Center for Relativistic Astrophysics

Cosmic Coffee
2017-09-20 15:00 - 16:00 (America/New_York) | GA

Cosmic Coffee - Pranav Dave
2017-09-13 15:00 - 16:00 | GA

Cosmic Coffee - Deborah Ferguson
2017-09-06 15:00 - 16:00 | GA

Labor Day (Official School Holiday)
2017-09-04 | GA

CRA seminar (Prof. Jeremiah Murphy)
2017-08-31 15:00 - 16:00 | Boggs 1-90 VizLab
Title: How Do Massive Stars Die?
The title of this talk remains one of the most important and challenging questions in theoretical astrophysics. The explosive deaths of massive stars, core-collapse supernovae, are some of the most energetic events in the Universe; they herald the birth of neutron stars and black holes, are a major site for nucleosynthesis, influence galactic hydrodynamics, trigger further star formation, and are prodigious emitters of neutrinos and gravitational waves. Though these explosions play an important and multifaceted role in many cosmic phenomena, the details of the explosion mechanism have remained elusive for many decades. The fundamental challenge of core-collapse theory is to understand what makes the difference between a fizzled result and successful explosions. Ultimately, answering this question will require both theory and observational constraints. In this talk, I will present a unifying theory for core-collapse supernova explosions, and I will present our observational constraints on which stars actually explode.

Cosmic Coffee -- Welcome to the CRA
2017-08-30 15:00 - 16:00 | GA

ECLIPSE 2017 @ GT
2017-08-21 13:00 - 15:00 | GA
Dear Georgia Tech Faculty and Staff,
The great American eclipse will sweep across the U.S. on Monday, Aug. 21, 2017, the first day of the Fall 2017 semester. Over Atlanta, the eclipse will start shortly after 1 PM, maximum overlap will occur at 2:37 PM, and the sun and moon will part ways completely at 3:57 PM.
The College of Sciences and the Office of Undergraduate Education, with participation from various Georgia Tech colleges and units, have arranged for the Georgia Tech community to safely experience this rare solar spectacle.
The College of Sciences has just announced the places on campus where solar eclipse glasses will be distributed at noon on Aug. 21, 2017: http://www.cos.gatech.edu/hg/item/594380
Distribution will take place in six high-traffic areas from noon until 1 PM or when supplies are exhausted at the location. After 1 PM, check for availability at Kessler Campanile.

By Kessler Campanile at 1-4 PM, everyone can participate in various activities:
Watch a livestream of the eclipse from the Georgia Tech Observatory
Sample other safe-viewing options, including pinhole cameras and solar-filter telescopes
Collect real-time data of temperature and visibility changes during the course of the eclipse
Learn about eclipse-related research at Georgia Tech
Experience an interactive auditory journey through the solar system
Enjoy astronomy-themed music and snacks
Take photos or selfies using eclipse-themed frame props
In the event of rain, we will move to Clough Undergraduate Learning Commons, at the Starbucks level.
Those unable to go to the Campanile can participate in other ways. They could use #GTEclipse2017 in Twitter and Instagram, view the livestream on YouTube through www.cos.gatech.edu/Eclipse, or comment on Facebook, http://bit.ly/2uDRaPN.
Sincerely,
A. Maureen Rouhi, Ph.D.
Director of Communications
College of Sciences
Allyson Tant
Academic Enrichment Coordinator
Office of Undergraduate Education

First Day of Class - Fall 2017
2017-08-21 | GA

CRA Welcome & Jamboree
2017-08-08 08:00 - 17:00 | GA

Special Cosmic Coffee -- Latest Gravitational Wave Detection by LIGO
2017-06-07 15:00 - 16:00 | GA

CRA special seminar (Jacob Daughhetee)
2017-05-15 15:00 - 16:00 | GA
Revealing the Neutrino through Double-Beta Decay

Characterization of the elusive neutrino has been the goal of many experiments over recent years, yet many fundamental properties of this elementary particle remain unknown. As the only neutral Standard Model fermion, it is possible that the neutrino is a Majorana particle, i.e. it’s own anti-particle. This intriguing possibility has important ramifications for physics including the necessity of lepton number violation, an explanation for the small neutrino mass, and a mechanism for producing the observed asymmetry between matter and anti-matter in our Universe. Neutrinoless double-beta decay (0vBB) represents the most sensitive way to probe the Majorana nature of the neutrino. The status of the search for 0vBB with the EXO-200 experiment and the prospects of its planned successor, nEXO, will be presented.

