Citation:
Date Published:
October 1, 2003Abstract:
Beyond its goals related to the extragalactic universe, the SloanDigital Sky Survey (SDSS) is an effective tool for identifying stellarobjects with unusual spectral energy distributions. Here we report onthe 53 new magnetic white dwarfs discovered during the first two yearsof the survey, including 38 whose data are made public in the 1500deg2 First Data Release. Discoveries span the magnitude range16.3<=g<=20.5, and based on the recovery rate for previously knownmagnetic white dwarfs, the completeness of the SDSS appears to be highfor reasonably hot stars with B>~3 MG and g>~15. The new objectsnearly double the total number of known magnetic white dwarfs andinclude examples with polar field strengths Bp>500 MG, aswell as several with exotic atmospheric compositions. The improvedsample statistics and uniformity indicate that the distribution ofmagnetic white dwarfs has a broad peak in the range ~5-30 MG and a tailextending to nearly 109 G. Degenerates with polar fieldsBp>~50 MG are consistent with being descendents ofmagnetic Ap/Bp main-sequence stars, but low- and moderate-field magneticwhite dwarfs appear to imply another origin. Yet-undetected magneticF-type stars with convective envelopes that destroy the orderedunderlying field are attractive candidates.A portion of the results presented here were obtained with the MMTObservatory, a facility operated jointly by the University of Arizonaand the Smithsonian Institution.