Telescope Observations of the Black Hole X - ray Transient GRO J 0422 + 32 Near Quiescence

We present HST /FOS ultraviolet and optical spectroscopy of the black hole X-ray transient GRO J0422+32 shortly before the system reached quiescence. We find that the accretion spectrum from 2500–9000Å can be very well fit by a self-absorbed synchrotron model, with superposed H i and Mg ii emission lines. The explanations we suggest for this spectrum are that it is either due to active coronal regions above a geometrically thin accretion disc, or that the disc is evaporated into an advective flow.