Spring 2026 Semester Schedule

Please click on any row to read the full abstract.

Date	Name	Title
Feb. 4th	Dr. Andrea Prestwich	Flares from the Ashes: Unexpected Variable X-ray Emission in M83's Supernova Remnants	The universe appears dramatically different in X-rays. At optical wavelengths, galaxies like the Milky Way are dominated by starlight. However, at X-ray wavelengths the dominant sources are compact object systems—primarily X-ray binaries where material from a donor star falls onto a neutron star or black hole, generating X-ray emission via an accretion disk. Also prominent are core-collapse supernova remnants (SNRs), where shock-heated gas from a massive stellar explosion emits thermal X-rays. Chandra has observed the nearby star-forming galaxy M83 repeatedly over a 13-year baseline, detecting hundreds of point sources—mainly high-mass X-ray binaries (HMXBs) and core-collapse SNRs. Unexpectedly, a significant fraction of the SNR candidates show evidence of temporal variability in their X-ray flux. This was surprising: mature SNRs span multiple light-years, so their brightness should evolve on much longer timescales. The observed variability—on the order of months and years—implies a more compact origin for the X-ray emission. Follow-up analysis suggests diverse origins for the variable sources. One is associated with SN1957D, a very young, compact supernova remnant still in an early evolutionary phase. A few are consistent with microquasars. However, the majority appear to be HMXBs spatially coincident with SNRs—possibly binaries that survived the supernova event that created the remnant. These systems show strong variability, are associated with massive stellar clusters (consistent with young, massive donor stars), and exhibit spectral changes between high and low states. In particular, the appearance of excess emission below ~1 keV during bright phases suggests variability in a cool accretion disk around a massive black hole. Future work includes searching for this population in other nearby galaxies and comparing the inferred black hole masses with predictions from X-ray binary evolutionary models.
Feb. 11th	Dr. Gabriel Freedman	The Background and Beyond: Landscape and Methods of Single Source Low Frequency Gravitational Wave Searches	The pulsar timing array (PTA) community has found evidence for a correlated signal following the Hellings-Downs pattern indicative of a stochastic background of nanohertz gravitational waves (GWB). The dominant source in this frequency band is expected to be a population of supermassive black hole binaries. One of the next major milestones for PTA experiments, as more data is collected, is the detection of continuous gravitational waves from individual supermassive black hole binaries, which would be of great importance for multimessenger studies. Searching for these single continuous wave sources adds additional computational complexity to an already time- and resource-strained analysis — increasing the already large parameter space and introducing strong covariance into the model between binaries emitting at low frequencies and the GWB. In this talk we highlight the current status of nanohertz gravitational wave science and present both the challenges as well as the recent development efforts towards performing joint Bayesian analyses of both the GWB and single sources. We end by discussing ongoing applications of this work to millihertz frequency sources detectable by the upcoming Laser Interferometer Space Antenna.
Feb. 18th	Dr. Léa Feuillet	Footprints in the Wind: Probing X-ray Outflows in NGC 7469 using Near-Infrared Emission Lines	Active Galactic Nucleus (AGN) outflows are known to play an important role in the co-evolution of supermassive black holes and their host galaxies. They also have been shown to consist of multiple phases of gas corresponding to various ionization states. Some of these phases have been investigated in the past using integral field spectroscopy, offering a detailed spatial and spectral view of their contribution to AGN feedback. Others, such as the crucial very high ionization X-ray phase have been missing from the picture. Indeed, while the X-ray phase has been repeatedly shown to have a significant impact on global feedback processes, the lack of an existing X-ray integral field unit has hindered our ability to study this essential phase in the required detail. In this presentation, I will demonstrate how we can use the footprint line method, where one uses high-ionization infrared emission lines that have been shown to originate from X-ray emitting gas, to examine the X-ray phase of AGN outflows both spatially and kinematically with the James Webb Space Telescope.
