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 B3: Astronomy, Astrophysics, Space Science, Cosmology and General Relativity I |
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Chair: Matt Benacquista, University of Texas at Brownsville Room: Salon Cassia, MAIN 2.402 |
Friday, October 11, 2013 10:30AM - 10:42AM |
B3.00001: The Thermally Compatible GodunovSPH: Implementation and Tests Seung-Hoon Cha, Matt Wood, Shu-ichiro Inutsuka GodunovSPH (GSPH) is a consistent numerical method based on particle hydrodynamics, while the standard SPH shows an unphysical numerical surface tension when there is a density contrast due a numerical inconsistency. However, an entropy violation has been observed in some test results of GSPH. In order to fix the violation, the thermally compatible GodunovSPH (tcGSPH) has been implemented. tcGSPH can reproduce the entropy solution even in the expansion wave region. The thermal incompatibility of the continuity and energy equations has been identified as the cause of the entropy violation, and the numerical volume of a particle has been introduced to fix the incompatibility. The fluid density around a particle is estimated not only with the number density of particles, but also with the compression (or expansion) of the numerical volume of the particle, while standard SPH considers only the spatial configuration of the particles in the density estimation. With the consistency and the satisfaction of the entropy condition, the convergence of the tcGSPH is guaranteed. Several tests showing the performance of the tcGSPH will be presented. The comparisons with the standard SPH and/or the previous implementation of GSPH will be shown as well. Plans to implement tcGSPH in a new public-release accretion disk simulation code will be discussed. [Preview Abstract] |
Friday, October 11, 2013 10:42AM - 10:54AM |
B3.00002: Black hole X-ray binaries in globular clusters Thomas Maccarone I will discuss the observational evidence for black hole X-ray binaries in globular clusters. Over the past few years, evidence for such objects has begun to be found in globular clusters in both the Milky Way and in nearby galaxies. I will discuss, in particular, the first such object, which shows a bizarre optical spectrum with strong, broad oxygen lines and no Balmer emission, suggesting that its donor star is a carbon-oxygen white dwarf. [Preview Abstract] |
Friday, October 11, 2013 10:54AM - 11:06AM |
B3.00003: Tidal interactions during neutron star mergers: equation of state considerations William Newton, Farrukh Fattoyev, Joshua Hooker, Jose Carvajal, Bao-An Li We review the possible constraints on the neutron star structure that can be inferred from various gravitational wave and electromagnetic observables during a binary neutron star merger. We focus particularly on examining the sensitivity of the tidal polarizability of neutron stars to the equation of state (EOS) of dense matter at more than 2-3 times nuclear saturation density, concluding that particularly soft or stiff high density EOSs can be distinguished by advanced LIGO observations of the gravitational wave signal immediately pre-merger. We also discuss neutron star structure effects on dynamical tides and crust shattering events during the inspiral phase, the latter of which has been proposed as a possible EM precursor to short GRBs. [Preview Abstract] |
Friday, October 11, 2013 11:06AM - 11:18AM |
B3.00004: Globular Cluster Simulation by N-body code and MOCCA code Dongming Jin N-body6$++$ is a descendant of the family of NBODY codes initiated by Sverre Aarseth, which has been extended to be suitable for parallel computers. MOCCA is an improved code combines Monte Carlo method for simulations of star clusters evolution and Fewbody code to perform scattering experiments. I use the model NGC 6397 from Mirek Giersz's work to compare MOCCA code with N-body6 and N-body6$++$. I analyze the structure of these codes and figure out a way to calibrate to same initial conditions. With the newly-assembled Kepler Cluster in Germany, N-body6 code takes less than 3 days to reach 4000 N-body Time for NGC 6397 model with 1 knot. From my first run, N-body6 and MOCCA have a good agreement with the binary mass {\&} radius distribution and eccentricity distribution, not with N-body6$++$. For semi-major axis, all the codes don't get a good match. [Preview Abstract] |
Friday, October 11, 2013 11:18AM - 11:30AM |
B3.00005: Spectroscopic Analysis of ROTSE Supernovae Govinda Dhungana We present the results from spectroscopic analysis of several of the recent SNe found by the 0.45m ROTSE-IIIb telescope, located at McDonald Observatory, Texas. The spectra are obtained from the 9.2m Hobby-Eberly Telescope (HET) located at the same site. Our analysis includes the identification of the SNe, study of spectral features and develop the understanding of possible inherent physical phenomenon that affects the evolution. Occasionally, we take multiple spectra of relatively interesting objects to better understand the evolution. We use SNID code (Blondin and Tonry 2007, Ap.J. 666, 1024) for preliminary identification and redshift estimation, and later generate the synthetic spectrum using Syn$++$ code (Thomas, R. C., Nugent, P. E., {\&} Meza, J. C., 2011, PASP, 123, 237) to identify and understand the spectral features. Often, we are able to infer some of pre-explosion properties also. [Preview Abstract] |
Friday, October 11, 2013 11:30AM - 11:42AM |
