Variability of The Old Nova V603 Aquilae in UV and X-ray bands

Abstract

We present the results of a campaign of simultaneous observations of V603 Aql in the X-ray and UV bands accomplished with the IUE and ROSAT satellites. Simultaneous observations cover 20 orbital cycles, while the total span of all the observations is 40 cycles. This constitutes the longest continuous UV time series of simultaneous space observations of a cataclysmic variable. As all high energy radiation is ultimately powered by accretion, it is perhaps remarkable that we observe some signs of correlations of the UV line and continuum emission with the X-ray flux at zero lag, but none over a range of time lags from . A hint of some lagged correlation was revealed for UV color and X-ray flux. We detect a very strong modulation of intensity of the UV lines of CIV and SiIV. The modulation appears coherent over the range of observation and its period of is consistent with the spectroscopic orbital period but differs significantly from the period of photometric modulation. Furthermore, we observe variable P-Cygni profiles of the CIV1550 line. Its absorption and emission components are modulated with the orbital period of the binary. These data present evidence for sustained asymmetry of the supersonic wind excited from the accretion disc yet pose difficulties for the current disc and wind models. Since no periodic modulation was found in the X-ray band nor in the UV continuum, the present data do not lend support to our earlier classification of V603 Aql as an intermediate polar.