Feb. 25th	Dr. Elizabeth Tarantino	The Origin and Nature of Dust at Low Metallicities: A JWST Case Study on the Nearby Dwarf Galaxy Sextans A	The formation, composition, and evolution of dust at low metallicities is poorly characterized, yet critical for understanding the lifecycle of dust at high redshifts. Since the far distances of these early galaxies prohibit detailed study, we use observations of nearby metal-poor galaxies that mimic the pristine gas conditions of these distant galaxies to constrain models of dust formation and destruction. In this talk, I will present JWST imaging and spectroscopy of the 7% Solar metallicity galaxy Sextans A to (1) characterize the abundance and properties of the smallest dust grains, polycyclic aromatic hydrocarbons (PAHs), and (2) determine the dust production and composition from asymptotic giant branch (AGB) stars. While mid-infrared PAH emission is ubiquitous in high-metallicity galaxies, metal-poor galaxies show a sharp decline in the fraction of PAHs relative to total dust abundance. I will discuss how JWST's exceptional sensitivity and resolution allow us to detect and resolve PAH emission in Sextans A into compact 3–10 pc clumps, marking the lowest metallicity detection of PAHs to date. Additionally, I will explore the dust production mechanisms in Sextans A, focusing on AGB stars. Dust formed through the winds from stars on the AGB branch can significantly contribute to a galaxy's overall dust budget, but it remains unclear whether metal-poor AGB stars can produce substantial dust reservoirs. I will show that our JWST mid-infrared imaging and spectroscopy reveal the presence of dust features, indicating that metal-poor AGB stars with metallicities as low as 7% Solar are capable of producing dust. Our results offer vital insights into dust formation and survival pathways at low metallicities, which can inform models of cosmic dust evolution at high redshifts.
Mar. 4th	Pramila Pohkrel	Deep Inside the Deuteron: Short-Range Nuclear Forces at High Missing Momentum	Scattering reactions are among the most fundamental and effective tools in nuclear physics for exploring nuclear structure and determining cross sections. Since Rutherford’s historic alpha-scattering experiment, such methods have proved to be powerful probes to study the nature of matter. The electron-induced disintegration (e,e′p) reaction is one example, where a high-energy electron beam is directed onto a target, and the resulting scattered particles are analyzed to study the underlying nuclear dynamics. Understanding the structure of the nucleus and the nucleons have always remained as one of the integral parts of nuclear physics. While long-range nucleon–nucleon (NN) interactions are relatively well understood, our knowledge of short-range NN interactions is still limited. Since the deuteron is the simplest two-body nuclear system, which proves itself as an ideal laboratory for investigating NN interactions at short distances. Insights gained from the deuteron can then be extended to understand and explain more complex many-body nuclear systems. In this study, we use the Plane Wave Impulse Approximation (PWIA) framework to calculate the recoil momentum of the neutron and examine the internal structure of the deuteron at high four momentum squared(Q2).
Mar. 18th	Avnish Singh	Deep Inelastic Scattering: Nucleon Tomography and Emergent Mass in QCD	The pion occupies a unique place in Quantum Chromodynamics (QCD): it is both a quark–antiquark bound state and the Goldstone boson of spontaneously broken chiral symmetry. This dual role tightly constrains its dynamics, making the pion an exceptionally clean system for testing non-perturbative QCD. Its simple two-body leading Fock structure further enhances its theoretical accessibility compared to more complex hadrons such as the nucleon. Precision measurements of pion electromagnetic form factors at large momentum transfer and determinations of its parton distribution function through tagged deep inelastic scattering have therefore become essential benchmarks for understanding QCD across distance scales. Connecting such measurements to underlying quark–gluon dynamics relies on factorization, which separates short-distance perturbative physics from long-distance structure encoded in universal distribution functions. Generalized Parton Distributions (GPDs) provide a multidimensional description of nucleon structure, correlating longitudinal momentum and transverse spatial degrees of freedom and linking quark orbital angular momentum to nucleon spin via the Ji sum rule. However, extracting GPDs requires demonstrating that experiments are performed in a kinematic regime where factorization is valid. This question is particularly pressing in exclusive π⁰ electroproduction. Jefferson Lab measurements in Hall A and CLAS revealed unexpectedly large transverse photon contributions and significant longitudinal–transverse interference, challenging the leading-twist handbag expectation of a 1/Q² suppression of transverse amplitudes. These results motivate systematic longitudinal–transverse separations and precision studies of Deeply Virtual Meson Production (DVMP), which complements DVCS by enabling flavor separation and access to transversity GPDs. In this talk, I will first outline the theoretical framework underlying the role of pions and GPDs, then review the experimental evidence that highlights open questions in π⁰ electroproduction. I will finally present my thesis research based on Jefferson Lab Hall C experiments E12-13-007 and E12-13-010 (September 2023–May 2024). E12-13-007 tests (x,z) factorization in semi-inclusive π⁰ production at small transverse momentum, while E12-13-010 measures high-precision DVCS and π⁰ cross sections and separates DVCS–Bethe–Heitler interference through detailed azimuthal and helicity studies. Together, these measurements aim to validate factorization, perform longitudinal–transverse separations, and enable reliable extraction of GPDs and TMDs.
