Bulletin of the American Physical Society
Joint Fall 2013 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 58, Number 10
Thursday–Saturday, October 10–12, 2013; Brownsville, Texas
Session C3: Astronomy, Astrophysics, Space Science, Cosmology and General Relativity II |
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Chair: Matt Benacquista, University of Texas at Brownsville Room: Salon Cassia MAIN 2.402 |
Friday, October 11, 2013 2:00PM - 2:12PM |
C3.00001: Core-halo formation in one-dimensional self-gravitating systems Bruce Miller, Kenneth Yawn, Erik Nguyen, Jean-Louis Rouet For many decades the one-dimensional self-gravitating sheet system has been studied as the simplest dynamical model for astrophysical systems of masses. The formation of core-halo structures has been of particular interest for astrophysical systems and their evolution. In one-dimensional systems, under the right conditions, similar structures can form in position-velocity space. In this work we study these formations using a dynamical simulation of a one-dimensional system of sheet masses. Specific particles identified in the initial distribution are tracked to the final core-halo distribution, and the evolution of the distribution of these particles in the system is identified and discussed. [Preview Abstract] |
Friday, October 11, 2013 2:12PM - 2:24PM |
C3.00002: Detection of gravitational wave signals from NS-NS inspirals in presence of non-stationary noise Wenhui Wang, Soma Mukherjee This work presents a study of the efficiency of detection of gravitational wave signals from neutron star - neutron star (NS-NS) binary systems as a function of stationarity of the underlying detector noise. A matched filter based search pipeline is used. First, NS-NS inspiral signals are injected in stationary noise and the detection efficiency is noted. Next, non-stationary noise is modeled in a realistic manner by using statistical ARMA models. The reason behind this choice is motivated by the fact that real noise from the LIGO detectors can be modeled (up to the second moment) in the same manner [1]. Detection efficiency of the search pipeline is studied for several non-stationary noise models thus created. Results show that when the noise is~non-stationary and the signal-to-noise-ratio (SNR) is low, the matched filter cannot provide a very good detection. We thus develop a variation of the matched filter that improves detection results in presence of non-stationary noise. [Preview Abstract] |
Friday, October 11, 2013 2:24PM - 2:36PM |
C3.00003: Black hole binary inspiral and trajectory dominance Richard Price, Gaurav Khanna, Scott Hughes Gravitational waves emitted during the inspiral, plunge and merger of a black hole binary carry linear momentum. This results in an astrophysically important recoil to the final merged black hole, a ``kick'' that can eject it from the nucleus of a galaxy. We had previously showed that the puzzling partial cancellation of an early kick by a late antikick, and the dependence of the cancellation on black hole spin, can be understood from the phenomenology of the linear momentum waveforms. Here we connect that phenomenology to its underlying cause, the spin-dependence of the inspiral trajectories. This insight suggests that the details of plunge can be understood more broadly with a focus on inspiral trajectories. [Preview Abstract] |
Friday, October 11, 2013 2:36PM - 2:48PM |
C3.00004: Detecting Gamma-ray Pulsations from Radio Pulsars Stephanie Cohen Using data from the \emph{Fermi} LAT survey, we evaluate ten known newly discovered radio pulsars, following standard analysis procedures, to see if detection of gamma-ray pulsations from these pulsars can be made. Given the number of radio pulsars discovered from gamma-ray point sources in the \emph{Fermi} LAT survey, we hope to find gamma-ray pulsars among these ten pulsars. In order to demonstrate our capability of detecting gamma-ray emission, we first confirm detection of gamma-ray pulsations for the known radio and gamma-ray pulsar J1816+4510. The H-test, along with its corresponding false alarm rate, is the statistical test by which we identify whether or not significant gamma-ray emission has been detected. [Preview Abstract] |
Friday, October 11, 2013 2:48PM - 3:00PM |
C3.00005: Towards optimal integration of multi-messenger information in a multi-trigger population study analysis Marc Normandin, Soumya Mohanty We present an algorithm for population parameter estimation that optimally incorporates multi-messenger information from triggered events. The assignment of suitable weights needs to take into account the background astrophysical distribution to be estimated. However, current methods lack suitable weight factors applied to the triggers besides trivial ones like a hard cutoff on flux. Our approach is an improvement in that the background distribution plays a direct role in the parameter estimation procedure. We use a likelihood-based method where the multi-messenger data is incorporated into a common likelihood before the population parameters are estimated. To demonstrate the method, we present preliminary results of this method as applied to simulated triggers that contain combined electromagnetic and gravitational radiation. [Preview Abstract] |
Friday, October 11, 2013 3:00PM - 3:12PM |