PhD. Thesis Defense -- Chao Shi -- The Dynamics of Black Holes in First Galaxies
2017-05-04 14:00 - 15:00 | Boggs 1-90 VizLab
Abstract:
Black holes(BHs) as massive as 10^9 solar masses has been discovered at redshift z >6,
that is within one billion years after the big bang. It is believed that some seed
black hole with large initial masses formed at very early times, which then grow
to the supermassive black holes we observe at z ~ 6. First stars (Pop III) remnants
are considered to be one of the promising pathways to form such seed BHs. We study
the dynamics of seed BHs formed out of Pop III star remnants through cosmological
simulation. We evolve a representative volume across 1Mpc in comoving coordinates,
and write 1000 outputs every ~0.5 Myr. We then extract all seed BHs in each output
and investigate the distribution and evolution of their orbital properties from redshift
z ~ 17 to z~9, which are crucial to their growth and merger rate. We show that most of
seed BHs in halos are gravitationally bounded, and a significant fraction of them have
orbits with short semi-major axes and high eccentricity. They are prime candidates for
black hole mergers as they are the ones that will venture closest to the halo center and
any massive black hole that might exist in the (proto-)galaxy center. We attempt to
estimate the merger rate of BHs by calculating the loss rate of angular momentum, but
find that this approach is not suitable for our simulation data.

CRA seminar (Prof. Tanmay Vachaspati)
2017-04-27 15:00 - 16:00 | GA
Title: Monopole-antimonopole creation and other numerical studies.
Abstract: I will describe magnetic monopoles, their properties, and recent numerical work on their creation from particles.

Cosmic Coffee -- James Clark
2017-04-26 15:00 - 16:00 | GA

CRA seminar (Prof. Richard Miller)
2017-04-20 15:00 - 16:00 | GA
Title: Ex Luna, Scientia: The Lunar Occultation Explorer (LOX)

Abstract: The Lunar Occultation Explorer (LOX) is a next-generation mission concept currently under consideration within NASA’s MIDEX program. LOX will provide new capabilities for time-domain astronomy and establish the Moon as a platform for nuclear astrophysics. Performance requirements are driven by our focused science goal: resolving the enigma of Type-Ia supernova (SNeIa). Specifically LOX will reveal new details of these profoundly radioactive objects, including their intrinsic diversity, probing their fundamental thermonuclear parameter space, performing a census of progenitors and their explosion mechanisms, and evaluating the environmental conditions and intrinsic systematics of these enigmatic objects. LOX provides new capabilities for all-sky, continuous monitoring in the MeV regime (0.1-10 MeV) by leveraging the Lunar Occultation Technique (LOT). Key benefits of the LOX/LOT approach include maximizing the ratio of sensitive-to-total deployed mass, low implementation risk, and demonstrated operational simplicity that leverages extensive experience with planetary orbital geochemistry investigations; LOX also enables long-term monitoring of MeV gamma-ray sources, a critical capability for SNeIa science. Proof-of-principle efforts validated all aspects of the mission using previously deployed lunar science assets, and led to the first high-energy gamma-ray source detected at the Moon. LOX mission performance, development progress, and expectations for science investigations will be presented.

Cosmic Coffee -- Karan Jani (Search for IMBH Binaries in the First Observing Run of Advanced LIGO)
2017-04-19 15:00 - 16:00 | GA

CRA seminar (Dr. Michael Briggs)
2017-04-13 15:00 - 16:00 | Boggs 1-90 VizLab
Title: Gamma-ray Transients from Fermi GBM in the Multi-messenger Era
Abstract:
As the Multi-Messenger era begins with observations from IceCube and
LIGO, the Fermi Gamma-ray Burst Monitor (GBM) is well suited to provide
context observations of gamma-ray transients between 10 keV and 40 MeV.
Fermi GBM has a wide field of view, high uptime and both in-orbit
triggering and high-resolution continuous data. GBM detects numerous
gamma-ray bursts, soft gamma-ray repeaters, x-ray bursters, solar flares
and terrestrial gamma-ray flashes. Longer timescale transients and
persistent sources are detected by the Earth occultation technique.
Using the continuous data, the GBM team has developed two ground-based
searches to enhance the detection of transients, and especially of short
gamma-ray bursts. The targeted search is initiated by a detection from
another instrument. In a Bayesian manner, the information for the other
instrument is used to coherently analyze the signals of the GBM
detectors, increasing the sensitivity to a transient. The untargeted
search agnostically searches the GBM data for all directions and times
in order to find weaker transients, especially short GRBs. This search
is finding about 80 short GRBs per year, in addition to the 40 that GBM
detects in orbit. Both searches provide results soon after the data is
available.

