Ultraviolet-excess sources with a red/infrared counterpart : Low-mass companions, debris discs and QSO selection
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Author
Verbeek, K.
Groot, Paul J.
Scaringi, Simone
Casares, Jorge
Corral-Santana, Jesus M.
Deacon, Niall
Drew, J.E.
Gänsicke, B.T.
Gonzalez-Solares, E.
Greimel, R.
Heber, U.
Napiwotzki, R.
Ostensen, R.H.
Steeghs, D.
Wright, N.J.
Zijlstra, A.
Attention
2299/13055
Abstract
We present the result of the cross-matching between ultraviolet (UV)-excess sources selected from the UV-Excess Survey of the Northern Galactic Plane (UVEX) and several infrared (IR) surveys (2MASS, UKIDSS and WISE). From the position in the (J - H) versus (H - K) colour-colour diagram, we select UV-excess candidate white dwarfs with an M-dwarf type companion, candidates that might have a lower mass, brown-dwarf type companion and candidates showing an IR-excess only in the K band, which might be due to a debris disc. Grids of reddened DA+dM and sdO+MS/sdB+MS model spectra are fitted to the U, g, r, i, z, J, H, K photometry in order to determine spectral types and estimate temperatures and reddening. From a sample of 964 hot candidate white dwarfs with (g - r) <0.2, the spectral energy distribution fitting shows that ~2-4 per cent of the white dwarfs have an M-dwarf companion, ∼2 per cent have a lower-mass companion, and no clear candidates for having a debris disc are found. Additionally, from WISE six UV-excess sources are selected as candidate quasi-stellar objects (QSOs). Two UV-excess sources have a WISE IR-excess showing up only in the mid-IR W3 band of WISE, making them candidate luminous infrared galaxies (LIRGs) or Sbc starburst galaxies.