2014 Summer Undergraduate Research Conference

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Cool Star Lab undergraduates participated en masse at the 2014 Summer Undergraduate Research Conference  (SURC) on August 14th.  Christian Aganze, Mike Lopez, Rosalinda Lopez, Caleb Choban, and Kieran Berton each presented their summer’s work in the Astrophysics session, moderated by PI Adam Burgasser. Morehouse-UCSD Physics Bridge Fellows Jeremy Ariche and Saidou Ngaide also presented in this session. Melisa Tallis and Morehouse Fellow Julian Pilate-Hutcherson, who worked in the Shpyrko Lab this summer, presented in the parallel Physics & Engineering session; Jarrhett Butler, another Morehouse Fellow, presented in the Biophysics session.  This was the first time Astrophysics had its own session at the SURC, and the room was filled with astronomy fans and proud mentors.

Congratulations to everyone on a successful summer of research!

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Here were the talks given by Cool Star Lab members and UCSD-Morehouse Bridge Fellows:

Christian Aganze (mentor: Adam Burgasser)

Characterization of the M Dwarf Binary System GJ 660 1.AB Separated by Over 120 A.U.

We present a characterization of the binary star system GJ 660 1.AB, a pair of nearby M dwarfs for which we have obtained resolved near-infrared spectra with the SpeX spectrograph. We used these data to classify both components and compare their spectra to theoretical models to infer physical properties. Previous work by Schneider et al. indicates that the binary system is separated by a distance of ~120 A.U. In addition GJ 660.1B is ~4 mag fainter than the host star in the J -band. This characterization of GJ 660 1.AB is important because it will identify whether this system should be considered as a benchmark and contribute to the understanding of binary systems of cool stars/dwarfs.

Jeremy Ariche (mentor: George Fuller)

Time Evolution of Helium-4 and Deuterium in Big Bang Nucleosynthesis

Sterile Neutrinos are a primary candidate for dark matter. Their origin is unknown, yet it is plausible that a lepton asymmetry could generate sterile neutrinos. In addition, observations of the Cosmic Microwave Background suggest the presence of extra radiation energy density. We aim to investigate how lepton asymmetry and extra radiation energy density affect the abundances of Helium-4 and Deuterium as determined in Big Bang Nucleosynthesis (BBN). We will utilize the Wagoner-Kawano code which employs a second order Runge-Kutta differential equation solver to time evolve the electron chemical potential, temperature, and baryon density as well as nuclear abundances. The first three quantities are significant because they are the thermodynamic variables that describe the early universe, hence setting the environment for the production of the light elements during BBN. We will compare the deviation of these abundances due to lepton asymmetry and extra radiation against the standard model for primordial nucleosynthesis.

Kieran Berton (mentor: Carl Melis)

The Lowest Rungs: Reducing Error in Stellar Parallax Measurements to More Accurately Measure Distances Throughout the Universe

Determining the age and expansion rate of the universe requires accurate distance measurements outside of the Milky Way Galaxy. However, such extragalactic distances cannot be measured through trigonometric parallax, and must be determined instead by extrapolating from known distances to objects assumed to have homogenous properties regardless of distance. By reducing the error in distance measurements to these standard candles, we can reduce the error propagated into subsequent distance measurements of objects further along the cosmic distance ladder. The orbit of a binary star system produces oscillations in the system’s motion on the sky that interferes with our attempts to measure accurately its distance with trigonometric parallax. With the Shane 3m Telescope at Lick Observatory we have obtained regular spectroscopic observations over roughly a year for a sample of approximately 20 stellar systems that are important distance indicators. By measuring the Doppler shift for each system as a function of time, we will identify and characterize any binary companions whose affect on the motion of the star system could inflate the error on any parallax measurement attempts.

Jarrhett Butler (mentor: Eva-Maria Schoetz-Collins)

Tissue Surface Tension Measurements of Hydra Epithelial Tissues and Its Role in Driving Hydra Regeneration from Aggregates

Hydra have the ability to regenerate their entire bodies from dissociated and reaggregated cells. A key step in the regeneration of Hydra from cellular aggregates is the separation of cell types to form the two characteristic epithelialized body layers, endoderm and ectoderm. The two cell types segregate such that endoderm occupies the inside and ectoderm occupies the outside of the cell aggregate, corresponding to their proper arrangement in the animal.

A popular theory, the Differential Adhesion Hypothesis, suggests that cell types separate from each other because of differential interfacial tissue tension. For interacting tissues, the tissue with the higher surface tension should end up in the interior, and thus in the case of Hydra correspond to endoderm. Using parallel plate compression, we can measure the surface tension of the two tissues thereby determining whether this theory alone can explain the cell arrangement during Hydra regeneration or whether additional parameters need to be considered.

