H1504+65 - The Naked Stellar C/O Core of a Former Red Giant Observed with FUSE and Chandra

Abstract

H1504+65 is an extremely hot hydrogen-deficient white dwarf with an effective temperature close to 200,000 K. We present new FUV and soft X-ray spectra obtained with FUSE and Chandra, which confirm that H1504+65 has an atmosphere primarily composed of carbon and oxygen. The Chandra spectra show a wealth of absorption lines from highly ionized oxygen, neon and magnesium and suggest relatively high Ne and Mg abundances. This corroborates an earlier suggestion that H1504+65 represents a naked C/O stellar core or even the C/O envelope of a O-Ne-Mg white dwarf.

To appear in: Proceedings IAU Coll. 187, Exotic Stars as Challenges to Evolution, eds. C.A. Tout, W. Van Hamme, The ASP Conference Series, 6 pages, 4 figures