Optical observations of the BL Lacertae object PKS 2155-304 and implications regarding the X-ray absorption feature at 600-700 eV

1984 ◽  
Vol 278 ◽  
pp. L103 ◽  
Author(s):  
S. Bowyer ◽  
J. Brodie ◽  
J. T. Clarke ◽  
J. P. Henry
1997 ◽  
Vol 483 (2) ◽  
pp. 774-782 ◽  
Author(s):  
Rita M. Sambruna ◽  
I. M. George ◽  
G. Madejski ◽  
C. Megan Urry ◽  
T. J. Turner ◽  
...  

1998 ◽  
Vol 502 (2) ◽  
pp. 630-639 ◽  
Author(s):  
Rita M. Sambruna ◽  
Richard F. Mushotzky
Keyword(s):  
X Ray ◽  

2007 ◽  
Vol 1050 ◽  
Author(s):  
Gerhard Jakob ◽  
Tobias Eichhorn ◽  
Michael Kallmayer ◽  
Hans-Joachim Elmers

AbstractA magnetically induced shape memory effect in Ni2MnGa results in huge magnetostrictive effects of several percent. Using x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) we investigated element specific magnetic moments and electronic structure of single crystalline, (110) oriented Ni2MnGa films on a-plane Al2O3 substrates in the austenite and martensite state. The structural phase transition of the samples is evident from temperature dependent x-ray diffraction and magnetization measurements. The Ni XAS differ significantly for temperatures above and below the martensite transition in agreement with published ab-initio calculations. Using XAS in transmission geometry on our thin film samples we observe the corresponding reduction of the absorption feature as predicted by theoretical calculations. The XMCD analysis shows the orbital contribution of the Ni electrons to be responsible for the magnetic anisotropy.


1998 ◽  
Vol 132 (3) ◽  
pp. 361-365 ◽  
Author(s):  
C. M. Raiteri ◽  
M. Villata ◽  
G. De Francesco ◽  
L. Lanteri ◽  
M. Cavallone ◽  
...  

2002 ◽  
Vol 184 ◽  
pp. 235-244 ◽  
Author(s):  
Andrea Comastri ◽  
Cristian Vignali ◽  
Marcella Brusa

AbstractMultiwavelength observations of the hard X-ray selected sources discovered by BeppoSAX, Chandra and XMM-Newton surveys have significantly improved our knowledge of the AGN population. The increasing number of X-ray obscured AGN so far discovered confirms the prediction of those AGN synthesis models for the X-ray background based on the Unified scheme. However, follow-up optical observations of hard X-ray selected sources indicate that their optical properties are quite varied and the simple relations between optical and X-ray absorption are by no means without exception. Moreover there is evidence of a substantial number of luminous X-ray sources hosted by apparently normal galaxies. In this paper the results obtained from multiwavelength observations of hard X-ray selected sources discovered by BeppoSAX and XMM-Newton are presented and briefly discussed.


1989 ◽  
Vol 341 ◽  
pp. 733 ◽  
Author(s):  
A. Treves ◽  
M. Morini ◽  
L. Chiappetti ◽  
A. Fabian ◽  
R. Falomo ◽  
...  

1991 ◽  
Vol 370 ◽  
pp. 198 ◽  
Author(s):  
Greg M. Madejski ◽  
Richard F. Mushotzky ◽  
Kimberly A. Weaver ◽  
Keith A. Arnaud ◽  
C. Megan Urry

2011 ◽  
Vol 89 (10) ◽  
pp. 985-990 ◽  
Author(s):  
D. Basu

CXO CDFS J033260.0-274748 is a quasi-stellar object (QSO) and identification of several emission lines observed in its optical spectrum has led to the determination of its redshift as 2.579. On the other hand, the Chandra ACIS-I spectrum has detected a strong absorption feature at the observed wavelength around 6.3 keV that cannot be identified under normal physical conditions. The authors have invoked an unusually large outflow bulk velocity of 0.7c–0.8c to explain the feature. However, such extraordinarily high bulk velocities are unprecedented in the extragalactic literature. We show here that the optical emission lines and the X-ray absorption feature can be identified with search lines of longer wavelengths that have been blueshifted and do not need any unusual physical conditions to be invoked. The blueshifted spectra are explained as being due to the net motion of the QSO along with the absorbing cloud towards the observer. Two scenarios are proposed, namely, the ejection mechanism and the multiverse.


2000 ◽  
Vol 144 (3) ◽  
pp. 481-485 ◽  
Author(s):  
M. Villata ◽  
C. M. Raiteri ◽  
M. D. Popescu ◽  
G. Sobrito ◽  
G. De Francesco ◽  
...  

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