Cygnus XR-1 Research Articles

A reanalysis of the orbital inclination of Cygnus XR-1 determined polarimetrically

The orbital inclination of the Cyg XR-1/HDE 226868 system was determined by Dolan and Tapia (1989) to be 62 deg (+5 deg, -37 deg) from polarimetric observations. Together with the spectroscopic mass function of the binary, this corresponds to a mass of 6.3 solar masses for the X-ray source. Numerical simulations show that there is no straightforward way to removing tidal deformation polarization (TDP) from polarimetric observations of close binaries. A reanalysis of the data shows that the existence of TDP in the Stokes parameter light curves observed from Cyg XR-1 does not significantly bias the mass derived to larger values. The mass of Cyg XR-1 must be significantly larger than 5 solar masses. This fact alone does not require Cyg XR-1 to be a black hole, however. Recent theoretical investigations of possible equations of state of matter at nuclear density show that the maximum mass of a compact object which is not a black hole may be much greater than 5 solar masses.

The orbital inclination of Cygnus XR-1 measured polarimetrically

The X-ray binary Cyg XR-1/HDE 226868 was observed polarimetrically over one orbit at three different optical wavelengths. The standard theory of Brown, et al. (1978) is used to derive an orbital inclination i = 62 deg (+5 deg, -37 deg), where the error is the 90-percent-confidence interval derived by the method of Simmons, et al. (1980). The value of the orbital inclination is significantly lower than values based on polarimetric observations. The difference is a result of the observational protocols used. A bias toward larger values of the inclination caused by the tidal distortion of the primary is still found in the present result. The inclination derived corresponds to a mass of the compact component of 6.3 solar masses, above the maximum mass of any degenerate configuration consistent with general relativity except a black hole.

The 78.4-day period of Cygnus XR-1

A search for a 78.4 day modulation in the high energy X-ray flux observed with OSO-8 and in the U-band optical polarization is reported. It is suggested that if such a modulation does exist, it is more likely to be related to the rotation of the free modes of oscillation of the primary than to the existence of a third body in the system.

High-energy X-ray spectra of Cygnus XR-1 observed from OSO 8

X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer on board the OSO-8 satellite during a period of one and one-half to three weeks in each of the years from 1975 to 1977. Observations were made when the source was both in a high state and in a low state. Typical spectra of the source between 15 and 250 keV are presented. The observed pivoting effect is consistent with two temperature accretion disk models of the X-ray emitting region. No significant break in the spectrum occurred at energies up to 150 keV. The high state as defined in the 3 to 6 keV bandwidth was found to be the higher luminosity state of the X-ray source. One transition from a low to a high state occurred during observations. The time of occurrence of this and other transitions is consistent with the hypothesis that all intensity transitions occur near periastron of the binary system, and that such transitions are caused by changes in the mass transfer rate between the primary and the accretion disk around the secondary.

Intensity transitions in Cyg XR-1 observed at high energies from OSO 8

THE high energy X-ray source, Cygnus XR-1, exhibits a variable intensity between states which differ in flux at lower energies (typically 3 to 6 keV) by a factor of three (refs 1–5). Although the transitions between these ‘high’ and ‘low’ flux states occur at irregular intervals, the transition itself usually takes no more than one day in either direction. We report here an observation of such a transition at energies above 20 keV which shows that the spectrum of Cyg XR-1 exhibits the pivoting effect during intensity transitions expected from two-temperature accretion disk models of the X-ray emitting region6,7.

OSO-8 Observations of Cygnus XR-1

Cygnus XR-1 was observed Nov. 11 to 18, 1975, in the energy range 20 to 400 keV with a Cgl scintillation crystal spectrometer on board the OSO-8 satellite. A drop in the count rate of ˜45% between 23 and 153 keV was observed to occur gradually over a full day on Nov. 16. Comparison with 2 to 7 keV proportional counter data taken simultaneously on OSO-8 by P. Serlemitsos et al. (private communication), the count rate of which rose ˜40% on Nov. 16, shows the 23 to 153 count rate to be generally anti-correlated with the 2 to 7 keV count rate over the entire 8 days of observation (Fig. 1). The observations are in agreement with the predictions of the two-temperature accretion disk model of Shapiro, Lightman and Eardley (Astrophys. J., 204, 187, 1976).

