Atmospheric Modelling of the Companion Star in GRO J1655-40

Abstract

We have measured the rotational velocity of the companion star to be v _rot sin i= 80 ± 10 km s ^-1 (1σ) by fitting Kurucz model spectra to our observed spectrum of the black-hole candidate GRO J1655–40. From this we have calculated q = 0·31 ± 0·08, the mass of the compact object to be M ₁ = 7·91 ± 3·79 Mô (1σ) and for the companion starM ₂ = 2·76 ± 1·79 Mô (1σ), which is consistent with previous studies. We have also determined T_eff = 6500 ± 50 K and [Fe/H] = −0·15 ^+0·15 _-0·10.