BL Lacs do not evolve in a manner similar to quasars and are, therefore, not substantial contributors to the X-ray background.

Stocke, J.↗
NASA NTRS1982

A morphological classification of clusters of galaxies from Einstein images

The earliest Uhuru observations showed that cluster X-ray sources were not associated with single individual galaxies but were extended sources. It has only been with the advent of the Einstein X-ray imaging observatory that a first look at cluster X-ray morphology and classification has been possible. The proposed classification system divides clusters into two families, including those with and those without X-ray dominant galaxies. Within each family, the dynamical indicators display a full range of values. One subgroup of clusters is those whose X-ray emission is not regular and which do not contain an X-ray dominant galaxy. One of the brighter, nearer and best studied members of this class is Al367. From the X-ray imaging observations, four clusters have been discovered to have double structure in their surface brightness distributions. The Coma cluster is the archtype of an evolved, fully relaxed cluster. Ellipticals in the Virgo core include M87, M86, and M84. It is concluded that the cluster images are useful in determining the cluster family and the cluster's dynamical state.

Jones, C.↗
NASA NTRS1982

Einstein Observatory solid state spectrometer observations of M87 and the Virgo cluster

X-ray observations of the galaxy M87 and of a region in the Virgo cluster displaced 7 arcmin from the center of M87 are reported. X-ray spectra were obtained at these two locations with the Solid State Spectrometer onboard the Einstein Observatory. Emission lines were observed in both locations, indicating the presence of heavy elements at abundances near solar. There is no strong abundance gradient, within the errors. A temperature gradient has been detected: T increases from about 1.4 keV at the position of M87 to about 3.35 keV 7 arcmin away. There is lower temperature thermal emission at the center of M87 with T about 0.6 keV, consistent with models for cooling flows in this cluster. A mass infall rate of nearly 20 solar masses/yr has been obtained. In addition to the thermal emission, a power-law component has been detected in the spectrum of M87, consistent with that observed by HEAO 1, indicating that this component probably originates in the galaxy itself. Comparison of the results with those of other observers and with theoretical models for this source indicates the presence of intracluster gas having density near 1/1000 per cu cm and temperature of about 30,000,000 K.

Lea, S. M.↗
NASA NTRS1982

Einstein Observatory pulse-phase spectroscopy of Hercules X-1

Spectra of the Her X-1 pulsations from 0.15 to 4.5 keV have been obtained with the Objective-Grating and Solid State Spectrometers on the HEAO 2 Einstein Observatory. The spectra show no distinct atomic emission or absorption features, except for broad emission near 1 keV possibly due to unresolved Fe L shell emission lines. Spectrally resolved pulse waveforms show a dramatic 240 deg phase shift for E less than 0.85 keV. The soft X-rays are interpreted as the result of the reprocessing of the hard X-ray beam by the inner disk at the magnetospheric boundary of the neutron star, and several spectroscopic and phase observations are suggested which could provide further knowledge of these structures.

Mccray, R. A.↗
NASA NTRS1982

Perfect fluids in the Einstein-Cartan theory

It is pointed out that whereas most of the discussion of the Einstein-Cartan (EC) theory involves the relationship between gravitation and elementary particles, it is possible that the theory, if correct, may be important in certain extreme astrophysical and cosmological problems. The latter would include something like the collapse of a spinning star or an early universe with spin. A set of equations that describe a macroscopic perfect fluid in the EC theory is derived and examined. The equations are derived starting from the fundamental variational principle for a perfect fluid in general relativity. A brief review of the study by Ray (1972) is included, and the results for the EC theory are presented.

Ray, J. R.↗
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 NTRS1983

Studies of BL Lacertae objects with the Einstein X-ray observatory - The absolute volume density

It is estimated that the local volume density of BL Lac objects which emit greater than 10 to the 44th ergs/s in the 0.5-4.5 keV band is about 10 to the -7th/cu Mpc. This is based on identifications of bright X-ray sources, and the fact that Einstein X-ray observations detect BL Lac objects over a wide, continuous range of flux up to the thresholds of the all-sky X-ray surveys. Since this density is of the same order of magnitude as the local density of Seyfert galaxies, or local density of optically selected quasars, emitting X-rays at the same luminosity, we argue that the difference between these particular astronomical classifications is not solely due to the orientation of a relativistic beam.

Schwartz, D. A.↗
NASA NTRS1983

X-ray observations of 4U 1626-67 by the monitor counter on the Einstein /HEAO 2/ observatory

The pulsing X-ray source 4U 1626-67 was observed with the Monitor Proportional Counter (MPC) on board the Einstein X-Ray Observatory on three occasions in early 1979. The MPC is a sealed, argon-filled proportional counter with a 1.5 mil beryllium window and is coaligned with the X-ray telescope on board the observatory. The spectral data spanning the energy range from 1.1 to 21 keV are divided into eight logarithmically spaced energy channels which integrate for 2.56 s. The Time Interval Processor (TIP) circuitry of the MPC measures time intervals between events to within 1 microsecond or 1.6%, whichever is larger, for a count rate dependent fraction of all events in all eight energy channels. It is found that in the energy range from 1 to 21 keV, the spectrum and 7.7 s pulse shape of 4U 1626-67 are variable on a time scale of minutes. The pulse shape variations correlate in a complex way with the intensity variations in this source.

