SN 1999be at the edge of the galaxy CGCG 089-013 in the constellation Cancer was one of almost 40 supernovae found by the Supernova Cosmology Project in 1999 as part of a project to improve our understanding of these objects as tools for cosmology. The graph shows a series of synthetic spectra produced on NERSC's IBM SP which aim at understanding the influence of the progenitor's metallicity on the spectra of supernovae such as 1999be.

Research Objectives
Using astrophysics techniques developed in the LBNL Physics Division's Supernova Cosmology Group, we have begun to measure the fundamental parameters of cosmology that shape our current understanding of particle physics through the observation of very distant Type Ia Supernovae. Our goals are: (1) Completion of spectrum synthesis calculations for both distant and nearby supernovae to look for any systematic differences which might bias the cosmological parameters we measure. (2) Development of an objective classification scheme for SNe~Ia to accurately describe their age and luminosity through their spectral features. (3) Creation of a grid of synthetic supernova spectra which will be used to understand the supernovae discovered via LBNL's Supernova Factory and prepare for the Supernova/Acceleration Probe (SNAP) satellite through a comprehensive set of simulations. (4) Detailed study of core-collapse supernovae and their use for determining the cosmological parameters and nucleosynthesis products.

Computational Approach
We use a MIMD approach utilizing Fortran 90 and the MPI message passing interface.

Accomplishments
We analyzed spectra from SN 1997ff, the most distant Type Ia supernova discovered to date. This widely publicized event, which strongly confirmed the existence of "dark energy," argues against the notion that observations of distant Type Ia supernovae may be systematically distorted by intervening gray dust or the chemical evolution of the universe.

We have run numerous models of Type IIP supernovae which will be extremely useful for determining the extragalactic distance scale (and determining the nature of the dark energy) independently of Type Ia Supernovae.

Two complete advanced model grids were calculated to analyze observations of very low mass stars and brown dwarfs. Normally it takes a few months to run such a grid, but NERSC's IBM SP took about four days. We included the calculation of very detailed radiation fields that are needed by people that try to observe stellar occultations or planetary transits. The models include the latest physics and detailed spherical radiation transport (never before done for this type of model). The grid will be used to analyze observed spectra and to better understand the physics behind these objects.

Significance
This project aims to provide theoretical justification of the empirical results found by the Supernova Cosmology Project, that we live in an accelerating universe. In other words, we want to be able to answer the question "How well do we know the cosmological parameters?" from a theoretical standpoint.

Supernovae are among the largest explosions in the universe, and the elements they eject form the basic building blocks for the stars and planets. Understanding the nature of their explosions and the materials synthesized during this process allows us to probe many different basic question in astrophysics, nuclear and high energy physics.

Publications
A. G. Riess, P. Nugent, et al., "The farthest known supernova: Support for an accelerating universe and a glimpse of the epoch of deceleration," Astrophys. J. 560, 49 (2001).

S. Podariu, P. Nugent, and B. Ratra, "Cosmological-model-parameter determination from satellite-acquired Type Ia and IIP supernova data," Astrophys. J. 553, 39 (2000).

M. Sullivan, R. Ellis, P. Nugent, I. Smail, and P. Madau, "A strategy for finding gravitationally-lensed distant supernovae," Mon. Not. R. Astron. Soc. 319, 549 (2000).

http://www.lbl.gov/~nugent/