A hot blue star near the center of the remnant of supernova A.D. 1006

Abstract

Results of a search for a blue object representing the remnant star of the supernova of 1006 A.D. are reported. The search was conducted using trailed prime-focus plates to detect optical pulsations of moderately bright stars and two-color plates to look for an unusually blue object. Although no object pulsing at between 0.1 and 8 Hz with a peak B magnitude brighter than 16.3 was detected, one very blue star was discovered on the two-color plates 2.45 arcmin from the center. Spectroscopy and photoelectric photometry in the UBVR of the blue star indicates an effective temperature of 38,500 + or - 4500 K, and absolute visual magnitude of 6.2 + or - 1.8, an interstellar reddening of 0.32 + or - 0.10, a distance of 1.1 kpc, a radial velocity of -14 km/sec and an upper limit of 320 km/sec on the transverse velocity. The star is classified as transitional between an O or a B subdwarf of high gravity and a WD star, with a temperature and location consistent with the remnant of the 1006 supernova.