Verbeek, Kars, Groot, Paul J., Scaringi, Simone, Napiwotzki, Ralf, Spikings, Ben, Østensen, Roy H., Drew, Janet E., Steeghs, Danny, Casares, Jorge, Corral-Santana, Jesus, Corradi, Romano L. M., Deacon, Niall, Drake, Jeremy J., Gänsicke, Boris T., González-Solares, Eduardo, Greimel, Robert, Heber, Ulrich, Irwin, Mike J., Knigge, Christian, and Nelemans, Gijs. 2012. "Spectroscopic follow-up of ultraviolet-excess objects selected from the UVEX survey." Monthly Notices of the Royal Astronomical Society, 426 1235–1261. https://doi.org/10.1111/j.1365-2966.2012.21615.x.
We present the results of the first spectroscopic follow-up of 132 optically blue ultraviolet (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 fitted to determine spectral types, temperatures, surface gravities and reddening. From this initial spectroscopic follow-up 95 per cent of the UV-excess candidates turn out to be genuine UV-excess sources such as white dwarfs, white dwarf binaries, subdwarf types O and B, emission-line stars and quasi stellar objects. 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 per cent with reddening smaller than E(B ‑ V) ≤ 0.7 mag. Relations between the different populations and their UVEX photometry, Galactic 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.