BHI Colloquium


Tuesday, November 26, 2019, 1:30pm to 2:30pm


BHI Meeting Room

Wlodek Kluzniak (University of Warsaw)

Title: Diskoseismic modes in radiative general-relativistic hydrodynamical simulations of thin disks

Abstract: High frequency quasiperiodic variability in accreting black hole sources is thought to reflect the underlying space-time metric. A detailed analytic theory of normal modes of thin disks has been worked out and can be found in books (e.g., Kato 2016) and review papers (e.g., Wagoner 2008). Other mechanisms, such as resonance resulting in a 3:2 ratio of frequencies have been proposed by Abramowicz and Kluźniak. Evidence for disk modes in hydrodynamic simulations in pseudo-Newtonian gravity was published in 2009 by Reynolds et al. and O’Neill et al. Here, I am reporting on a study of disk variability in global, radiative hydro simulations in the Schwarzschild and Kerr metric (Mishra, Kluźniak,
Fragile 2019, submitted). We find that a g-mode is present, as well as other modes. For the first time, in a simulation, evidence for a 3:2 resonance between the vertical and radial epicyclic motions is also
clearly present.

Tiffany Nichols (Harvard University)

Title: Detecting the Unknown: A Short History of the History of Gravitational Wave Signal Analysis and Waveform Template Development

Abstract: By focusing on the first observational run of the 1.5-m interferometer prototype by the MIT Gravitational-Wave Detection Team during the summer of 1985 and situating this event within the larger history of gravitational wave signal analysis and modeling, this talk seeks to highlight that gravitational wave physicists relied on theories of signal processing until and after the 2015 detection rather than waveform template matching.  This talk will further highlight the two distinct paths that were taken to develop techniques of detecting gravitational waves -- (1) analysis of aberrations in the signal to detect unknown sources since the 1970s and (2) accurate waveform template development which largely developed as a subfield in the early 2000s.