Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session X4: SNRs, PWNe, Binaries and other Galactic Sources |
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Sponsoring Units: DAP Chair: Sarah Gossan, California Institute of Technology Room: Virginia A |
Tuesday, January 31, 2017 10:45AM - 10:57AM |
X4.00001: The Monster Next Door: Fermi-LAT Observations of Supernova Remnant N132D in the Large Magellanic Cloud Daniel Castro, Elizabeth Hays, Fabio Acero, Patrick Slane, John Hughes, Paul Plucinsky Supernova remnant (SNR) N132D, located in the Large Magellanic Cloud, represents a unique opportunity for the study of $\gamma$-ray emission from shock accelerated cosmic rays (CRs) in another galaxy since it stands as the first and only extra-Galactic SNR detected in $\gamma$-rays. N132D is bright in the X-ray, infrared and radio bands, as well as being detected in TeV energy $\gamma$-rays, and hence, characterizing its emission in the Fermi-LAT band allows us to build a very complete picture of the properties of the system and its progenitor, and help us understand CR acceleration in SNRs. [Preview Abstract] |
Tuesday, January 31, 2017 10:57AM - 11:09AM |
X4.00002: Investigating very extended objects with HAWC: from Molecular Clouds to Fermi Bubbles Hugo Ayala, Matthew Coel, Petra Hüntemeyer, Sabrina Casanova The observation of large gamma-ray emission structures is useful for tracing the propagation and distribution of cosmic rays throughout our Galaxy. For example, the search for gamma-ray emission from Giant Molecular Clouds may allow us to probe the flux of cosmic rays in distant galactic regions and compare it with the flux measured at Earth. Also, by observing at the gamma-ray signal, the composition of the cosmic rays can be measured by studying the emission from hadronic or leptonic processes. In the case of emission from the Fermi Bubbles specifically , constraining the mechanism of gamma-ray production can point to their origin. The High Altitude Water Cherenkov (HAWC) Observatory is located at 4100m above sea level in Mexico. It is designed to measure high-energy gamma rays between 300GeV to 100TeV. HAWC possesses a large field of view and good sensitivity to spatially extended sources, which currently makes it the best suited ground-based observatory to detect extended regions. [Preview Abstract] |
Tuesday, January 31, 2017 11:09AM - 11:21AM |
X4.00003: TeV Gamma Ray Emission from Nearby Pulsar Wind Nebulae with HAWC Hao Zhou, Francisco Salesa Greus, Rubén López-Coto, Segev BenZvi, Sabrina Casanova Pulsar wind nebulae are considered efficient electron/positron accelerators in our Galaxy. It has been suggested that particles accelerated by nearby pulsar wind nebulae, such as Geminga, would possibly account for the observed multi-GeV positron excess. The Geminga pulsar is one of the closest middle-aged pulsars and its pulsations were first discovered in X-rays. Milagro reported an extended TeV source spatially coincident with the Geminga pulsar, but IACT observations using standard analysis techniques have only provided upper limits. The High Altitude Water Cherenkov (HAWC) Observatory, located in central Mexico at 4100 m above sea level, is sensitive to gamma rays between 100 GeV and 100 TeV. With a field of view of 2 steradians, HAWC has a good sensitivity to extended sources such as pulsar wind nebulae. Early data collected with HAWC reveals an extended source coincident with the Geminga pulsar, similar to what Milagro has reported. We will present results of spectral and morphological analyses on extended TeV gamma-ray emission from Geminga and other nearby pulsar wind nebulae with HAWC data. The interpretation of whether positrons from nearby pulsar wind nebulae can explain the observed positron excess will be discussed as well. [Preview Abstract] |
Tuesday, January 31, 2017 11:21AM - 11:33AM |
X4.00004: The Measurement of the Flux and Spectrum of the Crab by HAWC Andrew Smith The HAWC observatory was completed and began full operation in early 2015. Located at an elevation of 4100m, HAWC has an energy threshold for gamma-ray detection well below 1 TeV and a sensitivity to TeV-scale gamma-ray sources an order of magnitude better than previous air-shower arrays. The detector operates 24 hours/day and observes the overhead sky (~2 sr), making it an ideal survey instrument. We describe the details of the high significance detection (>100 sigma) of the Crab PWN and explain in detail the measurement the VHE spectrum of this important gamma-ray source. At the high end of the VHE range, above 10 TeV, HAWC’s sensitivity is better than that of IACTs due mainly to its large effective area and unprecedented exposure. Measuring the high energy behavior of this source is critical to the understanding of the acceleration dynamics and the environment in vicinity of the pulsar. Furthermore, as the Crab is bright, point-like and steady, as detected by VHE gamma-ray instruments, it serves as the best source for verification of detector performance and measurement of systematic errors. This presentation will also describe in detail the analysis methodology utilized by a number of presentations from the HAWC collaboration. [Preview Abstract] |
