Cool stars, stellar systems and the sun vol:1094 pages:931-934
AIP CONFERENCE PROCEEDINGS
15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun St Andrews, SCOTLAND, JUL 21-25, 2008
We present a catalog of 857 white dwarf-M binaries from the sixth data release of the Sloan Digital Sky Survey (SDSS), most of them known before. For 636 of them, we give a spectral analysis and derive the basic parameters of the stellar constituents and their distances from Earth. The analysis shall give a statistically relevant statement about the fundamental parameters of such systems. Our purpose is to test the models applied in the fitting procedure on the one hand and to confine the respective evolutionary scenarios on the other hand. The chi(2) minimization technique we use, in order to decompose each combined spectrum and yield independent parameter estimates for the components, differs from that typically applied to break down combined spectra. In the corresponding SDSS photometric data we find 41 optically resolved systems. For these we also derive a minimum real spatial separation and a lower limit for the orbital periods - typically some 10(4) yr. 167 spectra show significant hydrogen emission and mostly no additional He I or He II features. Furthermore, we identify 70 very low-mass objects, meaning secondaries with masses smaller than about 0.1 M-circle dot, as candidate substellar companions.