Volume 542, June 2012
|Number of page(s)||18|
|Section||Stellar structure and evolution|
|Published online||28 May 2012|
Characterization of new hard X-ray cataclysmic variables⋆
1 INAF - Osservatorio Astronomico di Capodimonte, salita Moiariello 16, 80131 Napoli, Italy
e-mail: email@example.com, firstname.lastname@example.org
2 International Space Science Institute (ISSI), Hallerstrasse 6, 3012 Bern, Switzerland
3 CRESST and X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 ; Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
4 Dipartimento di Fisica, Universitá Roma III, via della Vasca Navale 84, 00146 Roma, Italy
5 CEA Saclay, DSM/Irfu/Service d’Astrophysique, 91191 Gif-sur-Yvette, France
6 INAF Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy
7 Laboratoire APC, Université Denis Diderot, 10 rue Alice Domon et Léonie Duquet, 75005 Paris ; LUTH, Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon, France
Received: 16 March 2012
Accepted: 17 April 2012
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.
Key words: binaries: close / X-rays: binaries / accretion, accretion disks / novae, cataclysmic variables
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.