Bibcode
Webb, N. A.; Naylor, T.; Ioannou, Z.; Charles, P. A.; Shahbaz, T.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 317, Issue 3, pp. 528-534.
Fecha de publicación:
9
2000
Número de citas
43
Número de citas referidas
39
Descripción
We present 53 simultaneous photometric (I band) and spectroscopic
(6900-9500Å) observations of GRO J0422+32, taken during 1997
December. From these we determine that J0422+32 was in its lowest state
yet observed, at I=20.44+/-0.08. Using relative spectrophotometry, we
show that it is possible to correct very accurately for telluric
absorption. Following this, we use the TiO bands at 7055 and 7589Å
for a radial velocity study and thereby obtain a semi-amplitude of
378+/-16kms-1, which yields
f(M)=1.191+/-0.021Msolar and
q9.0+2.2-2.7, consistent with previous
observations. We further demonstrate that this little-explored method is
very powerful for such systems. We also determine a new orbital
ephemeris of HJD=2450274.4156+/-0.0009+0.2121600+/-0.0000002E. We see
some evidence for an ellipsoidal modulation, from which we determine the
orbital inclination of J0422+32 to be less than 45°. We therefore
calculate a minimum mass for the primary of 2.22Msolar,
consistent with a black hole, but not necessarily the supermassive one
proposed recently (1997) by Beekman et al. We obtain an M4-5 spectral
type for the secondary star, and determine that the secondary
contributes 38+/-2per cent of the flux that we observe from J0422+32
over the range 6950-8400Å. From this we calculate the distance to
the system to be 1.39+/-0.15kpc.