Bulletin of the American Physical Society
2012 Annual Fall Meeting of the APS Prairie Section
Volume 57, Number 14
Thursday–Saturday, November 8–10, 2012; Lawrence, Kansas
Session H1: Astrophysics, Cosmology and Space Science IV |
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Chair: Bruce Twarog, University of Kansas Room: Oread Hotel Hancock Room |
Saturday, November 10, 2012 10:00AM - 10:12AM |
H1.00001: Palladius and Horizontal Sundials - How 36 numbers and astronomy help us understand the ancient world Ran Sivron, John Richards, Mason Bruza Palladius was a Roman aristocrat ``gentleman farmer.'' He wrote the only surviving farmer's almanac from the Roman period. It includes advice on how to take care of grapes, olives, wheat, and manage a farm. Farming chores need to be done in season and in the right time of the day. For describing when things should be done, he used a sundial. That's why Palladius left a table of the length of the shadow of a pole - a GNOMON - for 11 hours in the first day of every month for 12 months, hence 132 numbers. Palladius presumed symmetries that cut this to 36 useful numbers, the only useful such table from Roman times That is a treasure trove for both historians and astronomers! Unfortunately we know little else about Palladius, except that his farm was probably in Sardinia, and his family had property somewhere in Gaul, present day France. Its not clear when and where he wrote this, and that could be one question answered by those numbers. In trying to answer that specific question using spherical trigonometry and (as calibration) a recipes for building a sundial from the first century BC, we discovered discrepancies. Those could indicate great error in assembling this table, great progress by assuming that Ptolemi's greatest ``discoveries'' were taken into account, or a combination of several minor factors. [Preview Abstract] |
Saturday, November 10, 2012 10:12AM - 10:24AM |
H1.00002: High Dispersion Spectroscopic Analyses of the Open Clusters NGC 6819 and NGC 7789 Barbara Anthony-Twarog, Constantine Deliyannis, Evan Rich, Bruce Twarog We have used the HYDRA multi-object spectrograph on the WIYN 3.5m telescope to obtain high resolution spectra in the region of Li 6708 A for 333 and 377 stars in the open clusters NGC 6819 and NGC 7789, respectively. Radial and rotational velocity measures have been obtained for the stars to identify and eliminate probable binaries and non-members from the sample through internal comparisons and external comparisons with previous work whenever possible. With the ultimate goal of mapping the evolution of Li with temperature, metallicity, and evolutionary phase, the samples cover the luminosity range from the tip of the giant branch to below the cluster turnoff. Reaching to V$=$16.5 in NGC 6819, we have identified and bracketed the location of the main sequence Li-dip in the turnoff region. A brighter limit to the sample in NGC 7789 at present allows us to just reach the hot side of the Li--dip in the turnoff, coincident with an apparent main sequence gap. [Preview Abstract] |
Saturday, November 10, 2012 10:24AM - 10:36AM |
H1.00003: A Broad-Band Photometric Survey of the Open Cluster NGC 7789 Samantha Brunker, Barbara Anthony -Twarog, Con Deliyannis, Bruce Twarog We have used approximately 200 frames of the open cluster NGC 7789 on the UBVRI system taken with the 0.9m WIYN telescope over four years to survey the cluster and to define its fundamental properties, in conjunction with a complementary study based on extended Stromgren, intermediate-band CCD data. Removing probable radial-velocity and proper-motion non-members, the color-magnitude diagram (CMD) for the cluster core is extremely well matched by Yale-Yonsei isochrones with an age of 1.5 $+$ - 0.1 Gyr for a derived solar [Fe/H] and E(B-V) $=$ 0.26 $+$ - 0.02, as well as an apparent distance modulus of (m-M) $=$ 12.2 $+$ - 0.1. The lower reddening and slightly younger age compared to previous work can be attributed to spatially dependent offsets in the published VI photometry of the cluster. The main sequence approximately one magnitude below the turnoff appears to exhibit a narrow break aligned with the predicted location of the blue edge of the Li-dip among main sequence stars. [Preview Abstract] |
Saturday, November 10, 2012 10:36AM - 10:48AM |
H1.00004: Zapping Charlemagne's Power Grid: A Solar Superflare in AD 774? Adrian Melott Radiocarbon data indicate a jump in 14C synthesis in AD 774-775. I show that, contrary to the original publication, this is consistent with a solar superflare close to current upper limits. It is also typical for the lower end of flare energies observed on solar-type stars. Such a solar proton event would cause moderate ozone depletion, but not a mass extinction event. About 20 times more powerful than the famous 1859 Carrington Event, it would be disastrous for modern electromagnetic technology. I discuss the probability of such an event in the near future. [Preview Abstract] |
Saturday, November 10, 2012 10:48AM - 11:00AM |
H1.00005: Formation and dynamics of an electromagnetic bubble during the NS binary inspiral: theory and observational signatures Mikhail Medvedev, A. Loeb We consider a merging binary system of either two magnetized neutron stars or magnetars, or a neutron star -- black hole binary during the last year days of its evolution. Both compact companions possess magnetic moments and hence are sources of low-frequency electromagnetic (EM) waves, whose frequency is the inverse orbital period and, hence, does not exceed a few kHz. Such EM waves are evanescent: they do not propagate in ambient ISM plasmas because the wave frequency is below the plasma frequency. As the EM energy is continuously pumped into the system by the binary, there forms a cavity (or a bubble) filled with EM radiation. The bubble pushes on the surrounding plasma and can drive a shock wave through the ISM. The shock dynamics is different from the Sedov blast wave solution describing a freely expanding shock from a point-like explosion. Instead, the shock in the system at hand is continuously driven by the ever-increasing pressure inside the bubble. Here we explain the dynamics and evolution of the bubble and the driven shock. We predict that such shocks can be observed just before the merger. These sources become brighter and spectrally harder as the binary evolves toward the final merger. After the merger, the shock should ultimately settle onto the Sedov solution. [Preview Abstract] |
Saturday, November 10, 2012 11:00AM - 11:12AM |
H1.00006: Cosmogenic nuclide production within Earth's atmosphere and long period comets Andrew Overholt Our atmosphere is continually bombarded by cosmic rays. These high energy particles create showers of secondary particles produced in collisions with the atmosphere. As rare isotopes are produced in these showers they have served as an indicator of cosmic ray climate. Our work simulates these showers both in the Earth's atmosphere and on long period comets. Long period comets spend a large amount of time outside the protection of the heliosphere where cosmic ray flux is greatly increased. Our work shows that this environment produces an abundance of cosmogenic nuclides on the comet. We find that the amount of $^{14}$C produced on large comets may be sufficient for creating anomalies within the $^{14}$C record. [Preview Abstract] |
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