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INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables | | R. Landi
; L. Bassani
; A.J. Dean
; A.J. Bird
; M. Fiocchi
; A. Bazzano
; J.A. Nousek
; J.P. Osborne
; | | Date: |
10 Oct 2008 | | Abstract: | The analysis of the third INTEGRAL/IBIS survey has revealed several new
cataclysmic variables, most of which turned out to be intermediate polars, thus
confirming that these objects are strong emitters in hard X-rays. Here we
present high energy spectra of all 22 cataclysmic variables detected in the 3rd
IBIS survey and provide the first average spectrum over the 20-100 keV band for
this class. Our analysis indicates that the best-fit model is a thermal
bremsstrahlung with an average temperature of <kT> ~22 keV. Recently, eleven
(ten intermediate polars and one polar) of these systems have been followed-up
by Swift/XRT (operating in the 0.3-10 keV energy band), thus allowing us to
investigate their spectral behaviour over the range ~0.3-100 keV. Thanks to
this wide energy coverage, it was possible for these sources to simultaneously
measure the soft and hard components and estimate their temperatures. The soft
emission, thought to originate in the irradiated poles of the white dwarf
atmosphere, is well described by a blackbody model with temperatures in the
range ~60-120 eV. The hard emission, which is supposed to be originated from
optically thin plasma in the post-shock region above the magnetic poles, is
indeed well modelled with a bremsstrahlung model with temperatures in the range
~16-33 keV, similar to the values obtained from the INTEGRAL data alone. In
several cases we also find the presence of a complex absorber: one totally
(with NH ~(0.4-28) x 10^{21} cm^{-2}) and one partially (with NH ~(0.7-9) x
10^{23} cm^{-2}) covering the source. Only in four cases (V709 Cas, GK Per, IGR
J06253+7334 and IGR J17303-0601), we find evidence for the presence of an iron
line at 6.4 keV. We discuss our findings in the light of the systems parameters
and cataclysmic variables/intermediate polars modelling scenario. | | Source: | arXiv, 0810.1844 | | Services: | Forum | Review | PDF | Favorites | |
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