MAGIC Contributions to the 35th International Cosmic Ray Conference (ICRC2017) [HEAP]

MAGIC (Major Atmospheric Gamma Imaging Cherenkov) is a system of two 17 m diameter, F/1.03 Imaging Atmospheric Cherenkov Telescopes (IACT). They are dedicated to the observation of gamma rays from galactic and extragalactic sources in the very high energy range (VHE, 30 GeV to 100 TeV).
This submission contains links to the proceedings for the 35th International Cosmic Ray Conference (ICRC2017), held in Bexco, Busan, Korea from the 12th to the 17th of July, 2017. Links will appear in the following weeks as long as the proceedings are uploaded in the arXiv.

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MAGIC. Collaboration, M. Ahnen, S. Ansoldi, et. al.
Fri, 18 Aug 17

Comments: HTML page with links (to be filled and updated in the following weeks)

The Giant Radio Array for Neutrino Detection (GRAND): Present and Perspectives [IMA]

The Giant Radio Array for Neutrino Detection (GRAND) aims at detecting ultra-high energy extraterrestrial neutrinos via the extensive air showers induced by the decay of tau leptons created in the interaction of neutrinos under the Earth’s surface. Consisting of an array of $\sim10^5$ radio antennas deployed over $\sim 2\times10^5\,\rm {km}^2$, GRAND plans to reach, for the first time, an all-flavor sensitivity of $\sim1.5\times10^{-10} \,\rm GeV\, cm^{-2} \,s^{-1}\, sr^{-1}$ above $5\times10^{17}$ eV and a sub-degree angular resolution, beyond the reach of other planned detectors. We describe here preliminary designs and simulation results, plans for the ongoing, staged approach to the construction of GRAND, and the rich research program made possible by GRAND’s design sensitivity and angular resolution.

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K. Fang, J. Alvarez-Muniz, R. Batista, et. al.
Fri, 18 Aug 17

Comments: Proceedings of the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea

An Inventory of Bispectrum Estimators for Redshift Space Distortions [CEA]

In order to best improve constraints on cosmological parameters and on models of modified gravity using current and future galaxy surveys it is necessary maximally exploit the available data. As redshift-space distortions mean statistical translation invariance is broken for galaxy observations, this will require measurement of the monopole, quadrupole and hexadecapole of not just the galaxy power spectrum, but also the galaxy bispectrum. A recent (2015) paper by Scoccimarro demonstrated how the standard bispectrum estimator may be expressed in terms of Fast Fourier Transforms (FFTs) to afford an extremely efficient algorithm, allowing the bispectrum multipoles on all scales and triangle shapes to be measured in comparable time to those of the power spectrum. In this paper we present a suite of alternative proxies to measure the three-point correlation multipoles. In particular, we describe a modal (or plane wave) decomposition to capture the information in each multipole in a series of basis coefficients, and also describe three compressed estimators formed using the skew-spectrum, the line correlation function and the integrated bispectrum, respectively. As well as each of the estimators offering a different measurement channel, and thereby a robustness check, it is expected that some (especially the modal estimator) will offer a vast data compression, and so a much reduced covariance matrix. This compression may be vital to reduce the computational load involved in extracting the available three-point information.

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D. Regan
Fri, 18 Aug 17

Comments: 14 pages

Improved calibration process for the WCDs of the LAGO project using semi-analytic model [IMA]

Direct measurements of VEM using scintillating plastic plates in water Cherenkov prototype detectors and a muon flux model were previously used to reproduce the charge histogram of a detector. In these measurements the VEM has a significantly lower value than would be obtained by locating the charge histogram maximum.
In this technical note we will use the inverse process, being known the charge histogram we will use a simple model to estimate the load distribution of the VEM. We will then use this VEM distribution and a one-hour secondary cosmic ray flux simulation to estimate the total muon component of the histogram.

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L. Otiniano and C. Alvarado
Fri, 18 Aug 17

Comments: in Spanish

Orbital advection with magnetohydrodynamics and vector potential [EPA]

Orbital advection is a significant bottleneck in disk simulations, and a particularly tricky one when used in connection with magnetohydrodynamics. We have developed an orbital advection algorithm suitable for the induction equation with magnetic potential. The electromotive force is split into advection and shear term, and we find that we do not need an advective gauge as solving the orbital advection implicitly precludes the shear term from canceling the advection term. We prove and demonstrate the third order in time accuracy of the scheme. The algorithm is also suited for non-magnetic problems. Benchmarked results of (hydrodynamical) planet-disk interaction and the of the magnetorotational instability are reproduced. We include detailed descriptions of the construction and selection of stabilizing dissipations (or high frequency filters) needed to generate practical results. The scheme is self-consistent, accurate, and elegant in its simplicity, making it particularly efficiently in straightforward finite-difference methods. As a result of the work, the algorithm is incorporated in the public version of the Pencil Code, where it can be used by the community.

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W. Lyra, C. McNally, T. Heinemann, et. al.
Fri, 18 Aug 17

Comments: 11 pages + 4 appendix; 8+1 figures. Submitted to AJ. Referee report received. Comments welcome

Field dynamics inference via spectral density estimation [CL]

Stochastic differential equations (SDEs) are of utmost importance in various scientific and industrial areas. They are the natural description of dynamical processes whose precise equations of motion are either not known or too expensive to solve, e.g., when modeling Brownian motion. In some cases, the equations governing the dynamics of a physical system on macroscopic scales occur to be unknown since they typically cannot be deduced from general principles. In this work, we describe how the underlying laws of a stochastic process can be approximated by the spectral density of the corresponding process. Furthermore, we show how the density can be inferred from possibly very noisy and incomplete measurements of the dynamical field. Generally, inverse problems like these can be tackled with the help of Information Field Theory (IFT). For now, we restrict to linear and autonomous processes. Though, this is a non-conceptual limitation that may be omitted in future work. To demonstrate its applicability we employ our reconstruction algorithm on a time-series and spatio-temporal processes.

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P. Frank, T. Steininger and T. Ensslin
Fri, 18 Aug 17

Comments: 12 pages, 9 figures

Mary, a pipeline to aid discovery of optical transients [IMA]

The ability to quickly detect transient sources in optical images and trigger multi-wavelength follow up is key for the discovery of fast transients. These include events rare and difficult to detect such as kilonovae, supernova shock breakout, and “orphan” Gamma-ray Burst afterglows. We present the Mary pipeline, a (mostly) automated tool to discover transients during high-cadenced observations with the Dark Energy Camera (DECam) at CTIO. The observations are part of the “Deeper Wider Faster” program, a multi-facility, multi-wavelength program designed to discover fast transients, including counterparts to Fast Radio Bursts and gravitational waves. Our tests of the Mary pipeline on DECam images return a false positive rate of ~2.2% and a missed fraction of ~3.4% obtained in less than 2 minutes, which proves the pipeline to be suitable for rapid and high-quality transient searches. The pipeline can be adapted to search for transients in data obtained with imagers other than DECam.

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I. Andreoni, C. Jacobs, S. Hegarty, et. al.
Thu, 17 Aug 17

Comments: Accepted for publication in PASA; 15 pages, 7 figures, 3 tables