Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session S13: MeV-GeV Gamma Rays and Cosmic RaysRecordings Available
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Sponsoring Units: DAP Chair: Jose Maria Ezquiaga, University of Chicago Room: Empire |
Monday, April 11, 2022 1:30PM - 1:42PM |
S13.00001: SuperTIGER Measurements Through 56Ba and Their Implications Brian F Rauch, Wolfgang Zober, Richard Bose, W R Binns, P. F Dowkontt, Martin H Israel, Ryan P Murphy, Jason T Link, Nathan E Walsh, John E Ward, Mark E Wiedenbeck, C. J Waddington, Edward C Stone, Makoto Sasaki, Kenichi Sakai, John W W Mitchell, Richard A Mewaldt, Thomas Hams, Theresa J Brandt, Allan W Labrador, Scott Nutter, John F Krizmanic, Georgia A de Nolfo, Nicholas W Cannady SuperTIGER (Super Trans-Iron Galactic Element Recorder) is a long-duration-balloon-borne cosmic-ray detector that had a 55-day record breaking Antarctic flight during the 2012-2013 austral summer and a 32-day one in 2019-2020. The first flight measured the relative abundances of Galactic cosmic-ray (GCR) nuclei with high statistical precision and well resolved individual element peaks from 10Ne to 40Zr, and preliminary lower-statistics measurements out to 56Ba. The measurements through 40Zr support an OB association model source where refractory elements are preferentially injected into the supernovae-shock accelerator over volatile ones superposed on a sputtering cross-section Z dependence. However, the preliminary GCR measurements above 40Zr are inconsistent with this model, requiring a modification to the injection mechanism and/or another GCR source component. Recent multi-messenger observations have established kilonovae as one of the sites of r-process nucleosynthesis, suggesting that a mixture of NS-NS mergers, other core-collapse events and supernovae may contribute significantly to the heavy r-process budget of the universe. We report the status of SuperTIGER and progress in refining the interesting GCR results above 40Zr and note that future heavy cosmic-ray abundance measurements in the Milky Way may be able to further constrain sites of r-process nucleosynthesis. |
Monday, April 11, 2022 1:42PM - 1:54PM |
S13.00002: Indications of a Cosmic Ray Source in the Perseus-Pisces Supercluster Jihyun Kim, Gordon B Thomson, Dmitri Ivanov The Telescope Array experiment is the largest observatory studying ultrahigh energy cosmic rays in the northern hemisphere. In this talk, we report a newly found excess of events on the sky with energies, E ≥ 1019.4 eV. The local significance of the excess is calculated to be about 4 standard deviations by using the Li-Ma oversampling method with a 20°-radius circle. The excess appears in the region of the Perseus-Pisces supercluster (PPSC). This is the closest supercluster within the TA’s field of view other than the local supercluster of which we are a part. In addition, the major portion of the foreground between the Earth and the PPSC as well as the space beyond the PPSC in the same direction, are nearly empty. This motivates us to conduct a Monte-Carlo study to estimate the probability that an excess of events can occur close to the PPSC by chance. The chance probability of having an excess close to the PPSC is estimated to be 3.5 standard deviations. The result indicates a cosmic ray source likely exists in the PPSC. |
Monday, April 11, 2022 1:54PM - 2:06PM |
S13.00003: Update on the Search for Microquasar Signatures in SuperTIGER Flight Data Allan W Labrador, W R Binns, Richard Bose, Theresa J Brandt, P. F Dowkontt, Thomas Hams, Martin H Israel, Jason Link, Richard A Mewaldt, John W W Mitchell, Ryan P Murphy, Brian F Rauch, Kenichi Sakai, Makoto Sasaki, Edward C Stone, C. J Waddington, Nathan E Walsh, J. E Ward, Mark E Wiedenbeck, Wolfgang Zober SuperTIGER (Trans-Iron Galactic Element Recorder) is a large-area, balloon-borne cosmic ray experiment designed to measure the galactic cosmic ray abundances of elements from Z=10 (Ne) to Z=56 (Ba) at energies from ~0.8 GeV/nuc to ~10 GeV/nuc. SuperTIGER flew for a record 55 days over Antarctica in 2012-2013 and for a second flight of over 32 days in 2019-2020. Heinz and Sunyaev (202) suggested that microquasar jets may be observable as near monoenergetic peaks in heavy ion spectra at GeV/nuc energies. The large area and long exposure times of SuperTIGER make it an instrument well-suited for looking for such signatures. In this presentation, we will provide an update to the SuperTIGER search for microquasar signatures in Fe and Si spectra, using our latest energy calibrations from our most recent comparison of flight data and simulations. We will discuss in detail the sensitivity of the instrument for such a search with respect to both the calibrated energy resolution as well as the absolute spectral intensities, for both the full 2012-2013 flight as well as for shorter time subsets. We will also address the microquasar signature search in the 2019-2020 flight. |
Monday, April 11, 2022 2:06PM - 2:18PM |
S13.00004: The anisotropy of the Fermi-LAT extragalactic sky: still blazars. Michela Negro, Michael Korsmeier, Elena Pinetti, Marco Regis, Nicolao Fornengo We analyze the angular power spectrum (APS) of the unresolved gamma-ray background (UGRB) emission, and combine it with the measured properties of the resolved gamma-ray sources of the Fermi-LAT 4FGL catalog. Our goal is to dissect the composition of the gamma-ray sky and establish the relevance of different classes of source populations in determining the observed UGRB anisotropy level, especially at low energies. We find that, under physical assumptions for the spectral energy dispersion, two populations are required to fit APS data, namely flat spectrum radio quasars (FSRQ) at low energies and BL Lacs (BLL) at high energies. The inferred luminosity functions agree well with the extrapolation of the FSRQ and BLL ones obtained from the 4FLG catalog. Bounds on an additional gamma-ray emission due to annihilating dark matter are also derived. |
