Emission Mechanisms and Broad Band Spectra of Pulsars

Abstract We report the results from analysis of six observations of Cygnus X-1 by Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope (SXT) onboard AstroSat, when the source was in the hard spectral state as revealed by the broad-band spectra. The spectra obtained from all the observations can be described by a single-temperature Comptonizing region with disc and reflection components. The event mode data from LAXPC provides unprecedented energy dependent fractional root mean square (rms) and time-lag at different frequencies which we fit with empirical functions. We invoke a fluctuation propagation model for a simple geometry of a truncated disc with a hot inner region. Unlike other propagation models, the hard X-ray emission (>4 keV) is assumed to be from the hot inner disc by a single-temperature thermal Comptonization process. The fluctuations first cause a variation in the temperature of the truncated disc and then the temperature of the inner disc after a frequency dependent time delay. We find that the model can explain the energy dependent rms and time-lag at different frequencies.

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An effect of the target position relative to the laser focus on X-ray emission from the laser plasma

Laser and Particle Beams ◽

10.1017/s0263034600004687 ◽

1992 ◽

Vol 10 (4) ◽

pp. 743-751 ◽

Cited By ~ 9

Author(s):

M. Chvojka ◽

B. Králiková ◽

E. Krouský ◽

L. Láska ◽

K. Maŝek ◽

...

Keyword(s):

Laser Plasma ◽

Laser System ◽

Broad Band ◽

Plasma Temperature ◽

Target Position ◽

Resonant Line ◽

X Ray ◽

Laser Focus ◽

Foil Target ◽

Band Spectra

The first harmonics beam generated by an iodine laser system was focused by an f/2 optics on an Al foil target. The X-ray output from the laser plasma both in the line and broad-band spectra was registered over an interval around the “ideal” focus. It was found that the maximum X-ray power is not obtained in the focus itself but for a somewhat larger focal spot outside the focus. To explain this phenomena, temperature and density measurements were in addition made. The plasma temperature evaluated from both the line (He-like Al XII resonant line and j, k, l satellites) and broad-band spectra (two foil method) was also measured and found to be largely constant in the vicinity of the focus. The line and broad-band temperatures differ, the broad-band temperature being about 25% higher. The electron density was equally determined using an intercombination line.

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CCD photometry of the BL Lacertae objects 1218+304, 1219+28, and 1727+50 - Point sources, associated nebulosity, and broad-band spectra

The Astrophysical Journal ◽

10.1086/159252 ◽

1981 ◽

Vol 249 ◽

pp. 3 ◽

Cited By ~ 9

Author(s):

D. Weistrop ◽

R. F. Mushotzky ◽

D. B. Shaffer ◽

H. J. Reitsema ◽

B. A. Smith

Keyword(s):

Broad Band ◽

Point Sources ◽

Ccd Photometry ◽

Bl Lacertae Objects ◽

Bl Lacertae ◽

Band Spectra

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BeppoSAX observations of the massive X-ray pulsar Cen X-3: Broad-band spectra and iron line diagnostic

Advances in Space Research ◽

10.1016/s0273-1177(99)00769-3 ◽

2000 ◽

Vol 25 (3-4) ◽

pp. 413-416 ◽

Cited By ~ 1

Author(s):

S. Del Sordo ◽

D. Dal Fiume ◽

M. Orlandini ◽

S. Piraino ◽

A. Santangelo ◽

...

Keyword(s):

Broad Band ◽

Iron Line ◽

X Ray ◽

Band Spectra

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The broad-band spectra and variability of compact nonthermal sources

The Astrophysical Journal ◽

10.1086/158571 ◽

1981 ◽

Vol 243 ◽

pp. 97 ◽

Cited By ~ 18

Author(s):

T. W. Jones ◽

L. Rudnick ◽

F. N. Owen ◽

J. J. Puschell ◽

D. J. Ennis ◽

...

Keyword(s):

Broad Band ◽

Band Spectra

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A NuSTAR view of GRS 1716−249 in the hard and intermediate states

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa017 ◽

2020 ◽

Vol 492 (2) ◽

pp. 1947-1956

Author(s):

Jiachen Jiang ◽

Felix Fürst ◽

Dominic J Walton ◽

Michael L Parker ◽

Andrew C Fabian

Keyword(s):

Power Law ◽

Broad Band ◽

High Density ◽

Density Parameter ◽

Reflection Spectroscopy ◽

Reflection Model ◽

Hard State ◽

Band Spectra ◽

Reflection Component ◽

Emission Line Feature

ABSTRACT We present a detailed analysis of the spectral properties of the black hole transient GRS 1716−249, based on the archival Swift and NuSTAR observations taken during the outburst of this source in 2016–2017. The first six NuSTAR observations show that the source is in a canonical hard state, where the spectrum is dominated by a power-law continuum. The seventh NuSTAR observation is taken during the intermediate state where both a disc thermal component and a power-law continuum are shown. All of our observations show a broad emission-line feature in the iron band and a Compton hump above 10 keV. We model the broad-band spectra using a high-density disc reflection model, where the soft X-ray emission in the hard state is interpreted as part of the disc reflection component. This model enables us to constrain the disc density parameter of GRS 1716−249 in the range of 1019–1020 cm−3. We only obtain an upper limit of the inner disc radius using high-density disc reflection spectroscopy and the results indicate either a non-truncated disc or a slightly truncated disc with Rin ≲ 20 rg.

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X/γ-rays from Active Galactic Nuclei

Symposium - International Astronomical Union ◽

10.1017/s0074180900162886 ◽

2000 ◽

Vol 195 ◽

pp. 143-152

Author(s):

R. Svensson

Keyword(s):

Active Galactic Nuclei ◽

Large Fraction ◽

Broad Band ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Spectral Components ◽

Γ Rays ◽

Γ Ray ◽

Band Spectra ◽

First Time

Recent progress using RXTE and BeppoSAX to study the X/γ emission from radio-quiet active galactic nuclei, i.e., Seyfert galaxies, is reviewed. These satellites allow simultaneous broad-band spectra extending from 0.1–200 keV to be observed for the first time and allow the various spectral components to be determined with some certainty. In particular, the new observations support the unified model of Seyfert galaxies. Most importantly, it has been found that a large fraction of Seyfert 2 galaxies have Compton-thick tori surrounding their nuclei. Spectral transitions in Seyfert galaxies are discussed, as well as recent efforts trying to synthesize the cosmic X/γ-ray background. Finally, thermal Comptonization in these sources are discussed.

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