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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Long term X-ray observations of systems with unusual optical counterparts and modulation measurement of selected astronomical sources

The OAO-3 satellite was used for several months' observation of the loss mass X-ray binary sources 2A18822-371 and 4U2129+47 in a search for variability similar to the 35 day on-off cycle observed in Her X-1. The related system Cyg X-2 was observed both optically and in X-rays covering one complete binary cycle of 9.8 days. The UCL X-ray telescope observations revealed no periodities nor obvious variability other than the known orbital periods; however, the ground-based optical spectroscopy supports the interpretation of the photometry periodicities as representing orbital motion in 2A1822-371 and detected radial velocity motions on the photometric period in 4U2129+47. The shape and the length of the 4.8 hour periodicity in the X-ray emission from Cyg X-3 was also studied. The quality OAO-3 data obtained to measure the light curve and look for a change in the period and/or obtain improved measurement of the slope of the light curve was insufficient.

Bowyer, C. S.↗
NASA NTRS1982

Errors in fixed and moving frame of references - Applications for conventional and Doppler radar analysis

Techniques for the correction of errors in Doppler radar scans due to advection effects are presented. A moving frame of reference is shown to be useful in least-squares estimates with stationary observations expressed in scalars or Cartesian coordinates. For non-Cartesian coordinates, such as the deduction of radial velocities from triple Doppler radar data, an integral is defined for accounting for advection effects and consequent coordinate transformations. The multiple radars are necessary for unambiguous characterization of the horizontal wind velocity. A scale analysis is employed to estimate errors with and without the error correction procedure. Improvements in correlations between scans are demonstrated when the error correction method is used.

Tzvi, G.-C.↗
NASA NTRS1983

X Persei - Optical polarization variation on the 580 day binary-like period

Observations of periodicities in the optical polarization of the weak X-ray source X Persei are reported. Polarization was measured in the V band 400 times over the course of 356 nights during 1977-1982. The Q and U Stokes parameters derived from the measurements show a definite variability with a typical amplitude of 0.1%, which is strongest at periods greater than 100 days. In particular, a strong peak is observed with a period of 297 days, consistent with the second-harmonic component of the known 580-day radial velocity cycle. A component with 590-day periodicity is not ruled out by the observations, although it was not detected. Observations imply the 580-day period to be an effect of orbital or rotational processes, with the corotating scattering body either close to the light source or very large in extent, and a system inclination close to 80 deg.

Kemp, J. C.↗
NASA NTRS1983

Laboratory and astronomical measurement of the millimeter wave spectrum of the ethynyl radical CCH

The N = 0 yields 1 and 1 yields 2 rotational transitions of CCH at 87 and 174 GHz, respectively, have been detected in a laboratory glow discharge in a mixture of He and C2H2. The spectroscopic constants of CCH derived from measurements of the hfs of the transitions agree well with those derived from astronomical observations, confirming the astronomical detection of CCH. As the CCH lines in the Orion Nebula are narrower than the laboratory lines but less certain in rest frequency owing to uncertainty in the radial velocity, the most accurate values for the spectroscopic constants of CCH are obtained from a simultaneous fit of both the laboratory and astronomical data. For the rotation, centrifugal distortion, spin-rotation, and hyperfine constants, respectively, the values found are within 0.006 of 43674.534 MHz, within 0.0008 of 0.1071 MHz, within 0.004 of -62.606 MHz, b = within 0.019 MHz of 40.426, and c is within 0.026 of 12.254 MHz.

Gottlieb, C. A.↗
NASA NTRS1983

A survey of ultraviolet interstellar absorption lines

A telescope-spectrometer on the Copernicus spacecraft made possible the measurement of many ultraviolet absorption lines produced by the interstellar gas. The present survey provides data on ultraviolet absorption lines in the spectra of 88 early-type stars. The stars observed are divided into four classes, including reddened stars, unreddened bright stars, moderately reddened bright stars, and unreddened and moderately reddened faint stars. Data are presented for equivalent width, W, radial velocity V, and rms line width, D, taking into account some 10 to 20 lines of N I, O I, Si II, P II, S II, Cl I, Cl II, Mn II, Fe II, Ni II, Cu II, and H2. The data are based on multiple scans for each line. Attention is given to details of observations, the data reduction procedure, and the computation of equivalent width, mean velocity, and velocity dispersion.

Bohlin, R. C.↗
NASA NTRS1983

Lightning propagation and flash density in squall lines as determined with radar

Lightning echo rise times and range-time variations due to discharge propagation are determined using S and L band radars, and the evolution of precipitation reflectivity and the associated lightning activity in squall lines is investigated using VHF and L band radars. The rise time of radar echoes can be explained by ionized channel propagation through the radar beams. Speeds of at least 250,000 m/s are found from measurements of the radial velocity of streamer propagation along the antenna beam. The range-time variations in lightning echoes indicate that either new ionization occurs as streamers develop into different parts of the cloud, channel delay occurs during which adequate ionization exists for radar detection, or continuing current occurs. Determinations of the lightning flash density for a squall line in the U.S. show that the maximum lightning density tends to be near the leading edge of the precipitation cores in developing cells. Long discharges are produced as a cell in the squall line develops and the total lightning density increases, although short discharges predominate. As the cell dissipates, short flashes diminish or cease and the long flashes dominate the lightning activity.

