X-Ray Pulse Profile and Celestial Position of Hercules X-1

Doxsey, R.; Bradt, H.; Levine, A. M.; Murthy, G. T.; Rappaport, S.; Spada, G.

doi:10.1086/181210

Cited by 27 publications

(7 citation statements)

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“…The total emission is pulsed with a heliocentric period of 1.237794 ± 0.000001 (la) sec (obtained from preliminary data). The double-peaked pulse has all the characteristics of previously observed Her X-1 pulses (Doxsey et al 1973, Holt et al 1974, Joss and Fechner 1975.…”

Section: Resultssupporting

confidence: 66%

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

Pravdo

Boldt

Holt

et al. 1978

ApJ

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Section: Resultssupporting

confidence: 66%

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

Pravdo

Boldt

Holt

et al. 1978

ApJ

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“…A binary system containing a 1.3 M neutron star with its optical companion HZ Her fits quite well the observations both in optical and in the X-ray band (Doxsey et al 1973). Pulse features and the bulk spectral properties of the source can be explained by the mass accretion on to the neutron star from the accretion disk, which in turn is fed by the mass flow from the companion star.…”

Section: Introductionsupporting

confidence: 65%

Hard X-ray behaviour of Her X-1 during second main-on after the anomalous low state

Manchanda

2003

A&A

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Abstract. The binary X-ray pulsar Her X-1 shows a variety of time variations both in luminosity and its pulse features. For the first time an about 600 days long anomalous low state was seen in the light curve of ASM on board RXTE during the period MJD 51200-51800. We observed the source in the 20-200 keV energy band during its second main-on in the post anomalous state on November 21, 2000. The source was found to be extremely bright at high energies and a total of 26 000 photons from the source were detected during the 35 min snapshot observation. The cyclotron absorption line at ∼34 keV and its second harmonics were clearly detected in the data. We present the spectral details and discuss its implication in terms of the geometrical properties of the source.

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“…Her X-1 is a well known persistent accreting X-ray pulsar. It is characterized by a 1.24 s pulse period (Tananbaum et al 1972) and a 1.7 d orbit (Deeter, Boynton, & Pravdo 1981) around the A/F star HZ Her (Doxsey et al 1973;Gottwald et al 1991). Her X-1 also exhibits a 35 d intensity cycle that is generally believed to be due to the precession of a tilted, warped accretion disk viewed nearly edge on, which periodically obscures X-rays from the central neutron star.…”

Section: Introductionmentioning

confidence: 99%

The 1999 Hercules X‐1 Anomalous Low State

Coburn

Heindl

Wilms

et al. 2000

ApJ

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A failed main-on in the 35 d cycle of Her X-1 was observed with the Rossi X-ray Timing Explorer (RXTE ) on 1999 April 26. Exceptions to the normal 35 d cycle have been seen only twice before; in 1983 and again 1993. We present timing and spectral results of this latest Anomalous Low State (ALS) along with comparisons to the main-on and normal low states. Pulsations were observed in the 3-18 keV band with a fractional RMS variation of (0.037 ± 0.003). Spectral analysis indicates that the ALS spectrum has the same shape as the main-on but is modified by heavy absorption and scattering. We find that 70% of the observed emission has passed through a cold absorber (N H = 5.0 × 10 23 cm −2 ). This partially absorbing spectral fit can be applied to the normal low state with similar results. We find that the ALS observations may be interpreted as a decrease in inclination of the accretion disk causing the central X-ray source to be obscured over the entire 35 d cycle.

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X-Ray Pulse Profile and Celestial Position of Hercules X-1

Cited by 27 publications

References 0 publications

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

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

Hard X-ray behaviour of Her X-1 during second main-on after the anomalous low state

The 1999 Hercules X‐1 Anomalous Low State

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