X-Ray Spectroscopy of the Classical Nova V458 Vulpeculae with Suzaku

We conducted a target of opportunity X-ray observation of the classical nova V458 Vulpeculae 88 days after the explosion using the Suzaku satellite. With a ∼20 ks exposure, the X-ray Imaging Spectrometer detected X-ray emission significantly harder than typical super-soft source emission. The X-ray spectrum shows Kα lines from N, Ne, Mg, Si, and S, and L-series emission from Fe in highly ionized states. The spectrum can be described by a single temperature (∼0.64 keV) thin thermal plasma model in collisional equilibrium with a hydrogen-equivalent extinction column density of ∼ 3× 10 cm, a flux of ∼10 erg s cm, and a luminosity of ∼6×10 erg s in the 0.3–3.0 keV band at an assumed distance of 13 kpc. We found a hint of an enhancement of N and deficiencies of O and Fe relative to other metals. The observed X-ray properties can be interpreted as the emission arising from shocks of ejecta from an ONe-type nova.