Bulletin of the American Physical Society
2005 TSAPS/AAPT/SPS Joint Fall Meeting
Thursday–Saturday, October 20–22, 2005; Houston, TX
Session D1: Astrophysics |
Hide Abstracts |
Room: Waldorf Astoria B 210B |
Friday, October 21, 2005 4:00PM - 4:12PM |
D1.00001: An Investigation of the Canis Major Overdensity W.L. Powell Jr., Ronald Wilhelm, Amy Westfall, Adam Lauchner, Abel Diaz Using 2MASS colors Martin et al. (2004) uncovered evidence for a remnant dwarf galaxy in Canis Major, in the form of an overdensity of M-giant stars. The spatial distribution of the M-giants indicate an extended, and likely disrupted, group of stars extending over roughly 30 degrees of the sky. The nature of this overdensity would have ramifications to our understanding of our Galaxy's thick disk population and its formation history. We made a photometric survey to find candidate horizontal branch stars that match the characteristics of the Canis Major overdensity. The goal was to find a group of horizontal branch stars, as is expected for an old population, in the Canis Major dwarf. We performed spectroscopy on a group of these candidate stars. We present new photometry and color magnitude diagrams for various Canis fields and include kinematic results. [Preview Abstract] |
Friday, October 21, 2005 4:12PM - 4:24PM |
D1.00002: Application of the Physics of the auroral current region in the VASIMR rocket Michael Brukardt, Edgar Bering, Franklin Chang-Diaz, Jared Squire, Timothy Glover, Verlin Jacobson Increasing demands made on spacecraft capabilities are making electric propulsion systems more important to space exploration. One of these electric propulsion systems is the variable specific impulse magnetoplasma rocket (VASIMR). The VASIMR applies and simulates several important physical processes occurring in the magnetosphere. Several auroral current region processes, such as lower hybrid heating, parallel electric field acceleration, and ion cyclotron acceleration are also simulated in the VASIMR. This paper will summarize the physics in the VASIMR engine. The helicon discharge uses lower hybrid heating as the physical mechanism of the ionization source of the VASIMR. Ion exit energy measurements show a substantial parallel field due to ambipolar charge separation in the axial magnetic field of the VASIMR engine. Ion cyclotron heating (ICRH) during a single pass through the resonance region has been achieved. Perpendicular ion cyclotron heating in the VASIMR is shown in ion velocity phase space distribution data. [Preview Abstract] |
Friday, October 21, 2005 4:24PM - 4:36PM |
D1.00003: Multifrequency VLBA Polarization Imaging of 3CR Lobe-dominated Quasars David Hough, Daniel Homan Studies of the parsec-scale radio polarization properties of quasars with intense radio cores beamed toward Earth have driven the development of models of relativistic jets and their environment. These models predict a strong orientation dependence of many source properties. To test these models, we selected a sample of 7 mildly beamed cores in lobe-dominated quasars from the 3CR survey with a wide orientation range. Dual-polarization VLBA observations at 5, 8, and 15 GHz were conducted between 1996 and 1999. Two sources exhibit long, faint jet extensions with longitudinal magnetic fields, consistent with shear effects. Four sources show significant rotation measures in their cores/inner jets that probe the surrounding Faraday screen. There is evidence for a helical jet in 3C245, a magnetized sheath in 3C207, and a transverse magnetic field associated with a jet-cloud collisional shock in 3C334. Implications for source models will be discussed. [Preview Abstract] |
Friday, October 21, 2005 4:36PM - 4:48PM |