Cosmic Coffee -- Thanassis Stavropoulos
2017-04-12 15:00 - 16:00 | GA

CRA seminar: Bülent Kiziltan (CfA)
2017-04-06 15:00 - 16:00 | GA
Title: Revealing black holes hiding in the centers of globular clusters
Abstract: It has been long theorized that intermediate-mass black holes (IMBHs) connecting the evolution of stellar-mass and supermassive-black holes should exist. There is mounting evidence suggesting that such black holes can form and may be retained in dense stellar environments. Observationally only upper limits have been placed on the mass of putative IMBHs based on the lack of electromagnetic counterparts. Standard observational approaches have not yielded any convincing constraints on their existence. I will talk about our ongoing efforts to combine multi-wavelength observations, N-body simulations, and information theory in order to probe the crowded centers of globular clusters more effectively. I will then highlight recent results for several globular clusters presenting evidence that IMBHs may indeed be formed and retained in compact clusters.

Cosmic Coffee -- Austin Gilbert
2017-04-05 15:00 - 16:00 | GA

Cosmic Coffee -- Karan Jani
2017-03-29 15:00 - 16:00 | GA

Cosmic Coffee -- Spring Break
2017-03-22 15:00 - 16:00 | GA

Cosmic Coffee -- Miguel Gracia Linares
2017-03-15 15:00 - 16:00 | GA

CRA seminar (Prof. Jong-Hak Woo)
2017-03-09 15:00 - 16:00 | GA
Title: Ionized gas outflows – delayed or no AGN feedback?
Abstract: AGN-driven gas outflows are considered as a channel of AGN feedback to star formation activity over galaxy scales. I will present 1) the statistical kinematic study of gas outflows in AGNs and star forming galaxies, 2) the constrains based on the biconnical outflow models, and 3) the spatially-resolved study based on the IFU data. While the strong outflows are detected in high luminosity AGNs, there is no direct evidence of star formation quenching as the outflow size is relatively small and the SSFR of outflow AGNs is comparable to that of star forming galaxies. These results show the complex nature of outflows, which may indicate delayed or no AGN feedback.

Cosmic Coffee -- Brian Day
2017-03-08 15:00 - 16:00 | GA

Cosmic Coffee -- Erika Cowan
2017-03-01 15:00 - 16:00 | GA

Public Lecture -- Prof. Tom Abel: How Things in the Universe Came About & How They Ended Up Within Us?
2017-02-28 18:00 - 19:00 | GA
Professor Tom Abel will take the audience on a journey through the early stages of the universe, using the latest computer animations of how the first stars formed and died and how stars built up the first galaxies.
His work has shown that the first luminous objects in the universe were massive stars, shining one million times as brightly as our Sun. They died quickly and seeded the cosmos with the chemical elements necessary for life. Galaxies started to assemble just one hundred million years after the Big Bang, and they are still growing now. Computer simulations of these events provide remarkable insights into the early history of the cosmos.
Abel is computational cosmologist who explores cosmic history using supercomputer calculations. His long-term goal is “to build a galaxy, one star at a time,” via computer modeling. Among his research interests are the processes and events of “the dark ages,” the first few hundred million years after the Big Bang.
Abel’s visualizations and simulations of dark-age events have been featured on PBS, the Discovery Channel, and on the cover of National Geographic.

Cosmic Coffee -- Paper Discussion
2017-02-22 15:00 - 16:00 | GA

Cosmic Coffee -- Kate Napier
2017-02-15 15:00 - 16:00 | GA

Cosmic Coffee -- Gen Chiaki
2017-02-08 15:00 - 16:00 | GA
