Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session J7: Gamma Rays and Neutrinos in the Galaxy |
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Sponsoring Units: DAP Chair: Julie McEnery, NASA Goddard Space Flight Center Room: Embassy D |
Sunday, April 1, 2012 1:30PM - 1:42PM |
J7.00001: Milagro Observations of Potential TeV Emitters Anushka Abeysekara, James Linnemann We searched for point sources in Milagro sky maps at the locations in four catalogs of potential TeV emitting sources. Our candidates are selected from the Fermi 2FGL pulsars, Fermi 2FGL extragalactic sources, TeVCat extragalactic sources, and from the BL Lac TeV Candidate list published by Costamante and Ghisellini in 2002. The False Discovery Rate (FDR) statistical procedure is used to select the sources. The FDR procedure controls the fraction of false detections. Our results are presented in this talk. [Preview Abstract] |
Sunday, April 1, 2012 1:42PM - 1:54PM |
J7.00002: Very High Energy Observations of the Supernova Remnant CTA1 with VERITAS Reshmi Mukherjee VERITAS (Very Energetic Radiation Imaging Telescope Array System) is an atmospheric Cherenkov telescope, located in Southern Arizona, providing sensitive measurements of gamma-ray sources sources in the 100 GeV to 50 TeV energy range. Galactic sources detected by VERITAS include supernova remnants, pulsar wind nebulae, a pulsar, and binary systems, and TeV emission is a key diagnostic of highly energetic particles in these objects. In this talk I will present recent results from VERITAS on Galactic sources, in particular the discovery of VHE gamma rays from the SNR CTA1. [Preview Abstract] |
Sunday, April 1, 2012 1:54PM - 2:06PM |
J7.00003: The Crab Nebula as a Standard Candle for TeV gamma-ray astronomy Trevor Weekes Since its discovery as a TeV gamma-ray source (Weekes et al., (1989) ApJ,342, 379), the Crab Nebula has been routinely observed with the Whipple 10m gamma-ray telescope in order to calibrate observations on other variable TeV sources. The assumption that the Crab can be regarded as a standard candle has been called in question by recent reports from the AGILE and Fermi groups (Tavani et al. (2010), Science, doi:10.1126/science.1200083; Abdo et al.(2011), 1011-3855, astro-ph.HE) of GeV flaring activity lasting one-two weeks on several occasions. The Whipple observations were taken nightly during the dark moon periods from October through March since 1986. The search for flares of one-two week duration in this rich data archive will be reported. [Preview Abstract] |
Sunday, April 1, 2012 2:06PM - 2:18PM |
J7.00004: Fermi LAT observations of the Crab Nebula during the exceptional April 2011 outburst Elizabeth Hays The Crab Nebula, formerly thought to be steady in gamma rays, shows unexpected and occasionally dramatic variability in high-energy gamma rays. The Large Area Telescope (LAT) on Fermi recorded several strong outbursts, including dedicated pointed observations of the brightest yet seen, a spectacular flare in April 2011. These observations provide a particularly detailed look at the temporal and spectral characteristics of the nebula during the flare. The LAT data show an additional component in the spectral energy distribution that peaks at a maximum of $375\pm26~\mathrm{MeV}$. In the probable scenario that this component is synchrotron emission, the electrons are accelerated to extreme energies that are difficult to reconcile with the very rapid change in flux and the expectation for acceleration processes and conditions occurring within the pulsar wind nebula. The physical location and mechanism driving the flares remains undetermined despite observations across the spectrum made by a variety of instruments including the Hubble Space Telescope, the Chandra X-ray Observatory, and the Very Large Array. I will present timing and spectral studies of the high-energy gamma-ray data, discuss implications for the origin of the flares, and highlight preparations for the next major flare. [Preview Abstract] |
Sunday, April 1, 2012 2:18PM - 2:30PM |
J7.00005: Detection of the Crab pulsar above 100 GeV A. Nepomuk Otte It has been long thought that gamma-ray emission from pulsars cuts off sharply above a few GeV and that no emission would be observable above 100 GeV. With the VERITAS array of four imaging atmospheric Cherenkov telescopes we conducted a deep observation of the Crab pulsar and detected significant pulsed emission above 100 GeV. We discuss the detection and put it into context with present theoretical interpretation. [Preview Abstract] |
Sunday, April 1, 2012 2:30PM - 2:42PM |
J7.00006: An engineering array for the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory Megan Longo, Miguel Mostafa The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is currently being deployed at 4100 m in Sierra Negra, Mexico. The HAWC observatory will have 300 Water Cherenkov Detectors (WCDs). Each WCD will be instrumented with 4 upward facing baffled photo multiplier tubes (PMTs) anchored to the bottom of a 5 m deep by 7.3 m diameter steel container with a multilayer hermetic plastic bag containing 200,000 liters of purified water. An engineering array of 6 WCDs was deployed in Summer 2011 at the HAWC site and has been operational since then. This array serves to validate the design and construction methods for the HAWC observatory. It has also been collecting data which allows for the development of data collection and analysis tools. Here we will describe the deployment of the engineering array, the lessons learned from this experience and the implications for HAWC, as well as give an introduction into data collection and initial analysis being done, which will be presented jointly. [Preview Abstract] |
Sunday, April 1, 2012 2:42PM - 2:54PM |
J7.00007: FPGA based trigger system for the HAWC experiment Ian Wisher, Michael DuVernois, Jakob De Maeyer A flexible and general-purpose trigger design, developed for the HAWC gamma ray observatory PMT signals, consists of a number of multiplicity triggers that allow it to recognize cosmic ray showers with different event angles and energies. The trigger system also includes a number of features that help to ensure: if errors occur they are recognized and reported. Although this trigger system was designed specifically for the HAWC gamma ray observatory PMT signals, its features can be easily transferred to other projects. [Preview Abstract] |
Sunday, April 1, 2012 2:54PM - 3:06PM |
J7.00008: High Energy Neutrinos from the Fermi Bubbles Soebur Razzaque, Cecilia Lunardini Recent discovery of two gamma-ray emitting bubble-shaped structures (Fermi Bubbles) at the Galactic center opens up a possibility to detect high-energy neutrinos from them as well, if the observed gamma rays have hadronic origin. This new predicted Galactic neutrino flux is hard, following gamma-ray data, compared to the atmospheric neutrino flux and can be detected with a kilometer scale neutrino telescope in the northern hemisphere, such as the planned KM3NeT, above 20-50 TeV. IceCube Neutrino Observatory at the South pole can also provide interesting constraints on the flux model. A detection or exclusion of this neutrino flux can discriminate between a leptonic or hadronic origin of the gamma-rays, as well as bring unique information on the activities at the Galactic center. [Preview Abstract] |
Sunday, April 1, 2012 3:06PM - 3:18PM |
J7.00009: Neutrino Oscillations Above A Black Hole Accretion Disk Annelise Malkus, Gail McLaughlin, James Kneller, Rebecca Surman Black hole accretion disks can occur in certain core collapse supernovae as well as in the mergers of compact objects. This environment produces a strong flux of electron neutrinos and electron antineutrinos. These neutrinos are instrumental in determining the type of elements produced in disk outflows. In the context of this scenario, using the single angle approximation and a constant temperature disk, we report on calculations of neutrino flavor transformation driven by neutrino self interactions. We comment on the impact on element synthesis. [Preview Abstract] |
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