Carbon stars and DZ white dwarfs are two types of rare objects in the Galaxy.In this paper,we have applied the label propagation algorithm to search for these two types of stars from Data Release Eight(DR8)of the Sloan Digital Sky Survey(SDSS),which is verified to be efcient by calculating precision and recall.From nearly two million spectra including stars,galaxies and QSOs,we have found 260 new carbon stars in which 96 stars have been identified as dwarfs and 7 identified as giants,and 11 composition spectrum systems(each of them consists of a white dwarf and a carbon star).Similarly,using the label propagation method,we have obtained 29 new DZ white dwarfs from SDSS DR8.Compared with PCA reconstructed spectra,the 29 findings are typical DZ white dwarfs.We have also investigated their proper motions by comparing them with proper motion distribution of 9,374 white dwarfs,and found that they satisfy the current observed white dwarfs by SDSS generally have large proper motions.In addition,we have estimated their efective temperatures by fitting the polynomial relationship between efective temperature and g-r color of known DZ white dwarfs,and found 12 of the 29 new DZ white dwarfs are cool,in which nine are between 6,000 K and 6,600 K,and three are below 6,000 K.
SI JianMinLUO ALiLI YinBiZHANG JianNanWEI PengWU YiHongWU FuChaoZHAO YongHeng
We introduce an algorithm to solve the block-edge problem taking advantage of the two diferent sky splitting functions:HTM and HEALPix.We make the cross-match with the two functions,and then we obtain the union set of the two diferent sets.We use the ThreadPool technique to speed up the cross-match.In this way improved accuracy can be obtained on the cross-match.Our experiments show that this algorithm has a remarkable performance superiority compared with the previous ones and can be applied to the cross-match between large-scale catalogs.We give some ideas about solving the many-for-one situation occurred in the cross-match.
