High-field magnetic white dwarfs as the progeny of early-type stars?

Abstract

We present an analysis of the newly resolved components of two hot, doubledegenerate systems, SDSS J074853.07+302543.5 + J074852.95+302543.4 and SDSS J150813.24+394504.9 + J150813.31+394505.6 (CBS 229). We confirm that each system has widely separated components (a > 100 au) consisting of a H-rich, non-magnetic white dwarf and a H-rich, high-field magnetic white dwarf (HFMWD). The masses of the nonmagnetic degenerates are found to be larger than typical of field white dwarfs. We use these components to estimate the total ages of the binaries and demonstrate that both magnetic white dwarfs are the progeny of stars with Minit > 2M⊙. We briefly discuss the traits of all known hot, wide, magnetic + non-magnetic double degenerates in the context of HFMWD formation theories. These are broadly consistent (chance probability, P≈0.065) with HFMWDs forming primarily from early-type stars and, in the most succinct interpretation, link their magnetism to the fields of their progenitors. Our results do not, however, rule out that HFMWDs can form through close binary interactions and studies of more young, wide double degenerates are required to reach firm conclusions on these formation pathways. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.