V4743 Sgr ( Nova Sgr 2002 No .
3 ) was discovered on 20 September 2002 .
We obtained a 5 ks ACIS-S spectrum in November 2002 and found that the nova was faint in X-rays .
We then obtained a 25 ks CHANDRA LETGS observation on 19 March 2003 .
By this time , it had evolved into the Super Soft 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 min ) followed by a decline in total count rate after \sim 13 ks of observations .
The count rate dropped from \sim 40 cts s ^ { -1 } to practically zero within \sim 6 ks and stayed low for the rest of the observation ( \sim 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 1–2 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 ToO observation , obtained on 4 April 2003 and a later LETGS observation from 18 July 2003 also showed oscillations , but with smaller amplitudes .