You're right. The tidal force must be huge. Especially since the orbiting star is losing mass to the black hole it cannot be in a perfectly circular orbit but must be somewhat eccentric. And those massive changes in gravitational forces it's subjected to are cycling over the space of just a few minutes! To add to the question about how close the star is to the Roche limit, does anybody know the mass of the black hole it's orbiting? How close is it to the black hole's event horizon? It would be very cool if the star is hurtling around the black hole at 1% speed of light within grazing distance of the event horizon.