Pulsed X-ray Flux Research Articles

Quantitative Study of Pulsed X-Ray-Induced Electromagnetic Response in Coaxial Cables

This article aims to quantify the radiation-induced electric responses of coaxial cables while irradiated by a pulsed X-ray flux. First, a precise characterization of the X-ray generator was performed using the 3-D Maxwell and Monte Carlo numerical simulations. These results were used to calculate the currents induced by the X-rays within the cables by using the 3-D Monte Carlo and 2-D transverse electromagnetic numerical codes. A systematic analysis of the responses of several cable references was performed by comparing the experimental and numerical results. This allows for the determination of gaps at the interface between the cable dielectrics and conductors. From these results, a parametric numerical extrapolation at high X-ray fluences was performed. It is shown that the system-generated electromagnetic pulse (SGEMP) responses are governed by photocurrents in gaps below 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> rad/s, while for greater dose rates, conduction currents in the dielectrics govern the responses. The approach developed in this article is useful for investigating electrical responses of systems subjected to highly ionizing environment, which is of paramount importance for addressing hardening issues.

XMM-Newtonobservations of 1A 0535+262 in quiescence

Accretion onto magnetized neutron stars is expected to be centrifugally inhibited at low accretion rates. Several sources, however, are known to pulsate in quiescence at luminosities below the theoretical limit predicted for the onset of the centrifugal barrier. The source 1A 0535+262 is one of them. Here we present the results of an analysis of a ~50 ks long XMM-Newton observation of 1A 0535+262 in quiescence. At the time of the observation, the neutron star was close to apastron, and the source had remained quiet for two orbital cycles. In spite of this, we detected a pulsed X-ray flux of ~3e-11 erg/cm2/s . Several observed properties, including the power spectrum, remained similar to those observed in the outbursts. Particularly, we have found that the frequency of the break detected in the quiescent noise power spectrum follows the same correlation with flux observed when the source is in outburst. This correlation has been associated with the truncation of the accretion disk at the magnetosphere boundary. We argue that our result, along with other arguments previously reported in the literature, suggests that the accretion in quiescence also proceeds from an accretion disk around the neutron star. The proposed scenario consistently explains the energy of the cyclotron line observed in 1A 0535+262, and the timing properties of the source including the spin frequency evolution within and between the outbursts, and the frequency of the break in power spectrum.

XMM-Newtonobservations of 1A 0535+262 in quiescence.

Accretion onto magnetized neutron stars is expected to be centrifugally inhibited at low accretion rates. Several sources including 1A 0535+262, however, are known to pulsate in quiescence at luminosities below the theoretical limit predicted for the onset of the centrifugal barrier. Here we present the results of an analysis of a ~ 50 ks long XMM-Newton observation of 1A 0535+262 in quiescence. At the time of the observation, the neutron star was close to the apastron, and the source had remained quiet for two orbital cycles. In spite of this, we detected a pulsed X-ray flux of ~ 3×10−11 erg cm−2 s−1 . Several observed properties, including the power spectrum, remained similar to those observed in the outbursts. Particularly, we have found that the frequency of the break detected in the quiescent noise power spectrum follows the same correlation with flux observed when the source is in outburst. We argue that, along with other arguments previously reported in the literature, our results suggest that the accretion in quiescence also proceeds from an accretion disk around the neutron star.

THE SPIN-DOWN OF SWIFT J1822.3–1606: A NEW GALACTIC MAGNETAR

On 2011 July 14, a new magnetar candidate, Swift J1822.3-1606, was identified via a rate trigger on the Swift/Burst Alert Telescope. Here we present an initial analysis of the X-ray properties of the source, using data from the Rossi X-ray Timing Explorer, Swift, and the Chandra X-ray Observatory, spanning 2011 July 16--September 22. We measure a precise spin period of P=8.43771963(5) s and a spin-down rate of 2.97(28)E-13, at MJD 55761.0, corresponding to an inferred surface dipole magnetic field strength of B=5.1E13 G, the second lowest thus far measured for a magnetar, though similar to 1E~2259+586 as well as to several high-magnetic field radio pulsars. We show that the pulsed X-ray flux decay in the 2--10 keV band is best fit by an exponential with a time constant of 16.4+/-0.3 days. After increasing from ~35% during the first week after the onset of the outburst, the pulsed fraction in the 2--10 keV band remained constant at ~45. We argue that these properties confirm this source to be a new member of the class of objects known as magnetars.

