Prof. Dinshaw Balsara
Email: dbalsara@nd.edu

Studying The Physics of Accretion onto Compact and Proto-Stellar Objects.

The problem of accreting matter onto compact stars as well as proto-stars that are in the process of building their mass is very interesting. In either case, an accretion disk supplies matter to the surface of the star. In the case of compact stars (white dwarfs and neutron stars) the accreted matter can release a significant amount of energy that can be observed by X-ray telescopes. In the case of proto-stars, the accretion actually helps build the mass of the star. Either case can be computationally studied by modeling the physics of the accretion disk as well as radiation from the star. The present project builds on on-going work at ND where the student will run simulations and help in the analysis of the results.

Prof. Christopher Howk
Email: howk.1@nd.edu
Professor Howk's group is studying the physics of the gas between the stars, the interstellar medium. Most of the interstellar medium in spiral galaxies like our Milky Way is located in a very thin rotating disk. However, the violent explosions of massive stars shock heat interstellar gas, ejecting some of it many thousands of light years above the thin disk, creating a gaseous "atmosphere" about galaxies.

Prof. Howk's work has shown that this atmosphere contains not only very hot gas, but also quite cool material from which stars can form. We will be studying the properties of a star forming region located far from the disk of a nearby galaxy. The unusual location of this group of newly-formed stars gives us the opportunity to investigate the star formation process in extreme environments as well as the circulation of newly-formed elements from the thin disk of galaxies to their "atmospheres."

Prof. Peter Garnavich
Email: pgarnavi@nd.edu
Supernovae are exploding stars that can get so bright that they outshine the total light from all other stars in their galaxy. Some types of supernovae are nearly "standard candles" that can be used to accurately measure distances to distant galaxies. This makes them useful probes for cosmology and supernovae have been used to discover the presence of dark energy dominating the universe. Garnavich and Krisciunas have images of several nearby supernovae and precise photometry of the stars will be done in order to construct a light curve for these events. Observations at the Vatican Advanced Technology Telescope may be needed to take images of the galaxy after the supernova has faded to remove any contaminating light. The supernova light curves will be analyzed to determine the absolute brightness of the supernovae, derive distances to the host galaxies and compare to other supernovae to check for peculiarities.

Prof. Terry Rettig
Email: trettig@nd.edu
We use high resolution spectra of absorption lines of CO from the KECK observatory to probe disk systems of various inclinations, the dust/gas ratio will provide a measure of stratification, importantly, providing a timely and crucial test of theoretical models. The results of these observations will define the initial conditions for models of gas giant planet formation. Gas and dust mixing in the extended disk around a young star is one of the most debated and untested results of theoretical modeling in recent years. Various theoretical models predict that dust preferentially settles to the mid-plane, leaving behind a predominantly gaseous atmosphere at higher vertical scale height). In a dense dusty disk, kilometer sized bodies can form by direct assembly (directly from grains to km-sized objects); however, work by others suggests that turbulence in the disk prohibits the preferential settling of dust to the mid-plane. Thus planetesimals cannot form by direct assembly and must form by the slower process of grain agglomeration (grains to cm- m- km-sized bodies). We use high resolution spectra of absorption lines of CO from the KECK observatory to probe disk systems of various inclinations, the dust/gas ratio will provide a measure of stratification, importantly, providing a timely and crucial test of theoretical models. The results of these observations will define the initial conditions for models of gas giant planet formation.