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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 NTRS1981

Observations of the giant radio lobes region of Centaurus A with SAS 3

Observations of the X-ray flux from the extended radio lobes of the galaxy Centaurus A obtained with the SAS 3 observatory are reported. The 15 x 15 deg region that includes the lobes was mapped by superposing data from raster scans with the horizontal tubular collimator detectors, which have a 1.7 deg FWHM circular field of view. Data obtained is consistent with the presence of superposed emission from the point sources NGC 5128 and MX 1312-42, a previously unreported source detected by the Einstein Observatory IPC. Fluxes of 4.63 + or - 0.14 x 10 to the -10th and 4.6 + or - 0.6 x 10 to the -11th ergs/sq cm per sec were measured for NGC 5128 and MX 1312-42, respectively, with best fit power law spectra of indices 0.83 + or - 0.04 and 0.62 + or - 0.10 and hydrogen column densities of 1.23 + or - 0.10 x 10 to the 23rd and 9.7 + or - 15.0 x 10 to the 21st atoms/sq cm. Results imply an upper limit of 2.9 x 10 to the 11th for the X-ray emission from the extended radio lobes of Cen A between 2 and 10 keV, which indicates a lower limit to the magnetic field in the lobes of 1.6 x 10 to the -6th gauss.

Marshall, F. J.↗
NASA NTRS1981

Simultaneous X-ray, ultraviolet, optical, and radio observations of the flare star Proxima Centauri

Results of coordinated program of observations in the X-ray, UV, optical and radio regions of the dM5e flare star Proxima Centauri are presented. Simultaneous observations of the star were obtained on March 6 and March 7, 1979, by the Einstein Observatory IPC, the IUE SWP and LWR cameras at low dispersion, three ground-based optical telescopes in Australia and the Parkes 64-m radio telescope. A total of 10 radio bursts and six optical flares was detected during three nights of simultaneous radio and optical observations, which appear to be broadly correlated. A major X-ray flare event was detected with temperatures of 1.7 x 10 to the 7th and 1.2 x 10 to the 7th K during the rise and decay phases, respectively, respective X-ray fluxes of 3.0 x 10 to the -11th and 3.7 x 10 to the -11th ergs/sq cm per sec, and changes in spectral flux distribution. No radio, optical or UV flare emission corresponding to the X-ray flare was detected. The X-ray flare is interpreted in terms of an arch model with cooling predominantly by X-ray radiation, with an electron density of 1.0 x 10 to the 11th/cu cm during the decay phase and a total arch length comparable to the size of the star itself. The X-ray flare observed is thus more similar to a typical strong solar flare than heretofore seen on a flare star.

Haisch, B. M.↗
NASA NTRS1981

Observations of the X-ray sources in the nearby Sc galaxy M33

Two observations of the Local Group spiral M33 with the Imaging Proportional Counter (IPC) on the Einstein Observatory reveal the presence of 11 point sources which, if at the distance of M33, have X-ray luminosities ranging from 10 to the 37th ergs/sec to 10 to the 39th ergs/sec. The brightest source, coincident with the nucleus of the galaxy, comprises approximately 70% of the total X-ray luminosity of the galaxy. If this source is a single source, it must be qualitatively different from the compact binary sources which dominate the X-ray luminosity of the Galaxy.

Long, K. S.↗
NASA NTRS1982

X-ray and UV spectra of two quasars: PKS0637-75 and PKS1004+13 (4C13.41)

Two quasars, 4C13.41 (1004+13, V approx. 15.2, z = 0.140) and PKS0637-75 (V = 15.75, z = 0.651) were observed in December 1980 with IUE. Both were detected in the short wavelength region. 4C13.41 has the lowest X-ray luminosity/optical luminosity measured in quasars. PKS0637-75 was observed quasi-simultaneously with the Einstein Observatory and a spectrum obtained with the IPC. The UV and soft X-ray spectra have been combined and are discussed together with the optical and infrared data for both objects.

