Princeton University Gravity Group Astrophysics|Cosmology Lunch(More about event)
Title: Roche Accretion Of Stars Close To Massive Black Holes
Speaker: Lixin (Jane) Dai Stanford University
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. New fitting formulae are presented for the inspiral time and the radiation-reaction torque in the relativistic regime. 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 (L1) to the hole. We give new relativistic interpolation formulae for the volume enclosed by the Roche lobe. 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 filling its Roche lobe. We calculate how the stellar orbital period and mass-transfer rate will change through the âRoche evolutionâ? for various types of stars in the relativistic regime. 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.
Location: Joseph Henry Room
Date/Time: 12/02/11 at 12:00 pm - 12/02/11 at 1:30 pm
Category: Gravity Group Seminar