Fifty-two magnetic white dwarfs have been identified in spectroscopic observations from the Sloan Digital Sky Survey (SDSS) obtained between mid-2002 and the end of 2004, including Data Releases 2 and 3. Though not as numerous nor as diverse as the discoveries from the first Data Release, the collection exhibits polar field strengths ranging from 1.5 MG to ∼1000 MG, and includes two new unusual atomic DQA examples, a molecular DQ, and five stars that show hydrogen in fields above 500 MG. The highest-field example, SDSS J2346+3853, may be the most strongly magnetic white dwarf yet discovered. Analysis of the photometric data indicates that the magnetic sample spans the same temperature range as for nonmagnetic white dwarfs from the SDSS, and support is found for previous claims that magnetic white dwarfs tend to have larger masses than their nonmagnetic counterparts. A glaring exception to this trend is the apparently low-gravity object SDSS J0933+1022, which may have a history involving a close binary companion.Subject headings: white dwarfs -stars : magnetic fields 1 A portion of the results presented here were obtained with the MMT Observatory, a facility operated jointly by The University of Arizona and the Smithsonian Institution.

Discoveries of two new white dwarf plus M star binaries with striking optical cyclotron emission features from the Sloan Digital Sky Survey (SDSS) brings to six the total number of X-ray faint, magnetic accretion binaries that accrete at ratesṀ 10 −13 M ⊙ yr −1 , or <1% of the values normally encountered in cataclysmic variables. This fact, coupled with donor stars that underfill their Roche lobes and very cool white dwarfs, brand the binaries as post common-envelope systems whose orbits have not yet decayed to the point of Roche-lobe contact. They are pre-magnetic CVs, or pre-Polars. The systems exhibit spin/orbit synchronism and apparently accrete by efficient capture of the stellar wind from the secondary star, a process that has been dubbed a "magnetic siphon". Because of this, period evolution of the binaries will occur solely by gravitational radiation, which is very slow for periods >3 hr. Optical surveys for the cyclotron harmonics appear to be the only means of discovery, so the space density of pre-Polars could rival that of Polars, and the binaries provide an important channel of progenitors (in addition to the asynchronous Intermediate Polars). Both physical and SDSS observational selection effects are identified that may help to explain the clumping of all six systems in a narrow range of magnetic field strength around 60 MG.

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V838 Her and V4160 Sgr were two of the fastest classical novae ever observed, exhibiting light curve declines of 2 mag in less than 2 days. Both novae also showed strong neon emission lines, indicative of an outburst occurring on an oxygen-neon-magnesium white dwarf. Being the brighter of the two, V838 Her has an extensive set of X-ray to radio observations obtained during its first year after outburst. V4160 Sgr has a more modest set of ultraviolet and optical spectra, which show it to be similar to V838 Her, not just in its light curve evolution but also in its spectral development. The observed attributes imply that these novae occurred on extremely massive white dwarfs. This paper uses the Cloudy photoionization code to fit multiple epochs of emission line spectra to determine the elemental abundances of the ejecta of V838 Her and V4160 Sgr.