Characterization of new hard X-ray cataclysmic variables

F. Bernardini D. De Martino M. Falanga K. Mukai G. Matt J.-M. Bonnet-Bidaud 1 N. Masetti M. Mouchet 2
2 APC - Cosmologie et gravitation
LUTH - Laboratoire Univers et Théories, APC - UMR 7164 - AstroParticule et Cosmologie
Abstract : Aims: We aim at characterizing a sample of nine new hard X-ray selected cataclysmic variable (CVs), to unambiguously identify them as magnetic systems of the intermediate polar (IP) type. Methods: We performed detailed timing and spectral analysis by using X-ray, and simultaneous UV and optical data collected by XMM-Newton, complemented with hard X-ray data provided by INTEGRAL and Swift. The pulse arrival time were used to estimate the orbital periods. The broad band X-ray spectra were fitted using composite models consisting of different absorbing columns and emission components. Results: Strong X-ray pulses at the white dwarf (WD) spin period are detected and found to decrease with energy. Most sources are spin-dominated systems in the X-rays, though four are beat dominated at optical wavelengths. We estimated the orbital period in all system (except for IGR J16500-3307), providing the first estimate for IGR J08390-4833, IGR J18308-1232, and IGR J18173-2509. All X-ray spectra are multi-temperature. V2069 Cyg and RX J0636+3535 posses a soft X-ray optically thick component at kT ~ 80 eV. An intense Kα Fe line at 6.4 keV is detected in all sources. An absorption edge at 0.76 keV from OVII is detected in IGR J08390-4833. The WD masses and lower limits to the accretion rates are also estimated. Conclusions: We found all sources to be IPs. IGR J08390-4833, V2069 Cyg, and IGR J16500-3307 are pure disc accretors, while IGR J18308-1232, IGR J1509-6649, IGR J17195-4100, and RX J0636+3535 display a disc-overflow accretion mode. All sources show a temperature gradient in the post-shock regions and a highly absorbed emission from material located in the pre-shock flow which is also responsible for the X-ray pulsations. Reflection at the WD surface is likely the origin of the fluorescent iron line. There is an increasing evidence for the presence of a warm absorber in IPs, a feature that needs future exploration. The addition of two systems to the subgroup of soft X-ray IPs confirms a relatively large (~30%) incidence. Based on observations obtained with XMM-Newton and INTEGRAL, ESA science missions with instruments and contributions directly funded by ESA Member States; and Swift, a NASA science mission with Italian participation.


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Submitted on : Tuesday, June 26, 2012 - 4:00:26 PM
Last modification on : Tuesday, June 26, 2012 - 4:00:26 PM

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F. Bernardini, D. De Martino, M. Falanga, K. Mukai, G. Matt, et al.. Characterization of new hard X-ray cataclysmic variables. Astronomy and Astrophysics, EDP Sciences, 2012, 542, pp.22. <10.1051/0004-6361/201219233>. <in2p3-00712215>

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