Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session J08: Advances in Gamma-ray Observatories |
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Sponsoring Units: DAP Chair: Daniel Grin, Haverford College Room: Sheraton Governor's Square 10 |
Sunday, April 14, 2019 1:30PM - 1:42PM |
J08.00001: Cryocooler Systems for Improved GeD Gamma-ray Imaging and Spectroscopy T. J. Brandt, S. Banks, S. E. Boggs, C. A. Kierans, J. Ku, S. McBride, B. Mochizuki, O. Quinones, J. Roberts, A. Shih, C. Sleator, J. A. Tomsick Placing germanium detectors (GeDs) in an MeV γ-ray Compton instrument on 100+day balloon and satellite platforms will enable unprecedented insight into nuclear line astrophysics, key multimessenger synergies, and new heliophysics applications. Compton telescopes with position-sensitive GeDs have excellent energy resolution, improved by two orders of magnitude compared to previous instruments, and are inherently sensitive to polarization. The Compton Spectrometer and Imager (COSI) 2016 balloon flight demonstrated the promise of this technology to realize key science goals. |
Sunday, April 14, 2019 1:42PM - 1:54PM |
J08.00002: Augmentation of VERITAS Telescopes for Stellar Intensity Interferometry David B Kieda, Nolan K Matthews, Andrew E Flinders, Rylee A Cardon The VERITAS gamma-ray Observatory, consisting of four 12-m diameter Imaging Air Cherenkov Telescopes, is being augmented with high-speed (250 MS/s) streaming and continuous photon counting capabilities to create a modern implementation of a Hanbury-Brown and Twiss optical interferometer. The VERITAS-Stellar Intensity Interferometer (SII) samples the Fourier image plane at 420 nm with greater than 100 m baselines, potentially enabling sub-milliarcsecond resolution imaging of nearby stars at visible wavelengths. This talk describes the instrumentation of VERITAS-SII, its potential imaging capabilities, and its commissioning and observation plan for 2018-2019. |
Sunday, April 14, 2019 1:54PM - 2:06PM |
J08.00003: First astrophysical results with the VERITAS Stellar Intensity Interferometer Nolan K Matthews, Andy Flinders, Rylee A Cardon, Stephan LeBohec, David B Kieda A digital implementation of a stellar intensity interferometry (SII) system onto imaging air-Cherenkov telescopes has long been foreseen as a way to perform long baseline optical interferometry for stars generally of the O/B/A stellar types. Since October 2018, SII observations have been ongoing during bright moon conditions using the VERITAS observatory, located in Amado, AZ. In this presentation, the first results, using observations with two of the VERITAS telescopes of Kappa Orion (Saiph), are reported. Observations and analysis are ongoing, and additionally the system is being extended to the two other telescopes in the VERITAS array, to soon enable 4-telescope SII observations. |
Sunday, April 14, 2019 2:06PM - 2:18PM |
J08.00004: All-sky Medium Energy Gamma-ray Observatory (AMEGO) - A Discovery Mission for the MeV Band Judith L Racusin The MeV domain is one of the most under-explored windows on the Universe. From astrophysical jets and extreme physics of compact objects to a large population of unidentified objects, fundamental astrophysics questions can be addressed by a mission that opens a window into the MeV range. AMEGO is a wide-field gamma-ray telescope with sensitivity from ~200 keV to >10 GeV. AMEGO provides three new capabilities in MeV astrophysics: sensitive continuum spectral studies, polarization measurements, and nuclear line spectroscopy. AMEGO will be an especially powerful resource for multi-messenger astrophysics in the next decade. AMEGO will consist of four hardware subsystems: a double-sided silicon strip tracker with analog readout, a segmented CZT calorimeter, a segmented CsI calorimeter and a plastic scintillator anti-coincidence detector, and will operate primarily in an all-sky survey mode. In this presentation we will describe the AMEGO mission concept and scientific overview. |
Sunday, April 14, 2019 2:18PM - 2:30PM |
J08.00005: Status of the All-sky Medium Energy Gamma-ray Observatory Prototype Sean Griffin The study of gamma rays from a few hundred keV to hundreds of MeV is challenging due to high gamma-ray backgrounds, multiple scattering within the detector, and the fact that there are two competing interactions in this regime, Compton scattering and pair production, with cross-sections which crossover at ~15 MeV. As such, this regime, known as the MeV gap, has been largely unexplored since the pioneering measurements made by COMPTEL aboard CGRO (1991-2000). The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a NASA Probe-class mission concept designed to operate at energies from ~200 keV to > 10 GeV. AMEGO comprises four subsystems: a silicon tracker for measuring the energy and track of Compton recoil electrons and electron/positron pairs, a CZT calorimeter for measuring the energy and interaction location of Compton scattered photons, a CsI calorimeter for measuring the energy of the electron/positron pair-production products at high energies, and an anticoincidence detector for rejecting cosmic-ray events. Prototypes of the subsystems are under development at the NASA Goddard Space Flight Center and the Naval Research Laboratory; in this contribution we provide details on the development of the various subsystems in preparation for beam tests and a balloon flight. |
Sunday, April 14, 2019 2:30PM - 2:42PM |
J08.00006: AMEGO: Simulations of the Instrument Performance Regina M Caputo, Carolyn Kierans, Judith L Racusin, Fabian Kislat The gamma-ray energy range from several hundred keV to a hundred MeV has remained largely unexplored since the observations by instruments on the Compton Gamma-Ray Observatory (1991- 2000) and on INTEGRAL (since 2002). This energy range is particularly challenging because it is firmly in the Compton-dominated regime where the interaction cross section is minimized. Accurate measurements are critical for answering a broad range of astrophysical questions. To address these questions, we are developing AMEGO: All-sky Medium Energy Gamma-ray Observatory, to investigate the energy range from 200 keV to >10 GeV with good energy and angular resolution and with sensitivity approaching a factor of 20-50 better than previous measurements. This instrument will be capable of measuring both Compton-scattering events at lower energies and pair-production events at higher energies. To achieve these ambitions goals Monte Carlo (MC) simulations will play a crucial role guiding the design of AMEGO. I will present an overview of the AMEGO simulation campaign using the MEGAlib framework, as well as the initial results for effective area and angular resolution, as well as sensitivity projections. |
Sunday, April 14, 2019 2:42PM - 2:54PM |
J08.00007: Diffuse gamma-ray line astronomy with AMEGO Carolyn Kierans, Andreas Zoglauer, Chris Fryer, Dieter Hartmann, Christopher Shrader Gamma-ray line astronomy began in the 1970s, but the field is still in its infancy. The signature of positron annihilation at 511 keV was the first gamma-ray line to be detected as originating outside of our solar system. After 40 years of observations, the Galactic sources of positrons are still unconfirmed and this remains one of the pioneering topics in gamma-ray astronomy. The next gamma-ray line to be detected was 1.8 MeV emission from the radioactive decay of Al-26, which was confirmation of active nucleosynthesis in our Galaxy. Nuclear emission lines from isotopes created in massive stars and their supernovae allow for fingerprint-like probes into stellar structure and evolution, a tool which has yet to be fully realized. The All-sky Medium Energy Gamma-ray Observatory (AMEGO), is an Astrophysics Probe concept design that can make significant progress in our understanding of cosmic nucleosynthesis and the source of Galactic positrons. AMEGO will have a wide field-of-view, good spectral resolution, and sensitivity 1-2 orders of magnitude better than previous telescopes. In this presentation we will focus on the topics that can be addressed with long-lived stellar nucleosynthesis products and discuss the intriguing open questions associated with Galactic positrons. |
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