Search NASA⌕ Search

SEARCH · Search NASA

Results for “close binary systems”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The 1979 X-ray outburst of Centaurus X-4

X-ray observations of the first major outburst of the classical transient X-ray source Centaurus X-4 since its discovery in 1969 are presented. The observations were obtained in May, 1979, with the all-sky monitor on board Ariel 5. The flare light curve is shown to exhibit many of the characteristics of other transients, including a double-peaked maximum, as well as significant, apparently random, variations and a lower peak flux and shorter duration than the 1969 event. Application of a standard epoch-folding technique to data corrected for linear decay trends indicates a possible source modulation at 0.3415 days (8.2 hours). Comparison of the results with previous other data on Cen X-4 and the characteristics of the soft X-ray transients allows a total X-ray output of approximately 3 x 10 to the 43rd ergs to be estimated, and reveals the duration and decay time of the 1979 Cen X-4 outburst to be the shortest yet observed from soft X-ray transients. The observations are explained in terms of episodic mass exchange from a late-type dwarf onto a neutron star companion in a relatively close binary system.

Kaluzienski, L. J.↗
NASA NTRS1980

A 5.57 hr modulation in the optical counterpart of 2S 1822-371

A periodic 5.57 hr modulation has been observed in the optical counterpart of the X-ray source 2S 1822-371. Two alternative periods are consistent with the data: P = 0.232114d and P = 0.232191d, with statistical uncertainties of 0.000015d in each case. Minimum light occurred at JD 2,444,105.668 + or - 0.005. The amplitude of the modulation is about 1 mag, independent of UBV color, and no variability exceeding the 2% level other than the 5.57 hr effect is found on time scales down to a few seconds. The light curve of the star can be understood in terms of a highly inclined close binary system which contains a relatively large, luminous accretion disk that is periodically occulted by a companion star and an associated gas stream. On the assumption that the companion is a main-sequence star, the distance of the system is found to be more than 600 pc, based on the absence of color variations commensurate with the 5.57 hr intensity cycle.

Mason, K. O.↗
NASA NTRS1981

A study of the Mg II k line in Beta Persei

Spectral scans of the Mg II k line in Beta Per were obtained with Copernicus during two primary eclipses. A brief description of observation in a short frame mode is given. The observed data are compared with computed line profiles based on the eclipse geometry of spherical stars. It is shown that a nonuniform circumstellar envelope, or cloud, probably is present. In one scan, a red-shifted line of P Cygni-type profile appeared, indicating the occurrence of an unusual event in the close binary system.

Chen, K.-Y.↗
NASA NTRS1981

Phase-correlated P Cygni profile variations of the C III multiplet in UW Canis Majoris

The interacting close binary system UW CMa has been observed, in the wavelength range from 1161 to 1188 A, continuously during a complete orbital cycle in 1979 with the Copernicus (OAO-3) U2 spectrometer. The C III multiplet at 1175 A, observed as a P Cygni feature, exhbits a clear dependence on the orbital phase of the binary; the radial velocity variation of this feature lags behind that of the O7 primary component by 0.1 orbital phase, which agrees with the anticipations in an earlier study by the same authors. The radiation-driven matter, flowing out of the binary, originates in the primary component.

Drechsel, H.↗
NASA NTRS1981

X-ray observations of selected cataclysmic variable stars using the Einstein Observatory

X-ray observations of 12 cataclysmic variable stars using the Einstein Observatory are reported. Nine of these stars, representing all subclasses of cataclysmic variables, were detected. Their fluxes range from 2 x 10 to the -13th to 1 x 10 to the -11th ergs/sq cm-s in the energy interval 0.16-4.5 keV. The spectra of all the sources detected are relatively hard (kT not less than 5 keV). There is no evidence for an ultrasoft emission component (kT of about 50 eV) such as has been observed from the dwarf novae SS Cyg and U Gem during optical outburst. The X-ray and optical fluxes of the objects observed can be understood in terms of differences in mass accretion rate if the accreting stars in these close binary systems possess a weak magnetic field.

