Student Projects

There are several ongoing and possible projects in which students can participate (often with pay!). What follows is a brief summary of each, including goals, responsibilities, and skills (don't worry - you're expected to learn many of these tools as you go).

• The Strange Case of K301 in NGC 6679: The star K301 in the nearby open cluster NGC 6679 appears to have an abnormally high abundance of lithium in its atmosphere - the question is why? The scenarios break down into two basic possibilities: 1) The star has somehow enriched itself in lithium. This is not expected, although very recent theories of the evolution of low mass stars suggest it might be possible, but the odds of catching one doing it is very low. 2) The lithium came from someplace else. The most likely source would be a massive planet falling into the star. Both of these mechanisms will leave behind tell-tale traces in the composition of the star's atmosphere - traces we should be able to detect.
  Responsibilities: Gather the data necessary for an abundance analysis of K301 and several other stars in NGC 6679 to use as a baseline.
  Tools: Unix, IRAF, Excel
  Probability of Success/Publication: Very High
  Current Students: Amber Noll
  
• The Metallicity of the Sextans Dwarf Spheroidal Galaxy: The dwarf spheroidals are a group of low mass (~ million solar mass) galaxies - the nearest of these are actual satellites of the Milky Way. Because of their lower masses and fewer stars, their chemical history is much simpler to untangle than the Milky Way's - they are an ideal laboratory to study the build up of heavy elements in star systems (e.g., as star formation takes place, how much of the material from previous stars is incorporated into the next generation?). To explore this, we've obtained very wide field images of the Sextans Dwarf with the Mosaic camera on the WIYN 0.9-m telescope. The images were taken with a set of filters sensitive to the overall heavy element makeup of the stars, so it should be possible to extract general compositions, ages, and locations within the galaxy for most of the brighter stars.
  Responsibilities: The images are completely reduced. The brightness of the stars in the images need to be measured and calibrated (photometry).
  Tools: Unix, IRAF (aperture photometry), a knowledge of image processing
  Probability of Success/Publication: High (but project is long and complex and the images are monstrously large!)
  Current Students:
  
• Strömgren Photometry of Globular Clusters: One of Dr. Briley's main research areas is studying the star-to-star abundance differences which occur among globular cluster stars. With a collaborator in Denmark, we believe we have figured out a way to quantify whether or not a star has been "enriched" in nitrogen through it's Strömgren c1 color. We currently have reduced and ready-to-go Strömgren photometry for hundreds of stars in about 15 different clusters and could use a little help in the modeling of this data. Our preliminary work shows some very interesting results - the cluster stars are modifying their own abundances as they evolve, but also there are star-to-star differences which have been in place since the beginning.
  Responsibilities: The first step will be to run grids of model stars of different ages to match the observed HR diagram of each color. This will set the temperatures, masses, and sizes of the cluster stars. Then, for each model point, synthetic photometry needs to be calculated for a few different compositions and compared with the observations.
  Tools: Unix, our modeling codes, possibly some programming (fortran - should be easy), plotting and interpreting data.
  Probability of Success/Publication: High
  Current Students:
  
• IR Spectroscopy of M71 Giants: One test of whether or not a cluster star has mixed material to its surface during the later stages of evolution is the presence of relatively large amounts of the 13C isotope in its atmosphere. The Sun's 12C/13C ratio is about 90, while that of a very mixed star can be as low as 3.5 (the equilibrium value for the CN-cycle). Unfortunately, 13C is difficult to measure in the visible - it is easier in the IR where the isotopic shift in molecular V-R states is bigger. So, with a collaborator at CalTech, we've obtained IR spectra of a sample of evolved stars in the globular cluster M71 to look at their 12C/13C ratios (at about 2.3 um). As an added bonus, we also have some bluer OH molecular features that can be used to extract O abundances.
  Responsibilities: The spectra have been obtained and reduced. The temperatures, overall compositions, surface gravities, etc. of the program stars are known. We need someone to compare model spectra of different C (and O) abundances and isotope ratios with the observed spectra. While it sounds easy, the mid-ir is a very difficult part of the spectrum to work in (the absorption by our own atmosphere is problem enough). This will be challenging.
  Tools: Unix, our modeling codes, plotting and interpreting data.
  Probability of Success/Publication: Medium - Also a Difficult Project
  Current Students:
  
• Homogeneity of Metal-Rich Globular Clusters: Most theories of deep mixing in globular cluster stars predict the efficiency of the mechanism to depend on composition - the higher the abundances of heavy elements, the less efficient the mechanism. The clusters that have been studied to date are for obvious reasons, among the easiest/simplest ones to observe/analyze - i.e., close by with little dust in the way. Unfortunately, the most "metal-rich" of these weighs in at only about 20% the heavy element composition of the Sun. Other, more metal-rich clusters are out there, but they are in the direction of the galactic center, making them harder to study (mostly due to the effects of dust). But, with a collaborator at UC Santa Cruz, we have started to do just that using telescopes in Chile and Hawaii. We are looking for someone to go through the spectra for Chile to look for differences in absorption by CN and CH molecules in a sample of stars from 3-4 different clusters.
  Responsibilities: The spectra have been reduced and are ready to go. The software for measuring the absorption has already been written, but will need to be modified slightly for this data. You will need to make these changes, run the software, and look at the results. If all is working, this project can be extended to modeling the spectra and extracting the underlying compositions.
  Tools: Unix, our modeling codes, possibly some programming (fortran - should be easy), plotting and interpreting data, some possibly IRAF.
  Probability of Success/Publication: Medium/High - some of the stars may be too faint for reliable measurements.
  Current Students:
  

Interested? Send me some mail.