A spectroscopic and proper motion search of Sloan Digital Sky Survey: red subdwarfs in binary systems

Zhang, Z. H.; Pinfield, D. J.; Burningham, B.; Jones, H. R. A.; Gálvez-Ortiz, M. C.; Catalán, S.; Smart, R. L.; Lépine, S.; Clarke, J. R. A.; Pavlenko, Ya. V.; Murray, D. N.; Kuznetsov, M. K.; Day-Jones, A. C.; Gomes, J.; Marocco, F.; Sipőcz, B.
Referencia bibliográfica

Monthly Notices of the Royal Astronomical Society, Volume 434, Issue 2, p.1005-1027

Fecha de publicación:
9
2013
Número de autores
16
Número de autores del IAC
0
Número de citas
30
Número de citas referidas
28
Descripción
Red subdwarfs in binary systems are crucial for both model calibration and spectral classification. We search for red subdwarfs in binary systems from a sample of high proper motion objects with Sloan Digital Sky Survey spectroscopy. We present here discoveries from this search, as well as highlight several additional objects of interest. We find 30 red subdwarfs in wide binary systems including: two with spectral type of esdM5.5, 6 companions to white dwarfs and 3 carbon-enhanced red subdwarfs with normal red subdwarf companions. 15 red subdwarfs in our sample are partially resolved close binary systems. With this binary sample, we estimate the low limit of the red subdwarf binary fraction of ˜10 per cent. We find that the binary fraction goes down with decreasing masses and metallicities of red subdwarfs. A spectroscopic esdK7 subdwarf + white dwarf binary candidate is also reported. 30 new M subdwarfs have spectral type of ≥M6 in our sample. We also derive relationships between spectral types and absolute magnitudes in the optical and near-infrared for M and L subdwarfs, and we present an M subdwarf sample with measured U, V, W space velocities.