Elvis, M.↗
NASA NTRS1981

The smothered coronae of T Tauri stars

Einstein IPC observations of 10 fields containing pre-main-sequence stars are presented. The detection of significant soft X-ray flux from eight cataloged T Tauri stars plus the optical identification of two new T Tauri-like stars associated with X-ray sources are reported. It is demonstrated than an inverse correlation between the H-alpha equivalent width and the detection of X-ray flux exists. This is interpreted in terms of a model wherein the X-ray emission arises in a corona similar to that of active late-type stars, which is small compared to the extent of the circumstellar envelope. It is postulated that the lack of correlation of X-ray flux (or H-alpha) with A(v) is due to a lack of grains in the envelopes of the more active T Tauri stars.

Walter, F. M.↗
NASA NTRS1981

X-ray and optical observations of the November 19, 1978 gamma-ray burst source region

The Nov. 19, 1978 gamma-ray burst (GRB) has a very well determined error box, 10 square arcmin (Cline et al., 1981). An 8000-sec IPC exposure with the Einstein Observatory detected, at a 3.4-sigma level, one low intensity (less than 3 x 10 to the -13th erg/sq cm per sec) X-ray source inside the error box. The probability of a serendipitous detection was 0.01. Inside the X-ray source error box there are two weak radio sources, one of them highly polarized (Hjellming and Ewald, 1981), and two 20-magnitude objects, not coincident with the radio sources visible in the ESO/SRC J and R plates. With the exception of N49, this is the first possible detection of X-ray emission inside a GRB box. Its low intensity justifies, in fact, the lack of detection for other events.

Pizzichini, G.↗
NASA NTRS1981

X-ray and optical observations of HD 155638 - A remarkably active cool star

X-ray and optical observations of the 8.5-mag star HD 155638 are reported which reveal a remarkably active chromosphere and corona for the star. The object was first observed in soft X-rays with the HEAO 1 A2 low-energy detectors, and later reobserved with the HEAO 2 IPC. X-ray fluxes of about 2 x 10 to the -11th and 3 x 10 to the -12th ergs/sq cm per sec were obtained on the two occasions, indicative of source variability over the 2.5-year period between observations. SIT spectrographs taken in July-August 1980 show evidence of Ca II H and K core emission reversals and filled-in H alpha, while spectra taken in March and July 1981 show evidence of asymmetry and variability in the Ca II reversals. The spectral data are consistent with a G8 IV-V classification, from which is inferred a distance of 35-120 pc, and an X-ray luminosity from 4 x 10 to the 29th to 4 x 10 to the 31st ergs/sec. An absence of emission lines characteristic of mass transfer in binary systems indicates the X-rays to be coronal in origin. The properties of the star are noted to be similar to those of the RS CVn binaries.

Stern, R. A.↗
NASA NTRS1981

X-ray sources in globular clusters

The Einstein X-ray Observatory globular cluster observation program has completed a survey of 30 clusters, using the HRI detector. Preliminary results are reported for a more sensitive survey being conducted with the imaging proportional counter (IPC) of the satellite, which has found four possible new sources in the first 32 clusters observed. Also described are detailed studies of several luminous, globular cluster sources, including the X-ray burst from Terzan 2, and an effort is made to locate the X-ray sources with respect to cluster centers. Sources of systematic error, required optical studies of globular cluster structure, and the implications of the plausible binary systems for cluster core evolution are discussed.

Grindlay, J. E.↗
NASA NTRS1982

Evidence for 200 second variability in the X-ray flux of the quasar 1525 + 227

Sixteen hundred seconds of Einstein Observatory IPC data for 1525 + 227, a bright, nearby quasar show significant intensity fluctuations on a time scale of 200 seconds. Similar fluctuations were not detected 13 months later during a follow-up 12,500 second observation. Interpretation of the time variations requires a Hubble constant equal to or greater than 100 km/s per Mpc to obtain even marginal consistency with standard isotropic emission models. An alternative interpretation invokes anisotropic emission probably due to the presence of relativistic motions with associated beaming effects.