A balloon-borne observation of the X-ray source Cygnus XR-1

An observation of the variable X-ray source Cygnus XR-1 was made with a balloon-borne proportional counter in the energy region 22–70 keV. The resultant spectrum indicates that the source was in a state of maximum flux during the time period 1915–2005 UT, 15 January, 1968.

X-Ray Intensity Fluctuations in Cygnus XR-1

view Abstract Citations (16) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray Intensity Fluctuations in Cygnus XR-1 Shulman, Seth ; Fritz, Gilbert ; Meekins, John F. ; Friedman, H. ; Meidav, Meir Abstract A reanalysis of 1967 September data shows apparent fluctuations in the X-ray intensity of Cyg XR-1 on a time scale of several seconds. There is no evidence, however, for the periodicities that have recently been reported by other observers. Publication: The Astrophysical Journal Pub Date: September 1971 DOI: 10.1086/180783 Bibcode: 1971ApJ...168L..49S full text sources ADS |

High-Energy X-Rays from Cygnus XR-1

Abstract : X-rays from Cyg XR-1 were observed on 3 May 1967 over the energy interval 20 - 130 keV. The estimated primary photon intensity from the star confirms a recently reported high x-ray flux at about 30 keV during May 1967. The differential x-ray spectrum of Cyg XR-1 is probably not just a simple power law or exponential function; however, a black-body curve can be excluded. (Author)

Time Variations in Scorpius X-1 and Cygnus XR-1

view Abstract Citations (38) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time Variations in Scorpius X-1 and Cygnus XR-1 Overbeck, James W. ; Tananbaum, Harvey D. Abstract In a series of balloon ifights in May and June 1967 we found significant time variations in the X-ray fluxes above 15 keY from Scorpius X-1 and Cygnus XR-1. On June 26-27 the fluxes we measured for Scorpius X-1 in energy bands from 16 6 to 23.4 and 23.4 to 303 keV agreed with those measured by Peterson and Jacobson in June 1965 and were 2.3 and 2.8 times those we had measured for the same bands on May 16 On June 26-27 the flux from Scorpius X-1 between 23.4 and 46 7 keY was 2 times the flux we had observed for this band on May 25. From Cygnus XR-1 on June 27 we found a flux between 23.4 and 46 7 keV that was a factor of 2 6 lower than the flux we had found on May 25. We had already found that the flux in this energy band during our two May flights was 2.3 times higher than the flux we had observed in September 1966. We also observed a positive flux from the Sagittarius region and have found upper limits for Cygnus X-3, Cygnus XR-2, Serpens XR-1, M87, and Cassiopeia A Publication: The Astrophysical Journal Pub Date: September 1968 DOI: 10.1086/149714 Bibcode: 1968ApJ...153..899O full text sources ADS |

Observations of cosmic X-ray sources in the 10–250 keV range

Observations of cosmic X-ray sources have been made from high-altitude balloons over Palestine, Texas, using actively collimated detectors. In this technique, a thin NaI central counter 10 to 50 cm2 in area is surrounded by a CsI well crystal shield several centimeters thick. The aperture, about 8° to 20° FWHM, is determined by either the well opening or an active honeycomb collimator. The background is determined mainly by diffuse cosmic and atmospheric X-rays entering the forward aperture. The detector is usually either servo-controlled to track the source or operated as a meridian device. Data are telemetered over the 20–250 keV range in a digital format from a 128-channel pulse-height analyzer. Several strong sources in the northern hemispheric sky have been observed. The Crab nebula has a power-law differential number spectrum with an index of –1.9 ± 0.1 and an intensity of about 10−2 photons/cm2-s-keV at 20 keV. Two observations in September 1965 and September 1966 on this object give the same flux and spectral index within about 5% over the 20–100 keV range. The source Cygnus XR-1 also has a power-law shape, very similar in slope and intensity to the Crab, which extends above background to at least 180 keV. These measurements are in general agreement with those of other workers. The power-law spectrum of the Crab and Cygnus XR-1 may be contrasted with that of SCO XR-1, which has an exponential spectrum, typical of a hot gas at 50 × 106 °K.

