Celestial Paleontology: The Legacy of Dying Stars

In their death throes, stars dole out their atmospheric material to the interstellar medium in dramatic stellar winds and spectacular explosions. The details of this profound metamorphosis, from star to remnant, play a key role in the next generation of star formation as well as the energetic and chemical evolution of galaxies and the universe as a whole. Dying stars are thought to be the source of all of the nuclei heavier than iron in the universe, as well as more complex molecules, such as carbon chains, which form the backbone of life as we know it. High mass Wolf-Rayet stars are likely progenitors of many types of Supernova, yet due to observational constraints we lack the most basic information about most of them: rather they are part of binary systems. This information is key to the determination of rather or not these stars will go supernova, since depending on its nature the companion can either draw mass off the Wolf-Rayet star, effectively quenching the march to explosion, or feed material onto the Wolf-Rayet star, speeding its demise as a supernova. Models of galactic evolution depend sensitively on the frequency of supernova for several reasons: they inject a great deal of energy into the Interstellar medium, they are the only known producers of nuclei heavier than nickel, and the shock waves that they create can stimulate star formation. In turn, the energy generated by supernova explosions drives the galactic wind, the heavier elements now present in the Interstellar Medium increase the efficiency of star formation, and the groups of new stars formed in the wake of a shock are thought to lead to the development of spiral arms in galaxies. In addition, because high mass stars are so short-lived, they can cycle through hundreds of generations in the time it takes one solar-type star\u27s to evolve. Though intermediate mass stars merely fizzle out in comparison, they are pivotal to the evolution of the universe because they make up over 97% of the stars that have had enough time to evolve off the Main Sequence since the Big Bang. These stars produce more than half of the carbon in the universe as well as much of the nitrogen, oxygen, and more complex molecules such as aromatic rings of carbon. This process, often referred to as chemical enrichment, strongly affects the star formation rates and the characteristics of the next generation of stars. In this work, we explore the contributions of these two classes of stars to our own galaxy: we quantify the nature of the chemical enrichment to the Milky Way from a large sample of intermediate mass stars, and determine the binary status of a sample of Wolf-Rayet stars in the Milky Way

Stellar Geometries with Spectro-Interferometry

The most massive stars are important contributors to their host galaxies. During their stellar lifetimes, and even in their demise as supernovae, they deposit a great deal of material and energy into their galactic neighborhood, thus providing the building blocks for the next generation of stars. Near the end of their lives, they begin to shed their outer layers into space via a stellar wind, creating what astronomers call a circumstellar envelope. These envelopes are thus cosmic fossils of the stars themselves. The physics of stellar winds- more generally referred to as mass loss, is poorly understood. The geometric structure and molecular composition of this circumstellar material can provide important clues to the mass loss process as well as constrain models of stellar evolution. This information can also help inform models of supernova ejecta by providing detailed information about the pre-existing material that the ejecta will slam into as it expands. Previously, these envelopes have been too small to observe from ground or space-based telescopes. The advent of near infrared interferometry has allowed us to resolve these structures for the ¯rst time. A survey of massive stars called Supergiants has been measured using such an instrument; the results of that study are presented here. Support for this work has been generously provided in part by the Rocky Mountain NASA Space Grant Consortium

Supernova Progenitors: Theory, Observation and Outstanding Questions

Supernovae play a prominent role in current theories of cosmology, galaxy evolution and stellar evolution. Key to understanding supernovae is a characterization of their progenitors. A robust body of theoretical work predicts the nature of these stars, but direct observations are lacking. Current theory and observations to date are summarized, as well as open questions in the field. Interferometric methods are proposed for the resolution of some of these questions

The Origin of Asymmetry in Proto-Planetary Nebulae

The transition from Asymptotic Giant Branch (AGB) star to Planetary Nebula is a short lived and mysterious evolutionary phase for intermediate-mass stars. Though it lasts only a few thousand years, it is thought to be the time when the asymmetries observed in subsequent phases arise. However, there are very few that we have caught in the act; those that have been identified are shrouded in thick clouds of dust and molecular gas. Thus, infrared observations are needed to reveal these objects at their most pivotal moment. I present preliminary results of an observational program carried out using the infrared Spitzer Space Telescope on targets spanning the range from post-AGB stars to young Planetary Nebulae with the goal of determining the genesis of asymmetry in these objects

Environmental impact assessment: Maddox Creek culvert removal and habitat restoration project

