Kars Verbeek, Paul J. Groot, Simone Scaringi, Ralf Napiwotzki, Ben Spikings, Roy H. Østensen, Janet Drew, Danny Steeghs, Jorge Casares, Jesus M. Corral-Santana, Romano Corradi, Niall Deacon, Jeremy Drake, Boris T. Gansicke, Eduardo González-Solares, Robert Greimel, Ulrich Heber, Mike Irwin, Christian Knigge, Gijs Nelemans
We present the results of the first spectroscopic follow-up of 132 optically blue UV-excess sources selected from the UV-excess survey of the Northern Galactic Plane (UVEX). The UV-excess spectra are classified into different populations and grids of model spectra are fit to determine spectral types, temperatures, surface gravities and reddening. From this initial spectroscopic follow-up 95% of the UV-excess candidates turn out to be genuine UV-excess sources such as white dwarfs, white dwarf binaries, subdwarfs type O and B, emission line stars and QSOs. The remaining sources are classified as slightly reddened main-sequence stars with spectral types later than A0V. The fraction of DA white dwarfs is 47% with reddening smaller than E(B-V)<0.7 mag. Relations between the different populations and their UVEX photometry, Galac- tic latitude and reddening are shown. A larger fraction of UVEX white dwarfs is found at magnitudes fainter than g>17 and Galactic latitude smaller than |b|<4 compared to main-sequence stars, blue horizontal branch stars and subdwarfs.
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http://arxiv.org/abs/1206.7012
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