ABSTRACT We report our discovery in Swift satellite data of a transient gamma-ray counterpart (3.2 confidence) to the fast radio burst (FRB) FRB 131104, the first such counterpart to any FRB. The ...transient has a duration T90 100 s and a fluence Sγ 4 × 10−6 erg cm−2, increasing the energy budget for this event by more than a billion times; at the nominal z 0.55 redshift implied by its dispersion measure, the burst's gamma-ray energy output is Eγ 5 × 1051 erg. The observed radio to gamma-ray fluence ratio for FRB 131104 is consistent with a lower limit we derive from Swift observations of another FRB, which is not detected in gamma-rays, and with an upper limit previously derived for the brightest gamma-ray flare from SGR 1806−20, which was not detected in the radio. X-ray, ultraviolet, and optical observations beginning two days after the FRB do not reveal any associated afterglow, supernova, or transient; Swift observations exclude association with the brightest 65% of Swift gamma-ray burst (GRB) X-ray afterglows, while leaving the possibility of an associated supernova at much more than 10% the FRB's nominal distance, D 320 Mpc, largely unconstrained. Transient high-luminosity gamma-ray emission arises most naturally in a relativistic outflow or shock breakout, such as, for example, from magnetar flares, GRBs, relativistic supernovae, and some types of galactic nuclear activity. Our discovery thus bolsters the case for an extragalactic origin for some FRBs and suggests that future rapid-response observations might identify long-lived counterparts, resolving the nature of these mysterious phenomena and realizing their promise as probes of cosmology and fundamental physics.
We present results of an archival coincidence analysis between Fermi Large Area Telescope (LAT) gamma-ray data and public neutrino data from the IceCube neutrino observatory's 40-string (IC 40) and ...59-string (IC 59) observing runs. Our analysis has the potential to detect either a statistical excess of neutrino + gamma-ray ( + γ) emitting transients or, alternatively, individual high gamma-multiplicity events, as might be produced by a neutrino observed by IceCube coinciding with a LAT-detected gamma-ray burst. Dividing the neutrino data into three data sets by hemisphere (IC 40, IC 59-North, and IC 59-South), we construct uncorrelated null distributions by Monte Carlo scrambling of the neutrino data sets. We carry out signal-injection studies against these null distributions, demonstrating sensitivity to individual + γ events of sufficient gamma-ray multiplicity, and to + γ transient populations responsible for >13% (IC 40), >9% (IC 59-North), or >8% (IC 59-South) of the gamma-coincident neutrinos observed in these data sets, respectively. Analyzing the unscrambled neutrino data, we identify no individual high-significance neutrino + high gamma-multiplicity events and no significant deviations from the test statistic null distributions. However, we observe a similar and unexpected pattern in the IC 59-North and IC 59-South residual distributions that we conclude reflects a possible correlation (p = 7.0%) between IC 59 neutrino positions and persistently bright portions of the Fermi gamma-ray sky. This possible correlation should be readily testable using eight years of further data already collected by IceCube. We are currently working with Astrophysical Multimessenger Observatory Network (AMON) partner facilities to generate low-latency + γ alerts from Fermi-LAT gamma-ray and IceCube and ANTARES neutrino data and distribute these in real time to AMON follow-up partners.
ABSTRACT We present a targeted search for blazar flux-correlated high-energy ( 1 TeV) neutrinos from six bright northern blazars, using the public database of northern hemisphere neutrinos detected ...during "IC40" 40-string operations of the IceCube neutrino observatory (2008 April to 2009 May). Our six targeted blazars are subjects of long-term monitoring campaigns by the VERITAS TeV γ-ray observatory. We use the publicly available VERITAS light curves to identify periods of excess and flaring emission. These predefined intervals serve as our "active temporal windows" in a search for an excess of neutrinos, relative to Poisson fluctuations of the near-isotropic atmospheric neutrino background, which dominates at these energies. After defining the parameters of an optimized search, we confirm the expected Poisson behavior with Monte Carlo simulations prior to testing for excess neutrinos in the actual data. We make two searches: one for excess neutrinos associated with the bright flares of Mrk 421 that occurred during the IC40 run, and one for excess neutrinos associated with the brightest emission periods of five other blazars (Mrk 501, 1ES 0806+524, 1ES 1218+304, 3C 66A, and W Comae), all significantly fainter than the Mrk 421 flares. We find no significant excess of neutrinos from the preselected blazar directions during the selected temporal windows. We derive 90% confidence upper limits on the number of expected flux-associated neutrinos from each search. These limits are consistent with previous point-source searches and Fermi GeV flux-correlated searches. Our upper limits are sufficiently close to the physically interesting regime that we anticipate that future analyses using already-collected data will either constrain models or yield discovery of the first blazar-associated high-energy neutrinos.
AMON: Transition to real-time operations Cowen, D.F.; Keivani, A.; Tešić, G.
EPJ Web of Conferences,
01/2016, Letnik:
116
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The Astrophysical Multimessenger Observatory Network (AMON) will link the world's leading high-energy neutrino, cosmic-ray, gamma-ray and gravitational wave observatories by performing real-time ...coincidence searches for multimessenger sources from observatories' subthreshold data streams. The resulting coincidences will be distributed to interested parties in the form of electronic alerts for real-time follow-up observation. We will present the science case, design elements, current and projected partner observatories, status of the AMON project, and an initial AMON-enabled analysis. The prototype of the AMON server has been online since August 2014 and processing archival data. Currently, we are deploying new high-uptime servers and will be ready to start issuing alerts as early as winter 2015/16.
A new small array of Cherenkov detectors has been deployed in Tehran, 1200 m above sea level. This array contains four tanks of distilled water with a diameter of 64 cm and a height of 130 cm. The ...effective area of each tank is about 1382 cm2. They are used to detect air showers and to record the arrival time of the secondary particles. We have collected about 640 000 extensive air showers (EAS) in 8298 h of observation time from November 2006 to October 2007. The distribution of air showers in zenith and azimuth angles has been studied and a cosntheta distribution with n = 6.02 +/- 0.01 was obtained for the zenith angle distribution. An asymmetry has been observed in the azimuthal distribution of EAS of cosmic rays due to geomagnetic field. The first and second amplitudes of the asymmetry are AI = 0.183 +/- 0.001 and AII = 0.038 +/- 0.001. Since the recent results are in good agreement with our previous results of scintillation detectors, and tanks of distilled water are cheaper, we prefer to use them instead of scintillators in a future larger array. By simulation, we have improved the size of the detectors to yield the highest efficiency. The best dimensions for each tank with a photomultiplier tube in the center of its lid are 40 cm in diameter and 60 cm in height.
The dynamic facility layout problem is the problem of assigning departments to the predetermined locations on the plant floor for multiple periods to minimize material handling and rearrangement ...costs. Nowadays, we encounters with shortage of lands to build factory, so we use of several floor. In this paper, we propose a simulated annealing algorithm for multi floor facility layout problem.
The Astrophysical Multimessenger Observatory Network (AMON) receives subthreshold data from multiple observatories in order to look for coincidences. Combining more than two datasets at the same time ...is challenging because of the range of possible signals (time windows, energies, number of events...). However, outlier detection methods can circumvent this issue by identifying any signal divergent from the background (e.g. scrambled data). We propose to use these methods to make a model independent combination of the subthreshold data of neutrino and gamma ray experiments. Using the python outlier detection (PyOD) package, it allows us to test several methods from a simple "k-nearest neighbours" algorithm to a more sophisticated Generative Adversarial Active Learning neural networks which generates data points to better discriminate inliers from outliers.
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