Abstract: When a star wanders too close to a SuperMassive Black Hole (SMBH), the star tidally disrupts, producing a luminous transient known as a Tidal Disruption Event (TDE). The compact accretion disks thought to form soon after a TDE were predicted to emit thermal radiation which peaked in the soft X-ray, but TDEs detected in the subsequent decades often peaked in the near UV and optical, sometimes emitting substantial amounts of non-thermal hard X-ray emission which displayed Quasi-Periodic Oscillations (QPOs). This talk discusses how relaxing the assumption of a circular disk co-planar with a spinning SMBH’s equatorial plane may give rise to the rich electromagnetic spectra observed from TDEs. In the first part of the talk, I will discuss the dynamics of a highly-eccentric TDE accretion disk, which forms when the stellar debris on highly-elliptical trajectories do not completely circularize. For our eccentric TDE disk model, we find it is possible to generate UV and optical thermal emission consistent with the optically-bright TDEs observed. In the talk’s second portion, I will discuss how a TDE disk tilted to the equatorial plane of a spinning SMBH is warped due to differential Lens-Thirring precession, how different effects drive and damp the disk’s precession, and discuss how this precession may drive QPOs in the hard X-ray emission of a TDE. Allowing a TDE disk to be eccentric and warped may give rise to the surprising diversity of TDE emission, not predicted by the original TDE models.
The dynamics and electromagnetic emission
J. J. Zanazzi (CITA) // June 8, 2020
Abstract: When a star wanders too close to a SuperMassive Black Hole (SMBH), the star tidally disrupts, producing a luminous transient known as a Tidal Disruption Event (TDE). The compact accretion disks thought to form soon after a TDE were predicted to emit thermal radiation which peaked in the soft X-ray, but TDEs detected in the subsequent decades often peaked in the near UV and optical, sometimes emitting substantial amounts of non-thermal hard X-ray emission which displayed Quasi-Periodic Oscillations (QPOs). This talk discusses how relaxing the assumption of a circular disk co-planar with a spinning SMBH’s equatorial plane may give rise to the rich electromagnetic spectra observed from TDEs. In the first part of the talk, I will discuss the dynamics of a highly-eccentric TDE accretion disk, which forms when the stellar debris on highly-elliptical trajectories do not completely circularize. For our eccentric TDE disk model, we find it is possible to generate UV and optical thermal emission consistent with the optically-bright TDEs observed. In the talk’s second portion, I will discuss how a TDE disk tilted to the equatorial plane of a spinning SMBH is warped due to differential Lens-Thirring precession, how different effects drive and damp the disk’s precession, and discuss how this precession may drive QPOs in the hard X-ray emission of a TDE. Allowing a TDE disk to be eccentric and warped may give rise to the surprising diversity of TDE emission, not predicted by the original TDE models.