Spectral and timing properties of the X-ray emission from the millisecond pulsar PSR B1821-24

We report results on the timing and spectral analysis of observations of the millisecond pulsar PSR B1821−24 with RXTE, BeppoSAX and Chandra. The X-ray light curve is characterized by two narrow peaks at a phase distance of 0.452 ± 0.002. The average pulsed emission, over the range 1.6-20 keV, is well represented by a single power law with a photon index α = 1.30 −0.02 +0.05 and unabsorbed (2-10 keV) pulsed X-ray flux of 3.9 × 10 −13 erg cm −2 s −1 . We searched for a possible bunching of X-ray photons to verify if the X ray emission has a time structure similar to that of giant pulses and found a negative result.

RXTE observations of single pulses of PSR B0531+21

This article is the first in the series that analyze about 1.87 million periods of PSR B0531+21 (Crab pulsar), observed by the PCA detector aboard the RXTE X-ray observatory. The Crab pulsar's X-ray light curve shows little variation over time scales ranging from days to a period (33.46 milliseconds). The standard deviation of its X-ray flux variation is ≈0.7% of its mean value, which is negligible compared to its radio flux variations. The phase resolved power spectrum of pulse to pulse X-ray flux variation shows no spectral feature; an upper limit to the peak of any possible broad spectral feature is 0.06% of the mean power. The X-ray fluxes in the two components of its integrated profile are unrelated to each other; their linear correlation coefficient is . "Giant pulses" that are routinely seen at radio wavelengths are absent here. This work sets very strong constraints on the connection (if any) between the flux variations at radio and X-ray energies, for example due to variation in the degree of coherence of the basic emitters. Its phase resolved X-ray flux variation shows a weak correlation with the integrated profile. If confirmed, this might be an important clue to understanding the X-ray emission mechanism of Crab pulsar.

The Discovery of an Outburst and Pulsed X-Ray Flux from SMC X-2 Using the [ITAL]Rossi X-Ray Timing Explorer[/ITAL

Rossi X-Ray Timing Explorer (RXTE) All-Sky Monitor observations of SMC X-2 show that the source experienced an outburst in 2000 January-April reaching a peak luminosity of greater than ~1038 ergs s-1. RXTE Proportional Counter Array observations during this outburst reveal the presence of pulsations with a 2.37 s period. However, optical photometry of the optical counterpart shows that the source was still significantly fainter than it was more than a half a year after the outburst in the 1970s when SMC X-2 was discovered.

Distribution function for photoelectrons in a pulsed x-ray flux in the presence of a magnetic field

A method for finding the distribution function of photoelectrons in a planar pulsed x-ray flux, propagating in a medium, is formulated in an approximation where the medium is collisionless for photoelectrons. Magnetic-field effects lead to amplitude modulation of the components of the electric field arising as a result of the electron current flow behind the x-ray front. It is shown that magnetic-field effects can lead to various instabilities in the ionization formations produced by an instantaneous x-ray pulse. 15 references.

Effect of secondary electrons on the electric field produced in a pulsed x-ray flux

Effect of secondary electrons on the electric field produced in a pulsed x-ray flux

Ferroelectric electron emission imaging of X-ray damage

X-ray irradiation of TGS crystals drastically suppresses ferroelectric electron emission excited during spontaneous polarization switching. Position sensitive electron detection made it possible to image a radiation damaged region by the use of continuous or pulsed X-ray flux.

PULSE CALIBRATION TECHNIQUE OF X-RAY DETECTOR

A pulsed CuK X-ray source with flux intensity 1018-1019 K X-rays per sr per s has been produced using high current electron beam technique, it has been employed to calibrate the response of the silicon PIN diode detector to pulsed X-ray photon. An absolute X-ray monitor——P10 gas pulse ionization chamber has been used as a standard of the pulsed X-ray flux density, the automatic pulsed charge measuring instrument is controlled and Corrected in real time by a microcomputer. The measured uncertainty of the flux density is ±5%. This chamber is suitable for the range of energy flux rate 4×10-9-2×102 W/cm2 and the range of photon energy 1.5-10 keV. The calibrated accuracy of the detector is ±7.0%. It is found that the pulsed sensitivity of the silicon PIN diode is about 30% higher than the sensitivity calibrated by a steady X-ray beams.

Upper Limits to the Pulsed X-ray Flux from PSR0833-45, MP0835-40 and MP0736-40

ON November 11, 1970, a collimated proportional counter sensitive to X rays in the energy range 2.8 to 9.9 keV was flown on a Sun-stabilized Skylark sounding rocket from Woomera, South Australia. During part of the flight the detector field of view was scanned across Vela, including the position of three radio pulsars. The time of each event was telemetered to ground with a time uncertainty of approximately 300 µs and this allowed a search for fluctuations in the X-ray flux at the period of the observed radio pulsations. The pulsars were PSR0833-45, the Vela pulsar (0.089 s period), MP0835-40 (0.766 s period) and MP0736-40 (0.375 s period).