Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003apj...594l.127n&link_type=abstract
The Astrophysical Journal, Volume 594, Issue 2, pp. L127-L130.
Astronomy and Astrophysics
Astronomy
61
Stars: Novae, Cataclysmic Variables, Stars: Individual: Constellation Name: V4743 Sagittarii, Stars: Oscillations, Stars: White Dwarfs, X-Rays: Binaries
Scientific paper
V4743 Sagittarii (Nova Sgr 2002 No. 3) was discovered on 2002 September 20. We obtained a 5 ks ACIS-S spectrum in 2002 November and found that the nova was faint in X-rays. We then obtained a 25 ks Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation on 2003 March 19. By this time, it had evolved into the supersoft X-ray phase exhibiting a continuous spectrum with deep absorption features. The light curve from the observation showed large-amplitude oscillations with a period of 1325 s (22 minutes) followed by a decline in the total count rate after ~13 ks of observations. The count rate dropped from ~40 counts s-1 to practically zero within ~6 ks and stayed low for the rest of the observation (~6 ks). The spectral hardness ratio changed from maxima to minima in correlation with the oscillations and then became significantly softer during the decay. Strong H-like and He-like lines of oxygen, nitrogen, and carbon were found in absorption during the bright phase, indicating temperatures between 1 and 2 MK, but they were shifted in wavelength corresponding to a Doppler velocity of -2400 km s-1. The spectrum obtained after the decline in count rate showed emission lines of C VI, N VI, and N VII, suggesting that we were seeing expanding gas ejected during the outburst, probably originating from CNO-cycled material. An XMM-Newton Target of Opportunity observation, obtained on 2002 April 4 and a later LETGS observation from 2003 July 18 also showed oscillations, but with smaller amplitudes.
Balman Soelen
Bond Howard E.
Burwitz Vadim
Butt Yousaf
Drake Jeremy J.
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