Cordova, F. A.↗
NASA NTRS1981

IUE observations of eight dwarf novae - A study of the outburst cycle from 0.12 to 3.5 microns

The dwarf novae are a class of close binary systems with a G-M star transferring mass to a white dwarf. The transferred material accumulates in a disk and accretes onto the white dwarf. Dwarf novae are characterized by outbursts on time scales of weeks to months possibly triggered by instabilities in the disk. To test the steady state models and the behavior of the disk at various stages of the outburst cycle, IUE observations were conducted for eight dwarf novae. Selected UV continuum points were joined to nonsimultaneous optical and IR spectrophotometry and broad-band photography to yield flux distributions over a large wavelength range. These flux distributions are discussed in terms of available accretion disk models.

Szkody, P.↗
NASA NTRS1982

A model for the 1979 outburst of the recurrent nova U Scorpii

A series of ultraviolet spectra were obtained of the recurrent nova U Sco during its recent outburst with the IUE satellite. These spectra were analyzed and found to consist primarily of emission lines although broad resonance absorption is present during the first week. These data, in combination with the optical data, show that the nova ejecta is very depleted in hydrogen relative to helium and is rich in nitrogen. An optical spectrum, obtained nine months after the outburst, shows predominantly He II emission lines, indicating that the gas being transferred from the secondary is very helium rich and that the secondary is highly evolved. These data are interpreted to imply that the outburst is associated with the accretion of helium rich material by a massive white dwarf in a close binary system. Neither the observational data nor the theoretical calculations, permit differentiation between a thermonuclear runway or an accretion event as the cause of the outburst. In both cases, an equal amount of material is ejected at equal speeds.

Starrfield, S.↗
NASA NTRS1981

A four-hour orbital period of the X-ray burster 4U/MXB1636-53

The characterization of X-ray burst sources and other, non-bursting galactic bulge X-ray sources as low-mass close binary systems is generally accepted. The companion stars of the transient burst sources Aql X-1 and Cen X-4 are of spectral types G7-K3V and K3-7V, respectively. If these stars fill their Roche lobe, their orbital periods are in the range of 5-8 hr. X-ray observations offer evidence for a Cen X-4 orbital period of about 8 hr. An analysis of average optical properties yields values for the typical companion star masses and orbital periods of this class of low-mass X-ray binaries of about 0.6 solar masses and 6 hr, respectively.

Pedersen, H.↗
NASA NTRS1982

Hot wind from Gamma/2/ Velorum observed in the ultraviolet carbon lines

The close binary system Gamma(2) Vel, consisting of a WC8 and an O9 I star, has been observed in the ultraviolet at various phases. Preliminary analysis of selected data shows that the temperature of the stellar wind from this binary increases outward. This suggests that an additional source of energy other than radiation pressure may exist for the wind. The mass flow occurs in all directions from the binary. However, there is evidence of an increase in the mass flow through the third Lagrangian point, although from the extant data it is not possible to decide whether or not a similar increase in the mass outflow occurs through the second Lagrangian point. There is also evidence of mass surge, which probably is independent of orbital phase.

Kondo, Y.↗
NASA NTRS1982

Nodding motions of accretion rings and disks - A short-term period in SS 433

It is pointed out that accretion disks and rings in mass transfer binaries have been observed spectroscopically and calculated theoretically for many years. The present investigation is partly based on the availability of several years of spectroscopic observations of the Doppler shifts of the moving lines in SS433. A formalism is presented to compute frequencies and amplitudes of short-term 'nodding' motions in precessing accretion disks in close binary systems. This formalism is applied to an analysis of the moving-line Doppler shifts in SS433. The 35d X-ray cycle of Hercules X-1 is also discussed. In the considered model, the companion star exerts a gravitational torque on the disk rim. Averaged over the binary orbit, this yields a steady torque which results in the mean driven counterprecession of the disk.