Elsner, R. F.↗
NASA NTRS1983

Coordinated Einstein and IUE observations of a disparitions brusques type flare event and quiescent emission from Proxima Centauri

The Einstein Imaging Particle Counter observed a major X-ray flare in its entirety during a 5-hr period of simultaneous observations, with the IUE, of the dM5e flare star Proxima Centauri in August, 1980. The detailed X-ray light curve, temperature determinations during various intervals, and UV line fluxes obtained before, during, and after the flare indirectly indicate a 'two-ribbon flare' prominence eruption. The calculated ratio of coronal to bolometric luminosity for the event is about 100 times the solar ratio. The Proxima Cen corona is analyzed in the context of static loop models, in light of which it is concluded that less than 6% of the stellar surface seems to be covered by X-ray emitting active regions.

Haisch, B. M.↗
NASA NTRS1983

X-ray studies of quasars with the Einstein Observatory. III The 3CR sample

Using X-ray emission detected by the Einstein Observatory from each of the 33 3CR quasars in Schmidt's complete sample, it is demonstrated that there is a relationship between the X-ray emission and centimeter wavelength radio emission even for steep-spectrum quasars, provided that only the radio emission from the central object is considered. The observations are summarized, and the estimation of the X-ray luminosity distribution, rather narrow compared to the radio and optical luminosity distributions, is presented. The relationship between X-ray and radio emission is discussed, as is the cosmological evolution of the X-ray luminosity function. The relationship between X-ray and optical luminosity provides an explanation for the finding that X-ray selected quasars have lower redshifts than optically selected quasars of the same optical magnitude.

Tananbaum, H.↗
NASA NTRS1982

Einstein Observatory results on active galactic nuclei

The results of Einstein Observatory surveys of active galactic nuclei (AGN) are reviewed. The ubiquity of X-ray emission from AGNs was confirmed. The relations between X-ray and optical luminosities, between X-ray and radio properties, and between X-ray and optical-UV line emission found by the surveys are summarized and briefly discussed. The possible causes of observed X-ray emission from jets in Cen-A, 3C273, and M87 are considered. The active nucleus discovered in the optically 'dull' galaxy NGC 4156 is covered, and a model for NGC 4151 based on detailed spectral studies is briefly discussed. This model establishes the global symmetry of the AGN clouds, their approximate sizes, and their ionization state. Difficulties encountered in attempting to explain the cosmic X-ray background in terms of AGN contributions are addressed.

Mushotzky, R. F.↗
NASA NTRS1983

Spinning fluids in the Einstein-Cartan theory

An Eulerian variational principle for a spinning fluid in the Einstein-Cartan metric-torsion theory is presented. The variational principle yields the complete set of field equations for the system. The symmetric energy-momentum tensor is a sum of a perfect-fluid term and a spin term.

Ray, J. R.↗
NASA NTRS1983

The optical identification content of the Einstein Observatory deep X-ray survey of a region in Pavo

Results are presented from the Einstein deep X-ray survey in Pavo, with correlated optical and radio observations of a complete sample of candidate identifications. There are 16 X-ray sources detected with positional accuracy better than 10 arcsec, of which five are identified, with a further seven (and a maximum nine) probable identifications. Of the identified sources, four are QSOs with J-magnitude about 20 (one is an inverted spectrum radio source) and one is associated with extended emission from a pair or cluster of galaxies. Of the probable identifications, one is a galaxy and the rest are a subset of a yellow stellar object population which may also be QSOs. Identifications with QSOs and QSO candidates with J less than 24 account for 60-80 percent of the detected sources.

Griffiths, R. E.↗
NASA NTRS1983

Einstein Observations of X-ray emission from A stars

Results are reported from the combined CfA Stellar Survey of selected bright A stars and an Einstein Guest Observer program for Ap and Am stars. In an initial report of results from the CfA Stellar Surveys by Vaiana et al. (1981) it was noted that the spread in observed X-ray luminosities among the few A stars observed was quite large. The reasons for this large spread was studied by Pallavicini et al. (1981). It was found that the X-ray emission from normal stars is related very strongly to bolometric luminosity for early-type stars and to rotation rate for late-type stars. However, an exception to this rule has been the apparently anomalous behavior of A star X-ray emission, for which the large spread in luminosity showed no apparent correlation with either bolometric luminosity or stellar rotation rate. In the present study, it is shown that the level of emission from normal A stars agrees with the correlation observed for O and B stars.

Golub, L.↗