An ancient planetary nebula surrounding the old nova GK Persei

Abstract

Classical novae are a subset of the cataclysmic variable (CV) class of objects which undergo outbursts with peak luminosities ˜5×l037–5×l038 erg s–1 every 104–105 years. Around 10–5–10–4M⊙ of material is ejected at velocities typically 1,000 km s–1 at outburst. The central system is a semi-detached binary containing a white dwarf and (usually) a late-type, main-sequence companion. The companion fills its Roche lobe, and loses material, via an accretion disk, onto the surface of the white dwarf. Orbital periods are normally found to be in the range 3–10 h with CV orbits generally of low eccentricity (see ref. 1 for a review). As part of a continuing programme of observations of the old nova GK Persei, we examined Infrared Astronomical Satellite (IRAS) images in the region of the nova, and discovered extended emission in the far infrared. These observations are interpreted in terms of an ancient planetary nebula ejected from the central binary system. If this interpretation is correct, then several unique phenomena associated with GK Per may be explained. In addition, GK Per would then provide valuable clues to the evolutionary status of classical novae, and the later stages of planetary nebula formation.