Bulletin of the American Physical Society
2013 Annual Meeting of the California-Nevada Section of the APS
Volume 58, Number 14
Friday–Saturday, November 1–2, 2013; Rohnert Park, California
Session C1: Astrophysics I |
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Chair: Nan Phinney, SLAC National Accelerator Laboratory Room: Darwin 107 |
Friday, November 1, 2013 2:00PM - 2:12PM |
C1.00001: A Candidate Recoiling SMBH in a Local Active Galaxy? Bryan Scott, Vardha Bennert, Stefanie Komossa, William Keel, Anna Pancoast, Tommaso Treu, Matthew Auger, Matthew Malkan Merging Supermassive Black Holes are a predicted key feature of models describing the co-evolution of galaxies and Active Galactic Nuclei (AGN). Following the merger, the SMBH is expected to undergo gravitational recoil velocities on the order of hundreds to thousands of km/s due to the anisotropic emission of gravitational radiation. Given that the majority of (massive) galaxies are thought to host a SMBH in the center, such events are expected to be relatively common. However, there have been only few candidates with no secure case so far. We present preliminary results of a recoiling SMBH candidate, discovered in a spectroscopic study of local AGNs selected from the SDSS. The SDSS image shows a blue knot offset from the center of the host galaxy by 1.5 arcsec, and SDSS fiber-spectra show asymmetric broad emission lines. Keck spectra centered on the host galaxy do not show broad lines; follow-up Lick spectroscopy associates AGN emission with the location of the blue knot. While these features are expected for a SMBH undergoing recoil, we discuss other possibilities such as a type IIn supernova or an ongoing merger. [Preview Abstract] |
Friday, November 1, 2013 2:12PM - 2:24PM |
C1.00002: Kinetic Decoupling and Small Scale Structure in Effective Theories of Dark Matter Jonathan Cornell, Stefano Profumo, William Shepherd After WIMP dark matter chemically decouples, setting its relic density, it remains in \textit{kinetic} equilibrium due to scattering processes with standard model particles. The temperature at which it then kinetically decouples sets the size of the smallest dark matter collapsed structure, or protohalo, which could form in the early universe. While previous work has focused on calculating the temperature of kinetic decoupling for specific models of particle physics beyond the standard model, in this talk I will present results for more general calculations where the interactions between WIMPs and standard model particles can be described by an effective field theory. With these results, I will present constraints on the size of the protohalos from a variety of direct and collider probes of particle dark matter. I will also discuss recent claims that kinetic decoupling can be a way to resolve the ``missing satellites problem'' of the Milky Way. [Preview Abstract] |
Friday, November 1, 2013 2:24PM - 2:36PM |
C1.00003: The Low Mass Luminosity Function in Globular Clusters Claire Dickey We present a novel technique for constraining the full stellar luminosity distribution for globular clusters through the measurement of the fraction of light from resolved stars as a function of the total integrated cluster light. This technique enables the characterization of the full range of the mass distribution of extra-galactic clusters, which will in turn provide a clearer picture of the formation and early evolution of the host galaxy. Our sample consists of six old, metal-poor globular clusters in the Large Magellanic Cloud, imaged with the WFPC2 instrument of the Hubble Space telescope, and we present color-magnitude diagrams down to V $\sim$ 25 mag in addition to the mass and luminosity functions. [Preview Abstract] |
Friday, November 1, 2013 2:36PM - 2:48PM |
C1.00004: The Mid-Infrared RR Lyrae Period-Luminosity Relation Meredith Durbin, Victoria Scowcroft, Wendy Freedman, Barry Madore, Andy Monson, Mark Seibert, Jeff Rich We present new period-luminosity (PL) relations for RR Lyrae variable stars in the globular cluster Omega Centauri in 3.6 and 4.5 microns, derived from time-resolved data from the Spitzer Warm Mission. We will discuss how these relations compare to previous work on RR Lyrae in other wavelengths and clusters, particularly with regards to the metallicity effect on the PL relation; as Omega Centauri contains over 100 RR Lyrae with literature values for metallicities spanning roughly 1.5 dex, it is the ideal cluster in which to study metallicity effects. Theoretical work has predicted no metallicity term in the mid-infrared PL relation, which this data corroborates. [Preview Abstract] |
Friday, November 1, 2013 2:48PM - 3:00PM |
