On the possibility of detecting remnants of novae in the X-rays and recovering the remains of an explosion after a century

Abstract

The nova shell of GK Per is the first classical nova shell resolved and detected in the X-ray wavelengths. I will present the spectral and spatial characteristics of the X-ray nebula derived from a CHANDRA ACIS-S observation. The nebula is brightest on the SW quadrant and towards West with a lumpy morphology. The X-ray shell has a symmetric bow-shaped structure detected in a [NeIX] emission line which shows the shock front most likely expanding into a less dense medium in the NW to SE direction. The X-ray nebula has a low temperature component which is a plasma possibly dominated by emission lines originating from the ejecta with kT = 0.11 - 0.18 keV and an X-ray luminosity of 1.6 x 10(31) ergs/s. The higher energy component above 2 keV has kT > 30 keV and an X-ray luminosity of 3.0 x 10(31) erg/s, which could be attributed to the emission from accelerated particles behind the shock. This component is found to be heavily absorbed with N-H = 1.7 x 10(22) cm(-2) suggesting that there is a colder shell of material between the two X-ray components in question. The low X-ray luminosity of both components indicates that most of the kinetic energy is still going into expansion of the shell and that the shock is adiabatic. This places the remnant in a late Pre-Sedov/transition to Sedov phase. It is evident from calculations that an adiabiatic nova remnant in X-rays would have luminosities in the range 10(32) - 10(26) ergs/s. Thus, recovering such low luminosity objects with the sensitivity of the present X-ray instruments will be largely limited with distance and surface brightness and thus, should be an intriguing challenge.