239.07 - Constraining spins of black holes using quasi-periodic oscillations produced after they tidally disrupt stars

Date & Time

Jan 8th at 3:20 PM until 3:20 PM




Rating ( votes)

Author(s): D.R. Pasham, R. Remillard, J.F. Steiner, D. Chakrabarty, F.K. Baganoff, Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, UNITED STATES|N. Stone, E.R. Coughlin, Columbia University, New York, New York, UNITED STATES|P. Fragile, College of Charleston, Charleston, South Carolina, UNITED STATES|
Institution(s): 1. Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, United States. 2. Columbia University, New York, NY, United States. 3. College of Charleston, Charleston, SC, United States.
Contributing team(s): (none)
SMBHs exist at the centers of almost all massive galaxies. However, most of them are dormant and thus remain undetected. Nevertheless, roughly once every 10,000-100,000 years a star will pass close enough to the black hole such that the tidal forces will disrupt the star to produce a flare that can shine across the entire electromagnetic spectrum. As the shredded material falls on the black hole it emits X-rays when closest to the event horizon. Thus, studying the X-rays that originate from strong gravity regime in the immediate vicinity of the black hole and thus encode the information about the black hole's mass and spin. I will discuss our recent discovery of a persistent, high-amplitude 131-second X-ray modulation from a recent quintessential tidal disruption event. The periodicity is remarkably stable over 2.5 years or 600,000 cycles and its fractional root-mean-squared (RMS) modulation amplitude is unprecedented with a value over 40%. This is unlike any known black hole system. Using a black hole mass implied from host galaxy scaling relations and comparing this stable periodicity/frequency to the fundamental frequencies of motion predicted from general relativity, we find that the oscillation is too fast for this black hole, unless it is rapidly spinning (dimensionless spin parameter > 0.7). This discovery provides a new means to constrain spins of several massive black holes in future tidal disruption events. I will also discuss our efforts to discover similar signals in other tidal disruption flares using the soft X-ray missions including NICER and XMM-Newton.