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XMM-Newton discovery of pulsations from IGR J21237+4218=V2069 Cyg

ATel #2089; D. de Martino (INAF-Obs. Napoli), J. M. Bonnet-Bidaud, (CEA, Saclay), M. Falanga (ISSI, Bern), M. Mouchet (Univ Paris-7, Obs Paris), C. Motch (Obs. Strasbourg)
on 19 Jun 2009; 14:18 UT
Credential Certification: Domitilla de Martino (demartino@oacn.inaf.it)

Subjects: Optical, X-ray, Binary, Cataclysmic Variable

We report on a preliminary analysis of a XMM-Newton observation of the INTEGRAL source IGR J21237+4218 identified as the cataclysmic variable RXJ2123.7+4217=V2069 Cyg (Motch et al. 1996 A&A 307, 459; Barlow et al. 2006, MNRAS 372, 224). This observation was performed on April 30, 2009 (Start time: 2009-04-30T10:45:58.000) for a total of 28ksec (Observation ID: 0601270101). The source is detected in the EPIC cameras at an average net countrate of 1.05 cts/sec (EPIC-pn) and 0.65cts/sec (EPIC-MOS). Fourier analysis reveals strong peaks at a fundamental frequency of 116.3 cycles/day and harmonics up to the third. A composite sinusoidal function fit to both EPIC-pn and MOS light curves gives a fundamental period of 743.2 +/- 0.4sec and 55% pulse fraction. Similar periodicity is also found in simultaneous B band photometry acquired with the OM. The X-ray pulse is anti-phased with that in the optical. A marked underlying sinusoidal (40%) variability is also detected in EPIC data that is consistent with the 7.5hr orbital spectroscopic period found by Thorstensen et al. (2001, MNRAS 326, 1235). The detection of strong X-ray and optical rapid pulsations adds V2069 Cyg as a secure member of the Intermediate Polar type cataclysmic variables. With its long orbital period this system has a very low spin-orbit period ratio of 0.03. The 0.2-10keV spectrum reveals multiple emission components affected by absorption. We find a best composite spectral fit consisting of a blackbody at 56eV plus a thermal plasma at 16keV and a Gaussian at 6.4keV with an equivalent width of 159eV, absorbed by a partial (69%) covering dense material with Nh=1.1x10^23 H-atom/cm^2 and a total absorber with Nh=5x10^21 H-atom/cm^2. The spectral characteristics reveal that V2069 Cyg is a hard X-ray emitting Intermediate Polar with a soft X-ray component.