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INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables

INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables
INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables
The analysis of the third INTEGRAL/Imager on Board Integral Satellite (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 third IBIS survey and provide the first average spectrum over the 20–100 keV band for this class. Our analysis indicates that the best-fitting model is a thermal bremsstrahlung with an average temperature of ?kT?? 22 keV . Recently, 11 (10 intermediate polars and one polar) of these systems have been followed up by Swift/X-ray telescope (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 ?16–35 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) × 1021 cm?2 ] and one partially [with NH? (0.7–9) × 1023 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.
novae, cataclysmic variables, gamma-rays: observations, x-rays: binaries
0035-8711
630-640
Landi, R.
b8243478-d7a1-4774-8a66-4158a65a33d3
Bassani, L.
07e5602c-f97e-4334-a0fa-c2212431a61a
Dean, A.J.
2f9093f2-855c-4769-b1aa-6dd621b5dcf1
Bird, A.J.
045ee141-4720-46fd-a412-5aa848a91b32
Fiocchi, M.
74d63e71-f43d-494b-92ee-07dc83d18de1
Bazzano, A.
8eef0c6e-1a5f-4bcd-a034-9a5c3b29104d
Nousek, J.A.
cac15a17-b409-46e8-b052-d70f72bdc64f
Osborne, J.P.
edc077a5-96df-4189-a3da-5bf63507101a
Landi, R.
b8243478-d7a1-4774-8a66-4158a65a33d3
Bassani, L.
07e5602c-f97e-4334-a0fa-c2212431a61a
Dean, A.J.
2f9093f2-855c-4769-b1aa-6dd621b5dcf1
Bird, A.J.
045ee141-4720-46fd-a412-5aa848a91b32
Fiocchi, M.
74d63e71-f43d-494b-92ee-07dc83d18de1
Bazzano, A.
8eef0c6e-1a5f-4bcd-a034-9a5c3b29104d
Nousek, J.A.
cac15a17-b409-46e8-b052-d70f72bdc64f
Osborne, J.P.
edc077a5-96df-4189-a3da-5bf63507101a

Landi, R., Bassani, L., Dean, A.J., Bird, A.J., Fiocchi, M., Bazzano, A., Nousek, J.A. and Osborne, J.P. (2009) INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables. Monthly Notices of the Royal Astronomical Society, 392 (2), 630-640. (doi:10.1111/j.1365-2966.2008.14086.x).

Record type: Article

Abstract

The analysis of the third INTEGRAL/Imager on Board Integral Satellite (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 third IBIS survey and provide the first average spectrum over the 20–100 keV band for this class. Our analysis indicates that the best-fitting model is a thermal bremsstrahlung with an average temperature of ?kT?? 22 keV . Recently, 11 (10 intermediate polars and one polar) of these systems have been followed up by Swift/X-ray telescope (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 ?16–35 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) × 1021 cm?2 ] and one partially [with NH? (0.7–9) × 1023 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.

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More information

Published date: January 2009
Keywords: novae, cataclysmic variables, gamma-rays: observations, x-rays: binaries

Identifiers

Local EPrints ID: 144791
URI: http://eprints.soton.ac.uk/id/eprint/144791
ISSN: 0035-8711
PURE UUID: 784bfdb8-abb2-4620-937c-e73d06c3457c
ORCID for A.J. Bird: ORCID iD orcid.org/0000-0002-6888-8937

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Date deposited: 24 May 2010 14:32
Last modified: 26 Nov 2021 02:36

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Contributors

Author: R. Landi
Author: L. Bassani
Author: A.J. Dean
Author: A.J. Bird ORCID iD
Author: M. Fiocchi
Author: A. Bazzano
Author: J.A. Nousek
Author: J.P. Osborne

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