Center for Relativistic Astrophysics

Cosmic Coffee (Howey IZ)
2024-01-17 15:30 - 16:30 (America/New_York)

CRA Seminar: Tae Baxter (UCSD)
2023-11-30 15:30 - 16:30 | Bogg 1-44 VizLab

Cosmic Coffee
2023-11-29 15:30 - 16:30, 2023-11-15 15:30 - 16:30, 2023-11-08 15:30 - 16:30, 2023-11-01 15:30 - 16:30, 2023-10-25 08:00 - 17:00, 2023-10-18 15:30 - 16:30, 2023-10-11 15:30 - 16:30, 2023-10-04 15:30 - 16:30 and 6 more dates | Howey N201/202, 837 State Street, Atlanta, GA, 30332, United States

CRA -Machine Learning + Astro Seminar : Alec Gunny (MIT)
2023-11-15 12:00 - 13:00 | Howey N201/202, 837 State Street, Atlanta, GA, 30332, United States
Title: Accelerating ML workflows in gravitational wave astronomy
Abstract: Commercial applications of machine learning (ML) have grown substantially in recent years, driven in no small part by an explosion in the ecosystem of so-called MLOps tools that have simplified the development and deployment of common ML use cases using domain-specific best practices. As the canon of ML applications in gravitational wave astronomy proliferates, it is worthwhile to consider what a similar ecosystem, optimized for this unique scientific and computing environment, might look like, and how it might help address the highest-value science goals in the coming years. In this talk, we will discuss some lessons learned from developing a few specific ML applications in this context, and introduce a growing suite of tools designed to encode these lessons and accelerate the pace at which robust, scalable ML applications can be built, tested and put into production.

CRA Seminar: Fred Adams (U. of Michigan)
2023-11-09 15:30 - 16:30 | Bogg 1-44 VizLab

CRA Seminar: Stefanie Milam (NASA Goddard)
2023-11-07 15:30 - 16:30 | Bogg 1-44 VizLab

CRA Seminar: Sarah Vigeland (U. Wisconsin Milwaukee)
2023-10-31 15:30 - 16:30 | Bogg 1-44 VizLab

CRA Seminar: Sreetma Goswami (IceCube)
2023-10-26 15:30 - 16:30 | Bogg 1-44 VizLab

CRA Seminar: Vasilis Paschalidis (U. of Arizona)
2023-10-19 15:30 - 16:30 | Bogg 1-44 VizLab
Title: Magnetohydrodynamic accretion onto binary black holes as a source for multimessenger astronomy with gravitational waves
Abstract: Supermassive black hole binaries can form in magnetized plasma following galaxy mergers, via bar-mode instability in rapidly rotating supermassive stars, or by other dynamical processes. After formation, a combination of dynamical friction and gas-driven migration is likely to catalyze the binary inspiral into the gravitational radiation-driven regime. Following this point, accreting binary black holes become prime targets for multimessenger astronomy with gravitational waves. In this talk we will discuss recent progress in understanding magnetohydrodynamic accretion onto binary black holes. We will focus particularly on variability of the mass accretion rate, Poynting outflows and how the existence of minidisks forming onto the individual black holes may affect observable quantities from these systems.

CRA Seminar: Marceline Bonilla (Cal State - Fullerton)
2023-10-12 15:30 - 16:30 | Bogg 1-44 VizLab
Title: Numerical Relativity and Beyond-GR Theories
Abstract: Future gravitational wave observatories will deepen our understanding of gravity in the most extreme environments we have probed so far. Ensuring that our measurements of black holes are increasingly accurate will require the calculation of increasingly accurate waveforms for the purposes of parameter estimation. Our next-generation numerical relativity code SpECTRE aims to meet this demand by taking advantage of the massively parallel capabilities of exascale supercomputers. I will give a brief discussion on numerical relativity and discuss the progress we have made in developing SpECTRE. I will also present on concurrent work to make use of modified waveform templates to constrain beyond-GR theories using existing GR waveform approximants.

