Modelling of complex absorption on high-resolution X-ray spectra of novae: The case of V4743 Sgr

Nova V4743 Sgr was discovered in outburst on September 2002 and was observed by XMM-Newton RGS (Reflection Grating Spectrometer) on April 2003. The RGS spectra of V4743 Sgr show complex absorption features and the previous studies indicate a blueshift in the spectra, hence we considered there exist a collisionally ionised hot absorber and/or a photoionized warm absorber component originating from wind and/or ejecta. We utilise SRON software SPEX 3.03.00 for our analysis and use its absorption models. The light curve showed oscillations in the count rate during the observation. The spectral analysis of the entire spectrum indicates that the models are inadequate. Taken into account the oscillations in the spectrum we considered to work on several resolved spectra on QPO time-scale.One of the best fit for a chosen RGS spectrum yields a blackbody for the continuum with temperature range ∼41-45 eV. We assumed two warm and one hot absorption components yielding blue shifts ∼1200-3500 km/s, along with an interstellar absorption and a dust absorption components. The resulting two warm absorption models have N_H_{1}≃3.5-4× 10^{21} cm^{-2} and N_H_{2}≃9-7.5×10^{20} cm^{-2} with ionization parameter Log (ξ_{1})∼3.7 erg cm s^{-1} and Log (ξ_{2})∼1.3 erg cm s^{-1}. The hot component has N_H ≃0.4-0.7× 10^{24} cm^{-2} and temperature deviating between 1.5-3.2 keV. The best fits for the other spectra can also be obtained with the same composite model.The χ^{2} values differs from region to region and ranges between 2.3-7.2.