TY - JOUR
T1 - A TiO study of the black hole binary GRO J0422+32 in a very low state
AU - Webb, N. A.
AU - Naylor, T.
AU - Ioannou, Z.
AU - Charles, P. A.
AU - Shahbaz, T.
PY - 2000/9/21
Y1 - 2000/9/21
N2 - We present 53 simultaneous photometric (I band) and spectroscopic (6900-9500 Å) 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 7589 Å for a radial velocity study and thereby obtain a semi-amplitude of 378 ± 16km s-1, which yields f(M) = 1.191 ± 0.021 M⊙ and q = 9.0+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 = 245 0274.4156 ± 0.0009 + 0.212 1600 ± 0.000 0002E. 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 2.22 M⊙, 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 ± 2 per cent of the flux that we observe from J0422+32 over the range 6950-8400 Å. From this we calculate the distance to the system to be 1.39 ± 0.15 kpc.
AB - We present 53 simultaneous photometric (I band) and spectroscopic (6900-9500 Å) 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 7589 Å for a radial velocity study and thereby obtain a semi-amplitude of 378 ± 16km s-1, which yields f(M) = 1.191 ± 0.021 M⊙ and q = 9.0+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 = 245 0274.4156 ± 0.0009 + 0.212 1600 ± 0.000 0002E. 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 2.22 M⊙, 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 ± 2 per cent of the flux that we observe from J0422+32 over the range 6950-8400 Å. From this we calculate the distance to the system to be 1.39 ± 0.15 kpc.
KW - Accretion, accretion discs
KW - Binaries: close
KW - Black hole physics
KW - Stars: fundamental parameters
KW - Stars: individual: GRO J0422 + 32
KW - Stars: late-type
UR - http://www.scopus.com/inward/record.url?scp=0000800757&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0000800757&partnerID=8YFLogxK
U2 - 10.1046/j.1365-8711.2000.03608.x
DO - 10.1046/j.1365-8711.2000.03608.x
M3 - Article
AN - SCOPUS:0000800757
SN - 0035-8711
VL - 317
SP - 528
EP - 534
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -