Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session S17: Neutrinos, Gamma Rays, and Cosmic Rays, oh my! |
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Sponsoring Units: DAP DPF Chair: Amy Connolly, Ohio State University Room: B234-235 |
Monday, April 16, 2018 1:30PM - 1:42PM |
S17.00001: Multi-messenger and Particle Astrophysics studies with the VERITAS Atmospheric Cherenkov Telescope Reshmi Mukherjee Multi-messenger astronomy is currently an emerging area of study, that employs different cosmic messengers such as neutrinos, photons, cosmic rays, and gravitational waves to obtain complementary information about energetic cosmic sources. With the recent detection of high-energy astrophysical neutrinos by IceCube, and the identification of electromagnetic counterparts to the gravitational waves detected by LIGO and Virgo, multi-messenger astronomy offers promising prospects. VERITAS plays a key role in multi-messenger astrophysics, operating at an opportune moment for making new discoveries. As both gamma-rays and neutrinos are produced in hadronic interactions, a joint study has the potential for revealing powerful cosmic accelerators. VERITAS looks for connections between very-high-energy gamma-rays and astrophysical neutrinos by following up on highly-energetic neutrinos discovered by IceCube. The Observatory is also involved in the follow up of gravitational wave events, as their progenitor sources may also emit gamma rays. VERITAS is an array of ground-based imaging air Cherenkov telescopes located in Arizona. VERITAS continues to provide high-quality gamma-ray observations with excellent sensitivity, operating in the energy range of 85 GeV to 30 TeV. In this talk, we present recent multi-messenger studies with VERITAS and discuss the prospects and goals for the future of the field in the era of the Cherenkov Telescope Array (CTA). [Preview Abstract] |
Monday, April 16, 2018 1:42PM - 1:54PM |
S17.00002: Rise of the Leptons: Pulsar Emission Dominates the TeV Gamma-Ray Sky Tim Linden Recent HAWC observations have found extended TeV emission coincident with the Geminga and Monogem pulsars. In this talk, I will show that these detections have significant implications for our understanding of the TeV gamma-ray sky. First, the spectrum and intensity of these TeV Halos indicates that a large fraction of the pulsar spindown energy is efficiently converted into electron-positron pairs. This provides observational evidence supporting pulsar interpretations of the rising positron fraction observed by PAMELA and AMS-02. Second, the isotropic nature of this emission provides a new avenue for detecting nearby pulsars with radio beams that are not oriented towards Earth. Lastly, I will show that the total emission from all unresolved pulsars produces the majority of the TeV gamma-ray flux observed from the Milky Way, allowing us to set strong constraints on TeV dark matter models. [Preview Abstract] |
Monday, April 16, 2018 1:54PM - 2:06PM |
S17.00003: Constraints on Lorentz-Invariance Violation Using HAWC Observations of the Crab Nebula Samuel Marinelli The High-Altitude Water-Cherenkov (HAWC) experiment is a $\gamma$-ray observatory located in the state of Puebla, Mexico. The detector consists of 300 water-filled tanks, each instrumented with four photomultiplier tubes (PMTs). These PMTs detect Cherenkov light produced by the charged particles found in extensive air showers that occur when cosmic $\gamma$ rays impinge on the Earth's atmosphere. The recent development of a new energy-reconstruction algorithm for HAWC utilizing an artificial neural network has enabled the precise measurement of $\gamma$-ray energies above \unit[100]{TeV} in Monte Carlo simulations. This makes HAWC sensitive to the highest-energy components of the energy spectra of astrophysical sources and in particular to the spectral signature of Lorentz-invariance violation (LIV). LIV models predict that above a certain energy, $\gamma$ decay to $e^+e^-$ is allowed, with a probability approaching 1 for photons propagating over astrophysical distances. Very-high-energy $\gamma$-ray energy spectra should therefore have a hard cutoff at this energy. We will present preliminary results of a search for this phenomenon using HAWC's measurement of the spectrum of the brightest TeV source, the Crab Nebula. [Preview Abstract] |
Monday, April 16, 2018 2:06PM - 2:18PM |
S17.00004: Search for diffuse gamma-ray emission from the Galactic plane with IceCube Hershal Pandya, Zachary Griffith We present a search for diffuse PeV gamma-rays arising from interactions of cosmic rays with the interstellar gas in the Galactic plane. We analyze air shower data recorded by the IceCube Observatory from May 2011 to May 2016 in the energy range of 0.6~PeV to 100~PeV for the presence of gamma-ray showers. Muon poor gamma-ray induced air showers are discriminated from the cosmic ray showers using the characteristics of signals recorded by IceTop as well as the in-ice IceCube array. We carry out an unbinned maximum likelihood analysis on the Galactic plane region ($270^{\circ} \lesssim l \lesssim 335^{\circ}$) located in the IceCube field of view. The pion decay component of the Fermi-LAT diffuse emission model is used as the spatial template for the analysis. No statistically significant evidence for diffuse gamma-ray emission was found. We derive an upper limit of 1.04 $\times$ 10$^{-9}$ GeV cm$^{-2}$ s$^{-1}$ (90\% confidence limit) on the normalization of the spectral energy distribution at 2~PeV assuming an E$^{-3}$ spectrum. [Preview Abstract] |
