Colloquium Archive

Thursday, February 24th
Professor Catrina Hamilton-Drager, Senior Associate Provost for Academic Affairs and Associate Professor of Physics and Astronomy
"The history of KH 15D (Google it!) and the status of observations and new interpretations"

Just over twenty years ago the variable star, V582 Mon, was re-discovered by Kearns and Herbst and henceforth has also been known as KH 15D. In this talk, I will review the history of this intriguing system, and what it represents: an opportunity to study a pre-main sequence (PMS) binary system still embedded in an accretion disk. The steady precession of the occulting circumbinary (CB) ring has allowed us to derive the stellar properties of both stars, and presents us with the opportunity to refine and expand current models of the system. This should lead to a strong test of PMS models. I will review the most recent observations and results, and discuss some new interpretations of “old” data.

Noon
Tome 115
Pizza provided beforehand (11:35am-Noon) Tome Hall 2nd Floor Lounge (by the Majors' Room)

Thursday, April 28th
New Majors Induction Ceremony

Join us as we induct and celebrate our new majors

Noon
Tome 115 (weather permitting; Tome outdoor classroom area)
Food will be provided

Tuesday, May 3rd
Physics Senior Research Talks

Maitland Witmer will present "Design and Assembly of PCB Electronic Self-Oscillators"
There are many phenomena in nature in which organisms have some type of synchronization, like heart cells all beating in unison. The purpose of this research is to model some of these phenomena using electronics. First, I started by learning how to make printed circuit boards (PCB) on a Voltera V-One machine and the software EAGLE so that I could create an electronic model for experimentation. Then I connected operational-amplifier-based oscillators in a universal coupling pattern to observe their behavior when they all could send and receive information. Experiments consisted of modifying the oscillators' natural frequencies to find regions of different types of synchronization patterns, such as one-to-one frequency locking up to a three-to-seven locking. The results have the potential to explain how different synchronization patterns can emerge in nature when systems communicate.

Cameron Shaw Graham will present "The GM Ori Mystery: A Possible Solution"
GM Ori is an RRc Lyrae variable star and therefore should be a “standard candle.”  However, published magnitude ranges and a light curve based on visual observations seem to imply that this star was significantly fainter during the period from ~1930 to 1957 than it has been in recent decades.  We suggest a possible solution to this mystery.

Emma Behta will present "Synchronization Patterns of Self-Sustained Mechanical and Electronic Oscillator Networks"
As human beings, we tend to hold synchronization in high regard. Typically, the occurrence of two distinct events at precisely the same moment in time is thought to be the result of careful planning and intentional coordination. We marvel at choreographed dances and synchronized diving routines, impressed by the levels of dedication and training such demonstrations must involve. It may thus be quite surprising to discover that similar conditions can arise in systems of mindless objects. This project investigated the phenomenon of synchronization through the observation and analysis of two unique dynamical systems, one mechanical and the other electronic. The mechanical system consisted of two metronomes coupled by their shared use of a rolling platform resting on two cylinders of equal radii, as initially presented in [1, 2]. The dynamics of this system, including its steady final states and symmetry-breaking transients, were experimentally studied using frame-by-frame motion tracking software. Subsequent analysis of the platform’s movements revealed the presence of Coulomb damping, and the original theoretical model was reconstructed to account for this. Additionally, each synchronization region was classified in terms of both the coupling strength of the system and the natural frequency mismatch between the two oscillators. Similar parameters were examined for the electronic system, namely, two coupled comparator-based relaxation oscillators. Various phase-locked ratios, including 1:1, 2:1, 3:1, and 4:1, were experimentally measured and portrayed in the form of Arnold tongues. These observed parameter regimes were then shown to almost perfectly match the predictions of the system’s theoretical model.

Noon
Tome 115
Pizza provided