Regenerating Hydra aggregates are a powerful system to study fundamental processes of pattern formation because they are accessible to quantitative physical measurements and undergo biologically relevant developmental processes.

Caleb Choban (mentor: Adam Burgasser)

Determining Brown Dwarf Types Through Clustering Algorithms

Brown dwarfs are stars that are not massive enough to sustain core hydrogen fusion, and thus fade and cool over time. The molecular composition of brown dwarf atmospheres can be determined by observing absorption features in their infrared spectrum, which can be quantified using spectral indices. Comparing these indices to one another, we can determine what kind of brown dwarf it is, and if it is young or metal-poor . We explored a new method for identifying these subgroups through the machine learning clustering algorithms k-means and expectation-maximization, which provide a quantitative and statistical way of identifying index pairs which separate rare populations. We specifically quantified two statistics, completeness and concentration, to identify the best index pairs. Starting with a training set, we defined selection regions for young, metal-poor and binary brown dwarfs, and tested these on a large sample of L dwarfs. We present the results of this analysis, and demonstrate that new objects in these classes can be found through these methods.

Mike Lopez (mentor: Adam Burgasser)

Determining the Age and Cluster Association of a Young Brown Dwarf

WISE J052857.69+090104.2 (hereon denoted as 0528) was first identified by Thompson et al (2013) as a peculiar star, because it is unclear what type of star it is: a giant, dwarf star, or young brown dwarf. If it is the last case, it is also unclear what cluster it is associated with. In my talk I will discuss how we have determined the nature and estimated the age of this source by analyzing its spectrum and kinematics and comparing these to similarly classified stars. In particular, by comparing to stars in the β Pictoris Group, I prove 0528 is a young brown dwarf. I will also show how its kinematics and comparison to nearby clusters (Gagne et al. 2014) allow us to associate this brown dwarf with a nearby cluster.

Rosalinda Lopez (mentor: Carl Melis)

Investigating the source of radio emissions from the Ultracool Dwarf 2MASSJ1315-2649

Brown Dwarfs are low mass “stars” unable to fuse Hydrogen and hence without a stable source of energy. Thought incapable of emitting high-energy emission like more massive stars, a few “hyperactive” brown dwarfs have been observed to produce non-thermal Hydrogen line and radio continuum emission. One of these is the L-dwarf 2MASSJ1315-2649, the first low-temperature dwarf that is both hyperactive (a persistent and prodigious Hydrogen line emitter) and a quiescent radio emitter. Its low temperature, low mass, old age and assumed short supply of hot plasma make these emissions a mystery. Given its unique level of magnetic activity, we aim to precisely characterize its radio emission to test models of the magnetic activity in brown dwarfs. In this talk, I present the results of radio observations from the Very Large Array, where we searched for variability associated with rotation and bursting emissions; and the Very Large Baseline Array, where we sought to resolve emission between the two components of the binary system in which our dwarf exists. Preliminary results show that 2MASSJ1315-2649 remains a significant radio source, but with a decline in radio flux over the past 3 years.

Saidou Ngaide (mentor: Brian Keating)

Radio Astronomy of the Local Universe

Jupiter, the biggest planet in our solar system, emits radiation in the form of radio waves with a frequency of approximately 20 MHz. 20 MHz is a frequency that is out of range of what the human ear can hear. Our group will be building an antenna, called Radio Jove which when connected to a receiver, can detect low frequency signals, like Jupiter’s 20 MHz radiation. The goal is to transduce these radio waves and those from other celestial bodies like the sun into a sound signal that our ears can hear. This research will enable us to understand the nature of Jupiter’s radiation and also be able to relate it to other radio wave sources.

Julian Pilate-Hutcherson & Melisa Tallis (mentor: Oleg Shpyrko)

Utilizing DLS to study the Dynamics and Pattern Formation in Nanoparticle Films

The wrinkling and buckling of thin films is a poorly-understood phenomenon. The study of these dynamics of thin films is gaining momentum in the fields of physics, chemistry, biology, and engineering. Fundamentally, we want to understand how film confinement affects the behaviors of phase transitions in the system. In addition, we are also interested in studying how the particles assemble themselves into thin films. These thin films are observed in various systems of biology. For instance, we see these dynamics in lung surfactants and membranes throughout the body. In addition, with the understanding of these dynamics, we can apply it to design optical coating and films. Utilizing the technique of Dynamic Light Scattering (DLS) we can study the collective dynamics of self-assembled iron oxide nanoparticle thin films. Dynamics dependence on film confinement is determined by placing the nanoparticle sample in a trough and compressing it by an enclosing wall. While under confinement, coherent light is scattered off the surface of the sample at various times. We then use time-resolved correlation of the scattered speckle intensity to analyze the buckling and wrinkling morphological instabilities of thin films.

 

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