VERITAS Very High Energy Observations of the Distant Blazar 1ES 0647+250

We perform an analysis of the long- and short-term variability of the very high energy (VHE; above 100 GeV) gamma-ray emission from the newly-detected distant blazar 1ES 0647+250. Both new and archival data from the VERITAS telescope were examined, and no strong evidence for integral flux variability on any timescale was found. This lack of variability is consistent with the application of current ultra-high energy cosmic ray (UHECR) models, which can produce secondary gamma-ray emission along the line of sight from the blazar; it also allows averaging over multiyear timescales without bias, aiding in the construction of spectral energy distribution plots (SEDs) for 1ES 0647+250. Because of its distance, 1ES 0647+250 is an object of interest for further study, particularly in efforts to constrain models of the extragalactic background light (EBL) and intergalactic magnetic field strength (IGMFs)

Methods for point source analysis in high energy neutrino telescopes

Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two.Comment: pdfLaTeX, 16 pages, 12 figures. Submitted to Astroparticle Physic

Time-Dependent Point Source Search Methods in High Energy Neutrino Astronomy

We present maximum-likelihood search methods for time-dependent fluxes from point sources, such as flares or periodic emissions. We describe a method for the case when the time dependence of the flux can be assumed a priori from other observations, and we additionally describe a method to search for bursts with an unknown time dependence. In the context of high energy neutrino astronomy, we simulate one year of data from a cubic-kilometer scale neutrino detector and characterize these methods and equivalent binned methods with respect to the duration of neutrino emission. Compared to standard time-integrated searches, we find that up to an order of magnitude fewer events are needed to discover bursts with short durations, even when the burst time and duration are not known a priori.Comment: LaTeX; 17 Pages, 4 figures; submitted to Astroparticle Physic

The On-Site Analysis of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) observatory will be one of the largest ground-based very high-energy gamma-ray observatories. The On-Site Analysis will be the first CTA scientific analysis of data acquired from the array of telescopes, in both northern and southern sites. The On-Site Analysis will have two pipelines: the Level-A pipeline (also known as Real-Time Analysis, RTA) and the level-B one. The RTA performs data quality monitoring and must be able to issue automated alerts on variable and transient astrophysical sources within 30 seconds from the last acquired Cherenkov event that contributes to the alert, with a sensitivity not worse than the one achieved by the final pipeline by more than a factor of 3. The Level-B Analysis has a better sensitivity (not be worse than the final one by a factor of 2) and the results should be available within 10 hours from the acquisition of the data: for this reason this analysis could be performed at the end of an observation or next morning. The latency (in particular for the RTA) and the sensitivity requirements are challenging because of the large data rate, a few GByte/s. The remote connection to the CTA candidate site with a rather limited network bandwidth makes the issue of the exported data size extremely critical and prevents any kind of processing in real-time of the data outside the site of the telescopes. For these reasons the analysis will be performed on-site with infrastructures co-located with the telescopes, with limited electrical power availability and with a reduced possibility of human intervention. This means, for example, that the on-site hardware infrastructure should have low-power consumption. A substantial effort towards the optimization of high-throughput computing service is envisioned to provide hardware and software solutions with high-throughput, low-power consumption at a low-cost.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

A prototype for the real-time analysis of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) observatory will be one of the biggest ground-based very-high-energy (VHE) γ- ray observatory. CTA will achieve a factor of 10 improvement in sensitivity from some tens of GeV to beyond 100 TeV with respect to existing telescopes. The CTA observatory will be capable of issuing alerts on variable and transient sources to maximize the scientific return. To capture these phenomena during their evolution and for effective communication to the astrophysical community, speed is crucial. This requires a system with a reliable automated trigger that can issue alerts immediately upon detection of γ-ray flares. This will be accomplished by means of a Real-Time Analysis (RTA) pipeline, a key system of the CTA observatory. The latency and sensitivity requirements of the alarm system impose a challenge because of the anticipated large data rate, between 0.5 and 8 GB/s. As a consequence, substantial efforts toward the optimization of highthroughput computing service are envisioned. For these reasons our working group has started the development of a prototype of the Real-Time Analysis pipeline. The main goals of this prototype are to test: (i) a set of frameworks and design patterns useful for the inter-process communication between software processes running on memory; (ii) the sustainability of the foreseen CTA data rate in terms of data throughput with different hardware (e.g. accelerators) and software configurations, (iii) the reuse of nonreal- time algorithms or how much we need to simplify algorithms to be compliant with CTA requirements, (iv) interface issues between the different CTA systems. In this work we focus on goals (i) and (ii)

Time-independent searches for astrophysical neutrino sources with the combined data of 40 and 59 strings of IceCube

We present the results of time-independent searches for astrophysical neutrino sources performed over the whole sky using data collected between April 2008 and May 2010 with the 40-string and 59-string configurations of the IceCube Neutrino Observatory. Muon tracks arriving in the detector from neutrino interactions are reconstructed using the time and charge information detected by an array of photomultiplier tubes (PMTs). In the northern sky, the data sample consists of 14,121 events collected with 40 strings and 43,339 with 59 strings, mostly muons induced by atmospheric neutrinos. In this sky region the search is sensitive to point sources of neutrinos with E-2 spectra mainly in the TeV-PeV energy range. In the opposite hemisphere, a much larger background of high-energy atmospheric muons dominate the data set. A zenith dependent energy cut is used to reduce the number of background events. This weakens the sensitivity for point sources with E-2 spectra with respect to the upgoing region. The downgoing region is more sensitive to harderspectrum sources for which the bulk of events can be detected between PeV-EeV energies. An unbinned maximum likelihood ratio test is used to search for astrophysical signals. For the first time it was adapted to combine data from different detector configurations. The combined sensitivity is about a factor ∼ 2.5 better than the previous 1-year limit of the 40-string configuration alone. A dedicated search based on a catalog of sources is also presented.Sponsors: China Center of Advanced Science and Technology (CCAST),Chinese Academy of Sciences (CAS),Institute of High Energy Physics (IHEP),National Natural Science Foundation of China (NSFC)info:eu-repo/semantics/publishe

IceCube time-dependent point source analysis using multiwavelength information

In order to enhance the IceCube's sensitivity to astrophysical objects, we have developed a dedicated search for neutrinos in coincidence with flares detected in various photon wavebands from blazars and high-energy binary systems. The analysis is based on a maximum likelihood method including the reconstructed position, the estimated energy and arrival time of IceCube events. After a short summary of the phenomenological arguments motivating this approach, we present results from data collected with 22 IceCube strings in 2007-2008. First results for the 40-string IceCube configuration during 2008-2009 will be presented at the conference. We also report on plans to use long light curves and extract from them a time variable probability density function.info:eu-repo/semantics/publishe