Hard X-ray Continuum Research Articles

Soft X-ray spectra of Seyfert 2 galaxies

The paper presents soft X-ray spectra of three Seyfert 2 galaxies obtained with the ROSAT PSPC. For two of these objects, NGC 5506 and MCG -5-23-16, most of the flux occurs at energies greater than 1 keV and probably represents a low-energy extension of the source seen at higher (greater than 2 keV) energies. The third source, Mrk 348, has very little flux in the ROSAT band, suggesting a photoelectric cutoff at energies above the ROSAT band, in agreement with Ginga observations. In all three galaxies, X-rays are detected at energies below these photoelectric cutoffs with flux above that expected from a model in which the source has the same spectral index as at higher energies (2-10 keV) and is covered by a uniform, cold, photoelectric absorber. This result indicates the presence of an additional component at soft energies, which is referred to as a 'soft excess'. The monochromatic flux of the soft excess measured at 1 keV is about 1-2 percent of the directly viewed hard X-ray continuum in all three galaxies.

The effects of photoionization on X-ray reflection spectra in active galactic nuclei

Recent work on the X-ray spectra of Seyfert galaxies has shown the presence of a reflection component due to the hard X-ray continuum scattering from and causing fluorescence by cold matter. The exact location of the matter in relation to the hard X-ray source is unclear, but the strength of the reflection spectrum is usually consistent with the hard X-rays being emitted above a flat accretion disc. In this paper we calculate reflection spectra for cases where the hard X-rays photoionize the surface layers of the disc to the extent that the main X-ray absorbers are significantly ionized. The temperature, ionization state and spectrum are computed in a fully self-consistent manner for the inner, radiation pressure dominated part of an accretion disc

Hard x-ray continuum crystal spectrograph for inertial confinement fusion (ICF) diagnostics

We describe absolutely calibrated instrumentation for measuring hard x-ray continuum produced during laser irradiation of ICF targets. The instrumentation includes a crystal spectrograph and two collimated filtered scintillators. The absolutely calibrated crystal spectrograph achieves high sensitivity to x-ray continuum over the energy range of 5 to 35 keV with continuous energy coverage and a resolving power E/ΔE between 20 and 100. Time integrated spectra are recorded and stored electronically on a shot basis using two dimensional charge coupled device (CCD) camera readout of a proximity focused MCP detector close coupled to the x-ray diffracting crystals. The filtered scintillators provide discrete, time-resolved, high energy channels for recording integrated continuum in the 40–60 and 60–90 keV bands. End-to-end calibration of the crystal spectrograph was performed over the design energy interval. We discuss instrument design, calibration, and alignment and the factors affecting sensitivity and resolving power.

Calibrated high-energy x-ray continuum crystal spectrometer for ICF diagnostics

Two separate crystal spectrometers are being developed for high-energy x-ray continuum measurements at Aurora and NOVA for ICF diagnostics. Both spectrometers are required to record hard x-ray continuum over the wide energy range of 5–35 keV. Continuous spectral coverage is required with low-energy resolution E/ΔE of the order of 10 to 20. The spectrograph for NOVA will use a Laue transmission geometry while the Aurora spectrograph will use a de Broglie curved crystal geometry. The instrumentation for Aurora will also include two discrete, time-resolved, high-energy channels for recording integrated continuum in the 40–60 keV and 60–90 keV bands. Individual component and end-to-end system calibration and alignment for both spectrographs will be done using the high-energy x-ray calibration facilities at KMS. We describe these spectrograph designs and discuss and compare the factors that affect their performance.

X- and gamma-ray signatures of type IA supernovae

Using a Monte Carlo code, the hard X-ray continuum and gamma-ray line emissions of various theoretical models of Type Ia supernova explosions are investigated. The influence of the distributions of velocity, mass, Ni-56, and heavy elements on the spectral and temporal evolution of the radiations (ultimately derived from the positrons and gamma-ray lines of the decay chain) is described. For the first 300-400 days of the explosion, the correspondence between the parameters of an explosion model and its hard photon signatures is derived. The effect of mixing instabilities is also studied, and estimates of the future detectability of the derived hard X- and gamma-ray features are presented. It is found that OSEE on the Gamma-Ray Observatory can detect both gamma-ray lines and the hard X-ray continuum from any Type Ia supernova within 10 Mpc of earth. 52 refs.