D1.00004: Electron precipitation and ionospheric electric field observations following the solar flare of 20 January 2005 and during the geomagnetic storm of 21 January 2005 Edgar Bering, Brandon Reddell, S. Bale, J.B. Blake, A.B. Collier, R.H. Holzworth, A.R. Hughes, M. Kokorowski, E. Lay, R.P. Lin, M.P. McCarthy, R.M. Millan, H. Moraal, T.P. O'Brien, G.K. Parks, M. Pulupa, J.G. Sample, D.M. Smith, P. Stoker, L. Woodger The MINIS balloon campaign was successfully conducted in January 2005 to investigate relativistic electron loss mechanisms. An X 7.1 solar flare occurred at 0636 UT on 20 January 2005. A CME from this flare arrived at the Earth 34 hours later. An SSC began at $\sim $1650 UT followed by a geomagnetic storm with a Dst perturbation of $\sim $ -100nT. The AE index shows that the 20 January flare was followed first by 6 hours of deep quiet and then 28 hours of moderate activity. The balloon data contain evidence for two interesting geoelectric responses to the flare. The arrival of the CME initiated an interval of very strong relativistic electron precipitation. The second and third Southern payloads and the first Northern payload made observations in both hemispheres of several extensive relativistic electron precipitation events that occurred from 1700 to 2000 UT on 21 January 2005. Each x-ray burst was preceded by a strong pulse of ionospheric convection. [Preview Abstract] |
Friday, October 21, 2005 4:48PM - 5:00PM |
D1.00005: Orbital Debris Photometric Study Heather Rodriguez In an effort to better understand differences between optical and radar size estimates of orbital debris, a photometric study of debris pieces from an exploded mock satellite has been initiated. This study will take brightness measurements of debris of various shapes and sizes at varying phase angles and orientations. The Orbital Debris Program Office at NASA Johnson Space Center (JSC) has an array of debris pieces from a mock satellite that was exploded in the European Space Operations Centre's ESOC2 test. A Xenon lamp will be used to simulate solar illumination and a CCD camera will record a digital image in filters defining specific bandpasses in the visible spectrum. The illumination of the debris will be varied by observing at different phase angles and orientations through the programming of the robotic arm. The ultimate goal in the optical measurements group at JSC is to create an optical Size Estimation Model (SEM) that will correlate with the current radar SEM. The radar SEM uses laboratory produced debris pieces observed at different orientations to convert radar cross section to characteristic length. The optical cross section (OCS) of a target is a product of albedo and physical cross section, where albedo is defined as the fractional flux reflected from a surface. The albedo of an object is necessary to convert the brightness into a size. By examining the brightness variations as functions of surface material, shape, and orientation, a better determination of albedo or size may be obtained. [Preview Abstract] |
Friday, October 21, 2005 5:00PM - 5:12PM |
D1.00006: Nuclear Equation of State: How can we learn about Neutron Stars from Atomic Nuclei? Dinesh Shetty, Sherry Yennello, George Souliotis The structure and the stability of a neutron star, a dense and neutron-rich object formed in a supernova collapse, depends on a complex relation between the pressure, density and temperature, known as the nuclear Equation Of State (EOS). The determination of the nuclear EOS is crucial for studying many astrophysical problems such as the cooling of neutron star, determining its maximum mass, radius, etc. I will show how by studying the structure of neutron-rich nuclei and the dynamics of collision between them in terrestrial experiments, one can learn about the nuclear equation of state. [Preview Abstract] |
Friday, October 21, 2005 5:12PM - 5:24PM |
D1.00007: Center for Gravitational Wave Astronomy, University of Texas at Brownsville Willem van Straten As a tool of modern astrophysics, high-precision pulsar timing has yielded the strongest constraints on theories of strong- field gravitation; it is also predicted to directly detect the stochastic background of gravitational waves from supermassive black hole binary systems. Fundamental to every pulsar timing experiment is a measurement known as the pulse time-of-arrival (TOA), the epoch at which a fiducial phase of the pulsar's periodic signal is received at the observatory. Pulse TOAs are typically measured using only the observed total intensity of the pulsed radio emission. A new technique is presented that exploits the additional timing information available in the polarization of the pulsar signal. For a number of millisecond pulsars, TOAs derived from polarization data are predicted to exhibit greater precision and accuracy than those derived from the total intensity alone. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700