Neutron Stars and Fast Radio Bursts

Because Neutron Stars have large dipolar magnetic fields, they emit electromagnetic radiation as they rotate, causing the star to loose angular momentum.  This angular momentum loss torques the neutron star, which works to align the magnetic dipole axis with the star's spin axis.  However, for the Crab pulsar, Lyne et al. (2013) found the inclination between the dipole and spin axis to increase, rather than decrease, with time.  I showed this could be explained by free and "inertial" precession from the Crab Pulsar's rigid bulge and magnetic field's inertia, causing the magnetic inclination angle to increase over short timescales, and decrease over long timescales.

Some time after, the CHIME/FRB collaboration reported a 16 day periodicity on the radio bursts emitted by FRB 180916.  With Dong Lai, I showed FRB 180916's periodicity can be explained by emission from a magnetar undergoing free/inertial precession.   In collaboration with Dongzi Li, we showed how the burst activity window becomes narrower and earlier at higher frequencies, due to curvature radiation from a precessing magnetar.  Our work is one of the leading theories to explain "periodic Fast Radio Bursts" (see review by Bing Zhang)

Warped and Eccentric Accretion Disks after Tidal Disruption Events

Tidal Disruption Events (TDEs) are highly energetic (super-Eddington) flares, which occur when a star gets so close to a Supermassive Black Hole (SMBH), and the tidal force on the star from the SMBH exceeds the star's self-gravity.  My work focuses on the dynamics of the accretion disk which forms soon after the star disrupts.  With Dong Lai, I studied how a TDE disk misaligned with a spinning SMBH is warped, precesses and aligns with the SMBH's equatorial plane over the disk's lifetime.  With Gordon Ogilvie, I showed highly eccentric TDE disks could explain the thermal emission from a large number of the optically-bright TDE.

Publications

Dongzi Li & J. J. Zanazzi, Emission Properties of Periodic Fast Radio Bursts from the Motion of Magnetars: Testing Dynamical Models.  2021, ApJL, 909, L25.  PDF 

J. J. Zanazzi and Gordon Ogilvie; Eccentric Tidal Disruption Event Disks around Supermassive Black Holes: Dynamics and Thermal Emission.  2020, MNRAS, 499, 5562, PDF 

J. J. Zanazzi & Dong Lai, Periodic Fast Radio Bursts with Neutron Star Free Precession.  2020, ApJL, 892, L15.  PDF

J. J. Zanazzi and Dong Lai; Tidal Disruption Event Disks around Supermassive Black Holes: Disk Warp and Inclination Evolution. 2019, MNRAS, 487, 4965, PDF

J. J. Zanazzi & Dong Lai, Electromagnetic Torques, Precession, and Magnetic Inclination Evolution of Magnetic Inclination of Pulsars. 2015, MNRAS, 451, 695. PDF