Detection of the Central Star of the Planetary Nebula NGC 6302

Szyszka, C.; Walsh, J. R.; Zijlstra, Albert A. and Tsamis, Y. G. (2009). Detection of the Central Star of the Planetary Nebula NGC 6302. The Astrophysical Journal, 707(1) L32-L36.

DOI: https://doi.org/10.1088/0004-637X/707/1/L32

Abstract

NGC 6302 is one of the highest ionization planetary nebulae (PNe) known and shows emission from species with ionization potential > 300 eV. The temperature of the central star must be > 200,000 K to photoionize the nebula, and has been suggested to be up to ~400,000 K. On account of the dense dust and molecular disk, the central star has not convincingly been directly imaged until now. NGC 6302 was imaged in six narrowband filters by Wide Field Camera 3 on the Hubble Space Telescope as part of the Servicing Mission 4 Early Release Observations. The central star is directly detected for the first time, and is situated at the nebula center on the foreground side of the tilted equatorial disk. The magnitudes of the central star have been reliably measured in two filters (F469N and F673N). Assuming a hot blackbody, the reddening has been measured from the (4688-6766 Å) color and a value of c = 3.1, A_v = 6.6 mag determined. A G-K main-sequence binary companion can be excluded. The position of the star on the H-R diagram suggests a fairly massive PN central star of about 0.64 M☉ close to the white dwarf cooling track. A fit to the evolutionary tracks for (T, L, t) = (200,000 K, 2000 L☉, 2200 yr), where t is the nebular age, is obtained; however, the luminosity and temperature remain uncertain. The model tracks predict that the star is rapidly evolving, and fading at a rate of almost 1% per year. Future observations could test this prediction.