The X-ray emission from Nova V382 Velorum - I. The hard component observed withBeppoSAX

Abstract

We present BeppoSAX observations of Nova Velorum 1999 (V382 Vel), carried out in a broad X-ray band covering 0.1–300 keV only 15 d after the discovery and again after 6 months. The nova was detected at day 15 with the BeppoSAX instruments which measured a flux Fx≃1.8×10−11 erg cm−2 s−1 in the 0.1–10 keV range and a 2σ upper limit Fx<6.7×10−12 erg cm−2 s−1 in the 15–60 keV range. We attribute the emission to shocked nebular ejecta at a plasma temperature kT≃6 keV. At six months no bright component emerged in the 15–60 keV range, but a bright central supersoft X-ray source appeared. The hot nebular component previously detected had cooled to a plasma temperature kT<1 keV. There was strong intrinsic absorption of the ejecta in the first observation and not in the second, because the column density of neutral hydrogen decreased from N(H)≃1.7×1023 to N(H)≃1021 cm−2 (close to the interstellar value). The unabsorbed X-ray flux also decreased from Fx = 4.3×10−11 to Fx≃10−12 erg cm−2 s−1.