Monday, April 16, 2018 2:18PM - 2:30PM |
S17.00005: A search for PeV gamma-ray point sources with five years of data from the IceCube Observatory Zachary Griffith, Hershal Pandya We present results of a search for PeV gamma-ray point sources using the IceCube Observatory, presently the most sensitive facility for PeV gamma-ray emission in the southern hemisphere. The surface component of the observatory, IceTop, makes possible the detection of gamma rays, while the in-ice component IceCube provides complementary information for hadronic background suppression. An unbiased scan for point sources was performed over the entire field of view of the analysis. Additionally, known TeV sources with no evidence of a cut-off in their energy spectra were used as a source catalog. Each was tested under a single source hypothesis in addition to a stacking test using the entire catalog. No evidence of signal was found, allowing for the most stringent limits for PeV gamma-ray emission from point sources to be set. [Preview Abstract] |
Monday, April 16, 2018 2:30PM - 2:42PM |
S17.00006: Analysis of Correlations Between Pierre Auger and IceCube IC59 Data George Filippatos The sources of ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory are yet unknown. It is natural to expect that cosmic-ray sources could produce high-energy neutrinos detectable by IceCube. In this work we analyze coincidences between publicly available IceCube data from IC59 and Auger events. A likelihood estimator is constructed from spatial and temporal correlations based on Monte Carlo simulations of the real data. This procedure can be used in a real time search, allowing for any coincidences with sufficiently high likelihood to be followed up with near real time multiwavelength observations. [Preview Abstract] |
Monday, April 16, 2018 2:42PM - 2:54PM |
S17.00007: IceCube Search for Galactic Neutrino Sources using the HAWC 2HWC Catalog Joshua Wood We present prospects for IceCube to detect neutrino emission from Galactic TeV gamma-ray sources outlined in the HAWC Observatory's recently published 2HWC catalog. We do this by evaluating the sensitivity of two analyses using IceCube data. The first is a stacked analysis of promising point sources from the catalog which are chosen based on their high TeV photon fluxes and lack of association with known pulsar wind nebula. Here we assume the highest energy photons originate from the decay of charged pions produced by hadronic interactions at each source. The second is a template analysis using the full Galactic plane morphology measured by HAWC. This morphology should trace neutrino emission if pion decay predominantly occurs in the environment surrounding identified HAWC sources. [Preview Abstract] |
Monday, April 16, 2018 2:54PM - 3:06PM |
S17.00008: Multimessenger TeV Gamma and TeV Neutrino Coincidence Alerts from HAWC and IceCube Hugo Ayala Multimessenger astrophysics is the next step in high-energy astrophysics. The combination of neutrino, cosmic-ray, gamma-ray and gravitational wave observatories is necessary for the understanding of astrophysical phenomena. We will present preliminary results on the generation of real-time ($<6$ hours) TeV gamma-ray and neutrino multimessenger transient alerts. Subthreshold data from the HAWC and IceCube Observatories are transmitted to Penn State via the Astrophysical Multimessenger Observatory Network (AMON). The analysis is based on a likelihood ratio framework, yielding real-time AMON coincidence alerts for HAWC ``hot spots" and IceCube neutrinos. These alerts will be distributed to AMON follow-up partners with a median anticipated delay of six hours from HAWC transit, will have angular resolution of $\sim 0.2^{\circ}$, and will be well-suited for deep electromagnetic follow-up observations. The HAWC and IceCube multimessenger alerts represent one of four real-time electromagnetic and neutrino alert streams that AMON plans to commission by the second half of 2018. [Preview Abstract] |
Monday, April 16, 2018 3:06PM - 3:18PM |
S17.00009: Searching for Counterparts to Cosmic Neutrinos Using the Fermi LAT Satellite Colin Turley, Michael Toomey, Derek Fox, Azadeh Keivani, Gordana Tesic We present the results of an archival coincidence analysis between public gamma-ray data from the Fermi LAT satellite and public neutrino data from the IceCube neutrino observatory during its 40-string and 59-string observing runs. The analysis has the potential to detect either a statistical excess of correlated neutrino + gamma-emitting sources or alternatively, one or more rare, high-multiplicity events such as gamma-ray burst + neutrino coincidences. This work is an example of the multimessenger studies currently being performed by the Astrophysical Multimessenger Observatory Network (AMON). We will present the relevant datasets, the statistical approach, and the results of the analysis. [Preview Abstract] |
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