Extragalactic y-rays

1981 ◽  
Vol 301 (1462) ◽  
pp. 577-602 ◽  
Keyword(s):  
Radio Galaxy ◽  
Line Emission ◽  
Seyfert Galaxy ◽  
Active Galaxies ◽  
Physical Conditions ◽  
Ngc 4151 ◽  
High Energies

Only a few extragalactic objects have been studied in the y-ray region of the spectrum. At high energies the COS-B experiment detected emission from the quasar 3C273 while at lower energies the results indicate that the emission from the Seyfert galaxy NGC 4151 is variable. A similar variability may also account for the conflicting reports of line emission from the radio galaxy Cen A. The implication of these and other observations in relation to the possible physical conditions in the nuclei of active galaxies.

Space Telescope Imaging Spectrograph Echelle Observations of the Seyfert Galaxy NGC 4151: Physical Conditions in the Ultraviolet Absorbers

2001 ◽  
Vol 551 (2) ◽  
pp. 671-686 ◽  
Author(s):  
S. B. Kraemer ◽  
D. M. Crenshaw ◽  
J. B. Hutchings ◽  
I. M. George ◽  
A. C. Danks ◽  
...  
Keyword(s):  
Seyfert Galaxy ◽  
Space Telescope ◽  
Physical Conditions ◽  
Ngc 4151 ◽  
Ultraviolet Absorbers ◽  
Imaging Spectrograph

scholarly journals The Properties of Extragalactic X-Ray Sources from Visible Light Observations

1973 ◽  
Vol 55 ◽  
pp. 184-198
Author(s):  
Wallace L. W. Sargent
Keyword(s):  
Radio Galaxy ◽  
Low Frequency ◽  
Seyfert Galaxy ◽  
Point Sources ◽  
Clusters Of Galaxies ◽  
X Rays ◽  
Detailed Structure ◽  
X Ray ◽  
Radio Halo ◽  
Ngc 4151

We describe the optical properties of the radio galaxy NGC 5128, the Seyfert galaxy NGC 4151 and the QSO 3C 273 all of which appear to be point sources of X-rays. We emphasize how the X-ray observations, particularly the low energy absorption cutoff, may help us to understand the detailed structure and source of energy in these diverse objects.The clusters of galaxies in Virgo, Perseus, Coma and Centaurus, all associated with extended X-ray sources are described. They have diverse shapes, central concentrations and galactic populations, but all contain a radio galaxy and, in several cases, a low frequency radio halo around it. It is concluded that the X-ray emission is likely to be non-thermal in origin.

scholarly journals Simultaneous Ultraviolet and X‐Ray Observations of Seyfert Galaxy NGC 4151. I. Physical Conditions in the X‐Ray Absorbers

2005 ◽  
Vol 633 (2) ◽  
pp. 693-705 ◽  
Author(s):  
S. B. Kraemer ◽  
I. M. George ◽  
D. M. Crenshaw ◽  
J. R. Gabel ◽  
T. J. Turner ◽  
...  
Keyword(s):  
Seyfert Galaxy ◽  
X Ray ◽  
Physical Conditions ◽  
Ngc 4151

A Discussion on solar studies with special reference to space observations - Solar flare X-ray spectra

1971 ◽  
Vol 270 (1202) ◽  
pp. 143-155 ◽  
Keyword(s):  
Solar Flare ◽  
Line Emission ◽  
Continuum Emission ◽  
Solar Abundance ◽  
Lower Corona ◽  
Steady State Condition ◽  
X Ray ◽  
Physical Conditions ◽  
High Energies ◽  
The Continuum

The solar X -ray spectrum provides a versatile method for determining physical conditions in the lower corona and corona—chromosphere interface which are associated with the chromospheric (Hα) flare phenomenon. Information is contained both in the continuum and line emission which exists at these wavelengths. Continuum emission is predominant below 0.13 nm because of the relatively low solar abundance of heavy elements capable of producing line emission at these wavelengths. During the initial phase of an X-ray event this continuum frequently appears in short, often quasi-periodic bursts whose spectrum is best described by a power law to 100 keV and decreasing more rapidly at high energies. The electron spectrum apparently responsible for these bursts has many similarities to that required for the production of type III radio bursts. The emission of flare-associated soft X-ray radiation (both line and continuum radiation) begins at the time of hard X-ray bursts but reaches maximum one to several minutes later. Line emission from ions up to Ni xxvii in the helium-like ion sequence and up to Fe xxvi in the hydrogen-like ion sequence has been observed during large flares. The evolution of the plasma in which this radiation originates can be studied by comparing emission lines in the same or adjacent stages of ionization of an element. From such observations we conclude that a steady-state condition rarely if ever exists in the X-ray emitting regions associated with a solar flare.

scholarly journals Optically Thin Gas in the BLR of Seyfert Galaxies

1989 ◽  
Vol 134 ◽  
pp. 135-136
Author(s):  
Simon L. Morris ◽  
Martin J. Ward
Keyword(s):  
Emission Line ◽  
Line Emission ◽  
Seyfert Galaxies ◽  
Active Galaxies ◽  
Broad Line ◽  
Line Profiles ◽  
Physical Conditions

Evidence has been accumulating that the gas which produces the broad line emission (BLR gas) in active galaxies has a range of physical conditions, and may indeed come from a distribution of spatially distinct regions (Gaskell 1982, Ulrich et al. 1984, Netzer 1987, Collin-Soufrin et al. 1988). In this paper, we try to separate out any contribution to the BLR emission line profiles from optically thin material. We do this by comparing the profiles of OI λ8446 (a flourescence line only produced by clouds very optically thick to Lyman α, Elitzur and Netzer 1985) and Hα (which can be produced by optically thick and optically thin clouds).

scholarly journals Simultaneous Ultraviolet and X‐Ray Observations of the Seyfert Galaxy NGC 4151. II. Physical Conditions in the UV Absorbers

2006 ◽  
Vol 167 (2) ◽  
pp. 161-176 ◽  
Author(s):  
S. B. Kraemer ◽  
D. M. Crenshaw ◽  
J. R. Gabel ◽  
G. A. Kriss ◽  
H. Netzer ◽  
...  
Keyword(s):  
Seyfert Galaxy ◽  
X Ray ◽  
Physical Conditions ◽  
Ngc 4151 ◽  
Uv Absorbers

scholarly journals Optical monitoring of the Seyfert galaxy NGC 4151 and possible periodicities in its historical light curve

2014 ◽  
Vol 14 (8) ◽  
pp. 923-932 ◽  
Author(s):  
Di-Fu Guo ◽  
Shao-Ming Hu ◽  
Jun Tao ◽  
Hong-Xing Yin ◽  
Xu Chen ◽  
...  
Keyword(s):  
Light Curve ◽  
Seyfert Galaxy ◽  
Optical Monitoring ◽  
Ngc 4151

scholarly journals The Mass of the Central Black Hole in the Seyfert Galaxy NGC 4151

2006 ◽  
Vol 647 (2) ◽  
pp. 901-909 ◽  
Author(s):  
Kyle G. Metzroth ◽  
Christopher A. Onken ◽  
Bradley M. Peterson
Keyword(s):  
Black Hole ◽  
Seyfert Galaxy ◽  
Central Black Hole ◽  
Ngc 4151
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