Upcoming Events For Astrophysics Seminar

Tue Mar 9, 2021

Astrophysics Seminar: Dr. Jason Hofgartner, NASA Jet Propulsion Lab

12:45 PM - 1:45 PM
zoom

Presently-active Physical Processes on Organic-rich Ocean Worlds

Dr. Jason Hofgartner
NASA Jet Propulsion Lab

Ocean Worlds, icy planetary bodies with subsurface water oceans, are now known to be prevalent in the outer solar system and are high priority targets for planetary science and exploration. The atmospheres and surfaces of Ocean Worlds provide important insights into their histories. Saturn’s Ocean World moon Titan has a methane cycle with clouds, rain, rivers, lakes, and seas; it is the only world known to presently have a volatile cycle akin to Earth’s water cycle. The discovery and characterization of transient features in Titan's hydrocarbon seas will be presented. Titan observations provide "ground-truth" in the search for oceans on exoearths and an important lesson: that identifying liquid surfaces by specular reflections requires a stringent definition of specular, will be discussed. Eris is a candidate Ocean World and the largest object in the solar system yet to be explored by a spacecraft. It will be argued that Eris, despite an anomalously high albedo of almost unity and solar distance of nearly 100 times that of the Earth, is likely a very active world with ongoing resurfacing.…

Posted In: Astrophysics Seminar

Tue Mar 16, 2021

Astrophysics Seminar: Dr. Kate Rubin, San Diego State University

12:45 PM - 1:45 PM
zoom

Title and abstract forthcoming

Dr. Kate Rubin
San Diego State University

All interested persons are invited to attend remotely—email physics@nd.edu for information.

Posted In: Astrophysics Seminar

Tue Mar 23, 2021

Astrophysics Seminar: Dr. Sarah Wellons, Northwestern University

12:45 PM - 1:45 PM
zoom

Title and abstract forthcoming

Dr. Sarah Wellons
Northwestern University

All interested persons are invited to attend remotely—email physics@nd.edu for information.

Posted In: Astrophysics Seminar

Tue Mar 30, 2021

Astrophysics Seminar: Dr. Nina Hernitschek, Vanderbilt University

12:45 PM - 1:45 PM
zoom

Machine Learning for Classification Strategies for Astronomical Sources

Dr. Nina Hernitschek
Postdoctoral Fellow, Data Science Institute & Department of Physics and Astronomy
Vanderbilt University

In the era of large-scale astronomical surveys, methods to investigate these data, and especially to classify astronomical objects, become more and more important. Various techniques for extracting information, such as structure function fitting and template-based period fitting, are applied before a subsequent machine-learning classification searches for and classifies variable sources. I will give a brief overview of state-of-the-art methods of data handling and machine learning techniques used in astronomy, as well as in more detail describe how to apply specific methods to typical problems occurring from large time-domain surveys such as Pan-STARRS1, ZTF and finally LSST. …

Posted In: Astrophysics Seminar

Tue Apr 6, 2021

Astrophysics Seminar: Dr. Terese Hansen, Texas A&M University

12:45 PM - 1:45 PM
zoom

Chemical Signatures of the Milky Way Halo Building Blocks

Dr. Terese Hansen
Postdoctoral Research Associate
Physics & Astronomy, Texas A&M University

Recent years large photometric surveys, like the Sloan Digital Sky Survey and the Dark Energy Survey, have resulted in the detection of numerous small substructures in and around the Milky Way, in the form of ultra-faint dwarf galaxies and stellar streams. Detailed chemical analysis of stars in these systems, combined with dynamical analysis using Gaia data, has provided exciting new insights into our Galaxy's chemical evolution and hierarchical build-up. I will present recent results from abundance analysis of stars in ultra-faint dwarf galaxies and stellar streams. The ultra-faint dwarf galaxies are excellent laboratories to investigate specific nucleosynthesis enrichment events, while the chemical signatures of stream stars can be used to characterize the nature of the stream progenitor. I will also talk about future photometric and spectroscopic surveys, which will produce a wealth of data allowing us to map structures in and around the Milky Way in unprecedented detail.…

Posted In: Astrophysics Seminar

Tue Apr 13, 2021

Astrophysics Seminar: Dr. Aleksandra Hamanowicz, Space Telescope Science Institute

12:45 PM - 1:45 PM
zoom

Title and abstract forthcoming

Dr. Aleksandra Hamanowicz
Space Telescope Science Institute

All interested persons are invited to attend remotely—email physics@nd.edu for information.

Posted In: Astrophysics Seminar

Tue Apr 20, 2021

Astrophysics Seminar: Prof. Peng Oh, UC Santa Barbara

12:45 PM - 1:45 PM
zoom

Title and abstract forthcoming

Prof. Peng Oh
UC Santa Barbara

All interested persons are invited to attend remotely—email physics@nd.edu for information.

Posted In: Astrophysics Seminar

Tue Apr 27, 2021

Astrophysics Seminar: Dr. Mohammadtaher Safarzadeh, UC Santa Cruz / Harvard

12:45 PM - 1:45 PM
zoom

The Astrophysical Context of Gravitational Wave Events

Dr. Mohammadtaher Safarzadeh
Postdoctoral Fellow in Theoretical Astrophysics
UC Santa Cruz / Harvard

We live in an era of breakthrough discoveries in gravitational waves (GW) astronomy. Every month or so, such discoveries by LIGO/Virgo have been making headlines because these events’ nature has been far from the expectations. But why are we puzzled? And what is the road ahead for us to a deeper understanding? I discuss two of the puzzling events that LIGO has discovered: 1) The most massive binary black hole merger with masses above the pair-instability limit. After a deep dive into the physics of pair-instability supernova, I will discuss how a broader perspective on the host environment of binary black holes can hold the key to understanding the nature of such massive systems. 2) The most massive binary neutron star merger. I will present possible scenarios to explain why we have not detected such systems in the radio observations before and how the key to understanding these events might lie in the r-process enrichment in the early universe and magnetic field evolution of neutron stars. Through these two examples, I will conclude that the synergy of traditional electromagnetic-wave astronomy with gravitational wave astronomy is essential for gaining insights into the surprises that are being uncovered with these new observations.…

Posted In: Astrophysics Seminar