ASD Colloquium Series - Fall 2026
ASD Colloquium Series - Fall 2026
The Astrophysics Science Division colloquia occur on Tuesdays at 3:45 pm in a Hybrid format. For in person attendees, the colloquia will be held in building 34, room W150 (unless otherwise noted), with an opportunity to meet the speaker at 3:30 pm. Virtual attendees should use connection information in the calendar invites.
Below is the list of scheduled talks for this period. Confirmed speakers are shown in bold face, while tentatively scheduled speakers are listed in normal face.
Schedules from past colloquium seasons are available.
Contact: Scott C. Noble
| September | |
|---|---|
| Sep 22 | Special Location: B34, W120B Probing the gamma-ray sky on longer timescales Akash Anumarlapudi (UNC Chapel Hill) |
| Sep 29 | Special Location: B34, W120A/B The Resonant Structure of Galaxy Disks John Beckman (Instituto de Astrofísica de Canarias) |
| October | |
| Oct 6 | A NICER legacy for neutron star radii M. Coleman Miller (University of Maryland) |
| Oct 20 | The Nature of Astronomy Engagement in Rural Communities: K-12 Education Spencer Wilken (University of Illinois Urbana-Champaign) |
| November | |
| Nov 3 | Special Location: B34, W120A Old Disks Die Hard: The Impact of AGN Feedback on Morphology in Simulated Milky Way Mass Galaxies Patricia Fofie (University of California, Irvine) |
| Nov 10 | Special Location: B34, W120A/B Quasi-periodic eruptions: past, present, and future Riccardo Arcodia (Harvard University) |
| December | |
| Dec 15 | TBD Keigo Fukumura (James Madison University) |
| March | |
| Mar 9 | TBD David Coulter (STScI) |
Abstract
Gamma-ray bursts (GRBs) are usually observed to have active emission timescales of a few milliseconds to a few seconds. In addition, there are sources in which the emission lasts for multiple minutes to a few hours, the ultra-long GRBs (UL-GRBs), which currently push the stable timescale of the central engine powering the GRBs. GRB search pipelines exploit the short timescale (milliseconds to seconds) increase in the photon flux to discover GRBs. But this can decrease their detection sensitivity to slowly varying, long-lived (upwards of a few hours) emission from gamma-ray sources. In this talk, I will introduce our detection method that utilizes time-integrated images from the Swift Burst Alert Telescope to discover gamma-ray transients. This complements the current searches on high time-resolution data by expanding the detection timescales from a few minutes to multiple days. Using the archival data from the Swift observatory, I will introduce initial results from our search. In the remaining limited lifetime of Swift, I will also highlight the prospect of near-real-time discoveries.
Abstract
Disk galaxies such as the Milky Way represent more than half of the population of galaxies in the local universe. Among their most recognizable properties are their spiral arms and some two thirds of them have characteristic barred concentrations of their stellar populations. It is now classical astrophysics that the presence of stable long-lived arms can only be explained by the presence of a spiral density wave in the disk, strongly stimulated by the bar. But theorists showed, around the turn of the millenium, that they could use the angular rotation speed of the bars in local galaxies to determine the predicted braking effect of dark matter halos on them, and when they did this they found that bars in general are rotating too fast. No evidence of the dark matter braking. Was there a basic flaw in the CDM cosmological scenario? In the talk I will explain how, in my group, we aimed to verify this, using a new technique to relate the internal kinematics of bars and arms to the dynamics of the rotating galaxies. We found a compex, but surprisingly elegant resonant structure in disks, and resolved the problem of the bars spinning too quickly. I will end by showing how our technique has probed the history of the dynamical interaction of M51 with its satellite galaxy NGC 5195.
Abstract
Precise and reliable measurements of neutron star radii and other properties are essential to our understanding of cold, catalyzed matter beyond nuclear saturation density. Over the last fifteen years, measurements of high-mass neutron stars, gravitational waves from the double neutron star merger GW170817, and X-ray observations have dramatically improved our understanding of neutron star structure. In particular, NASA's Neutron star Interior Composition Explorer (NICER) satellite has provided high-quality data sets that have yielded published measurements of the mass and radius of several neutron stars. I will discuss our group's analyses of these pulsars and will in particular discuss our assumptions and potential systematic errors, to help in the assessment of our work. I will also discuss the implications of our results, combined with other observations, for the properties of the dense matter in the cores of neutron stars.
Abstract
Astronomy is often framed as a uniquely powerful entry point into science, and yet its presence in small, rural communities remains poorly understood. Using national datasets alongside semi-structured interviews with 62 rural science teachers and many of their students, Spencer probes the complex systems that underpin astronomy's presence in America's small towns. They quantify the frequency, nature, and purpose of astronomy courses, teacher demographics, and topic areas of student interest. Their results show that astronomy's presence within rural communities is much more precariously positioned than previous national studies suggest. Dedicated astronomy courses appear in approximately 8-14% of rural high schools—lagging far behind urban and suburban counterparts (~30% of schools)—and are constructed from informal, non-standardized materials. Spencer argues that astrobiology, in particular, is perfectly suited to align with existing classroom structures and teacher/student skillsets, and proposes a new research framework to assess astronomy outreach outcomes.
Abstract
The connection between a galaxy's visual shape and its star formation rate is one of the oldest established trends in galaxy evolution, yet the origin of this trend remains unsettled. We analyze two Milky Way-mass halos simulated with FIRE-2 galaxy formation physics, each run without active galactic nuclei (AGN) feedback and with up to three implementations of AGN feedback. We use them to study how AGN feedback suppresses star formation and affects morphology over cosmic time. Runs without AGN feedback produce prominent, thin, star-forming spiral disks at z = 0, while runs with AGN feedback have less late-time star formation and higher spheroid fractions. In two instances, the AGN runs produce quenched lenticular galaxies with no cool gas at z = 0. We find that the main reason for these morphological differences is that in every run, AGN feedback becomes effective after the onset of disk formation, around "spin-up". This time-differentiated impact preferentially suppresses the formation of disk stars, especially thin-disk stars, since thin-disk formation occurs late.
Abstract
X-ray Quasi-Periodic Eruptions (QPEs) are the latest and perhaps the most peculiar addition to the zoo of extragalactic nuclear transients. They are high-amplitude bursts of X-ray radiation recurring every few hours to few days with a lifetime of years to decades, originating from the central black holes in the nuclei of low-mass galaxies. So far, only a dozen of such events has been found, although with rising interest in the broader community given their observational and theoretical connection with tidal disruption events and as possible low-frequency gravitational wave sources. I will begin with an outline of the observational properties of QPE sources and their current interpretation, and conclude with an outlook on the future of QPEs and X-ray nuclear transients in light of the next generation of X-ray missions.