Hard X-ray spectrum of Supernova 1987A on day 407

view Abstract Citations (15) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hard X-Ray Spectrum of Supernova 1987A on Day 407 Ubertini, P. ; Bazzano, A. ; Sood, R. ; Staubert, R. ; Sumner, T. J. ; Frye, G. Abstract We report evidence for a hard X-ray continuum emission from a source in the LMC region centered on the optical position of SN 1987A. The supernova region was observed on day 407 with a hard X-ray and a high-energy (>50 MeV) gamma-ray detector flown together on a balloon payload. The X-ray data show a very hard power-law spectrum with a photon index α = 1.1 in the range 17-165 keV, with an intensity of 1.2 x 10^-4^ photons cm^-2^ s^-1^ keV^-1^ at 50 keV. If compared with previous observations our data indicate an almost steady, if not increasing, high-energy emission from SN 1987A in the last 9 months. Our data are compared with the predictions expected from theoretical models based on the Comptonization of the ^56^Co nuclear lines or the presence of an internal continuum power source. Publication: The Astrophysical Journal Pub Date: February 1989 DOI: 10.1086/185369 Bibcode: 1989ApJ...337L..19U Keywords: Stellar Spectrophotometry; Supernova 1987a; X Ray Spectra; Compton Effect; Emission Spectra; Power Spectra; Stellar Evolution; Astrophysics; STARS: SUPERNOVAE; X-RAYS: SPECTRA full text sources ADS | data products SIMBAD (5) NED (2)

Acceleration of interplanetary solar electrons in the 1982 August 14 flare

The solar flare on August 14, 1982 (about 0507 UT) produced hard X-rays, gamma-rays, and an electron-rich interplanetary particle event. Because of its location (N11, W61), the flare site was magnetically well connected to the ISEE 3 spacecraft. The ISEE 3 observations have provided a detailed time history of 15 keV-1.9 MeV photon emission from the flare and the relativistic (greater than 3 MeV) solar electrons in interplanetary space. These observations indicate that a significant fraction of the relativistic electrons escaping from the sun were accelerated during the impulsive phase simultaneously with the energetic electrons producing the hard X-ray and gamma-ray continuum at the sun.

The hydrogen line spectra of narrow-line radio galaxies

The results of the first detection of Ly-alpha in a narrow-line radio galaxy are reported. Nearly simultaneous optical and UV observations of 3C 192 and 3C 223 allow the measurement of both Balmer and Lyman decrements. These line ratios are approximate functions of the interstellar reddening and of a parameter which is proportional to the amount of H I collisional excitation present. The reddening of 3C 192 is slightly larger than that due to the Galaxy, although 3C 223 may have a larger value. Both galaxies have intrinsic Balmer and Lyman decrements which are significantly steeper than case B, suggesting that the gas is photoionized by a fairly hard X-ray continuum. The deduced values of L-alpha/H-beta and H-alpha/H-beta compare favorably with predictions of recent models.

Hot-electron energy deposition profiles in CO2 laser target interaction: A comparison between Kα and continuum measurements

In CO2 laser target interaction, the axial and lateral hot-electron energy deposition profiles are determined from Kα emission and compared with those inferred from hard x-ray continuum spectra, in the same experimental conditions. The two approaches are complementary and give the same results provided that the continuum and the Kα are produced by a similar electron distribution.

On the X-ray continuum and iron-line emission of the low state of Hercules X-1

The hard X-ray continuum observed during low-state periods of Hercules X-1 is interpreted as being due to Compton scattering, by the coronal gases above and below the accretion disk, of the primary hard X-rays from the neutron star, which is hidden from our view during these periods. A similar interpretation holds for the low-state soft-X-rays. Because of photoionization, most iron ions in the corona are fully stripped and only a small fraction of them retain one electron. Because of such a high degree of iron ionization, the iron K photons from the corona, even if there are some, will make a line feature at 6.9 keV, and no line feature has been detected at this energy. The low-state iron line at 6.4 keV therefore, cannot be due to the coronal gases. The main production mechanism of this line is most likely fluorescence from the accretion disk.