Properties of Carbon-Oxygen White Dwarfs From Monte Carlo Stellar Models

We investigate properties of carbon-oxygen white dwarfs with respect to the composite uncertainties in the reaction rates using the stellar evolution toolkit, Modules for Experiments in Stellar Astrophysics (MESA) and the probability density functions in the reaction rate library STARLIB. These are the first Monte Carlo stellar evolution studies that use complete stellar models. Focusing on 3 M$_{\odot}$ models evolved from the pre main-sequence to the first thermal pulse, we survey the remnant core mass, composition, and structure properties as a function of 26 STARLIB reaction rates covering hydrogen and helium burning using a Principal Component Analysis and Spearman Rank-Order Correlation. Relative to the arithmetic mean value, we find the width of the 95\% confidence interval to be $\Delta M_{{\rm 1TP}}$ $\approx$ 0.019 M$_{\odot}$ for the core mass at the first thermal pulse, $\Delta$$t_{\rm{1TP}}$ $\approx$ 12.50 Myr for the age, $\Delta \log(T_{{\rm c}}/{\rm K}) \approx$ 0.013 for the central temperature, $\Delta \log(\rho_{{\rm c}}/{\rm g \ cm}^{-3}) \approx$ 0.060 for the central density, $\Delta Y_{\rm{e,c}} \approx$ 2.6$\times$10$^{-5}$ for the central electron fraction, $\Delta X_{\rm c}(^{22}\rm{Ne}) \approx$ 5.8$\times$10$^{-4}$, $\Delta X_{\rm c}(^{12}\rm{C}) \approx$ 0.392, and $\Delta X_{\rm c}(^{16}\rm{O}) \approx$ 0.392. Uncertainties in the experimental $^{12}$C($\alpha,\gamma)^{16}\rm{O}$, triple-$\alpha$, and $^{14}$N($p,\gamma)^{15}\rm{O}$ reaction rates dominate these variations. We also consider a grid of 1 to 6 M$_{\odot}$ models evolved from the pre main-sequence to the final white dwarf to probe the sensitivity of the initial-final mass relation to experimental uncertainties in the hydrogen and helium reaction rates.Comment: Accepted for publication in The Astrophysical Journal; 19 Pages, 23 Figures, 5 Table

Growth, micro-structuring, spectroscopy, and optical gain in as-deposited Al2O3:ErAl_2O_3:Er waveguides

Deposition and micro-structuring of $Al_2O_3:Er$ layers with low background losses (0.11 dB/cm) and lifetimes up to 7 ms have been optimized for active devices. Net gain of 0.7 dB/cm at 1533 nm has been measured.\ud \u

Field quantization for chaotic resonators with overlapping modes

Feshbach's projector technique is employed to quantize the electromagnetic field in optical resonators with an arbitray number of escape channels. We find spectrally overlapping resonator modes coupled due to the damping and noise inflicted by the external radiation field. For wave chaotic resonators the mode dynamics is determined by a non--Hermitean random matrix. Upon including an amplifying medium, our dynamics of open-resonator modes may serve as a starting point for a quantum theory of random lasing.Comment: 4 pages, 1 figur

R-process nucleosynthesis calculations with complete nuclear physics input

The r-process constitutes one of the major challenges in nuclear astrophysics. Its astrophysical site has not yet been identified but there is observational evidence suggesting that at least two possible sites should contribute to the solar system abundance of r-process elements and that the r-process responsible for the production of elements heavier than Z=56 operates quite robustly producing always the same relative abundances. From the nuclear-physics point of view the r-process requires the knowledge of a large number of reaction rates involving exotic nuclei. These include neutron capture rates, beta-decays and fission rates, the latter for the heavier nuclei produced in the r-process. We have developed for the first time a complete database of reaction rates that in addition to neutron-capture rates and beta-decay half-lives includes all possible reactions that can induce fission (neutron-capture, beta-decay and spontaneous fission) and the corresponding fission yields. In addition, we have implemented these reaction rates in a fully implicit reaction network. We have performed r-process calculations for the neutrino-driven wind scenario to explore whether or not fission can contribute to provide a robust r-process pattern