Mazur, V.↗
NASA NTRS1983

Identification and properties of the M giant/X-ray system HD 154791 = 2A 1704+241

The Aerial V X-ray source 2A 1704+241 (= 4U 1700+24 = 3A 1703+241) is identified with the M3 II star HD 154791. The identification is based on a precise X-ray position determined by the HEAO 1 scanning modulation collimator and the Einstein Observatory imaging proportional counter, together with a spectrum measured by the International Ultraviolet Explorer. The ultraviolet spectrum shows strong emission of C IV 1550 A, N v 1238 A, and Mg II 2800 A, which is very unusual among M giants. This is the first X-ray detection of an M giant which has a completely normal optical spectrum. The X-ray luminosity reaches three orders of magnitude above the mean upper limit for the coronal X-ray flux from M giants. Although there is no direct evidence for a binary system, since radial velocity variations have not been observed, it is shown that a plausible neutron star binary model can be constructed.

Garcia, M.↗
NASA NTRS1983

Revised orbits for 105 Herculis and Pi Cephei A and a model for the Pi Cephei system

New orbital elements for the giant primary components of 105 Herculis and Pi Cephei A are derived using radial velocities from Dominion Astrophysical Observatory coude plates. These data are combined with those of Harper (1925) in order to estimate the velocity amplitude of Pi Cephei A in the visual orbit of this triple system. Two models of this system are developed. In the first model, the unseen spectroscopic secondary component is a single main-sequence star, although this seems unlikely, while in the alternative model the unseen secondary component is itself double.

Scarfe, C. D.↗
NASA NTRS1983

HR 7578 - A K dwarf double-lined spectroscopic binary with peculiar abundances

The number of double-lined K and M dwarf binaries which is currently known is quite small, only a dozen or less of each type. The HR 7578 system was classified as dK5 on the Mount Wilson system and as K2 V on the MK ystem. A summary of radial-velocity measurements including the observatory and weight of each observation is given in a table. The star with the stronger lines has been called component A. The final orbital element solution with all observations appropriately weighted was computed with a differential corrections computer program described by Barker et al. (1967). The program had been modified for the double-lined case. Of particular interest are the very large eccentricity of the system and the large minimum masses for each component. These large minimum masses suggest that eclipses may be detectable despite the relatively long period and small radii of the stars.

Fekel, F. C., Jr.↗
NASA NTRS1983

MM Herculis - An eclipsing binary of the RS CVn

V, B and U differential photoelectric photometry has been obtained for the RS Canum Venaticorum-class eclipsing binary star MM Her, with the light outside the eclipse being Fourier-analyzed to study wave migration and amplitude. These, together with the mean light level of the system, have been monitored from 1976 through 1980. Observations within the eclipse have revealed eclipses to be partial, rather than total as previously thought. The geometric elements of the presently rectified light curve are forced on the pre-1980 light curves and found to be compatible. With these elements, and previously obtained double line radial velocity curves, new absolute dimensions of 1.18 solar masses and 1.58 solar radii are calculated for the hotter star and 1.27 solar masses and 2.83 solar radii for the cooler star. The plotting of color indices on the color-color curve indicates G2V and K2IV spectral types.

Sowell, J. R.↗
NASA NTRS1983

Profiles and intensity ratios of the C IV lambda 1548, 1550 emission lines in planetary nebulae

The C IV resonance doublet at lambda 1548, 1550 is an important diagnostic tool in the study of planetary nebulae. The predicted theoretical intensity ratio of 2:1 is, however, rarely observed in the high dispersion IUE spectrograms. Values of 0.8-2.0 are observed for a sampling of 11 planetary nebulae of various excitation classes and for three proto-planetary nebulae. A diversity of line profiles is observed. In addition to the C IV doublet, weak subsidiary lines are seen. The spacing between these pseudo-lines happens to correspond to the separation of the C IV lines but are believed to be due to hot pixels and do not conform to the radial velocity displacement of the C IV lines.

Feibelman, W. A.↗
NASA NTRS1983

Mass loss, levitation, accretion, and the sharp-lined features in hot white dwarfs

A study has been conducted of eight white dwarfs, including seven DA and one He-rich types. The study is based on high-resolution observations conducted with the aid of the International Ultraviolet Explorer. Four of the dwarfs show features related to heavy elements which are not interstellar in origin. It is tentatively suggested that, at least in the hottest low-gravity DA white dwarfs, the observed narrow-lined features are formed in expanding halos or winds associated with the white dwarfs. Theoretically, stable white dwarf halos should actually be coronae with temperatures in excess of 1,000,000 K. However, the observed narrow-lined features do not suggest such high temperatures. The observed radial velocities suggest weak stellar winds in two hot white dwarfs, namely, G191-B2B and 2111+49. It is tentatively proposed that radiative levitation can explain the appearance of the observed metallic lines in the hot DA white dwarfs.

