Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session E4: Galactic and Stellar Astronomy |
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Chair: Drew Milsom, University of Arizona Room: UA Student Union Copper |
Friday, October 21, 2011 3:25PM - 3:37PM |
E4.00001: On the Na-O Anticorellation and Other Abundances in NGC 1261 Dan Filler, Inese I. Ivans, Jennifer Simmerer A key to understanding our Milky Way Galaxy lies in globular clusters, which are spherical clusters of millions of some of the oldest stars in the Galaxy. Globular clusters are extremely old and they intrinsically possess information about their host galaxy. In this talk, we present the first high-resolution spectroscopic analysis of the Galactic globular cluster NGC 1261. Multi-line equivalent width analysis and spectrum syntheses were employed to derive elemental abundances. The overall chemical enrichment, as measured by the abundance of iron, [Fe/H] = -1.19 $\pm$ 0.02 ($\sigma$ = 0.01), is within expectations based upon photometric estimates. However, the Na-O anticorrelation, spanning a factor of 15 in sodium, is larger than any other cluster measured to date. We will also present abundances for the neutron capture element Eu, (created from core collapse supernovae [SNe]), abundances for the alpha elements (Mg, Ca, Si and Ti), created by both core collapse and thermonuclear SNe, iron peak elements (V, Cr, Mn, Co and Ni) and the light elements (C, N and O), which trace stellar nucleosynthesis. [Preview Abstract] |
Friday, October 21, 2011 3:37PM - 3:49PM |
E4.00002: Constraints on the galactic magnetic field with two-point cumulative autocorrelation function Yevgeniy Petrov The fact that ultra high energy cosmic rays are charged particles complicates identification of their sources due to deflections by the intervening cosmic magnetic fields. On the other hand, the information about the fields is encoded in the amount of deflection experienced by a charged particle. It is possible to deduce the most favorable galactic magnetic field (GMF) by examining the parameter space of different models of the GMF. I analyze arrival directions of ultra-high energy cosmic rays with energies above 50 EeV detected by the Pierre Auger observatory using two-point cumulative autocorrelation function and backtracking technique to find models of the galactic magnetic field that are compatible with statistically significant clustering on the extragalactic sky. This approach is independent from any catalog of sources. The results suggest that among several tested fields pure bisymmetric spiral disk field is favored with even vertical symmetry. Addition of the toroidal halo field further improves the focusing properties of the spiral fields and favors the field with even vertical symmetry for both bisymmetric and axisymmetric spirals. Fields with ring structure are disfavored. [Preview Abstract] |
Friday, October 21, 2011 3:49PM - 4:01PM |
E4.00003: Numerical simulations of a stellar intensity interferometer Janvida Rou, Paul Nunez, David Kieda, Stephan LeBohec The revival of stellar intensity interferometry may allow large arrays of gamma ray telescopes to reconstruct high resolution images of stars. Intensity interferometry measurements rely on the fact that the different Fourier components of the light collected at each telescope produce low frequency beats resulting in small intensity fluctuations displaying correlation between the different telescopes in an array. The correlations provide access to the squared degree of mutual coherence of the light at the different telescopes, which is related to the size and shape of the star via the Cittert-Zernike theorem. Here, we discuss our work toward a detailed and realistic numerical simulation of intensity interferometry with two telescopes, which provides insight into the effects of the finite size of the telescopes, the photodetectors and electronics response, and excess noise on the performances of future intensity interferometry experiments. [Preview Abstract] |
Friday, October 21, 2011 4:01PM - 4:13PM |
E4.00004: Hi-mass star formation in the region IRAS 19217+1651 Victor Migenes, Tatiana Rodriguez, Miguel A. Trinidad The study of massive proto-stars is very difficult. This sources are embedded in regions of dense gas and dust limiting their study to radio and infrared frequencies. In addition, they formed in groups, their evolution is much faster than low-mass proto-stars and are distributed much farther away. Hence, they can not be studied directly. But we can study them by learning about the ionized regions in which they are formed, the molecular, IR and mm emission associated with them and MASER emission. We present and discuss hi sensitivity and spatial resolution observations of water MASERs towards the hi-mass star forming region IRAS 19217+1651, an UC-HII cometary region at a distance of 10.5 kpc. [Preview Abstract] |
Friday, October 21, 2011 4:13PM - 4:25PM |
E4.00005: Anisotropy studies at the Galactic Center with the Pierre Auger Observatory Sara Mueller, Miguel Mostafa Anisotropy studies in the direction of the Galactic Center at EeV energies were studied using data from the Surface Detector of the Pierre Auger Observatory. Data from January 2004 until August 2011 showed no significant excesses above 1 EeV, for zenith angles below 60\r{ } based on the analysis at small angular scales. [Preview Abstract] |
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