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

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

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.

scholarly journals NEW INSIGHTS INTO THE SPECTRAL VARIABILITY AND PHYSICAL CONDITIONS OF THE X-RAY ABSORBERS IN NGC 4151

2016 ◽  
Vol 833 (2) ◽  
pp. 191 ◽  
Author(s):  
J. D. Couto ◽  
S. B. Kraemer ◽  
T. J. Turner ◽  
D. M. Crenshaw
Keyword(s):  
Spectral Variability ◽  
X Ray ◽  
Physical Conditions ◽  
Ngc 4151

scholarly journals X-Ray Properties of Galactic Nuclei

1980 ◽  
Vol 5 ◽  
pp. 623-630
Author(s):  
Daniel W. Weedman
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Strong Emission ◽  
X Ray ◽  
Ngc 4151 ◽  
Survey Results ◽  
Emission Line Galaxies

Preparing this review was my just punishment for stating only two years ago - in another review (Weedman 1977) - that Seyfert galaxies are not strong X-ray sources. I said that because, as recently as three years ago, NGC 4151 was the only Seyfert galaxy known as an X-ray source. Now we have 36 Seyfert 1 galaxies, along with 12 other galaxies with strong emission-line nuclei, that are X-ray sources. And this is all without even having HEAO-2 data at our disposal yet. The study of active galactic nuclei with X-ray astronomy is progressing so rapidly that a reviewer feels almost hopeless. The best I can do is summarize what is known as of the summer of 1979 and give a simple overview of how X-ray and other properties relate.Some excellent reviews of the X-ray properties of Seyfert and other emission-line galaxies already exist. I especially recommend that by Andrew Wilson (1979). He provides very complete references as of a year ago, but X-ray astronomy is progressing so rapidly that he then had only somewhat more than half the active nuclei now in Tables 1 and 2. It was the group working with the Ariel V SSI that made the initial comprehensive X-ray studies of Seyfert galaxies (Ward et al. 1977, Elvis et al. 1978). The UHURU results for Seyfert galaxies followed soon after and are summarized by Tananbaum et al. (1978); the HEAO-A-2 survey results are now in press (Marshall et al. 1979) I have tried to incorporate these and other recent results in Tables 1 and 2.

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

Low energy y-ray observations with the MISO telescope

1981 ◽  
Vol 301 (1462) ◽  
pp. 603-606
Keyword(s):  
Seyfert Galaxy ◽  
Effective Area ◽  
Low Energy ◽  
Field Of View ◽  
Total Period ◽  
X Ray ◽  
Ngc 4151 ◽  
Orientation System ◽  
The Mean ◽  
Right Ascension

The MISO telescope, which has been described elsewhere, (Baker et al. 1979), has a sensitive area of 560 cm 2 and an aperture of 3° f.w.h.m. in both the azimuthal and zenithal planes. An alt—azimuth orientation system was used to point the telescope with a precision of ± 20'. A passively shielded hard X-ray detector (20—280 keV) having an effective area of 600 cm 2 was also mounted in parallel with the axis of the main telescope and had a field of view of 3° x 3° f.w.h.m. This instrument was used to study the region of the sky containing NGC 4151 on 30 September 1979 between 15h01 U.T. and 20h40 U.T. A series of five drift scans were performed to survey the region contained within the coordinate points 11h32 and 12h33 in right ascension. The declination was centred on + 39.8°. The Seyfert galaxy NGC 4151 was in the field of view of the telescope for a total period of 7.5 x 10 3 s. The total time spent on the background measurements associated with the data presented here, was 8.6 x 10 3 s. The mean float altitude during the observation was close to 4 mbar (400 Pa) and the telescope was set at a series of zenith angles between 9° and 30°.

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.

Concurrent radio, infrared, optical and X-ray observations of the nucleus of the Seyfert galaxy NGC 4151

1981 ◽  
Vol 247 ◽  
pp. 458 ◽  
Author(s):  
J. H. Beall ◽  
W. K. Rose ◽  
B. R. Dennis ◽  
C. J. Crannell ◽  
J. F. Dolan ◽  
...  
Keyword(s):  
Seyfert Galaxy ◽  
X Ray ◽  
Ngc 4151

Variable X-ray Absorption in NGC 4151

1989 ◽  
Vol 134 ◽  
pp. 182-183
Author(s):  
R. S. Warwick ◽  
T. Yaqoob ◽  
K. A. Pounds
Keyword(s):  
Seyfert Galaxy ◽  
Spectral Form ◽  
Iron Line ◽  
X Ray ◽  
Ngc 4151 ◽  
Hard Power ◽  
Edge Features ◽  
Partial Covering ◽  
Covering Model ◽  
X Ray Absorption

The medium energy X-ray spectrum of the Seyfert galaxy NGC 4151 is characterised by a hard power-law continuum, a variable low-energy cut-off and iron line and edge features. Holt et al. (1980) found the spectral form below 4 keV to be incompatible with absorption in a uniform screen of cold gas and interpreted the apparent soft X-ray excess in terms of a partial covering model. However, recent observations point to a somewhat different description of the X-ray absorbing medium present in the nucleus of this galaxy.

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