The X-Ray Spectra of Cygnus XR-1 and the Crab Nebula

In this paper we wish to present briefly the latest results which have been obtained on the hard X-ray spectra of two strong sources in the Northern skies. These observations, which have been discussed in detail previously (Peterson et al., 1967), were made from balloons launched at Palestine, Texas, to 3 gm/cm2 atmospheric depth during September 1966. The Crab Nebula and the Cygnus XR-1 were observed to have a differential number power law spectra with an index of about –2 over the 20–200 keV range. Both sources have the same intensity within about 10%. The Crab Nebula has been observed on two occasions, one year apart, and showed no change in intensity over this range at about a 5% significance level.

Twofold Increase of the High-Energy X-Ray Flux From Cygnus XR-1

Twofold Increase of the High-Energy X-Ray Flux From Cygnus XR-1

High-Energy X-Rays from Cygnus XR-1

view Abstract Citations (19) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-Energy X-Rays from Cygnus XR-1 Overbeck, James W. ; Womack, E. Allen ; Tananbaum, Harvey D. Abstract On September 19, 1966, we used a balloon-flown, oriented scintillation counter with good energy resolution to measure X-rays above 15 keV from Cygnus XR-1 and to search for X-rays from Cassiopeia A and the remnant of Tycho's supernova (SN 1572). Knowledge of the counter's orientation has permitted us to conclude that the X-rays between 23 and 97 keV we observed from the Cygnus region came from Cygnus XR-t rather than from Cygnus A or Cygnus X. Cygnus XR-2 was never in the counter's field of view. By comparing our data with those of McCracken we have found evidence for a decrease in flux from Cygnus XR-1 at high energies, although not so large as that at low energies reported by Byram, Chubb, and Friedman. We have found no positive flux of high-energy X-rays above the background from Cas A and SN 1572. The absence of a positive high-energy flux from these sources is not inconsistent with Byram et aI.'s detection of weak fluxes from them at lower energies, provided that their energy spectra are as steep as that of Sco X-t. If one assumes X-rays from Cas A and SN 1572 are produced in hot, optically thin, ionized gas our result, combined with that of Byram et at. implies a characteristic temperature less than 8.5 X i070Kforthegas. Publication: The Astrophysical Journal Pub Date: October 1967 DOI: 10.1086/149311 Bibcode: 1967ApJ...150...47O full text sources ADS | data products SIMBAD (3)

Cosmic X-Ray Sources-Galactic and Extragalactic.

Instruments carried aboard an Aerobee rocket in April 1965 provided evidence for x-ray emission from the directions of the radio galaxies Cygnus A and M-87 and from the galactic supernova remnant Cassiopeia A. A survey of the Cygnus region revealed a marked decrease in the flux of x-rays from Cygnus XR-1, which was identified in June 1964 as the second brightest object in the first Naval Research Laboratory list of x-ray sources. The detection sensitivity was improved over previous surveys and several new sources were detected at lower flux levels.

Cosmic X-ray Sources, Galactic and Extragalactic

Instruments carried aboard an Aerobee rocket in April 1965 provided evidence for x-ray emission from the directions of the radio galaxies Cygnus A and M-87 and from the galactic supernova remnant Cassiopeia A. A survey of the Cygnus region revealed a marked decrease in the flux of x-rays from Cygnus XR-1, which was identified in June 1964 as the second brightest object in the first Naval Research Laboratory list of x-ray sources. The detection sensitivity was improved over previous surveys and several new sources were detected at lower flux levels.