Katz, J. I.↗
NASA NTRS1982

Evolution of close binary stars - Observational aspects

Detached close binary systems define the main sequence band satisfactorily, but very little is known about the masses of giants and supergiants. High-dispersion IUE observations promise an improvement, since blue companions are now frequently found to late-type supergiants. The interesting cases of Mu Sagittarii and in particular of Epsilon Aurigae are discussed in more detail. The barium star abundance anomaly appears now to be due to mass transfer in interacting systems. The symbiotic stars are another type of binary systems containing late-type giants; several possible models for the hotter star and for the type of interaction are discussed. The W Serpentis stars appear to be Algols in the rapid phase of mass transfer, but a possible link relating them to the symbiotics is also indicated. Evidence of hot circumstellar plasmas has now been found in several ordinary Algols; there may exist a smooth transition between very quiescent Algols and the W Serpentis stars. Bet2 Lyrae is discussed in the light of new spectrophotometric results.

Plavec, M. J.↗
NASA NTRS1983

The LSS 4300: A hot counterpart of Upsilon Sgr and KS Per?

A number of observations indicate that the star LSS 4300 is a high temperature analog of the hydrogen-deficient binaries upsilon Sgr and KS Per. A preliminary model-atmosphere analysis based on high-dispersion spectra obtained at Kitt Peak and Cerro Tololo yields T(eff) = 14,400 K, log(g) = 1.4, n(H)/n(He) = 0.003, and n(N)/n(C) = 20 (the corresponding values for upsilon Sgr are T(eff) = 10,000 K, log(g) = 1, n(H)/n(He) = 0.0005, and n(N)/n(C) = 20). The optical emission-line spectrum of LSS 4300 is nearly identical to that of upsilon Sgr, including strong, broad H alpha, FeII and Ca II emission. The ultraviolet spectrum of LSS 4300 was observed with IUE, and can be attributed almost entirely to the visible star. The JHKL photometry of LSS 4300 obtained at Cerro Tololo reveals an infrared excess nearly identical to that of upsilon Sgr. It is suggested that LSS 4300, like upsilon Sgr and KS Per, is a close binary system consisting of a helium supergiant of about one solar mass, and a secondary which is overluminous for its mass due to the accretion of matter from the primary, which is undergoing its second mass exchange.

Drilling, J. S.↗
NASA NTRS1981

X-ray astronomy from Uhuru to HEAO-1

The nature of galactic and extragalactic X-ray sources is investigated using observations made with nine satellites and several rockets. The question of X-ray pulsars being neutron stars or white dwarfs is considered, as is the nature of Population II and low-luminosity X-ray stars, the diffuse X-ray emission from clusters of galaxies, the unidentified high-galactic-latitude (UHGL) sources, and the unresolved soft X-ray background. The types of sources examined include binary pulsars, Population II X-ray stars (both nonbursters and bursters) inside and outside globular clusters, coronal X-ray emitters, and active galactic nuclei. It is concluded that: (1) X-ray pulsars are strongly magnetized neutron stars formed in the evolution of massive close binaries; (2) all Population II X-ray stars are weakly magnetized or nonmagnetic neutron stars accreting from low-mass companions in close binary systems; (3) the diffuse emission from clusters is thermal bremsstrahlung of hot matter processed in stars and swept out by ram pressure exerted by the intergalactic gas; (4) most or all of the UHGL sources are active galactic nuclei; and (5) the soft X-ray background is emission from a hot component of the interstellar medium.

Clark, G. W.↗
NASA NTRS1982

Infrared photometry of the X-ray binary 2A 1822-371 - A model for the ultraviolet, optical, and infrared light curve

The X-ray source 2A 1822-371 may be prototypical of a class of accreting close binary systems in which the X-ray emission is diffused by a cloud of ionized material which is associated with the accretion disk. The present investigation provides a report on infrared photometry of 2A 1822-371 in the J (1.25 micrometer), H (1.65 micrometer), and K (2.2 micrometer) bands. A complete 5.57 hr light curve has been obtained at J which makes it possible to extend the investigations of the energy dependence of the ultraviolet and optical curve begun by Mason and Cordova (1982). The work conducted by White and Holt (1982) is extended to the long wavelength light curve by incorporating the influence of emission from the inner and outer rim of the disk and from the companion star. Including such effects, and assuming that reprocessed X rays are the major source of light at wavelengths greater than 1100 A, it is found possible to reproduce the morphology and energy dependence which is observed in the light curve of 2A 1822-371 from the far-ultraviolet to the near-infrared.

