XMM-Newton Observations of Nova Sagittarii 1998

Abstract

We report on X-ray observations of Nova Sagittarii 1998 (V4633 Sgr) performed with XMM-Newton at three different epochs, 934, 1083, and 1265 days after discovery. The nova was detected with the EPIC cameras at all three epochs, with emission spanning the whole energy range from 0.2 to 10 keV. The X-ray spectra do not change significantly at the different epochs and are well fitted for the first and third observations with a multitemperature optically thin thermal plasma, while lower statistics in the second observations lead to a poorer fit. The thermal plasma emission is most probably originated in the shock heated ejecta, with chemical composition similar to that of a CO nova. However, we cannot completely rule out reestablished accretion as the origin of the emission. We also obtain upper limits for the temperature and luminosity of a potential white dwarf atmospheric component and conclude that hydrogen burning had already turned off by the time of our observations.