CRA Seminar: Steve Sclafani (UMd)
2023-10-05 15:30 - 16:30 | Bogg 1-44 VizLab

CRA Seminar: Sarah Shandera (Penn State)
2023-09-26 15:30 - 16:30 | Bogg 1-44 VizLab
Title: Dark Black Holes
Abstract: Gravitational wave detections of merging ultracompact objects provide a completely new way to constrain a large class of dark matter models. If the dark matter consists of a rich spectrum of particles, it will generically contain channels for dissipative energy loss that can lead to the formation of compact objects. We have recently calculated a crucial set of molecular cooling processes for “atomic dark matter” that enable the first complete numerical simulations of structure formation in dissipative dark matter. I will show how the results enable a more accurate calculation of black hole masses in the model and inform gravitational wave searches. Current data, especially from searches for sub-solar mass objects, already provide new constraints on the particle physics properties of dark matter. A detection of a dark matter black hole in an upcoming search would be revolutionary, providing particle physics information through a purely gravitational channel.

CRA Seminar: DJ Pasham (MIT Kavli Institute)
2023-09-21 15:30 - 16:30 | Bogg 1-44 VizLab

CRA Seminar: Jacob Lange (UT Austin)
2023-09-14 15:30 - 16:30 | Bogg 1-44 VizLab
On the Importance of Expanding and Improving Numerical Relativity Simulations

Speaker: Jacob Lange (University of Texas at Austin)
Date: Thursday, September 14th, 2023
Time: 3:30PM – 4:30PM
Location: CRA Visualization Lab (Boggs 1-44)
Host: Chad Henshaw

Abstract: Since the original breakthrough of the numerical relativity (NR) evolution codes, multiple research groups have been able to solve Einstein’s equations numerically on supercomputers to simulate merging binary black hole gravitational wave sources. While these NR simulations can be directly compared to the data using special configurations of parameter estimation codes, these waveforms are mostly used to calibrate and verify the accuracy of semi-analytical gravitational wave models. These models are in turn used for production level parameter estimation analyses of gravitational wave detections from the LIGO-Virgo-KAGRA Collaboration. Because of this, it is essential not only to expand our current NR simulation grid into more exotic parts of parameter space (i.e. more unequal mass ratios, more extreme precessing spins, inclusion of eccentricity) but also to improve the accuracy of our current simulations as we prepare for next generation detectors. For the former, I present a novel algorithm that suggests new NR simulation placement based off of the interpolated likelihood as well as the error to that interpolated likelihood when directly comparing the NR waveforms to a real event. This allows the placement of new simulations to be in relevant parts of parameter space (high likelihood) as well as in sparse parts of parameter space for the existing grid (high error in interpolated likelihood). For the latter, I present parameter estimation results investigating the effects of waveform systematics due to NR resolution. With our current expected signal-to-noise ratios (SNR) for signals from our current ground-based detectors, the resolutions used to generate the current catalogs of NR simulations are considered large enough to be indistinguishable from an infinite resolution simulation (i.e. statistical errors dominate). As our current and next generation detectors increase our sensitivity, the systematic errors due to our finite resolution becomes more important. Following up from a previous mismatch study by Ferguson et. al. comparing different resolutions for a given simulation using different detectors, I present preliminary work that quantifies the impact of resolution error by injecting these different resolution simulations at different SNRs based off the criteria investigated in Ferguson et. al.
Bio: Jacob Lange was born in Tampa, FL and graduated from Jesuit High School in 2010. For undergrad, he went to Florida Institute of Technology and received a dual BS degree in Astronomy/Astrophysics and Physics in 2014. Finally, Jacob received his MS and PhD in 2016 and 2020 respectively from Rochester Institute of Technology where he received the 2021 RIT Graduate School’s Dissertation Award for his work called: “RIFT’ing the Waves: Developing and applying an algorithm to infer properties of gravitational wave sources”.
After graduating from the AST program in the summer of 2020, Jacob moved to Providence, Rhode Island to continue his work at Brown University’s Institute for Computational and Experimental Research in Mathematics as a semester-long postdoc. He then moved to Austin, Texas at the beginning of 2021 to work with Dr. Deirdre Shoemaker at the University of Texas at Austin as a research postdoc.