Tuesday, January 31, 2017 11:33AM - 11:45AM |
X4.00005: HAWC Analysis of the Crab Nebula Using Neural-Net Energy Reconstruction Samuel Marinelli The HAWC (High-Altitude Water-Cherenkov) experiment is a TeV $\gamma$-ray observatory located 4100 m above sea level on the Sierra Negra mountain in Puebla, Mexico. The detector consists of 300 water-filled tanks, each instrumented with 4 photomuliplier tubes that utilize the water-Cherenkov technique to detect atmospheric air showers produced by cosmic $\gamma$ rays. Construction of HAWC was completed in March, 2015. The experiment's wide field of view (2 sr) and high duty cycle ($> 95\%$) make it a powerful survey instrument sensitive to pulsar wind nebulae, supernova remnants, active galactic nuclei, and other $\gamma$-ray sources. The mechanisms of particle acceleration at these sources can be studied by analyzing their energy spectra. To this end, we have developed an event-by-event energy-reconstruction algorithm employing an artificial neural network to estimate energies of primary $\gamma$ rays. The Crab Nebula, the brightest source of TeV photons, makes an excellent calibration source for this technique. We will present preliminary results from an analysis of the Crab energy spectrum using this new energy-reconstruction method. [Preview Abstract] |
Tuesday, January 31, 2017 11:45AM - 11:57AM |
X4.00006: Analysis on TeV Gamma-ray Binary Systems and Candidates in the Northern Hemisphere with HAWC Chang Dong Rho Binary systems, which emit high-energy radiation, are natural testbeds for studying astrophysical particle acceleration and the production of Galactic cosmic rays. The emitted radiation may be modulated in time by the orbital period of the system, or may occur in very strong and unpredictable flares. However, while hundreds of binary systems have been observed in X-rays and radio, only a handful has been detected through TeV gamma rays. The High Altitude Water Cherenkov (HAWC) Observatory is a wide-field and high-uptime detector of TeV gamma rays that is particularly well suited to observe transient systems such as TeV binaries. Preliminary measurements of the 3 known TeV binary systems and 28 TeV binary candidates in the Northern Hemisphere were analyzed with HAWC at $>$ 1 TeV using 17 months of data. HAWC does not decisively observe any significant traces of the 31 systems / candidates yet. However, 95\% upper limits were successfully assembled for the candidates with significance below 2 sigma. [Preview Abstract] |
Tuesday, January 31, 2017 11:57AM - 12:09PM |
X4.00007: Stacking Analysis of Binary Systems with HAWC Chad Brisbois Detecting binary systems at TeV energies is an important problem because only a handful of such systems are currently known. The nature of such systems is typically thought to be composed of a compact object and a massive star. The TeV emission from these systems does not obviously correspond to emission in GeV or X-ray, where many binary systems have previously been found. This study focuses on a stacking method to detect TeV emission from LS 5039, a known TeV binary, to test its efficacy in HAWC data. Stacking is a widely employed method for increasing signal to noise ratio in optical astronomy, but has never been attempted previously with HAWC. HAWC is an ideal instrument to search for TeV binaries, because of its wide field of view and high uptime. Applying this method to the entire sky may allow HAWC to detect binary sources of very short or very long periods not sensitive to current analyses. [Preview Abstract] |
Tuesday, January 31, 2017 12:09PM - 12:21PM |
X4.00008: The gamma-ray sky above 50 TeV with the HAWC Observatory Kelly Malone High-energy observations of gamma-ray sources are important probes of cosmic-ray accelerators. The High Altitude Water Cherenkov (HAWC) Observatory, located at an altitude of 4100m in the state of Puebla, Mexico, is designed to study TeV gamma rays from air showers. Each of the 300 water Cherenkov tanks contains 4 PMTs; the entire array covers ~22,000 m$^{2}$. Due to its large instantaneous field of view ($\sim$2 sr) and high duty cycle ($>$95$\%$), it is well-suited to perform surveys of the entire overhead sky. This includes transient, extended, and diffuse searches. I will present maps of the gamma-ray sky above 50 TeV as seen by HAWC. Observations in this energy range are essential in distinguishing between different particle acceleration models. [Preview Abstract] |
Tuesday, January 31, 2017 12:21PM - 12:33PM |
X4.00009: HAWC 1st year catalog Colas Rivière The High Altitude Water Cherenkov (HAWC) Observatory was inaugurated in March 2015. With its high duty cycle and wide field of view, it observes 2/3 of the TeV sky daily. After a single year of observation, the integral sensitivity already exceeds that of the previous generation of wide field instruments by a factor of five. We will present the results of the first all sky search with a year of data of the complete HAWC detector. Some known sources as well as new TeV point and extended sources will be highlighted. [Preview Abstract] |
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