The EIA was completed as a class project for the ESCI 493 class of Huxley College of the Environment at Western Washington University in regards to a culvert removal proposal to help restore inaccessible salmonid habitat. A group of students performed an analysis of the environmental impacts that will arise from removing the culvert to open up fish passage making spawning and rearing habitat available for coho salmon, steelhead and sea-run cutthroat trout. The proposed project is to remove an eroding 6-foot diameter by 210-foot long culvert pipe that is acting as a fish passage barrier to traditional spawning and rearing habitat of sea-run cutthroat trout, threatened steelhead trout, and coho salmon. The culvert is situated in Maddox Creek with South Laventure Road to the northeast and residential housing to the northwest. Removing the culvert will expose approximately two miles of spawning and rearing habitat for spawning and rearing salmon and trout. The proposed action includes removing approximately 262 thousand cubic feet of fill covering the culvert, excavating the pipe, and restoring the riparian habitat. Alternatives to this action include: 1) installing a slip liner on the inside of the existing culvert and weirs systems inside the slip line and downstream in the channel to backwater the culverts outlet in order to flood the culvert to allow for fish passage; or 2) the “No Action” alternative which will leave the culvert and creek in its current condition. Mitigation for the proposed and alternative actions will consist of stabilizing the surrounding vegetation and soil using silt fences, planting, hydroseeding/fertilizing, and mulching and installation of erosion control mats for erosion and sediment control

Interferometric Studies of the extreme binary, ϵ\epsilon Aurigae: Pre-eclipse Observations

We report new and archival K-band interferometric uniform disk diameters obtained with the Palomar Testbed Interferometer for the eclipsing binary star $\epsilon$ Aurigae, in advance of the start of its eclipse in 2009. The observations were inteded to test whether low amplitude variations in the system are connected with the F supergiant star (primary), or with the intersystem material connecting the star with the enormous dark disk (secondary) inferred to cause the eclipses. Cepheid-like radial pulsations of the F star are not detected, nor do we find evidence for proposed 6% per decade shrinkage of the F star. The measured 2.27 +/- 0.11 milli-arcsecond K band diameter is consistent with a 300 times solar radius F supergiant star at the Hipparcos distance of 625 pc. These results provide an improved context for observations during the 2009-2011 eclipse.Comment: Accepted for Ap.J. Letters, Oct. 200

Identification of three new proto-Planetary Nebulae exhibiting the unidentified feature at 21 um

Among its great findings, the IRAS mission showed the existence of an unidentified mid-IR feature around 21 um. Since its discovery, this feature has been detected in all C-rich proto-PNe of intermediate spectral type (A-G) and - weakly - in a few PNe and AGB stars, but the nature of its carriers remains unknown. In this paper, we show the detection of this feature in the spectra of three new stars transiting from the AGB to the PN stage obtained with the Spitzer Space Telescope. Following a recent suggestion, we try to model the SEDs of our targets with amorphous carbon and FeO, which might be responsible for the unidentified feature. The fit thus obtained is not completely satisfactory, since the shape of the feature is not well matched. In the attempt to relate the unidentified feature to other dust features, we retrieved mid-IR spectra of all the 21-um sources currently known from ISO and Spitzer on-line archives and noticed a correlation between the flux emitted in the 21-um feature and that emitted at 7 and 11 um (PAH bands and HAC broad emission). Such a correlation may point to a common nature of the carriers.Comment: Accepted for publication in Ap

Expanding 4-H Horizons Livestock Leader Guides

What does a 4-H volunteer do when a child asks to start a project they don’t know anything about? The Expanding 4-H Horizons Swine Leader Guide offers information and activities that can be used by anyone in a club or clinic setting. A team of western regional extension professionals have created and piloted a user friendly tool that can be utilized by 4-H leaders and state/county extension staff. The swine specific manual is the first of four being created that will eventually offer information and activities for the beef, sheep and goat projects. This series of leaders guides are being created to serve as a useful tool that can be utilized across a variety of counties and states by supplementing already existing member manuals. With this curriculum, adults will be able to conduct highly effective activities that emphasize project skills, life skill learning, the experiential learning model and 4-H SET

The Grizzly, February 7, 2013

Trustees Plan the Future of Ursinus • Forum Changes Time, Place • Graduation Speakers Selected • Writing Center to Expand Resources • New Exhibit at Berman Museum of Art • Summer Internship Profile • Students Set to Perform Noises Off on February 20 • Students Discuss Queer Life on Liberal Arts Campus • Opinion: U.S. Gun Legislation Needs to be Amended; Our Reliance on Technology is Changing the Way we Think • February 1 Banner Day for Spring Athletes • Swimming Sweeps WAChttps://digitalcommons.ursinus.edu/grizzlynews/1874/thumbnail.jp