Phase Resolved UV Spectroscopy of RX J0019.8+2156

Abstract

We present orbital phase-resolved UV spectroscopy of the supersoft X-ray source RX J0019.8+2156 obtained with IUE in 1992-93. The UV and optical light curves show a quasi-sinusoidal orbital modulation with wavelength dependent amplitude and a deep secondary minimum at Φ∼0.6. The UV spectrum is of lower excitation than in other SSS. The various metal absorption lines are consistent with the source being located outside the gas layer of the galactic disc, though there is some evidence for intrinsic absorption. The UV spectrum of RX J0019 differs from those of the LMC sources CAL 83 and RX J0513.9-6951. A simple model where the UV light originates from the hot primary, the accretion disk and the heated secondary fails to reproduce the observed UV continuum.