Spectroscopic follow-up of ultraviolet-excess objects selected from the UVEX survey

Abstract

We present the results of the first spectroscopic follow-up of 132 optically\nblue UV-excess sources selected from the UV-excess survey of the Northern\nGalactic Plane (UVEX). The UV-excess spectra are classified into different\npopulations and grids of model spectra are fit to determine spectral types,\ntemperatures, surface gravities and reddening. From this initial spectroscopic\nfollow-up 95% of the UV-excess candidates turn out to be genuine UV-excess\nsources such as white dwarfs, white dwarf binaries, subdwarfs type O and B,\nemission line stars and QSOs. The remaining sources are classified as slightly\nreddened main-sequence stars with spectral types later than A0V. The fraction\nof DA white dwarfs is 47% with reddening smaller than E(B-V)<0.7 mag. Relations\nbetween the different populations and their UVEX photometry, Galac- tic\nlatitude and reddening are shown. A larger fraction of UVEX white dwarfs is\nfound at magnitudes fainter than g>17 and Galactic latitude smaller than |b|<4\ncompared to main-sequence stars, blue horizontal branch stars and subdwarfs.\n