This new UV study of the ex-nova HR Del is based on all of the data obtained with the International Ultraviolet Explorer ( IUE ) satellite , and includes the important series of spectra taken in 1988 and 1992 that have not been analyzed so far .
This has allowed us to make a detailed study of both the long-timescale and the short-timescale UV variations , after the return of the nova , around 1981-1982 , to the pre-outburst optical magnitude .
After the correction for the reddening ( E _ { B - V } = 0.16 ) , adopting a distance d =850 pc we have derived a mean UV luminosity close to L _ { UV } \sim 56 L _ { \odot } , the highest value among classical novae in ” quiescence ” .
Also the ” average ” optical absolute magnitude ( M _ { v } = +2.30 ) is indicative of a bright object .
The UV continuum luminosity , the HeII 1640 Å emission line luminosity , and the optical absolute magnitude all give a mass accretion rate \dot { M } very close to 1.4 \times 10 ^ { -7 } M _ { \odot } yr ^ { -1 } , if one assumes that the luminosity of the old nova is due to a non-irradiated accretion disk .
The UV continuum has declined by a factor less than 1.2 over the 13 years of the IUE observations , while the UV emission lines have faded by larger factors .
The continuum distribution is well fitted with either a black body of 33,900 K , or a power-law F _ { \lambda } \sim \lambda ^ { -2.20 } .
A comparison with the grid of models of Wade and Hubeny ( 1998 ) indicates a low M _ { 1 } value and a relatively high \dot { M } but the best fittings to the continuum and the line spectrum come from different models .
We show that the ” quiescent ” optical magnitude at m _ { v } \sim 12 comes from the hot component and not from the companion star .
Since most IUE observations correspond to the ” quiescent ” magnitude at m _ { v } \sim 12 , the same as in the pre-eruption stage , we infer that the pre-nova , for at least 70 years prior to eruption , was also very bright at near the same L _ { UV } , M _ { v } , \dot { M } , and T values as derived in the present study for the ex-nova .
The wind components in the P Cyg profiles of the CIV 1550 Å and NV 1240 Å resonance lines are strong and variable on short timescales , with v _ { edge } up to -5000 km s ^ { -1 } , a remarkably high value .
The phenomenology in the short-time variations of the wind indicates the presence of an inhomogeneous outflow .
We discuss the nature of the strong UV continuum and wind features and the implications of the presence of a ” bright ” state a long time before and after outburst on our present knowledge of the pre-nova and post-nova behavior .