Institute for Advanced Study Informal Astrophysics Seminar - ADDED

ABSTRACT: We consider the Roche accretion in an Extreme Mass-Ratio Inspiral (EMRI) binary system formed by a star orbiting a massive black hole. The ultimate goal is to constrain the mass and spin of the black hole and confirm general relativity in the strong-field regime from the resulted quasi-periodic signals. Before accretion starts, the star orbits the hole in a circular, equatorial stellar orbit, which shrinks due to gravitational radiation. If the inspiralling star fills its Roche lobe outside the Innermost Stable Circular Orbit (ISCO) of the hole, gas will flow through the inner Lagrange point to the hole. If this mass-transfer happens on a time scale faster than the thermal time scale but slower than the dynamical time scale, the star will evolve adiabatically, and, in most cases, will recede from the hole. We calculate how the stellar orbits and mass-transfer rates will change as various types of stars are tidally stripped in the relativistic regime, and discussed the stability during the process. We envisage that the mass stream eventually hits the accretion disc, where it forms a hot spot orbiting the hole and may ultimately modulate the luminosity with the stellar orbital frequency. The observability of such a modulation is discussed along with possible interpretation of an intermittent 1 hour period in the X-ray emission of RE J1034+396.