CRA Seminar - Matthew Liska (GT)
2023-09-07 15:30 - 16:30 | Bogg 1-44 VizLab
Please join us this Thursday, September 7, 2023, for our next CRA seminar, given by Matthew Liska, a Hubble Fellow who has just arrived to the CRA.

Speaker: Matthew Liska (GA Tech)
Date: Thursday, September 7, 2023
Time: 3:30PM – 4:30PM
Location: CRA Visualization Lab (Boggs 1-44)
Host: John Wise
Title: How do the most luminous black holes accrete and expel gas?

Abstract:
The gravitational pull of a black hole attracts gas and forms an accretion disk where the interplay between hydromagnetic processes and the warping of space-time releases gravitational energy in the form of radiation, relativistic jets, and winds. Most gas falls into supermassive black holes when the accretion rate approaches the Eddington limit (L=Ledd), at which point radiation pressure overcomes gravity. To date, our knowledge of such `luminous’ black hole accretion disks mostly relies on semi-analytical models, supplemented by a very limited set of numerical simulations. In my talk I will discuss new insights gained from state-of-the-art radiative general relativistic magnetohydrodynamics (GRMHD) simulations of accretion near the Eddington limit. After demonstrating that magnetic fields lead to the formation of a hot corona, I will show that, when the accretion disk is misaligned with the spin axis of the black hole, accretion is driven by shocks. This challenges the current paradigm of turbulence-driven accretion. I will subsequently demonstrate that the spin of a black hole can tear misaligned disks apart, which naturally explains both low and high frequency quasi-periodic oscillations (QPOs). I will finish my talk by discussing the opportunities the next-generation of GRMHD simulations will bring in addressing accretion from event horizon scales to galaxy-scales.

Special Lecture: Solar System Science from the James Webb Space Telescope
2023-09-01 11:00 - 12:00
Please join us on September 1st for a special lecture on JWST hosted by Georgia Tech Astrobiology in collaboration with Spelman College Physics Department!
This event has been changed to fully virtual.
Title: Solar System Science from the James Webb Space Telescope
Presenter: Dr. Naomi Rowe-Gurney, Postdoctoral Research Associate, NASA Goddard & University of Maryland, College Park
Date/Time: Friday September 1 at 11am Eastern
Location: Zoom (https://gatech.zoom.us/s/98324828756)Suddath Seminar Room, Parker H. Petit Institute for Bioengineering and Bioscience (IBB) Room 1228

Livestream – https://www.youtube.com/live/0263lN3xC0s?feature=share
Abstract: It has been just over a year since the JWST has completed its commissioning phase and started sending back ground-breaking science, not just from distant stars and galaxies but also from our own Solar System. Heidi Hammel’s cycle 1 GTO programs focused on Solar System science. This includes the investigation into the potential of ocean worlds to exhibit chemical signatures of astrobiological interest, short- and medium-term climate monitoring of the giant planets, and exploratory spectroscopic studies of the full menagerie of asteroids and comets, from near-Earth objects to the Kuiper belt. These programs were designed to be benchmark observations for the JWST mission. In this talk I will introduce the JWST, its capabilities for the Solar System and show off the ground-breaking science that this huge observatory has already done. I will outline the plans for the future and what to look forward to in the next JWST cycles using Ice Giant (Uranus and Neptune) atmospheric science as a detailed example.
Dr. Naomi Rowe-Gurney is a postdoctoral scholar supporting the JWST missions in observing the ice giant planets. Her research interest are in atmospheric characterization of Uranus and Nepture through observations from space telescopes. Her talk will be focused on capabilities of JWST in observing the Solar System and upcoming plans for future observations of the ice giants. She also is the 2023 Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) and National Society of Black Physicists (BSBP) Speaker Awardee.

CRA Seminar: Amy Secunda
2023-04-20 15:30 - 16:30 | Bogg 1-44 VizLab
