Bibcode
Southworth, John; Gänsicke, B. T.; Marsh, T. R.; de Martino, D.; Hakala, P.; Littlefair, S.; Rodríguez-Gil, P.; Szkody, P.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 373, Issue 2, pp. 687-699.
Fecha de publicación:
12
2006
Número de citas
52
Número de citas referidas
43
Descripción
We present medium-resolution VLT/FORS2 spectroscopy of six cataclysmic
variables (CVs) discovered by the Sloan Digital Sky Survey (SDSS). We
determine orbital periods for SDSSJ023322.61+005059.5 (96.08 +/-
0.09min), SDSSJ091127.36+084140.7 (295.74 +/- 0.22min),
SDSSJ103533.02+055158.3 (82.10 +/- 0.09min) and SDSSJ121607.03+052013.9
(most likely 98.82 +/- 0.16min, but the one-day aliases at 92 and 107min
are also possible) using radial velocities measured from their Hα
and Hβ emission lines. Three of the four orbital periods measured
here are close to the observed 75-80min minimum period for CVs,
indicating that the properties of the population of these objects
discovered by the SDSS are substantially different to those of the CVs
found by other means. Additional photometry of SDSSJ023322.61+005059.5
reveals a periodicity of approximately 60min which we interpret as the
spin period of the white dwarf, suggesting that this system is an
intermediate polar with a low accretion rate. SDSSJ103533.02+055158.3
has a period right at the observed minimum value, a spectrum dominated
by the cool white dwarf primary star and exhibits deep eclipses, so is
an excellent candidate for an accurate determination of the parameters
of the system. The spectroscopic orbit of SDSSJ121607.03+052013.9 has a
velocity amplitude of only 13.8 +/- 1.6kms-1, implying that
this system has an extreme mass ratio. From several physical constraints
we find that this object must contain either a high-mass white dwarf or
a brown-dwarf-mass secondary component or both.