Matilsky, T.↗
NASA NTRS1982

Aircraft sampling of the sulfate layer near the tropopause following the eruption of Mount St. Helens

Twenty-three filter sampling flights of the NASA Lewis F-106 aircraft, were conducted in the Great Lakes region between June 4 and Dec. 23, 1980, following the major eruption of Mount St. Helens on May 18. The IPC-1478 filters were exposed over an altitude range spanning the local tropopause. A filter sample exposed above the tropopause on June 5 indicated a sulfate level 50 times the baseline measurements, which is consistent with the trajectory predictions of the leading edge of the cloud on its second transit around the earth. Subsequent measurements over a period of 7 months revealed the existence of a layer of sulfate above the tropopause that decayed to a level of about 4 times previously measured background levels by the beginning of August. Concentration of nitrate above the tropopause exhibited considerable variability and showed some enhancement compared with previously measured concentration levels. On the basis of the null results of X ray fluorescence measurements, there is no evidence of ash particle concentrations of greater than 3.4 microns/cu m persisting in the layer above the tropopause following the second transit of the cloud.

Lezberg, E. A.↗
NASA NTRS1982

An efficient low- and moderate-resolution spectrograph for the Hale telescope

A new low-to-moderate resolution spectrograph has been designed and built for the Cassegrain focus of the Hale 5.08-meter telescope. To maximize efficiency, resolution, and wavelength coverage the light is divided into two spectra regions by a dichroic filter behind the entrance slit, after which there are two completely separate spectrographs. The blue spectrograph operates from 3200 A to 5200 A while the red one goes from 5200 A to 10,000 A. The red detector is an 800 x 800 TI CCD while the blue detector is a 320 x 512 RCA CCD or a Shectrograph image pulse-counting system. A Boksenberg IPCS can also be mounted on the blue camera. The overall efficiency of the Cassegrain telescope, spectrographs, and CCD's combined, ranges from 5 percent to 13 percent between 3600 A and 8200 A. The spectrograph is usable from 3200 A to 10,400 A.

Oke, J. B.↗
NASA NTRS1982

Aircraft sampling of the sulfate layer near the tropopause following the eruption of Mount St. Helens

Twenty filter sampling flights of the NASA Lewis F-106 aircraft were conducted in the Great Lakes region between June 4 and August 8, 1980, following the major eruption of Mount St. Helens, Washington on May 18. The IPC-1478 filters were exposed over an altitude range spanning the local tropopause. Quarter sections were analyzed for sulfate and nitrate by ion chromatography and selected samples were analyzed for chloride by selective ion electrode. Trace elements were searched by X-ray fluorescence analysis. A filter sample taken above the tropopause on June 5 indicated a sulfate level of 50 times the baseline measurements. Subsequent measurements over a period of 2 months showed an initial dropoff and formation of a persistent layer of sulfate above the tropopause with a concentration of 10 to 18 times previously measured background-levels. Concentrations of nitrate above the tropopause exhibited considerable variability and some enhancement compared with previously measured concentration levels. It is suggested that the source of the nitrate may also be volcanic as evidenced by its temporal relationship to the sulfate concentration changes. Based on the null results of X-ray fluorescence measurements, there is no evidence of ash particle concentrations greater than 3.4 microns g/cubic m persisting in the layer above the tropopause after the second transit of the cloud.

Lezberg, E. A.↗
NASA NTRS1982

Stellar contributions to the hard X-ray galactic ridge

The number density of serendipitous sources in galactic plane Einstein Observatory IPC fields are compared with predictions based on the intensity of the HEAO-1 A2 unresolved hrd X-ray galactic ridge emission. It is concluded that theoretically predicted X-ray source populations of luminosity 8 x 10 to the 32nd power to 3 x 10 to the 34th power ergs s have 2 KeV to 10 KeV local surface densities of less than approximately .0008 L(32) pc/2 and are unlikely to be the dominant contributors to the hard X-ray ridge. An estimate for Be/neutron star binary systems, such as X Persei, gives a 2 keV to 10 keV local surface density of approximately 26 x 10 to the -5 power L(32) pc/2. Stellar systems of low luminosity, are more likely contributors. Both RS CVn and cataclysmic variable systems contribute 43% + or - 18% of the ridge. A more sensitive measurement of the ridge's hard X-ray spectrum should reveal Fe-line emission. We speculate that dM stars are further major contributors.

