Author: mbabcock9

September 24, 2024 at 11am: The Center for Relativistic Astrophysics presents Michael Eracleous (Penn State) September 24 @ 11:00 am – 12:00 pm

Event details here.

September 23, 2024 at 3:30pm: As part of the School Of Physics Fall Colloquium Series, Jessie Runnoe (Vanderbilt University) presents: Electromagnetic and multi-messenger searches for supermassive black hole binaries

Supermassive black hole binaries are thought to be an inevitable product of the prevailing galaxy evolution scenarios where most massive galaxies host a central black hole and undergo mergers over cosmic time. The early stages of this process have been observed in the form of interacting galaxy pairs and widely separated dual quasars, but the close, gravitationally bound binaries that are expected to follow have proven elusive. The detection of this population is important because at the smallest separations they become bright sources of low-frequency gravitational waves and are prime targets for multi-messenger detections with pulsar timing arrays (PTAs) and the upcoming Laser Interferometer Space Antenna (LISA). In this talk, I will discuss observational signatures of binary supermassive black holes and prospects for multi-messenger detections with electromagnetic facilities and gravitational wave detectors.

Date/Time: Date: Monday, September 23, 2024 – 3:30pm to 4:30pm

Location: Marcus Nanotechnology 1116-1118

Event details here.

September 20, 2024 at 1pm: ExplOrigins Meeting – September 20, 2024 | 1:00 p.m. – 2:00 p.m.
Ford ES&T 1229 or online
Sign-up to lead a meeting!

September 19, 2024 at 11am:

Are you interested in science or speculative fiction? Afro-futurism? Space exploration? 

Join the Library and Science Fiction Professor Lisa Yaszek Thursday, September 19  at 11 a.m. in welcoming the authors of Spacefunk! edited by Milton J. Davis.  Times: 11:00 AM – 12:30 PM

Authors will read selections from their work at the Crosland Tower stairs, then participate in a meet-and-greet afterwards in the area outside the Sci-Fi Lounge on Crosland Tower’s first floor. You will have a chance to learn about and meet many Atlanta-based authors of sci-fi, horror, fantasy and more!  

Detailed event information can be found here.

September 12, 2024 at 3:30pm: CRA Seminar: Nick Kaaz – Northwestern UN

Title: Challenging the standard accretion disk paradigm with warps, strong magnetic fields and super-Eddington accretion in quasar disks

Abstract: “Classical” accretion disks are geometrically thin, radiatively efficient and mechanized by turbulent viscosity. Yet, many observational and theoretical issues challenge this paradigm, especially in quasars. This is perhaps unsurprising, as classical disks do not take into account certain key physics. For instance, the infalling gas that eventually forms a disk around a black hole has no prior knowledge of the black hole spin axis. Thus, most accretion disks will be at least initially misaligned with respect to the black hole spin axis. As the black hole rotates, it drags the surrounding space-time, inducing ‘Lense-Thirring’ torques which cause the disk to undergo precession and become warped. This can drastically alter the accretion process and drive rapid variability, similar to that which is seen in changing-state active galactic nuclei. Additionally, quasars are generally fed from cold, highly magnetized gas complexes, which determines the initial conditions of the disk. This can result in a disk that is magnetically dominated, enabling high accretion rates that are sometimes above the Eddington limit, which has important consequences for the inner accretion flow. In this talk,  I will discuss my recent work on both radiative and non-radiative general-relativistic magnetohydrodynamic simulations of both thin, highly tilted accretion disks and super-Eddington, highly magnetized disks around rapidly rotating black holes. In the former case, I will present novel dissipation mechanisms unique to these systems that drive accretion on timescales much shorter than the usual viscous time. In the latter case, I will discuss the physics that governs the magnetic state of the disk, the resulting emission and outflow properties, and the implications for the cosmological growth of supermassive black holes.

September 12 @ 3:30 pm – 4:30 pm

Event info here.

September 6, 2024 at 1pm: ExplOrigins Meeting – September 6, 2024 | 1:00 p.m. – 2:00 p.m.
Ford ES&T 1229 or online
Sign-up to lead a meeting!