C1.00005: Fluid Oscillations of Neutron and Quark Stars Anashe Bandari, Prashanth Jaikumar Quasi-toroidal modes--or r-modes--are modes of oscillation on a neutron star in which the Coriolis force is the restoring mechanism, and the frequency of the oscillation is proportional to the star's rotational speed. By starting with the Euler equations for fluid dynamics and applying linear perturbations to the pressure and density terms, we obtain a system of equations from which, when we take into account the equation of state of the star, we can solve for the frequencies of these oscillations. We describe these calculations for a neutrally stable star and an incompressible star. We indicate how these calculations will proceed in neutron stars or hybrid stars with quark matter. These results will be used in the study of gravitational waves. [Preview Abstract] |
Friday, November 1, 2013 3:00PM - 3:12PM |
C1.00006: r-modes in Strange Stars with a Crystalline Crust Prashanth Jaikumar The r-mode instability, believed to limit the rotation speed of compact stars, can provide empirical confirmation for the existence of stable deconfined phases of quark matter that are predicted by weak coupling calculations in Quantum Chromodynamics. We construct a model for strange quark stars as heavy as 2 solar masses that are made of superconducting quark matter in the bulk and a thin crystalline quark matter crust. This crystalline quark crust is sufficiently robust to withstand r-mode heating and viscous rubbing for realistic mode amplitudes, unlike a crust made of neutron-rich nuclei. The dissipation provided by viscous rubbing at the core-crust boundary is barely sufficient to obtain stable rotation speeds that are consistent with the majority of rapidly spinning pulsars in low mass X-ray binaries suggesting additional unknown sources of damping. Our analysis implies that while bare strange stars are ruled out by the existence of rapidly spinning pulsars, a strange star with a crust is a distinct possibility. [Preview Abstract] |
Friday, November 1, 2013 3:12PM - 3:24PM |
C1.00007: r-Java: a GUI-based code for nucleosynthesis calculations Joshua Arenson, Prashanth Jaikumar r-Java is an r-process code for open use, that performs r-process nucleosynthesis calculations. Equipped with a simple graphical user interface (GUI), r-Java is capable of carrying out nuclear statistical equilibrium (NSE) as well as static and dynamic r-process calculations for a wide range of input parameters. Recent updates to the code allow us to take into account spontaneous, beta-delayed and n-induced fission rates, as well as fission fragmentation and neutron evaporation. In this talk we present the details behind r-Java, and its capabilities. We can examine high-entropy winds of supernovae, neutron star mergers and decompressing neutron-rich matter as sites for the r-process. The code can run in the waiting-point approximation as well as with a full network, generating the resulting abundance pattern based on a general entropy expression that can be applied to degenerate as well as non-degenerate matter, allowing us to track the rapid density and temperature evolution during fast ejecta expansions. [Preview Abstract] |
Friday, November 1, 2013 3:24PM - 3:36PM |
C1.00008: Multilateration of Cosmic Ray Muons Nathaniel Milgram, R. Cribbs, K. McArdle, R. Morshead Cosmic rays produce showers of muons when they collide with molecules in the upper atmosphere. The incident cosmic ray's direction can be reconstructed from the times of arrival of shower muons at detectors placed on the ground. We developed a simulation and reconstruction algorithm based on standard multilateration techniques using iPython to study the feasibility of building a cosmic air shower array at Cal Poly. An overview of the project and current status of the feasibility study will be presented. [Preview Abstract] |
Friday, November 1, 2013 3:36PM - 3:48PM |
C1.00009: Raspberry Pi Readout of a Cosmic Muon Detector Tristan Paul, Jennifer Klay We have designed a readout system for a scintillator-based cosmic ray detector using inexpensive electronic components and a Raspberry Pi (RPi) microcomputer. The light signal from two scintillator paddles is detected by avalanche photodiodes connected to an amplifier and coincidence circuit that is fed to the input pins of the RPi. The microcomputer's readout rate is more than adequate for the expected event rate. This prototype will be upgraded with a GPS unit and wireless networking to enable remote sensing of cosmic ray arrivals. Plans for deployment of a suite of detectors across campus will be discussed. [Preview Abstract] |
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