B3.00006: Ultraviolet Spectroscopy of X-ray Binary Systems Cynthia Froning, Thomas Maccarone, Edward Robinson, Robert Hynes, Kevin France, Lisa Winter, Fraser Lewis We have obtained the far-ultraviolet spectroscopy of the X-ray binaries A0620-00, Swift J1753.5-0127, 4U0614+091, and MS1603.6+2600 using the Cosmic Origins Spectrograph on the Hubble Space Telescope. The UV observations have been accompanied by contemporaneous multiwavelength X-ray, optical/NIR, and (for A0620-00) radio observations. The data provide constraints on the structure of the accretion disk and disk outflows, the evolutionary histories of the systems, and the physical properties of the accreting material. We will present the observations and analysis of the multiwavelength data. [Preview Abstract] |
Friday, October 11, 2013 11:42AM - 11:54AM |
B3.00007: HD314884: A Slowly Pulsating B star in a Close Binary Christopher B. Johnson We present the results of a spectroscopic and photometric analysis of HD314884, a binary system with detected soft X-ray emission. A reclassification of the optical counterpart reveals a B5V-B6V star with T$_{eff}$ = 15,490 $\pm$ 310 K, log $g$ = 3.75 $\pm$ 0.25 dex, and a photometric period of 0.889521(12) days. A spectroscopic period search reveals an orbital period for the system of P$_1$ = 1.3654(11) days. The discrepancy in the two periods and the identification of a second distinct frequency in the photometric fourier transform at P$_2$ = 3.1347(56) days provides evidence that one of the stars is a slowly pulsating B star (SPB) with at least two oscillation frequencies. Using the dynamical parameters obtained from the radial velocity curve, we find the most probable companion mass to be M$_1$ = 0.8 M$_{\odot}$. We conclude that the X-ray source in HD314884 is most likely a coronally active G-type star or a white dwarf (WD), with no apparent emission lines in the optical spectrum. The probability distribution of the companion star mass spans 0.6-2.3 M$_{\odot}$ at 99\% confidence which allows the possibility of a neutron star companion. Our analysis does rule out a black hole as the primary X-ray source unless it is of a very low mass. [Preview Abstract] |
Friday, October 11, 2013 11:54AM - 12:06PM |
B3.00008: Cataclysmic Variables in the Kepler Field Matt Wood, Martin Still, Steve Howell, John Cannizzo, Alan Smale, Thomas Barclay, Gavin Ramsay The NASA Kepler mission has been monitoring the SU UMa cataclysmic variables V1504 Cyg and V344 Lyr continuously at short cadence since June 2009. These systems both display dwarf nova outbursts as well as superoutbursts. Signals indicating positive and negative superhumps are observed - sometimes simultaneously - indicating an oscillating disk precessing in the prograde direction and a tilted disk precessing in the retrograde direction, respectively. The most remarkable finding from the V1504 Cyg data is that the year-long display of negative superhumps reveals period changes between and during dwarf nova and superoutbursts, providing a probe of the radial mass distribution of the tilted, precessing accretion disk. The eclipsing system V447 Lyr shows evidence for a larger disk during outburst and outburst orbital humps. These and and other highlights of the Kepler CV data will be discussed. [Preview Abstract] |
Friday, October 11, 2013 12:06PM - 12:18PM |
B3.00009: Seeing the Evolution of Cataclysmic Variables for the First Time Bradley Schaefer Cataclysmic Variables are expected to have long term cycles, where the accretion rate changes greatly on time scales of centuries to millennia. For the first time, I and my colleagues can test the prediction by constructing century-long light curves for many cataclysmic variables. (1) Nova Aql 1918 (V603 Aql) is declining at the rate of 0.44+-0.04 mag/century from 1938-2013. (2) Nova Cyg 1876 (Q Cyg) has been brightening at the rate of 0.41+-0.05 mag/century from 1891-2013. (3) Nova Aur 1964 (QZ Aur) faded from 1980-2009 at a rate of 1.5 mag/century. (4) QZ Aur had its orbital period get shorter by 0.00028. (5) For recurrent nova T CrB, my 110,000 magnitude light curve from 1855-2013 shows a unique and weird structure wherein the star was in a high state (1.5 mag brighter than the usual quiescence) from -8 to -1 year and +0.4 to +5 years, after both the 1866 and 1946 eruption. (5) I have measured changes in the orbital period across the eruptions of T CrB (1946), U Sco (1999 \& 2010), CI Aql (1946), and T Pyx (2011). All four recurrent novae ejected greatly more mass than they accreted in the prior inter-eruption time interval, so none of these recurrent nova can become Type Ia supernovae. [Preview Abstract] |
Friday, October 11, 2013 12:18PM - 12:30PM |
B3.00010: Pulsar J0453+1559, the 10th Double Neutron Star System in the Galaxy Jose Martinez, Kevin Stovall, Paulo Freire, Julia Deneva, Fredrick Jenet, Maura McLaughlin Double neutron star (DNS) systems are valuable physical laboratories that open the doors for many precise experimental tests of gravitational theories. PSR J0453+1559 is a pulsar with a spin period of 45.7 ms. It was discovered and is currently being followed up with the world's largest radio telescope, the Arecibo Observatory. The system has an orbital period of 4.07 days and an eccentricity of 0.1125. The semi-major axis of the orbit is 14.5 light-seconds, which implies, for a pulsar mass of 1.35$M_{\odot}$, the minimum and median companion masses are 1.0$M_{\odot}$ and 1.2$M_{\odot}$, respectively. This strongly suggests this is a new DNS system, only the tenth discovered in the Galaxy. [Preview Abstract] |
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