Monday, April 11, 2022 2:18PM - 2:30PM |
S13.00005: Ex Luna, Scientia: The Lunar Occultation eXplorer (LOX) and the Future of MeV γ-Ray Astrophysics Richard S Miller, Marco Ajello, Katie Auchettl, John F Beacom, Peter F Bloser, Adam S Burrows, Anna Frebel, Chris Fryer, Dieter Hartmann, Peter Hoeflich, Aimee Hungerford, Mark D Leising, Laura Lopez, Peter Milne, Patrick N Peplowski, Friedrich Roepke, Daniel Scolnic, Ivo Seitenzahl, Lih-Sin The, C. Alex Young The Lunar Occultation eXplorer (LOX) will perform the first systematic population studies of thermonuclear supernova (type-Ia, SNeIa) using their emergent nuclear radiation. LOX will probe the fundamental nuclear processes that govern these "beacons of the Cosmos" by characterizing the temporal and spectral evolution of their emergent gamma-rays throughout pre-, peak, and post-explosion epochs. LOX measurements of the radioactivity left behind in the wake of nuclear burning will reveal characteristic trends via population studies that individual detections cannot, further our understanding of the matter–energy life cycles within galaxies, and provide critical diagnostic evidence for the multiple evolutionary pathways responsible for SNeIa. LOX will directly test the assumption of SNeIa homogeneity by quantifying the diversity of thermonuclear scenarios and progenitors. To achieve these goals LOX performance fills a long-standing astrophysical capability gap at MeV energies, including the scientific priority for space-based time-domain multi-messenger capabilities. The LOX mission implementation approach mitigates the challenges associated with increasingly complex space-based instrumentation. Science goals are achieved with a simple, low-cost, cross-cutting implementation based on the Lunar Occultation Technique (LOT); implementation and operational simplicity are its hallmarks. LOX leverages the benign, well-characterized lunar environment to achieve transformational performance, and employs a single-instrument payload consisting of an array of identical gamma-ray sensor modules that leverage decades of heritage derived from planetary exploration endeavors. LOX is under review as part of NASA's astrophysics MIDEX program, has significant potential for discovery, will further establish the Moon as a platform for science, and once again pry open a new window on the Cosmos. |
Monday, April 11, 2022 2:30PM - 2:42PM |
S13.00006: Surveying the MeV gamma-ray sky with AMEGO-X Henrike Fleischhack Recent detections of gravitational wave signals and neutrinos from gamma-ray sources have ushered in the era of multi-messenger astronomy, while highlighting the importance of gamma-ray observations for this emerging field. AMEGO-X, the All-sky Medium Energy Gamma-Ray Observatory eXplorer, is an MeV gamma-ray instrument proposed to the 2021 call for medium-sized explorer mission. AMEGO-X will survey the sky in the energy range from 100 keV to 1 GeV with unprecedented sensitivity and detect and localize transient events such as gamma-ray bursts and magnetar activity down to 25 keV. AMEGO-X will detect gamma-ray photons both via Compton interactions and pair production processes, bridging the "sensitivity gap" between hard X-rays and high-energy gamma rays. AMEGO-X will provide important contributions to multi-messenger science and time-domain gamma-ray astronomy, studying e.g. high-redshift blazars, which are probable sources of astrophysical neutrinos, and gamma-ray bursts. I will present an overview of the instrument and anticipated science program. |
Monday, April 11, 2022 2:42PM - 2:54PM |
S13.00007: AstroPix: ATLAS-Inspired Silicon Pixels for Future Space-Based Gamma-ray Telescopes Amanda Steinhebel, Isabella Brewer, Michela Negro, Nicolas Striebig, Carolyn Kierans, Regina M Caputo, Richard Leys, Ivan Peric, Henrike Fleischhack, Jessica E Metcalfe, Jeremy S Perkins Space-based gamma-ray telescopes such as the Fermi Large Area Telescope have used single sided silicon strip detectors to measure the position of incident gamma-rays with high resolution. At lower energies, two dimensional position information within a single detector is required. This talk investigates the use of monolithic CMOS active pixel silicon sensors – AstroPix – as a novel technology for use in future gamma-ray telescopes. Based upon detectors designed for use in the ATLAS detector at the LHC, AstroPix has the potential to maintain the high energy and angular resolution required of a medium-energy gamma-ray telescope while reducing noise with the dual detection and readout capabilities of a CMOS chip. The status of AstroPix development and testing, as well as outlook for application in future telescopes such as the proposed medium-energy gamma-ray telescope AMEGO-X, will be presented. |
Monday, April 11, 2022 2:54PM - 3:06PM |
S13.00008: Multiwavelength variability of flaring gamma-ray blazars: Lessons learned. Janeth Valverde Blazars are variable sources on a wide range of timescales at all wavelengths. Their classification (into flat spectrum radio quasars, low-, intermediate- or high-frequency-peaked BL Lac objects; FSRQs, LBL, IBL, HBL) is based on broadband spectral characteristics that do not consider the source being at, possibly, different states of activity. |
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