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XMM-Newton RGS observation of V2491 Cyg

ATel #1561; J.-U. Ness and S. Starrfield (Arizona State University), R. Gonzalez and E. Kuulkers (ESAC), J. P. Osborne and K. Page (University of Leicester), G. Schwarz and K. M.Vanlandingham (West Chester University), J. J. Drake (Smithsonian Astrophysical Observatory), M. Hernanz (CSIC-IEEC), A. Evans (Keele University), N. Gehrels (NASA-GSFC), J. Krautter (Landessternwarte Heidelberg), R. D. Gehrz and C. Woodward (University of Minnesota)
on 5 Jun 2008; 18:30 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Jan-Uwe Ness (Jan-Uwe.Ness@asu.edu)

Subjects: X-ray, Binary, Cataclysmic Variable, Nova, Transient

Referred to by ATel #: 1573

On 2008, May 20.6 (39.9 days after outburst) we obtained an XMM-Newton observation of the recent nova V2491 Cyg during the supersoft source (SSS) phase (Osborne et al. 2008, ATel #1542). The exposure time in the Reflection Grating Spectrometers (RGS) was 39.2ksec, and the average count rate in the RGS1 is 13.1 counts per sec (c/s). The light curve extracted from the RGS1 is highly variable. The initial count rate is 15c/s, and 10ks into the observation it drops to 2c.s. The count rate then reaches a level of 23c/s about 20ks into the observation and remains at that level until the end of the observation. The spectrum is that of a bright SSS (hot white dwarf atmosphere) with continuous emission ranging from 15Å to 35Å and a peak at 23Å. We find broad absorption lines at 15.84Å (OVIII at 16Å), 18.44Å (OVII at 18.62Å), 18.69Å (OVIII at 18.97Å), 20.70Å (NVII at 20.9Å), 21.36Å (OVII at 21.6Å), 24.51Å (NVII at 24.78Å), and 28.48Å (NVI at 28.78Å). Assuming the rest wavelengths given in brackets the lines are blue shifted by 3000km/s. This agrees with the high expansion velocities determined early in the outburst from optical (Tomov et al. 2008, ATel #1475). We further identify extremely broad emission lines from NeX at 12.13A and NeIX triplet at 13.45/13.55/13.7A which are at their rest wavelengths. We also find a weak line at the rest wavelength of MgXII at 8.42Å. These emission lines are broadened by more than 3000km/s (FWHM). The deepest absorption lines originate from oxygen and the strongest emission lines originate from neon, which suggests that V2491 Cyg may be an ONe nova.