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XMM-Newton observation of V2362 Cyg

ATel #1226; M. Hernanz and C. Ferri (IEEC-CSIC), G. Sala (MPE)
on 30 Sep 2007; 22:15 UT
Credential Certification: Margarita Hernanz (hernanz@ieec.uab.es)

Subjects: X-ray, Cataclysmic Variable, Nova

V2362 Cyg = Nova Cyg 2006 (Nakano et al. IAUC # 8697 ), observed on May 7 2007 in the infrared with the Lick 3-m telescope (0.4-2.5 micron) and with the Infrared Telescope Facility (0.8-5.5 micron) during its nebular phase (Lynch et al. IAUC # 8849 ), was also observed by XMM-Newton on 5 May 2007. The total exposure was of 9.6 ks with the EPIC-MOS and 7.7 ks with the EPIC-PN cameras. However, the first part of the observation was affected by high background radiation, reducing the useful exposure times to 6.2 ks for MOS1, 6.1 ks for MOS2 and 5.2 ks for PN cameras.

The source was detected by the EPIC cameras as a bright source with most of the emission in the energy range 0.2-4 keV. The source count-rates were 0.130+/-0.005 cts/s for MOS1 and MOS2 and 0.47+/-0.02 cts/s for PN. The EPIC spectra are poorly fitted with a single component absorbed model (blackbody, white dwarf atmosphere or thermal plasma). The fit is also unacceptable with a thermal plasma, simulated with the MEKAL model (Mewe, Kaastra & Liedhal 1995), plus photospheric white dwarf emission (simulated either with a blackbody or a model atmosphere for a CO or ONe white dwarf, from MacDonald and Vennes 1991). A better fit (reduced chi^2=1.5) is obtained with a two-temperature thermal plasma model with low and high temperatures of 0.2 keV and 2.3 keV, respectively.

The absorbing column density is N(H) = 2(+/-1)x10^21 cm^-2. This value is smaller than the interstellar absorption in the direction of the source, N(H) = 4x10^21 cm^2 (Dickey & Lockman, 1990, ARAA, 28, 215). We note, however, that our N(H) value is marginally compatible (within the errors) with the extinction from outburst spectroscopy, E(B-V)= 0.56 (IAUC 8702 ), which implies N(H)=3e21cm^-2 (Zombeck 2007). The E(B-V) from outburst spectroscopy is also smaller than the galactic extinction from Schlegel et al. (1998) dust maps, E(B-V)=0.8. The small absorption column density may indicate a small distance to the nova, as pointed out from the equivalent width of the interstellar lines in ATel #792, which suggest a distance of about 1.5 kpc. The nova distance was however estimated as 5-12 kpc by Steeghs et al. (ATel #795) from photometric observations of the pre-nova cataclysmic variable. For d=5 kpc, the luminosity in the 0.2-4 keV range is 5x10^33 erg/s.