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

Abstract

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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• New binaries among UV-selected, hot subdwarf stars and population properties
• Cataclysmic Variables in the First Year of the Zwicky Transient Facility
• Interesting Features in the Combined GALEX and Sloan Color Diagrams of Solar-like Galactic Populations
• A determination of the space density and birth rate of hydrogen-line (DA) white dwarfs in the Galactic Plane, based on the UVEX survey
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• A GALEX view of the DA White Dwarf Population
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