We report the discovery of the ninth pre-polar, consisting of a late-type ZAMS secondary and a magnetic white dwarf. The white dwarf accretes at extreme low rate, dot{M} ~ 10**-14 Msun/yr, from the wind of the companion donor star. The source was found in our systematic search for WD/MS binaries within SDSS/SEGUE. Based on seven Sloan-spectra we estimate a binary period of ~200, 230, or 270 min. The UV to IR spectral energy distribution was decomposed into a dM3-dM4 ZAMS secondary and a cool white dwarf, ~9000 K, which consistently imply a distance between 360 and 420 pc. The optical spectrum displays one pronounced cyclotron hump, likely originating from a low-temperature plasma, ~1 keV, in a field of 108 MG. We comment on the evolutionary link between polars and pre-polars.
@article{arxiv.0903.5417,
title = {Post common envelope binaries from the SDSS. VI. SDSS J120615.73+510047.0: a new low accretion rate magnetic binary},
author = {A. D. Schwope and A. Nebot Gomez-Moran and M. R. Schreiber and B. T. Gaensicke},
journal= {arXiv preprint arXiv:0903.5417},
year = {2011}
}
Comments
7 pages, 5 figures, accepted for publication in A&A