Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session B3: Invited Session: Atomic and Molecular Astrophysics |
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Chair: Daniel Savin, Columbia University Room: Grand Ballroom E |
Tuesday, June 5, 2012 10:30AM - 11:00AM |
B3.00001: Observing the chemical signatures of the oldest, most metal-poor stars Invited Speaker: Anna Frebel In their atmospheres, oldest, most metal-poor Galactic stars retain detailed information about the chemical composition of the interstellar medium at the time of their birth shortly after the Big Bang. Extracting such stellar abundances enables us to reconstruct the onset of the chemical evolution. About 5\% of metal-poor stars display in their spectrum a strong enhancement of neutron-capture elements associated with the rapid (r-) nucleosynthesis process that is responsible for the production of the heaviest elements in the Universe. This fortuity provides a unique opportunity of bringing together astrophysics, nuclear physics and laboratory astrophysics because these objects act as ``cosmic lab" for these fields of study.\newline \newline In order to carry out the spectroscopic chemical abundance analyses of these and other stars, atomic data is required for each absorption line to be measured in the spectrum. Only then abundances can be derived. This is of particular importance in those `r-process' stars: Among many other elements, we find the long-lived radioactive isotopes 232Th (half-life 14 Gyr) and 238U (4.5 Gyr) in some of these rare objects. Their abundances, in combination with abundances of stable r-process nuclei, such as Eu, yield stellar ages of $\sim$ 13 billion years [Preview Abstract] |
Tuesday, June 5, 2012 11:00AM - 11:30AM |
B3.00002: Atomic Data and the Modeling of Supernova Spectra Invited Speaker: Christopher Fontes The modeling of supernovae (SNe) incorporates a variety of disciplines, including hydrodynamics, radiation transport, nuclear physics and atomic physics. These efforts require numerical simulation of the final stages of a star's life, the supernova explosion phase, and the radiation that is subsequently emitted by the supernova remnant, which can occur over a time span of tens of thousands of years. While there are several different types of SNe, they all emit radiation in some form. The measurement and interpretation of these spectra provide important information about the structure of the exploding star and the supernova engine. In this talk, the role of atomic data is highlighted as it pertains to the modeling of supernova spectra. Recent applications [1,2] involve the Los Alamos OPLIB opacity database, which has been used to provide atomic opacities for modeling supernova plasmas under local thermodynamic equilibrium (LTE) conditions. Ongoing work includes the application of atomic data generated by the Los Alamos suite of atomic physics codes under more complicated, non-LTE conditions [3]. As a specific, recent example, a portion of the x-ray spectrum produced by Tycho's supernova remnant (SN 1572) will be discussed [4].\\[4pt] [1] C.L.~Fryer {\it et~al.}, Astrophys.~J.~{\bf 707}, 193 (2009).\\[0pt] [2] C.L.~Fryer {\it et~al.}, Astrophys.~J.~{\bf 725}, 296 (2009).\\[0pt] [3] C.J.~Fontes {\it et~al.}, Conference Proceedings for ICPEAC XXVII (Belfast, Northern Ireland), in press, (2011).\\[0pt] [4] K.A.~Eriksen {\it et~al.}, Presentation at the 2012 AAS Meeting (Austin, TX). [Preview Abstract] |
Tuesday, June 5, 2012 11:30AM - 12:00PM |
B3.00003: The Need for Oscillator Strengths to Study the Molecular Universe Invited Speaker: Steven Federman Oscillator strengths, or equivalently absorption cross sections, are needed to convert the amount of absorption seen in spectra into abundances and to determine dissociation rates in photochemical models of astronomical environments. In turn, the measurements provide important information on molecular structure. I will focus on CO, which is observed in planetary atmospheres and comets, in interstellar clouds and disks surrounding newly formed stars, and in gas associated with the late stages of stellar evolution. Its photodissociation involves line absorption, and oscillator strengths are needed for calculating the amount of self shielding, where optically thick absorption drastically lowers the photodissociation rate. [Preview Abstract] |
Tuesday, June 5, 2012 12:00PM - 12:30PM |
B3.00004: Herschel and SOFIA Observations, Interpretations and the Laboratory Data Required Invited Speaker: John C. Pearson The Herschel Space Observatory and the Stratospheric Observatory for Infrared Astronomy are allowing the far infrared region of the spectrum to be exploited completely for the first time. Interpreting the wealth of new data from these missions which perform photometry in many colors, moderate resolution spectroscopy and high resolution spectroscopy spanning 3 to 680 microns poses an enormous challenge to astronomers, modelers, databases and laboratory astrophysics. Large differences in instrument capability, beam sizes and the regions that can be studied as a function of wavelength place a premium on supporting data for accurate interpretation. The supporting data must include line frequencies, line strengths, transition degeneracy, and energy for assignments and local dynamics, collisional cross sections and strengths of allowed transitions for excitation, and chemical formation and destruction rates for local chemistry. Even for understanding the continuum the properties and nature of the solid state as well as the contribution of gas phase lines is important. [Preview Abstract] |
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