Photoionization modelling of quiescence-phase spectra of novae and a symbiotic star

Abstract

Using observed and published spectra in the optical region, we have studied a handful of novae and symbiotic stars that show novae-like variability in the quiescence phase. We present results for the novae T Coronae Borealis, GK Persei, RS Ophiuchi, V3890 Sagittarii and V745 Scorpii, and for a symbiotic star BX Monocerotis. Observations were carried out at the 2-m Himalayan Chandra Telescope (HCT). Generally, the spectra show prominent low-ionization emission features of hydrogen, helium, iron and oxygen and TiO absorption features resulting from the cool secondary component; T Coronae Borealis and GK Persei show higher ionization lines. We used the photoionization code cloudy to model these spectra. From the best-fitting models, we have estimated the physical parameters (e.g. temperature, luminosity and hydrogen density), the elemental abundances and other parameters related to the system. By matching the spectra of various giants with the absorption features and using the best fit, we have determined the types of secondaries and also their contribution to the spectra.