AST-0709181/AST-0707704/AST-0708873/AST-0708855 Kohkhlov/Baron/Wang/Hoeflich
This project is a comprehensive theoretical analysis of thermonuclear Type Ia supernovae (SNe Ia), which will account for any three-dimensional (3D) processes affecting SNe Ia explosions, and will provide a rigorous comparison of model predictions with existing and future high quality observations. The methods and techniques will be combined into the remote-access SNe Ia computational pipeline, which comprises sophisticated 3D simulation algorithms for fluid dynamics, nucleosynthesis, and radiation transport, as well as tools for the 3D analysis of SNe Ia data. SNe Ia are crucial for identifying the nature of dark energy, one of the most important problems facing modern science, because they serve as one of the most direct and precise distance indicators in the Universe. The results of this study will improve the cosmological calibration of these critical tools, by trying to understand what affects their status as standard candles, notably the different types of progenitor systems, deviations from spherical symmetry, and interaction with circumstellar matter. One important outcome will be a comprehensive set of observationally verified first-principles multidimensional explosion models of SNe Ia. Identifying physical correlations among predicted and observed signatures of SNe Ia will be crucial for improving the accuracy of their calibration.
This work is an exceptional platform for introducing students to cross-disciplinary and multi-field science, through the many areas involved in studying SNe Ia, such as numerical methods, large-scale hydrodynamics and radiation transport simulations, observations, and cosmological applications. Research results will be made available to the broad scientific community via the developed computational pipeline, and will be disseminated to the wider non-technical audience. The results will also benefit current and future ground- and space-based observing programs.
Stellar explosions, so called supernovae (SN), triggered one of the most stunning discoveries of the last decade. The Universe is undergoing an accelerated expansion and that a new form of energy that comprises 70% of the energy budget of the Universe --- Dark Energy' --- is pushing the Universe apart, unlike ordinary matter that tends ``clumps'' due to gravitational attraction. Type Ia Supernovae (SNe Ia) are thermonuclear explosions of end stages of stellar evolution of low mass stars, so called white dwarfs (WDs). If the WD is member of a binary system, an explosion can be triggered by accretion from the compagnion star or the merging of two WDs. SNe Ia play a crucial role in fundamental physics, the origin of elements and cosmology. The origin of heavy elements such as Carbon, Silicon and Iron is important beyond stellar explosions for the formation of planets and the evolution life. We all are made out of ashes of stellar explosions. SNe Ia can be used as cosmic light beacons to measure the universe because they are as bright 10,000,000,000 suns and they can be used as 'quasi-standard' beacons because the relation between brightness and the evolution of the light emitted, called light curves (LC), over months to years following the explosion. SNeIa are so similar because basic nuclear physics determines the WD structure, the triggering mechanism, the explosion, and the LC. This strength which allows to use SNeIa to measure the Universe also causes problems when probing the explosion. Higher precision are needed to decypher the nature of the dark energy and to understand how, in detail, the elements are build up over the last 13,800,000,000 years since the Big Bang. We needed a better understanding of the underlying physics and the progenitors. Are our models complete with respect to the physics or do we miss some basic clue ? If we see some changes when we look far away and in the past with the upcoming James Webb Space Telescope (JWST) and the LSST, are these changes cause by the shape of the Universe or due to changes in the population of SNe? What are the tell-tails to detect intrinsic variations? How can we understand the observed diversity in local SNe Ia? In this project, we used a three-prong approach to link SN-physics to observations: 1) We compared the statistical properties of SNe Ia with our model predictions based on the differential comparison between pairs of supernovae. 2) We analysised individual supernovae for which we have obtained very accurate data, commonly not available, and established the shape of spectral lines as diagnostical tools. 3) We opened up a new wavelength domain previously not accessable to evaluate what we can expect from the next generation of instruments. We found from LCs that most of the progenitors originiate from stars with 4-7 solar masses at birth rather than lower masses indirectly inferred from galactic evolution models . Apparently, SNe Ia have as 'short fuse'. Some will explode only a few million years after the Big Bang, and their numbers should be correlated with periods of star burst. JWST will see SNe Ia during the 'dark ages' before the reionization of hydrogen. Our studies of individual SNe showed that most of those objects can be understood in the framework of the explosions close to the M(Ch) mass. This evidence is based on line profiles and the detection of stable isotopes of Ni, the hallmark of high density burning. Most suprisingly, we found strong evidence in several SNeIa for ultra-high magnetic fields of 1,000,000 G which are sufficiently high to alter the early stages of the explosion. An important outcome of this project was the broader impact on students, STEM education and the general public. This NSF award was instrumental to build up a new astrophysics group at Florida State University. With the start of this grant, a new major in "Physics and Astrophysics" was established starting with 5 Undergraduate Students. By now, we have 49 understudents persuing this major. About 25 have already finished their degree, and about 20 UGs have been involved directly or indirecty in this NSF projects which have been involved in code development and simulations, and data reductions. 3 graduate students have finished their PhD and 14 more PhD students are in the program. The impact may also be measured by middle and hight school students. During the last years, about a dozent of outstanding students from were attanding 'Astrophysics' classes or have been involved in research projects over the summer. Their interest was mostly triggered by the FSU planetarium (which is led by the PI) and has some 3000-4000 visitors per year including a wide range of visitors from elementary schools to seniors.
