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ATEL # 1910; Thomas Nelson and Marina Orio (INAF-Padova and U Wisconsin), and see below full list
on 26 Jan 2009; 22:23 UT
Distributed as an Instant Email Notice (Nova)
Password Certification: Marina Orio (firstname.lastname@example.org)
Nova CSS 081007:030559+054715 (ATEL #1825, #1835, #1847, and #1873) was observed with the Chandra LETG grating and HRC-S camera on 2008 December 18 for 35000 s (about 9.7 hours). The observation was carried out around the time of the maximum in the 1.77 days period detected in X-rays with Swift (ATEL #1873). At the time of the observation, the X-ray flux has started to decrease after a plateau at maximum. The combined +1/-1 order count rate was 0.31 counts/s. The spectrum exhibits a supersoft continuum superimposed with prominent emission lines, most notably those of N VII Ly alpha (24.74 Angstrom) and O VII (21.6 and 21.8 Angstrom). The continuum component of the spectrum can be fitted with atmospheric models developed for hot hydrogen burning white dwarfs. The best fit is obtained with a photospheric temperature 650,000 K and an intervening interstellar absorbing column N(H) = 7.2 x 10^(20) cm(-2). The total flux in the 5-50 A wavelength range with this model is 1.22 x 10(-11) erg/cm^2/s, implying an unabsorbed flux 5.2x10(-11) erg/cm^2/s. However, more accurate work is necessary to further constrain the parameters, since due to the emission lines and uncertainties in the abundances we cannot rule out yet models with an atmospheric temperature of only 400,000 K, much higher absorption and an unabsorbed flux as high as 2 x 10^(-7) erg/cm^2/s.