The X-ray emission from Nova V382 Velorum - II. The super-soft component observed with BeppoSAX

Abstract

Nova Velorum 1999 (V382 Vel) was observed by BeppoSAX six months after optical maximum, and was detected as a bright X-ray supersoft source, with a count rate 3.454 ± 0.002 cts-1 in the Low-Energy Concentrator Spectrometer (LECS). It was the softest and most luminous supersoft source observed with this instrument. The flux in the 0.1-0.7 keV range was not constant during the observation. It dropped by a factor of 2 in less than 1.5 hr and then was faint for at least 15 min, without significant spectral changes. The observed spectrum is not well-fitted with atmospheric models of a hot, hydrogen burning white dwarf. This is due mainly to a supersoft excess in the range of 0.1-0.2 keV, but the fit can be significantly improved at higher energy if at least one emission feature is superimposed. We suggest that a 'pseudocontinuum' was detected, consisting of emission lines in the supersoft X-ray range superimposed on the thermal continuum of a white dwarf atmosphere. As a result, an accurate determination of the effective temperature and gravity of the white dwarf at this post-outburst stage is not possible.