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Results for “X-ray binaries”

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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At least 163 records · Page 9
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NASA NTRS1975

Intense soft X-ray flux from Hercules X-1

An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption, the luminosity in the 0.16-0.28 keV band is comparable to that from 2 to 10 keV. This confirms the conclusion of Shulman et al. (1975) but extends the detection of this flux to higher energy, a different binary phase, and to a time 19 periods later in the 35-day cycle. These observations suggest that this soft emission may be a stable feature in the spectrum of Her X-1 during its X-ray on state. It appears difficult to account for the high soft X-ray luminosity by current simple models of the X-ray source.

Catura, R. C.↗
NASA NTRS1978

Discovery of iron line emission in the Hercules X-1 low-state spectrum with HEAO 1

Results are reported for HEAO 1 observations of Her X-1 which confirm the existence of the iron line-emission feature discovered with OSO 8 in the high-state spectrum and also reveal an iron emission feature in the low-state spectrum. The iron line-emission feature in the low-state spectrum was detected at a significance level greater than 5 sigmas and is characterized by a line energy of 6.4 keV, an equivalent width larger than that of the high-state line, a binary phase dependence of the line intensity, and a line width that is intrinsically narrow in contrast to the broad high-state line. The observed line energy and narrow line width are shown to be consistent with an interpretation in terms of fluorescence emission due to X-ray heating. It is suggested that HZ Her contributes no more than about 10% of the predicted line flux, that this emission is reflected from a highly ionized plasma, and that a hot coronal gas is an important source of the low-state X-rays.

Pravdo, S. H.↗
NASA NTRS1978

Ultraviolet and optical spectral variability in the Be star Gamma Cassiopeiae - A coronal model for the emission

This paper reports the presence of Mg II emission, the probable presence of Si IV emission, and the possible presence of N V absorption in the UV spectrum of the B0.5 IVe star Gamma Cas. Changes in these features on time scales of several months are described. The detached-ring and mass-exchange binary models are briefly discussed and shown to be inadequate for Gamma Cas. An ad hoc generalization of the detailed stellar-wind model of Poeckert and Marlborough (1978) is presented and suggested as being qualitatively compatible with the UV data as well as with photoelectric H-alpha observations and the X-ray outburst observed in 1976. The presence of a 1-solar-mass neutron star companion with an orbital period of about 4 yr is hypothesized.

Marlborough, J. M.↗
NASA NTRS1977

Spectrophotometry of the transient X-ray source A0620-00

Optical observations of the transient X-ray source A0620-00 over the wavelength range from about 3200 to 6600 A are analyzed which were made with the 5-m Hale telescope using a multichannel spectrometer, a digital spectrograph with a cooled integrating SIT vidicon, and an image photon-counting system attached to the camera of the coude spectrograph. Infrared observations at 1.65, 2.2, and 3.5 microns are also examined. Individual spectral lines of special interest are discussed, the E(B-V) color excess is estimated to be about 0.40, and a distance of 1200 pc is adopted. Analysis of the continuous spectrum yields several simple binary models. A specific model is proposed in which one of the continuum sources is an optically thick object characterized by a model atmosphere at a temperature of 25,000 to 30,000 K and the second source is either a cool black body at 4000 K or a partially optically thick source of bound-free plus free-free radiation from a hydrogen gas with an electron temperature of at least 100,000 K. Some possible parameters of these sources and of the accretion disk are considered.

Oke, J. B.↗
NASA NTRS1976

The transient periodic X-ray source in Taurus, A0535+26

Eighteen X-ray light curves of the 104-sec periodicity in the Taurus X-ray nova A 0535+26 are analyzed which were obtained by SAS-3 in six energy intervals between 1 and 35 keV during the period from May 30 to June 2, 1975. It is shown that the pulse structure is relatively simple at energies above 19 keV, but develops a complex series of five irregularly spaced maxima at lower energies. The energy spectrum averaged over the 104-sec period is found to be extremely hard, with a best-fit temperature of about 30 keV for the exponential spectrum, an excess at about 15 keV, and a steepening above 20 keV. It is suggested that A 0535+26 may be a compact object in a binary system containing the peculiar Be star HDE 245770. The transient behavior could arise due to episodic mass loss by the primary or because the compact object is in a highly eccentric orbit about the companion, with appreciable mass transfer occurring only at periastron.

Bradt, H.↗
NASA NTRS1976

High-energy X-ray observations of the southern sky

Results are reported for high-energy (above 17 keV) balloon-borne X-ray observations in the southern sky which detected at least five sources that produced X-ray counts above background with a significance of four or more standard deviations. The probable sources observed include GX 301-2 (3U 1223-62), GX 1+4 (3U 1728-24), GX 5-1 (3U 1758-25), GX 3+1 (3U 1744-26), and GX 331-1. It is noted that some or all of the flux attributed to GX 5-1 might be due to 3U 1820-30 and that GX 3+1 was not completely resolved from GX 1+4. Energy spectra are given for each source along with upper limits to periodic fluctuations of the detected fluxes in the frequency range from 0.01 to 100 Hz. A possible observation of a flux from the eclipsing binary source 3U 1700-37 is discussed.

