Detection of Radio Emission from Scorpio X-1

Andrew, B. H.; Purton, C. R.

doi:10.1038/218855a0

Cited by 43 publications

(11 citation statements)

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“…Although the system properties are consistent with it containing a neutron star with a weak magnetic field, no type I bursts have been observed so far (Mirabel & Rodrigues 2003). Radio emission from the vicinity of Sco X‐1 was first reported by Andrew & Purton (1968), with later high‐resolution radio interferometry unveiling compact jets through the formation of twin radio lobes with variable morphology (Fomalont, Geldzahler & Bradshaw 2001). A distance of 2.8 ± 0.3 kpc was determined from trigonometric parallax (Bradshaw, Fomalont & Geldzahler 1999).…”

Section: Sourcesmentioning

confidence: 99%

Superorbital variability in hard X-rays

Farrell

Barret

Skinner

2009

Monthly Notices of the Royal Astronomical Society

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We present the results of a study with the Swift Burst Alert Telescope in the 14–195 keV range of the long‐term variability of five low‐mass X‐ray binaries with reported or suspected superorbital periods – 4U 1636−536, 4U 1820−303, 4U 1916−053, Cyg X‐2 and Sco X‐1. No significant persistent periodic modulation was detected around the previously reported periods in the 4U 1916−053, Cyg X‐2 or Sco X‐1 light curves. The ∼170‐d period of 4U 1820−303 was detected up to 24 keV, consistent with variable accretion due to the previously proposed triple system model. The ∼46‐d period in 4U 1636−536 was detected up to 100 keV, with the modulation in the low‐ and high‐energy bands found to be phase shifted by ∼180° with respect to each other. This phase shift, when taken together with the near‐coincident onset of the ∼46‐d modulation and the low/hard X‐ray state, leads us to speculate that the modulation could herald transient jet formation.

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Section: Sourcesmentioning

confidence: 99%

Superorbital variability in hard X-rays

Farrell

Barret

Skinner

2009

Monthly Notices of the Royal Astronomical Society

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“…Several attempts to detect the stronger X-ray sources have been made. Andrew & Purton (1968) looked at Sco X -l at a wavelength of 4.6 cm and measured a flux density of 0.021 + 0.007 f.u.…”

Section: Sco X-lmentioning

confidence: 99%

Discrete X-ray sources—a theoretical appraisal

Burbidge

1969

Proc. R. Soc. Lond. A

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X-ray and γ -ray astronomy is in its infancy. Parallels in its development with the early history of radio astronomy have often been drawn. In this paper I attempt to unravel the theoretical questions which have been raised by the discovery of the discrete sources. To do this we divide the discussion up into three sections: (1) galactic sources, (2) extragalactic sources; (3) possible discrete sources of γ -rays.

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“…The most significant result of these measurements was the discovery of Cen XR-2 and the measurement of the variation in its intensity and spectrum. 1 The third flight, launched in December 1967, carried three X-ray detectors of total area 140 cm 2 . One of the main results from this flight, evidence for a new X-ray source at high galactic latitude, will be presented in the following paper.…”

Section: Department Of Physics University Of Adelaidementioning

confidence: 99%

Time Variation of the Radio Emission from Sco X-1

Ables

1969

Publ. Astron. Soc. Aust.

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of Adelaide and Tasmania (UAT) was launched from Woomera. Of the four X-ray detectors on board, two (A and B) operated satisfactorily. Both were xenon-filled proportional counters with 0.005 in beryllium windows of 10 cm 2 area, and sensitive to X-rays in the 2-8A wavelength band. Slat collimators in front of the windows restricted the fields of view to 3° X 38° FWHM. The long axes of the collimators were inclined at 45° to each other, with that of detector B being parallel to the rocket spin axis.Above the atmosphere, the rocket spun with a 23 s period and precessed very slowly about a cone of 60° half angle. Over the 250 s of useful observing time, the rocket spin axis had moved only 60° from its original orientation. This meant that although only a fraction of the sky was observed, any point in this area was scanned several times. Hence the sensitivity for the detection of X-ray sources was increased by integrating the count-rates for all times that any potential source was observed-that is to say, by superposing all the scans that passed across the position in question.The most significant increase in count-rate arose from superposition of 5 scans of detector B and 3 scans of detector A. The result was a peak 3.6 standard deviation above the background generated by diffuse X-rays and charged particles. This peak is shown in Figure 1. Such a peak implies an X-ray source with an intensity of approximately 1.5 photons cm -2 s _1 or 10~8 ergs cm~2 s _1 . This is about 1/15 as strong as Sco XR-1-the most intense galactic source at these wavelengths.The configuration of the two collimators allowed the position corresponding to this count-rate peak to be calculated accurately relative to the rocket axes. The orientation of the rocket axes is determined from data from three orthogonal magnetometers and solar sensors with crossed slits. However the motion of this particular rocket was such that in-flight calibration of one magnetometer was not possible, and the diagonal slits of the solar sensors did not see the Sun. These factors have seriously restricted the accuracy of the position deduced for this source. Our position is l n = 145°, b 11 = -60° (2 h .0 R.A., -6° dec.) with an error circle of 15° radius. It is interesting to note that no survey of greater sensitivity has been made of this particular area of the sky.This position was, however, scanned by the earlier UAT experiments, Flights I and II, launched in April, 1967. 1 During the first flight, the 10°.5 FWHM angular response of the collimators meant that the Sun was observed at the same time as the above source position. Consequently any X-rays from this position were obscured by the large flux from the Sun. During the second flight the detectors were able to resolve the Sun and the aforementioned position. Superposition of four scans revealed a peak 2.7 standard deviations above background which implies a source intensity compatible with that from Flight III. If the Flight II peak is considered together with the larger peak from Flight III, we are con...

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Detection of Radio Emission from Scorpio X-1

Cited by 43 publications

References 11 publications

Superorbital variability in hard X-rays

Superorbital variability in hard X-rays

Discrete X-ray sources—a theoretical appraisal

Time Variation of the Radio Emission from Sco X-1

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