Worrall, S. M.↗
NASA NTRS1982

X-ray observations of AM Herculis in its low state

AM Her was observed with the Einstein Imaging Proportional Counter during the low state of 1980 August. The light curve shows an eclipse at phi sub m = 0.0 similar to the one observed in the customary high state. The spectral distribution of the X-ray photons does not show any soft component. The IPC flux suggests that the intensity of the hard component in the low state is about one-tenth of the intensity of the hard component during the high state, similar to the variation in the optical magnitude. The comparison of the present data with a previous SAS 3 X-ray observation of AM Her in the low state suggests that the soft component is different in similar accretion regimes. The possibility that this component originates from reprocessing of the hard flux becomes then more unlikely.

Fabbiano, G.↗
NASA NTRS1983

The peculiar radio galaxy 3C 433

Radio, optical and X-ray observations are presented of the peculiar radio galaxy 3C 433, a Seyfert 2 object with luminosity an order of magnitude greater than that expected from its complex, shell-type morphology. Observations conducted at 6 and 12 cm with the VLA and at 21 cm with the Westerbork telescope show a striking asymmetry between the northern and southern radio emissions, and an overall X-shaped morphology. Optical observations using the Video Camera and High Gain Video Spectrometer on the 4-m telescope and the Intensified Image Dissector Scanner on the 2.1-m telescope at Kitt Peak confirm the identification of the source with a pair of bright galaxies. Observations in the X-ray from the Einstein Observatory IPC reveal an unresolved source at the position of 3C 433, as well as two serendipitous X-ray sources. The observations may be used to explain the overall structure of the source either in terms of tidal torquing or precessing models of double galaxies; however, it is argued that the tidal torquing model requires fewer assumptions to account for the brightness asymmetry.

Van Breugel, W.↗
NASA NTRS1983

Stellar contributions to the hard X-ray galactic ridge

The number density of serendipitous sources in galactic plane Einstein Observatory IPC fields are compared with predictions based on the intensity of the HEAO 1 A-2 unresolved hard X-ray galactic ridge emission. It is concluded that it is unlikely that X-ray sources with 2-10 keV luminosities from about 8 x 10 to the 32nd to about 3 x 10 to the 34th ergs/s are dominant contributors to the hard X-ray galactic ridge. Their surfacea density is less than about 8 x 10 to the -4th/L(32)/sq pc. In particular, Be/neutron star systems such as X Per are not expected to be dominant contributors, both because the 2-10 keV luminosity is roughly 10 to the 33rd ergs/s and their scale height is too small. Lower luminosity stellar systems are likely to be major contributors to the ridge. RS CVn and CV systems with 2-10 keV luminosities between 2 x 10 to the 30th and 4 x 10 to the 32nd ergs/s contribute about 43 + or 18 percent.

Worrall, D. M.↗
NASA NTRS1983

X-ray observations of radio-jet galaxies

The possibility that the morphology of radio-galaxy jets may be influenced by interaction with X ray emitting gaseous halos led to a study of several jet galaxies with the Einstein Observatory. These observations carried out with the IPC had a high detection rate (5 out of the 6 radio galaxies observed). The X ray data for these objects are presented. The X ray luminosities lie between about 10 to the 42nd and 10 to the 45th erg/sec. The X ray emission was found to be extended for the two galaxies with the most counts. 3C130 and 3C449. Three of the detected galaxies are known to be associated with clusters and we suggest that 3C130 may also be associated with a cluster.

Miley, G. K.↗
NASA NTRS1983

The X-ray emission of the old Nova V603 Aquilae (1918)

X-ray observations of the old Nova V603 Aql have been obtained with the IPC and MPC instruments aboard the Einstein Observatory during 1.7 consecutive orbital cycles. Periodic orbital phase-dependent flux variations are detected with large-amplitude flickering superimposed on the sinusoidal X-ray light curve. The spectrum is hard, characterized by a temperature of 20-30 keV, and the maximum X-ray luminosity observed was about 3 x 10 to the 33rd erg/s. The X-ray measurements are compared with recent optical photometric observations, and origin of the periodic modulation of the optical and X-ray flux is discussed.

Drechsel, H.↗