Bruhweiler, F. C.↗
NASA NTRS1983

The dynamics of rich clusters of galaxies. II - The Perseus cluster

The dynamics of the Perseus cluster are analyzed using self-consistent equilibrium analytical models. Using existing data in the literature plus new radial velocities reported here, composite surface density and velocity dispersion profiles are derived. These profiles have been compared with dynamical models described by Kent and Gunn (1982). The best fit suggest the presence of a significant degree of anisotropy in the velocity distribution: galaxy orbits are constrained to pass within a radius of seven cluster radii, or 1.3 deg of the cluster center. For Hubble constant = 50, a core radius of 340 kpc 11 arcmin and a mass to visual light ratio M/L = 300 are found. Using these results, X-ray observations of the intracluster medium in Perseus are reanalyzed. A previously noted discrepancy between the observed temperature of the hot gas and the cluster velocity dispersion is reduced but not eliminated. A cooling accretion flow previously deduced to exist in this cluster is shown to extend to only about one-third of the cluster radius.

Kent, S. M.↗
NASA NTRS1983

IUE observations of the perplexing bipolar planetary nebula NGC 2346

A preliminary analysis of International Ultraviolet Explorer (IUE) low-dispersion spectrograms of NGC 2346, obtained at various phases of the eclipsing nucleus, shows features typical of a high-excitation planetary nebula. Variations in line profiles, intensities, and stellar continuum are observed as a function of time. An orbital period of 16.0 days was determined from 1.8m(v) variations measured by the IUE Fine Error Sensor (FES) and agrees with the period derived from radial velocity measurements by Mendez.

Feibelman, W. A.↗
NASA NTRS1983

The photometric period of 39 AY Ceti

A photometric period of 77.65 days is derived for 39 AY Ceti through a comparison of photoelectric photometry obtained in 1971 and 1972 with that obtained in the periods 1980-1981 and 1981-1982. JD 2444636.0 is an epoch of minimum light, and the full amplitude is found to have been as large as 0.18 mag in V. It is noted that the mean light level has dropped by almost 0.2 mag over the last decade. The present binary star is also noteworthy in light of the recently discovered white dwarf secondary component, and because radial velocity measurements indicate an eccentricity as large as 0.1 and an orbital period which, at 57.1 days, differs considerably from the photometric period presented.

Hopkins, J. L.↗
NASA NTRS1983

Discovery of a massive unseen star in LMC X-3

Spectroscopic observations of the optical counterpart of LMC X-3 show it to be a spectroscopic binary in the Large Magellanic Cloud with an orbital period of 1.70 days. The B3 main-sequence primary has a large radial velocity amplitude indicating a mass function of 2.3 solar masses. LMC X-3 is an extremely luminous and variable X-ray source, but no 1.7 day X-ray periodicity has been detected. The lack of optical and X-ray eclipses limits the inclination to less than 70 degrees and implies a mass for the unseen star of more than 9.0 solar masses, if the B star has a normal mass. The system now appears to be the strongest evidence for the existence of a stellar mass black hole and is the first extragalactic example.

Remillard, R.↗
NASA NTRS1982

Measurement of ocean surface currents by synthetic aperture radar

Synthetic aperture radar (SAR) is a coherent imaging device which uses the Doppler-induced phase changes of the received signals to locate scatterers in the along-track direction. In principle, the recorded data can be analyzed to obtain the radial velocity of moving objects in the scene relative to the flight path of the SAR platform. The application of this concept for measuring ocean surface currents has been evaluated using data from SAR systems mounted in aircraft and spacecraft platforms. This paper describes the results of these experiments and summarizes the limitations of the technique using existing SAR systems. Considerations involved in the design of optimum systems for this application are also discussed.

Lyzenga, D. R.↗
NASA NTRS1983

A multiwavelength study of the short-period cataclysmic variable V442 Ophiuchi

The results of a program of observations of the cataclysmic variable V442 Oph from UV to IR wavelengths are reported. The observations comprise IUE SWP and LWR-camera spectra from October, 1981; UBVr and R photometry at Manastash Ridge Observatory from August, 1980; UBV photometry and IR measurements at Kitt Peak from July, 1981; and Coudespectroscopy at Mt. Wilson from June, 1980, and at Mt Lemmon from July, 1982. Tables of data, plots of H-alpha and He-II radial velocity, sample spectra, light curves, and a log-log diagram of F(lambda) vs lambda are given. Flux-ratio analysis of the IR data indicates a disk with very little optically thin material anad an outer-edge temperature of about 7920 K. The calculated period (3.37 h) and mass-accretion rate (1 x 10 to the -8th solar mass/yr) are compared to those of similar objects, and V442 Oph is found to be similar in this respect to systems like H2252-035. Its lack of a rotational period and the weakness of the optical and UV line emissions, however, are more like the old nova V603 Aql.

Shafter, A. W.↗