Ricker, G. R.↗
NASA NTRS1976

The discovery of rapidly repetitive X-ray bursts from a new source in Scorpius

Rapidly repetitive X-ray bursts have been observed from a new X-ray source in Scorpius. More than 2000 bursts were observed during the 4-day continual SAS-3 observations of this source designated MXB 1730-335. The time interval between bursts varied from a minimum of about 6 s to a maximum of about 5 minutes. The energy in a given burst is approximately linearly proportional to the time interval to the next burst. The largest bursts observed last for about 60 s and represent an energy release of approximately 10 to the 40th ergs for an assumed distance to the source of 10 kpc. The smallest bursts observed last only for a few seconds. We suggest that the bursts are caused by sporadic precipitations of plasma from a reservoir in the magnetosphere of a neutron star. The reservoir is replenished at a nearly constant rate by mass transferred from a binary companion.

Lewin, W. H. G.↗
NASA NTRS1972

Optical candidates for two X-ray sources.

Suggestion of the bright stars X Per and HD 77581 as possible candidates for the X-ray sources 2U 0352+30 and 2U 0900-40 respectively. The first is an active, rapidly rotating Be star which is losing mass. The second is similar to BD+34.3815 deg, a likely candidate for Cyg X-1, in spectral type and in the possibility that it may be a short-period binary.

Brucato, R. J.↗
NASA NTRS1973

High energy and solar astronomy, overview

A survey of our own galaxy and neighboring galaxies using X-rays, gamma rays, and cosmic rays is outlined. High energy astrophysic results suggest the presence of a new acceleration mechanism where the inflow of matter on collapsed objects seems to be one of the sources of complex time variations in binary systems.

Mcdonald, F. B.↗
NASA NTRS1972

Discovery of the binary nature of SMC X-1 from Uhuru.

The X-ray source in the Small Magellanic Cloud SMC X-1 was observed by Uhuru on numerous occasions from December 1970 through April 1972. As previously reported by Leong et al. (1971), the source was seen to be variable. It was found that SMC X-1 occults with a period of 3.8927 days. The energy spectrum is cut off at low energies and flat. There is no large-amplitude periodic pulsation. The luminosity observed makes the binary source SMC X-1 comparable in strength to both the stronger galactic sources and the discrete sources in the Large Magellanic Cloud.

Schreier, E.↗
NASA NTRS1976

Pulsed X-ray observations of Cen X-3 from Ariel-5

The 4.8 second X-ray pulsations from Centaurus X-3 were monitored by the MSSL collimated proportional counter on board Ariel-5 between 18-27 January 1975. Analysis of the source Doppler effect shows that the pulsation period of Cen X-3 decreased by 3.70 + or - 0.04 milliseconds during the preceding 2.3 years. The Doppler analysis also yields updated values for the binary phase and period of Cen X-3. Phase zero occurred at JD 2442438.628 + or - 0.003, and the average heliocentric binary period between October 1972 and January 1975 was 2.087129 + or - 0.000007 days. Light curves of the 4.8 second pulsations in the 3-9 keV band are characterized by two pronounced peaks, in contrast with the single peak profiles observed by Uhuru.

Tuohy, I. R.↗
NASA NTRS1976

Optical observations of HDE 226868 = Cygnus X-1: A review

The present state of knowledge of the binary system HDE226868 = Cygnus X-1 is summarized, including system dimensions, nature of the secondary X-ray source, and mass transfer properties. Some deficiencies in the optical observations are pointed out; these deficiencies make interpretation of the system difficult, but can be corrected.

Bolton, C. T.↗
NASA NTRS1976

The X-ray variability of Vela X-1 (3U 0900-40)

From observations of Vela X-1 with the MSSL 2.5-7.5 keV detector onboard Copernicus, the behavior of the source can be characterized by three phases: (1) high intensity, (2) low intensity, and (3) eclipse. Combining data from the 1972 Uhuru observations with eclipse observation yields a binary period of 8.963 + or - 0.001 days with zero phase on 1975 Feb. 6.97 + or - 0.04 UT. The low intensity phase is interpreted as being due to increased absorption in an accretion wake traveling across the line of sight (the spectral slope remains relatively constant throughout the cycle). Another period of enhanced absorption immediately after exit from eclipse may be due to a bow shock. Comparison of the two observations suggests that these structures vary from cycle to cycle and, since the orbital period is long, probably during each cycle.

Charles, P. A.↗
NASA NTRS1976

Evidence for a 17-d periodicity from Cyg X-3

Data are presented from the Ariel-V All-Sky Monitor which indicate a 17-day periodicity of the X-ray spectra from Cyg X-3 (3U2030+40). The data are consistent with data from the Ariel V Sky Survey Experiment. Assuming that the high intensity state of Cyg X-3 is well fitted by a structureless black body (Serlemitsos et al., 1975), and that the 17-day maxima correspond to increased electron scattering in the source, it is suggested that the 17-day effect is analogous to the 35-day variation in Her X-1. The possible explanation of this phenomenon as a result of the 17-day orbital period of the binary system containing Cyg X-3 is severely constrained by the stability of the well-known 4.8-hour variation.

Holt, S. S.↗
NASA NTRS1978

Observation of X-ray eclipses from LMC X-4

Observations made with the Rotation Modulation Collimator system (RMC) have revealed that X-ray source X-4 in the Large Magellanic Cloud (LMC X-4) is most likely part of a binary system. An analysis of the star's coordinates is presented, with attention given to orbital period and flux intensity variations. Stellar mass and orbital inclination angle are estimated for both X-4 and its companion star.

Li, F.↗