Pulsed X-ray Emission Research Articles

Compact Binary X-Ray Sources

AbstractCompact binary X-ray sources include white dwarfs, neutron stars, and black holes that are accreting matter from a companion star. The X-ray emission from these systems is produced by the accreting matter as it flows through an accretion disk and strikes the surface of the compact object. The emitting regions have opacities dominated by electron scattering, and radiation pressure is likely to play an important role in the hydrodynamics. Strong magnetic fields greatly modify the hydrodynamics and radiation transfer in the pulsating neutron star sources. Accretion disks have complex structure, including an electron scattering corona, a cool outer region, and possibly a thick torus in their inner region. The structure and stability properties of accretion disks are only partially understood. Major problems exist with the interpretation of the spectra and luminosities of the X-ray burst sources. The pulsed X-ray emission from the pulsating binary X-ray sources probably comes from “mounds” of accreting gas at the magnetic poles of neutron stars, in which the accreting matter is decelerated by radiation pressure. The physics of these systems is reviewed, with an emphasis on problems for which hydrodynamical simulations may be especially useful.

Einstein observations of VELA X and the VELA pulsar

The imaging detectors of the Einstein X-ray observatory have been used to study the Vela pulsar and its surrounding region. Although the pulsar is a relatively strong source of X-rays, there are not detectable pulsations at the pulsar period; the pulsed X-ray luminosity is less than approximately 10 to the 31st ergs/s in the 0.1-4.5 keV band. Nor is there evidence for other types of variability in the pulsar's X-ray emission. The images reveal structure on four spatial scales: (1) a pointlike object coincident with the pulsar; (2) a relatively bright, approximately 4-arcmin nebula of diffuse emission about the pulsar; (3) an approximately 1-degree nebula of hard emission that lies between the pulsar and the radio feature Vela X; and (4) thermal emission from the entire approximately 5-degree Vela supernova remnant. Spectral data from the small nebula are well fitted by a synchrotron model. Under the assumption that emission from the pulsar itself is thermal blackbody radiation, the surface temperature of the neutron star is calculated to be 1 million K.

Observations of G320.4–1.2 and Speculations on Supernova Remnant Morphology

The galactic radio source G320.4–1.2 (MSH15–52) consists of several components, the most prominent of which is situated in the north-west quadrant and is associated with the Hα nebula RCW89. Caswell et al. (1981) mapped the source at 1.4 GHz with a resolution of 50″ arc and concluded that it was a single supernova remnant with all components having spectral index α ≈ −0.34. This SNR has become more significant with the recent discovery (Seward and Harnden, 1982) of an X-ray pulsar of period 150 ms at the position (1950) R.A. 15h09m59s.5, Dec. −58°56′57″ near the centre of the remnant and the detection of this pulsar at radio frequencies (Manchester et al., 1982). The pulsar has some similarities to the Crab pulsar in that its period derivative is extremely high and hence its characteristic age low, ∼1570 years, comparable to that of the Crab pulsar. Timing observations (Manchester and Durdin, unpublished) indicate that the pulsar is not a member of a binary system and hence that the pulsed X-ray emission is powered by rotational energy, as in the Crab pulsar.

X-ray spectra of the Crab pulsar and Nebula

The X-ray spectra of the Crab pulsar and Crab Nebula are analyzed. Observations were made with OSO 8 on March 17-18, 1978, with all spacecraft telemetry assigned to one detector during seven dwell mode experiments. A resolution of 1.25 ms was obtained for pulse-height-analyzed counts in 64 channels. Progressive hardening and subsequent softening of the spectrum across the pulse was found. The fraction of the pulsed flux, exhibiting a spectral variability of about 0.14 was concentrated solely in the region between the two peaks. A model is suggested in which the pulsed X-ray emission from the Crab pulsar consists of two components: one is physically related to the double-peaked gamma-ray pulse and possibly to radio and optical pulses, but has no spectral dependence on the pulse phase, while the other exhibits spectral variability with the pulse phase but is confined to the interpeak emission seen with X-ray energies.

Observation of X-rays from the Crab Pulsar

A measurement of the pulsed X-ray emission from the Crab Nebula made during a lunar occultation is presented. Comparison is made with previous observations, and possible variations in this pulsed emission are discussed.

New observations of pulsed X-ray emission from NP 0532

Large-area proportional counters sensitive from 0.6 to 23 keV were used to observe about 3 min of pulsed X-ray emission from NP 0532 during two lunar-occultation experiments. A detailed pulse profile with 65-microsec resolution shows that the X-ray primary-pulse shape is essentially identical to its optical counterpart. Spectral data on the pulsed X-ray emission are presented. A pulse-by-pulse examination of the data shows no evidence for temporal variability.

Limit on X-ray emission from a supernova during maximum light.

view Abstract Citations (8) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Limit on X-ray emission from a supernova during maximum light. Sprott, G. F. ; Bradt, H. V. ; Clark, G. W. ; Lewin, W. H. G. ; Schnopper, H. W. ; Pigatto, L. ; Rosino, L. Abstract The MIT 1-60 keV X-ray detector on the OSO-7 satellite observed the supernova SN 1971s in NGC 493 during the period of its optical rise and maximum. The data were examined for steady and pulsed X-ray emission. Analysis of the light curve shows that the supernova was most likely of Type II. The upper limit (3 a) to the continuous X-ray luminosity during the week of the optical rise and maximum is 5 >c 10 ergs s ' (1-5 keY), a factor of 40 less than previous upper limits for this portion of the light curve. The upper limit to the energy of an X-ray pulse of duration between 2 seconds and 3 minutes is 5 x 1048 ergs (1-9 keV). The data examined for such a pulse covered 31 percent of the total observation time. Subject headings: supernova - X-ray sources Publication: The Astrophysical Journal Pub Date: August 1974 DOI: 10.1086/153016 Bibcode: 1974ApJ...191..739S full text sources ADS | data products SIMBAD (6) NED (6)

Hard X-ray Spectrum of NP 0532

WE report here final results of the analysis, of data obtained in a balloon flight, launched from Gap (France) in June 1970. The aim of this experiment was the observation of the energy spectrum of the pulsed X-ray emission from NP 0532 in the range 20–200 keV. Results of a preliminary analysis, in which the pulse profile for the integral emission was obtained, have been published already1. The measurement apparatus, basically consisting of two identical NaI (T1) detectors, as well as the general technique of analysis were also reported in the previous letter1.

Pulsed X-ray Emission from NP 0532 in the 20–200 keV Range

AN experiment was launched by balloon on June 23, 1970, at 05 h 30 min UT from Gap in France to study the pulsating emission from NP 0532 in the 20–200 keV energy range. Preliminary results are reported here.

Pulsed X-ray Emission of NP 0532 in March 1968

Pulsed X ray emission associated with pulsar NP 0532 in Crab Nebula measured by six element detector on Aerobee 150 rocket