Mason, K. O.↗
NASA NTRS1982

Cool luminous stars

The consequences of magnetic fields for the atmospheres of cool stars are addressed based on IUE and Einstein Observatory observations. Gross atmospheric structure data for cool luminous stars are discussed, and the relevance of the observations for the energy balance and nonradiative heating rates is considered. Data from X-ray fluxes, low dispersion UV spectra, and high dispersion spectra in the region of the Mg II resonance lines are presented. New results on cool star atmospheres provided by high dispersion UV spectra are considered, including those pertaining to spectral line identification, identification of emission components in close binary systems, densities and atmospheric extension, emission line widths, properties of stellar winds as derived from IUE data, and systematic flows of transition region plasma. An explanation for the observed spectra of cool giants and supergiants is proposed in terms of active, quiet, and hybrid stars.

Linsky, J. L.↗
NASA NTRS1984

LSS 4300 - A hot counterpart of Upsilon Sagittarii and KS Persei?

A number of recent observations indicate that the star LSS 4300 (HDE 320156) is a high-temperature analog of the hydrogen-deficient binaries Upsilon Sgr and KS Per. A preliminary model-atmosphere analysis based on high dispersion spectra obtained at Kitt Peak and Cerro Tololo yields Teff = 14,400 K, log (g) = 1.4, n(H)/n(He) = 0.003, and n(N)/n(C) = 20 for the visible component. The optical emission-line spectrum of LSS 4300 is nearly identical to that of Upsilon Sgr, including strong, broad H-alpha, Fe II, and forbidden Ca II emission; and JHKL photometry obtained at Cerr Tololo reveals an infrared excess nearly identical to that of Upsilon Sgr. It is suggested that LSS 4300, like Upsilon Sgr and KS Per, is a close binary system consisting of a helium supergiant of about 1 solar mass, which is undergoing its second mass loss, and a less luminous secondary, which is accreting matter from the primary.

Schoenberner, D.↗
NASA NTRS1984

X-ray observations of a large sample of cataclysmic variable stars using the Einstein Observatory

This paper presents the results of an X-ray survey of 31 known or suspected cataclysmic variables. Eighteen of these close binary systems are detected with inferred luminosities in the 0.1-4.0 keV band of between 10 to the 30th and 10 to the 32nd erg/sec. The majority have relatively hard X-ray spectra (kT greater than 2 keV) irrespective of luminosity state. Of seven dwarf novae observed during optical outbursts only U Gem exhibited enhanced ultrasoft X-ray emission (kT of about 10 eV) in addition to weak, hard X-ray emission. Variability of the X-ray flux is observed in many of these stars, on time-scales ranging from tens of seconds to hours. The contribution to the flux from extended X-ray emission is investigated for SU UMa and GK Per. Several possibilities for the origin of the hard X-rays are considered.

Cordova, F. A.↗
NASA NTRS1985

Evidence for Non-radiative Activity in Stars with T Sub Eff 10000 K

Major advances in the acquisition of evidence for and the understanding of nonradiative heating and other activity in stars cooler than T sub eff = 10,000 K has occurred in the last few years primarily as a result of the IUE and Einstein spececraft. This evidence is critically reviewed and trends that are now becoming apparent are noted. The existence for nonradiatively heated outer atmospheric layers (chromospheres, transition regions, and coronae) in dwarf stars cooler than spectral type A7, in F ang G giants, pre-main sequence stars, and close binary systems in unambiguous, and chromospheres exist in the K and M giants and supergiants. The existence of nonradiative heating in the outer layers of the A stars remains undetermined despite repeated searches at all wavelengths. Some important trends in these data are the decrease in plasma emission measure with age on the main sequence and decreasing rotational velocity. Variability and atmospheric inhomogeneity is commonly seen, and there is considerable evidence that magnetic fields define the geometry and control the energy balance in the outer atmospheric layers.

Linsky, J. L.↗