Spectral behavior of Nova GQ Mus in the ultraviolet

Abstract

We present ultraviolet spectroscopic study of nova GQ Mus observed with the International Ultraviolet Explorer (IUE) during the period 1983–1985. Different spectra showing the changes in line fluxes at different times are presented. The outflow velocity of the ionized ejecta was calculated to be 1010–2900 kms‑1 (FWHM). We estimated a new value of the reddening from the 2200 Å absorption feature, E(B‑V)=0.16±0.02. The models generated by Jose and Hernanz (1998) indicate that GQ Mus is a CO5/CO6 nova with WD mass of ∼1.15M⊙. We calculated the line fluxes of NIV], C IV and N III] emission lines produced in the expanding shell of the ejecta. The average wind mass loss rate is estimated to be ∼6×10‑5M⊙yr‑1. The average temperature of the central source is estimated to be ∼2×105K, and average ultraviolet luminosity of 2×1036ergs‑1 about 1000 days after outburst. Our results reveal that the line fluxes increase after outburst and then decrease with time. We attribute these spectral variations to the large expansion of the ejected matter from the white dwarf after outburst. The estimation of some physical parameters from the IUE observations is consistent with a photoionization model of the novae ejecta, (Diaz et al. 1995) and with an optically thick wind model of novae outburst, (Hachisu et al. 2008).