C3.00006: Recent Progress on Testing General Relativity at Cosmological Scales and Implications for Cosmic Acceleration Mustapha Ishak, Jason Dossett, Jacob Moldenhauer Cosmic acceleration can be caused by a cosmological constant/dark energy component in the universe or a modification to general relativity that takes effect at cosmological scales. An important question is to be able to distinguish between these two possibilities. I will report about some of our work on this topic including the framework developed and the results obtained using some recent available data sets. I will also report on our recent work to explore the robustness and decisiveness of this type of tests. [Preview Abstract] |
Friday, October 11, 2013 3:12PM - 3:24PM |
C3.00007: The Self-Calibration of the Galaxy Intrinsic Alignment Contamination to the Cosmic Shear Signal Michael Troxel Weak gravitational lensing due to large scale structure (cosmic shear) has been identified as a critical tool in studying the evolution of large scale structure in the universe, as well as shedding light on the nature and influence of dark matter and dark energy. One of the primary systematic biases in weak lensing, the intrinsic alignment (IA) of galaxies, poses a barrier to precision weak lensing measurements, and methods for identifying and removing its effects on cosmological information are key to the success of current and planned lensing surveys. We have addressed this problem by expanding model-independent techniques to indirectly measure and remove the IA contamination from the lensing signal. These self-calibration techniques take advantage of complimentary survey information to self-calibrate the lensing signal, which along with the unique lensing and IA geometry and separation dependencies, allow us to reconstruct the various IA correlations at the level of the spectrum and bispectrum. For cross-correlations, we have demonstrated that the self-calibration approach can reduce the IA bias over most relevant scale and redshift ranges by up to a factor of 10 or more. In the case of auto-correlations, we have demonstrated the feasibility of implementing the self-calibration for conservative estimates of photo-z accuracy in planned surveys. In both cases, the self-calibration has the added benefit of preserving the IA signal, which itself provides additional information which can be used in studying the formation and evolution of large scale structure in the universe. [Preview Abstract] |
Friday, October 11, 2013 3:24PM - 3:36PM |
C3.00008: Formation of naked singularities in gravitational collapse Sourabh Nampalliwar An important consequence of the cosmic censorship conjecture is that all singularities formed in a gravitational collapse are hidden inside black holes. Several examples that violate the conjecture have been found, but all of them are either too specialized or unphysical. We are studying the causal structure of spherically symmetric gravitational collapses to find if such singularities form generically. [Preview Abstract] |
Friday, October 11, 2013 3:36PM - 3:48PM |
C3.00009: Astronomy at Tarleton State University: Photometric Investigation of the Eclipsing Binary Star CygIV-16062 Shaukat Goderya Tarleton State University observatory is located at the Hunnewell Ranch about 10 miles from the campus in Stephenville, Texas. It has the largest telescope of any undergraduate only institution, a 32 inch (.8m) research grade remotely controlled telescope from ACE equipped with a high quality FINGERLAKES CCD camera and UBVRI filters from custom scientific. The observatory has been used for a variety of research projects as well as teaching observational astronomy to undergraduate students. A research initiative to obtain detail photometric data on poorly studied and faint eclipsing binary stars was started in late 2011. In addition, new binary systems discovered by the Kepler mission have also been included in this project. This paper presents work that our students have performed on CygIV-16062 (2MASS J19155176$+$4306271) a new eclipsing binary star identified in Kepler field of view. [Preview Abstract] |
Friday, October 11, 2013 3:48PM - 4:00PM |
C3.00010: Search for Rapidly Varying Eclipsing Binaries with ROTSE-III Farley Ferrante, Robert Kehoe We present the results of a search for eclipsing binary stars exhibiting rapid optical variations using observations made by the 0.45m Robotic Optical Transient Search Experiment-IIIb (ROTSE-IIIb) telescope located at McDonald Observatory in the Davis Mountains of west Texas. For each candidate in a particular field we analyze the time variation of optical light output as recorded in ROTSE-III images to generate light curves for each night of observations. Examination of the light curve shape determines the variable type and magnitude range. Using a cubic spline fit, multiple nights of observations are then phased into one plot to determine the period and amplitude of variation. After analysis of a star field in the constellation Sagittarius originally imaged by ROTSE-IIIb as a gamma-ray burst (GRB) trigger response, we identified a candidate W UMa-type (EW) contact binary star that was previously uncatalogued. We submitted it to The International Variable Star Index (VSX) for review. The discovery was confirmed and the contact binary is now listed in the VSX catalog. [Preview Abstract] |
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