Mar. 25th	Shivam Raj	From Detector to Physics Analysis: Machine Learning in High Energy Physics	Modern high energy physics experiments, such as the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC), rely on reconstructing and interpreting complex data from high-energy proton–proton collisions. As the LHC enters the high-luminosity era, increasing event complexity and data rates pose significant challenges for traditional methods. Machine learning (ML) provides a powerful framework to address these challenges across the full experimental pipeline. In this talk, I will show how ML is applied from detector level information to physics analysis. At the reconstruction level, I will focus on machine Learning particle flow (MLPF) algorithms based on graph neural networks, which reconstruct particles directly from detector signals by learning complex correlations. I will also discuss efforts to make these models efficient for realistic deployment. At the analysis level, I will present ongoing work on the search for new resonances in the (X → Y H → bbγγ) final state using Run 3 CMS data, where ML techniques are used to improve signal–background separation. As this analysis is currently in the pre-approval stage, I will focus on the methodology and current progress. I will also briefly discuss ML-based data quality monitoring and ongoing work at the Catholic University of America on the CMS pixel detector for future upgrades. Together, these efforts highlight how machine learning connects detector development, event reconstruction, and physics analysis in modern high energy physics.
Apr. 1st	Dr. Mona Zebarjadi	2D Material Thermal Metrology and Usage for Solid-State Cooling	Micron-scale on-chip cooling, heat management, and precise temperature control are increasingly critical as electronic technologies advance toward nanoscale transistors, compact systems, wearables, and portable thermal devices. Conventional mechanical refrigerators with moving parts are unsuitable at these length scales due to fundamental limits on miniaturization. As a result, solid-state cooling approaches that rely on passive and active heat transfer, without moving components, are required. Among these approaches, two-dimensional (2D) materials and thin films are particularly attractive due to their compatibility with chip-scale integration. A key first step toward implementing such technologies is accurate thermal characterization, especially in-plane thermal conductivity measurements of supported 2D materials and thin films. In this talk, I will review our work on thermal conductivity measurements in supported 2D systems and thin films, as well as the design of micro- and nanoscale solid-state coolers that offer alternatives to conventional thermoelectric devices. These approaches focus on controlling heat flow using electric and magnetic fields via the Ettingshausen and Thomson cooling effects. In particular, enhanced Thomson cooling is possible near structural, electronic, or magnetic phase transitions. Finally, I will present our recent studies of metallic alloys for active solid-state cooling applications.
Apr. 8th	Dr. Mitchell Revalski	A Tale of Three Telescopes: Advancing Astronomy with Hubble, Webb, and Roman	The Hubble Space Telescope has transformed our understanding of the Universe over the last 35 years. Now, the James Webb Space Telescope is building on Hubble’s successes, pushing our view of the cosmos to the very limits of current technology to unveil new discoveries from nearby exoplanets to the dawn of cosmic time itself. The Nancy Grace Roman Space Telescope will soon join this incredible fleet of observatories to conduct multiple ambitious surveys across the sky, providing more data than any other space mission in the history of humankind. I will share some of the incredible discoveries that these observatories have allowed us to make in recent years, and how they’ll continue to revolutionize astronomy well into the future. Finally, I will share new resources that can aid you in using the data from these powerful telescopes for your research.
Apr. 15th	Research Day
Apr. 22nd	Dr. Emma Schwartzman	The Search for Multi-AGN: A Multiwavelength Approach	Most massive galaxies host supermassive black holes (SMBHs), some of which are observed as active galactic nuclei (AGN). These systems play a central role in our understanding of SMBH-galaxy co-evolution and serve as fundamental anchors of the International Celestial Reference Frame (ICRF). Galaxy mergers are predicted to be a key phase in SMBH growth, during which multiple SMBHs may simultaneously light up as AGN (multi-AGN). Systems hosting more than one AGN are therefore a powerful observational tool for studying the dynamics of merging black holes and their host galaxies. High-resolution radio interferometry is essential for identifying and confirming such systems, from the sub-arcsecond scales accessible with the Very Large Array (VLA) to the sub-milliarcsecond regime of the Very Long Baseline Array (VLBA). While most existing searches focus on AGN pairs, triple AGN systems are far more rare and significantly more difficult to confirm - only two have been identified in the local Universe to date. This seminar will present a summary of an ongoing multiwavelength search for multi-AGN, including multi-frequency radio observations, a new mid-infrared selection method, and the high precision astrometric measurements made by the spacecraft Gaia. Three newly identified triple AGN systems will be presented, all selected using the mid-IR selection method. All three are triple radio-bright AGN, in which each nucleus hosts a compact radio AGN, making them the first known examples of this class. We will further discuss the confirmation of a significant population of dual AGN in this same mid-IR sample. Finally, the seminar will connect the use of astrometric measurements in the search for multi-AGN, and highlight their importance to the ICRF.